Review Article Cell-Based Therapies Used to Treat Lumbar ... · Cell-Based Therapies Used to Treat Lumbar Degenerative Disc Disease: A Systematic Review of Animal Studies and Human

Review ArticleCell-Based Therapies Used to Treat LumbarDegenerative Disc Disease A Systematic Review ofAnimal Studies and Human Clinical Trials

David Oehme1 Tony Goldschlager2 Peter Ghosh34

Jeffrey V Rosenfeld56 and Graham Jenkin7

1The Ritchie Centre Monash Institute of Medical Research (MIMR-PHI) Monash University Clayton Branch PO Box 6178South Yarra VIC 3141 Australia2Departments of Surgery andThe Ritchie Centre Monash Institute of Medical Research (MIMR-PHI) Monash UniversityClayton Branch 27-31 Wright Street Clayton VIC 3168 Australia3Proteobioactives Research Laboratories PO Box 35 Brookvale NSW 2100 Australia4Mesoblast Ltd Melbourne VIC 3000 Australia5Department of Surgery Monash University Clayton VIC 3168 Australia6Department of Neurosurgery AlfredHospital Level 5TheAlfredCentre Commercial Road PrahranMelbourne VIC 3168 Australia7The Ritchie Centre Monash Institute of Medical Research (MIMR-PHI) Monash University Clayton Branch 27-31 Wright StreetClayton VIC 3168 Australia

Correspondence should be addressed to David Oehme drdavidoehmemaccom

Received 20 January 2015 Revised 8 April 2015 Accepted 15 April 2015

Academic Editor Bruno Peault

Copyright copy 2015 David Oehme et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Low back pain and degenerative disc disease are a significant cause of pain and disability worldwide Advances in regenerativemedicine and cell-based therapies particularly the transplantation ofmesenchymal stem cells and intervertebral disc chondrocyteshave led to the publication of numerous studies and clinical trials utilising these biological therapies to treat degenerative spinalconditions often reporting favourable outcomes Stem cell mediated disc regeneration may bridge the gap between the two currentalternatives for patientswith lowback pain often inadequate painmanagement at one end and invasive surgery at the otherThroughcartilage formation and disc regeneration or via modification of pain pathways stem cells are well suited to enhance spinal surgerypractice This paper will systematically review the current status of basic science studies preclinical and clinical trials utilising cell-based therapies to repair the degenerate intervertebral discThemechanism of action of transplanted cells as well as the limitationsof published studies will be discussed

1 Introduction

Low back pain is the leading cause of disability in the devel-oped world and has an enormous social impact on patientsand their families as well as a devastating economic impacton healthcare budgets [1]The annual cost of back pain in theUnited States is estimated to be as high as $500 billion [2]Studies have shown that 75ndash80of peoplewill experience lowback pain at some stage with a prevalence ranging from 15 to45 [3] Severe disc degeneration is associated with a twofoldincrease in chronic low back pain [4 5] however despite

this strong link between pain and disc degeneration [6ndash10]it is well recognised that not all patients with radiologicalevidence of disc degeneration will have symptoms Thereare many potential pain generators in the lumbar spine inaddition to the disc Moreover differentiating the ageing discfrom the symptomatically degenerate disc remains a majorchallenge [11 12]

The intervertebral disc (IVD) is a fibrocartilaginousarticulation between adjacent vertebrae which has a centralhydrated gelatinous core the nucleus pulposus (NP) sur-rounded by an outer fibrous-cartilaginous ring the annulus

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2 Stem Cells International

fibrosis (AF) which consists of concentrically lamellated col-lagen fibres Thin hyaline cartilage endplates attach the discto the adjacent vertebral bodies and disc nutrition passesthrough these end plates to the predominantly avascular IVD[13 14] The IVD functions to facilitate movement and flexi-bility of the vertebral column whilst also having the ability torecover from deformation following axial loadingThe nativecell population of the disc represents approximately 1 of thedisc tissue but is pivotal in maintaining disc metabolism [1315] Cells of the NP and inner AF demonstrate chondrocyticmorphologywhilst cells in the outer AF aremore fibroblastic-like [16 17]

The causes of disc degeneration are complex and mul-tifactorial including genetic nutritional and mechanicalinfluences [17] An imbalance between extracellular matrixdegradation and synthesis results in progressive collapseand mechanical failure of the disc An overall decrease inresident disc cell number and function and cellular responsesto nutritional deficiencies leads to alterations in both thecartilaginous and proteoglycan matrix components of thedisc [13 18] The loss of the pivotal water binding proteogly-can component leads to dehydration of the NP impactingthe discs ability to adequately distribute and recover frommechanical loading As degeneration progresses neovascu-larisation with concurrent neoinnervation can occur withinthe degenerative AF and extend to within the NP [10 19 20]this pathological ingrowth of nerve fibres and vessels has beenlinked to the mechanical back pain experienced by patientswith disc disease [10] Endplate changes occur with thinningcalcification and alterations in vascularity as nutritionallydeprived discs attempt to increase their nutrient supplyThis creates a hostile environment that is a major challengeto maintain cell viability of both native cells or cells thatare implanted in regenerative therapies Moreover changeswithin the adjacent vertebral bodies and endplates occurincluding sclerosis and subchondral bone microfracture [13]

Whilst the degenerative cascade is well understood lowback pain can be a source of frustration for patients and clin-icians due to difficulties in identifying the pain generator anda lack of treatment options available to successfully manageall patients Initial treatments include conservative therapiessuch as analgesics physical therapies and psychological painmanagement strategiesWhen these nonoperative treatmentsfail surgical interventions such as lumbar fusion or total discarthroplasty are commonly performedThese treatments areoften successful however they do not address the underlyingcause and despite these interventions some patients remainwith chronic pain and disability

Substantial progress has occurred in the fields of regen-erative medicine tissue engineering and stem cell therapieswith the aim of treating and reversing disc degeneration aswell as augmenting and enhancing current treatments Clini-cal trials have commenced utilising cell-based biological ther-apies to treat many common diseases including those affect-ing the musculoskeletal system and in particular degener-ative discopathies Culture expanded disc chondrocytes andmesenchymal stem cells isolated from bonemarrow or othersources are the two cell types most commonly used byresearchers to biologically repair the degenerate disc Other

types of stem or progenitor cells used in either an autologousor allogeneic fashion have also been investigated in studiesSeveral small clinical trials have recently been published withanother larger randomised phase-2 trial currently underway[21ndash24]

This paper will comprehensively review the current statusof basic science studies as well as preclinical and clinicaltrials utilising cell-based therapies to repair the degenerateintervertebral disc Significant positive and negative findingsof trials published to date will be highlighted and therelative benefits and limitations of various cell types andtreatment strategies will be discussed Animal models ofdisc degeneration and the applicability of these models tothe human condition will also be addressed Knowledge ofwhat has been achieved to date as well as the limitations ofthese achievements is important to guide future trials as thisexciting field of regenerative medicine translates toward theclinic

2 Methods

We performed a literature search using theMEDLINE onlineelectronic database between 1950 and 2013 Google Scholarand the Cochrane Database The following keywords werequeried in combination with intervertebral disc stem cellmesenchymal stem cell progenitor cell nucleus pulposus celldisc chondrocyte disc regeneration and tissue engineeringThesearch was limited to articles published in English Studiesutilising either stem cells progenitor cells or intervertebraldisc chondrocytes to regenerate the intervertebral disc wereincluded in the analysis The indexes of suitable articles werereviewed for further relevant published studies Publicationscomprised of in vitro work only were excluded Studies werethen grouped into one of the following four categories foranalysis (1) studies utilising chondrocyte transplantationobtained from intervertebral disc tissue or other cartilagesources (2) studies utilising stem and progenitor cell trans-plantation including mesenchymal stem cells (MSCs) andother cell types obtained from noncartilaginous tissues (3)studies comparing chondrocyte and stem cell transplanta-tion and (4) human clinical trials utilising any form ofcell-based therapy to repair degenerative discs includingchondrocytes and stem cell therapies The flow diagram forour search is outlined in Figure 1

3 Results

31 Studies Utilising Intervertebral Disc or Chondrocyte (orChondrocyte-Like) Cell Transplantation There were 14 stud-ies identified assessing the ability of disc derived and nondiscderived chondrocytes to regenerate IVDs as shown inTable 1

311 Animal Models Utilised 214 studies utilised a rodentanimalmodel (rat) [28 33] whilst 1214 studies utilised largeranimal models (rabbit canine or monkey) [15 25ndash27 29ndash32 34] 1214 studies utilised nucleotomy as the method ofinducing degeneration one study used a laser to damagethe disc and in the remaining study a total discectomy wasperformed It should be noted that the amount of nuclear

Stem Cells International 3

Table 1 Studies assessing the ability of disc derived and non-disc derived chondrocytes to regenerate lumbar intervertebral discs

Author Animalmodel

Degenerationmodel

Cellstransplanted

Method of celladministration Resultsconclusions

Bertram et al[25] Rabbit

Nucleotomyand axialcompressionAmount ofnucleusremoved

AutologousNPCs

Percutaneousinjection infibrin gel

(i) 90 of cells leak out of disc space wheninjected in aqueous form(ii) Injection within fibrin-thrombin gel decreasedleakage to 50(iii) Intradiscal pressure limited cell survival

Ganey et al [26] Canine NucleotomyAutologousdiscchondrocytes

Intradiscalinjection

(i) Transplanted cells remained viable andproduced matrix similar in composition to nativedisc including PGs(ii) Increased types II and I collagen(iii) Disc height maintained in cell treated group

Gorensek et al[27] Rabbit Nucleotomy

Autologousauricularcartilagederivedchondrocytes


(i) Production of hyaline cartilage in the NP(ii) Chondrocytes survived

Gruber et al[28] Rat

Partialannulotomyandnucleotomy

Autologousdiscchondrocytes

Surgicalimplantation

(i) Transplanted cells remained viable producingmatrix for up to 8 months(ii) Cells in AF had fibroblast appearance cells inNP had chondrocyte appearance

Huang et al [29] Rabbit Nucleotomy AllogeneicNPCs

NPC-seededcollagen120572hyaluronanchondroitin-6-sulfatetri-copolymerconstructs

NPC treated discs(i) Increased MRI T2 signal(ii) Retard loss of disc height(iii) Produced cartilaginous matrix within NP(iv) Cells remained viable

Hohaus et al[30] Canine

Annularinjury andpartialnucleotomy

AutologousNPCs Injection

NP cells(i) Remain viable following implantation(ii) PG and ECM cartilage produced(iii) Types I and II collagen demonstrated(iv) Maintain disc height

Iwashina et al[31] Rabbit

Percutaneousaspiration ofNP

XenogeneicHumanNPCs

Percutaneousinjection

NPC treated discs(i) Increased disc height(ii) Significantly less degeneration usingmorphological and histological analysis(iii) Increased proteoglycan synthesis(iv) Increased expression of aggrecan versicanand collagen II

Luk et al [32] Rhesusmonkey

Totaldiscectomy

Allogeneicwhole disc

Allogeneicwhole discsurgicaltransplant

Fresh disc allografts(i) Survive following transplantation(ii) Undergo severe degeneration after 24 months

Meisel et al [15] Canine DiscectomyAutologousdisc derivedchondrocytes


Transplanted cells(i) Remain viable(ii) Produce matrix similar to normal disc(iii) Type I and II collagens demonstrated inregenerated intervertebral disc(iv) Maintained disc height

Nishimura andMochida [33] Rat Percutaneous

nucleotomyAutologousNP tissue


Implantation of NP tissue(i) Delayed degenerative changes(ii) Preserved disc height

Nomura et al[34] Rabbit


AllogeneicNP cells andintact NPtissue


(i) No immune or inflammatory response fromallogeneic cell implantation(ii) Implantation of intact nucleus and NP cellsreduced degeneration(iii) Increased type II collagen post implantation


Table 1 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted


Okuma et al[35] Rabbit Percutaneous

NP aspirationAutologousNP cells

Percutaneousinjection of NPcells coculturedwith AF cells

Cell treated discs(i) Delayed cell clustering(ii) Rate of degeneration slowed histologically(iii) Cells elaborated type II collagen

Ruan et al [36] Canine Nucleotomy AutologousNPCs

NP cells seededonto L-lactic-co-glycolic acid(PLGA) scaffold

(i) Disc height segmental stability and MRI T2signal preserved in NP treated discs(ii) PKH-26 labelled cells found in NP at 8 weeks

Sato et al [37] Rabbit Vaporizedusing laser

Allogeneicannulusfibrosus cells

Annulusfibrosus cellscultured inatelocollagenhoneycomb-shaped scaffoldand labelledwith PKH-26fluorescent dye

Transplanted cells(i) Prevented loss of disc height(ii) Remained viable at 12 weeks(iii) Produced hyaline cartilage

AF annulus fibrosis ECM extracellular matrix NP nucleus pulposus NPCs nucleus pulposus cells and PGs proteoglycans

Studies identified throughdatabase searching

(n = 42)

Studies identified through

Studies after duplicates removed

(n = 22)

(n = 62)

(n = 62) (n = 16)

(n = 4)(n = 3)

(n = 46)

(n = 25)(n = 14)

other sources

Studies excludedStudies screened

Studies included in analysis

Clinical trialsassessing cell-based

disc therapy

Studies comparingchondrocytes and

MSCs

Studies assessingStudies assessingstemprogenitor

cell transplantationchondrocyte

transplantation

Figure 1 Flow diagram demonstrating the systematic analysis process

material removed in the nucleotomy procedure differedbetween studies and is listed in Table 1

312 Cell Types Utilised 1014 studies transplanted cultureexpanded NP cells into target discs The remaining studiesutilised AF cells NP tissue or whole disc Allogeneic admin-istration was performed in 1014 studies and was autologousin 314 and xenogeneic administration was performed in onestudy where humanNP cells were injected into the rabbit disc[31] 814 studies injected the cells into the target disc withouta cell carrier whilst 5 coadministered cells with either fibringlue or another tissue engineered scaffold

313 Outcomes In 1214 studies (92) in discs receivingcell treatment degeneration was slowed or reversed on

gross morphological or histological assessment and hadincreased matrix deposition either proteoglycan or collagenwhen compared to controls 714 studies also demonstratedfavourable radiological outcomes being either preservationof disc height or increased T2 signal on MRI 8 studiesdemonstrated viability of transplanted chondrocytes follow-ing injection with Gruber et al [28] demonstrating survivalfor up to 8 months following transplantation

The study by Bertram et al [25] showed that 90 of cellsleaked out of the disc following injection in aqueous solutionhowever this was reduced to 50with fibrin glue coadminis-tration Luk et al [32] found that whole disc transplant couldbe performed however despite surviving the transplanteddisc underwent severe degeneration No other cell related


morbidity or negative outcomes were reported in any otherstudy utilising chondrocyte transplantation

32 Studies Utilising Stem Cell and Progenitor Cell Transplan-tation There were 25 studies assessing the ability of differenttypes of stem cells or progenitor cells to regenerate the IVDidentified as shown in Table 2

321 Animal Models Utilised 625 studies used rodent ani-mal models (rat ormouse) whilst 1625 utilised larger animalmodels (rabbit canine porcine or ovine) 325 studies usednormal nondegenerate discs The remaining 2225 studiesused either needle puncture nucleotomy matrix degradingenzymes annular injury or axial loading to induce degener-ation prior to the administration of cell therapy

322 Cell Type Utilised Bone marrow derived MSCs werethe most commonly used stem cell treatment used in 2025(80) studies [40 41 49 52ndash54 57ndash59 61] 9 of thesestudies used autologous administration of MSCs 725 usedallogeneic administration and 425 studies utilised humanMSC xeno-transplantation to treat degenerate animal discs325 studies used adipose derived MSCs either autologousor xenogeneic human MSCs whilst other cell types investi-gated included human embryonic stem cells (ESCs) autolo-gous synovial derived MSCs human olfactory neurospherederived stem cells and allogeneic mesenchymal precursorcells (MPCs) 325 studies utilised hyaluronic acid as thecell carrier 525 studies used another hydrogel (hyaluronanPuramatrix or PFG-TGF-beta1) or fibrin based scaffoldwhilst in the remaining studies the vehicle carrier was notdefined and cells were presumably injected into discs inaqueous culture medium only

323 Outcomes The outcomes of these studies are summa-rized inTable 2 1525 studies reported favourable radiologicaloutcomes either preservation of disc height or increasedMRI T2 signal following cell administration 225 studiesreported no improvement whilst the remaining studies didnot specifically assess radiological outcomes 1425 studiesdemonstrated improved histological structure following celltransplantation whilst 1525 studies reported positive find-ings in terms of matrix restoration utilising either total GAGor collagen II content or measuring expression of genesknown to be important formatrix restoration such as Col2a1aggrecan and Sox-9

1225 studies assessed the viability of cells followingtransplantationwith varying survival times reported rangingfrom 15 days to 48 weeks Several other studies howeverreported leakage or nonviability of cells following injectionOmlor et al [49] reported that only 9 of cells remainedin the disc 3 days following implantation with fibrin gluewhilst Vadala et al [57] found no evidence of regenerationor the transplanted cells 9 weeks after intradiscal injection ofallogeneic bone marrow MSCs

33 Studies Comparing MSC and Chondrocyte Transplanta-tion Three studies directly compared the ability ofMSCs andchondrocytes to regenerate IVDs [62 63 66] as shown in

Table 3 Feng et al [66] showed that autologous MSCs andNPCswere equivalent inmaintaining disc height andMRI T2signal aggrecan and collagen II expression and proteoglycanproduction Allon et al [63] found that transplantation ofbilaminar coculture pellets of allogeneic MSCs and NPCsincreased disc height and proteoglycan production Whenused alone however both the MSCs and NPCs were equallyineffective in repairing the damaged rat disc

Acosta et al [62] found that nucleotomised porcinediscs treated with allogeneic nondisc juvenile articular chon-drocytes had increased glycosaminoglycan (GAG) DNAand cartilage content compared to bone marrow derivedMSCs These allogeneic MSCs were found not to be viableat 3 months and there was no evidence of proteoglycanproduction in their model

34 Clinical Trials Utilising Cell Based Disc Therapies Fourpublished clinical studies utilising cell-based therapies totreat human lumbar disc degeneration were identified [1522 23 65] as shown in Table 4 Three of these studiesreported favourable results The EuroDISC study by Meiseland colleagues [15] investigated the percutaneous transplan-tation of autologous disc chondrocytes Patients enrolledunderwent a single level microdiscectomy procedure fromwhich disc chondrocytes were harvested and expanded invitro and subsequently injected into the NP three monthspostoperatively Analysis at two years demonstrated thatpatients who received chondrocyte transplantation had sig-nificantly less back pain and increased NP T2 signal onMRI in both the treated and adjacent discs Yoshikawaet al [23] reported favourable outcomes following percuta-neous intradiscal administration of autologous MSCs withincollagen sponge in two elderly patients with degenerativedisc disease [23] At two years both patients demonstratedalleviation of both back and radicular symptoms Orozco etal [22] reported a pilot study of 10 patients with chroniclow back pain and degenerative disc disease again treatedwith percutaneously intradiscal administration of autologousMSCs In this study 90 of participants reported clinicalbenefit with significant decrease in pain and disability andimprovement in quality of life

Haufe andMork [65] reported no improvement in clinicalstatus following the transplantation of autologous noncultureexpanded haematopoietic precursor stem cells (HSCs) intothe discs of 10 patients No patient demonstrated clinicalimprovement in back pain or disability Notably 85 ofpatients underwent surgery at the stem cell treated level atone year

4 Discussion

41 The Influence of Animal Models The ideal animal modelof lumbar disc degeneration would mimic the human degen-erative process in terms of cellularmatrix and biomechanicalchanges Given the complex nature of disc degeneration itsmultifactorial aetiologies and lengthy time-course an animalmodel that exactly parallels the human condition is notfeasible Nonchondrodystrophoid animal species in whichthere is persistence of notochordal cells are less favourable as


Table 2 Studies assessing the ability of different types of stem cells or progenitor cells to regenerate lumbar intervertebral discs

Author Animalmodel

Degenerationmodel

Cellstransplanted


Crevenstenet al [38] Rat Needle puncture Allogeneic

MSCs

Intradiscal injectionof MSCs with 15hyaluronan gel

MSCs(i) Trend towards increased disc height(ii) Retained in disc remain viable and canproliferate for at least 28 days

Ganey et al[39] Canine Partial

nucleotomy

Non cultureexpandedautologousadipose derivedstem cells

Intradiscal injectionwith HA

Transplantation of adipose MSCs improved(i) MRI T2 signal at 12 months(ii) Disc histology assessment(iii) Increase collagen II expression

Ghosh et al[40] Sheep

Chondroitinase-ABCinjection

AllogeneicStro-3+MesenchymalPrecursor Cells(MPCs)

Injection withhyaluronic acid(Euflexxa) carrier

MPCs + HA(i) Restore disc height(ii) Improved MRI Pfirrmann scores(iii) Improved histological degeneration scores(iv) Restoration of extracellular matrix

Hee et al[41] Rabbit Axial loading Allogeneic bone

marrow MSCs

Injection of MSCscombined with axialdistraction

(i) MSCs increase disc height and improvehistology scores(ii) MSCs Survive for 8 weeks

Henrikssonet al [42]

Porcineminipig Nucleotomy Xenogeneic

Human MSCs

Xenotransplantationof hMSCs withPuramatrix hydrogelcarrier or F12 mediasuspension

MSCs(i) Survive in pig disc space for 6 months(ii) Differentiated into cells representing discchondrocytes(iii) Improved MRI appearance in MSChydrogeltreatment groups(iv) Combination of with Puramatrix hydrogelincreased cell differentiation matrix productionand survival(v) At three and six months expressed SOX9aggrecan and collagen II

Hiyama etal [43] Canine Nucleotomy Autologous

MSCs

Percutaneousinjection of MSCsinfected withAcGFP1 retrovirusvector

MSCs(i) Increased disc height and MRI T2 signal(ii) Increased production of proteoglycans(iii) Improved histological structure including AF(iv) Proportion of FasL-positive cells increasedfollowing MSC injection

Ho et al[44] Rabbit Percutaneous

needle punctureAutologousMSCs

Intradiscal injectionof BrdU-labelledMSCs

MSCs(i) Found in disc at 16 weeks post injection(ii) Discs injected at 6 months post nucleotomyless degenerate than controls but not returned tobaseline(iii) Increased PG in posterior inner annulus(iv) Did not restore disc height(v) Only partial arrest possible followingadministration and more effective at later point ofdegeneration

Hohaus etal [30] Canine

Annular injuryand partialnucleotomy

Autologousadipose derivedMSCs

Intradiscal injection

Adipose MSCs(i) Remain viable in disc(ii) Maintain disc morphology disc height andMRI T2 signal(iii) HA alone insufficient to prevent degeneration

Jeong et al[45] Rat Annular injury Xenogeneic

human MSC Intradiscal injection

MSCs(i) Maintain disc height and T2 signal(ii) Restore AF structure(iii) Survive for 2 weeks after injection but not 4weeks


Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted


Jeong et al[46] Rat Needle injection

Xenogeneicadipose derivedhuman MSCs


MSCs(i) Less loss of disc height following injection(ii) Restore T2 MRI signal(iii) Restore AF structure(iv) Upregulate collagen 2 and aggrecan

Miyamotoet al [47] Rabbit NP aspiration Autologous

synovial MSCs Intradiscal injection

MSCs(i) Identified in NP at 24 weeks(ii) Preserve disc height(iii) Preserve MRI T2 signal for 6 weeks(iv) Preserve NP histological structure(v) Increase expression of collagen-II

Murrell etal [48] Rat NP aspiration

Xenogeneichuman olfactoryneurosphere-derived stemcells

Intradiscal injection (i) 70 cells identified in discs(ii) Cells assumed NP cell like phenotype

Omlor et al[49] Porcine Partial

nucleotomy

AutologousBone marrowMSCs

Injection of MSCstransfected withRv-eGFP withinfibrin glue

(i) After 3 days only 9 of injected cells remainedin disc

Prologo etal [50] Porcine Needle biopsy of

discXenogeneichuman MSCs

Xenogenicpercutaneousadministration ofiodine-12421015840-flouro-21015840ndashdeoxy-1B-D-arabinofuranosyl-5-iodouracil ndashlabeledhMSCs

(i) PET-CT confirmed cells in NP on day 0 andday 3 following injection(ii) Immunohistological staining at 15 daysconfirmed presence of cells in treated discs

Sakai et al[51] Rabbit Nucleotomy ndash

NP aspirationAutologousMSCs

MSCs embedded inatelocollagenhydrogel

MSCs(i) Preserved histological structure(ii) Retained and proliferated in disc(iii) Increased PGs on histological staining


NP aspiration

Autologousbone marrowMSCs

GFP labelled MSCinjection

(i) MSCs present in NP at up to 48 weeks(ii) GFP positive cells expressed collagen IIaggrecan suggesting site dependentdifferentiation(iii) MSCs increased PG content of NP to baseline(iv) Increased collagen II and aggrecan mRNAdecreased collagen I following MSC injection


NP aspiration



(i) MSCs increased disc height and MRI T2 signal(ii) MSCs preserve histological structureincluding AF(iii) Restoration of PGs suggested fromimmunohistochemistry and gene expression

Serigano etal [54] Canine NP Aspiration



(i) MSCs significantly increase DHI and MRI T2signal(ii) 106 and 107 cell doses showed improved NPand inner annular histological structure(iii) 105 dose group had more degenerativechanges(iv) 106 dose group had less apoptosis than 105 or107 groups(v) 106 dose group had more live cells at 16 weekscompared to other groups


Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted


Sheikh et al[55] Rabbit Needle puncture

Xenogeneicmurine ESCswere culturedwith cis-retinoicacidtransforminggrowth factorbeta ascorbicacid andinsulin-likegrowth factor

Intradiscal injection (i) Discs treated with ESCs demonstratedincreased population of new notochordal cells

Sobajima etal [56] Rabbit Normal discs Allogeneic

MSCs

Injection with MSCsretrovirallytransfected withlacZ marker gene

(i) MSCs detected up to 24 weeks followingtransplantation(ii) No inflammatory response observed in discsfollowing MSC injection(iii) At 24 weeks more cells located in transitionzone and inner AF taking on more spindle shapedappearance(iv) Synergism with NPCs and MSCs to increaseGAG production most at 75 35 MPCMSC ratio

Vadala et al[57] Rabbit Needle Stab Allogeneic bone

marrow MSCs Intradiscal injection

(i) No evidence of regeneration at 9 weeks on MRI(ii) X-ray demonstrated osteophyte formation intreated discs(iii) No cells found in NP using GFP label

Wei et al[58] Rat Nil

Xenogeneichuman bonemarrow MSCs ndashCD34minus (MSCs)and CD34+(Haemopoeiticcells) bonemarrow cells


(i) CD34minus cells (MSCs) remain in NP for 42 days(ii) CD34+ cells not visible after day 10(iii) CD34minus cells expressed CTOcollagen II orCTOSox-9 indicating chondrocytic phenotypedifferentiation(iv) No inflammatory cells visible

Yang et al[59] Mouse Annular

punctureAllogeneic bonemarrow MSCs Intradiscal injection

MSCs(i) Preserve NP and AF structure up to 24 weeks(ii) Preserve disc height(iii) PGs upregulated(iv) Decrease in Col2a1 aggrecan and Sox9arrested(v) GAGDNA increased(vi) Underwent chondrocytic differentiation(vii) Increased notochordal cells suggesting MSCspromote NCC survival and proliferation(viii) Cells survive 24 weeks using GFP labelling

Yang et al[60] Rabbit Needle puncture

and nucleotomyAutologousMSCs

Injection of MSCswith pure fibrinousgelatin-transforminggrowth factor-beta1(PFG-TGF-beta1)

(i) MSCs inhibited apoptosis(ii) MSCs slowed the rate of loss of DHI andincreased T2 signal at 12 weeks(iii) Increased type II collagen in MSC treatedgroup

Zhang et al[61] Rabbit Normal discs Allogeneic bone

marrow MSCsInjection of LacZlabelled MSCs

(i) MSCs survive in disc(ii) MSCs increase expression of Type II collagenand PGs

AF annulus fibrosis DHI disc height index ESCs embryonic stem cells GAG glycosaminoglycan content GFP green fluorescent protein HA hyaluronicacid MSCs mesenchymal stem cells MPCs mesenchymal precursor cells NP nucleus pulposus NCC notochordal cell NPCs nucleus pulposus cells andPG proteoglycans


Table 3 Studies comparing the efficacy of MSCs and chondrocytes to regenerate lumbar intervertebral discs

Author Animalmodel

Degenerationmodel Cells transplanted Method of cell

administration Results

Acosta Jret al [62] Mini pig Nucleotomy

Allogeneic juvenilearticular nondiscchondrocytes (JCs)and allogeneic bonemarrow MSCs

Injection of MSCs orchondrocytes in fibrincarrier

(i) Higher GAG and DNA content in JCgroup(ii) JC group higher cartilagecollagen IIproduction(iii) JC cells viable at 12 months(iv) MSCs not viable at 3 months and noevidence of PG production

Allon et al[63] Rat Nucleotomy

Allogeneic bonemarrow MSCs andallogeneic NPCs

Bilaminar coculturepellets (BCPs) ofMSCs and NPCs in afibrin sealant

(i) Increased disc height in BCP group ndashcombined MSC + NPC(ii) PG produced by BCP(iii) Less viability of MSCs in disc comparedto NPCs otherwise no differences betweenMSCs and NPCs

Feng et al[64] Rabbit Nucleotomy

Autologous bonemarrow MSCs andautologous NPCs


MSCs and NPCs comparable in(i) Maintaining disc height and T2 signal(ii) Maintaining gene expression of aggrecanand collagen II(iii) Producing PGs

BCP bilaminar coculture pellets GAG glycosaminoglycan content JC juvenile chondrocytes MSCs mesenchymal stem cells NPCs nucleus pulposus cellsand PG proteoglycans

Table 4 Clinical studies utilising cell-based therapies to treat human lumbar disc degeneration

Author Clinical details Cells transplanted Method of celladministration Results Level of

evidence

Haufe et al[65]

10 patients with lowback pain due todegenerative discdisease

Autologous bonemarrowhaematopoieticprecursor stem cells(HSCs)

Percutaneousinjection withconcurrenthyperbaric oxygentherapy

(i) No improvement in backpain in any patient(ii) 80 of patients underwentsurgical intervention within 1year

(i) 3

Meisel et al[15]

28 patientsundergoingmicrodiscectomywith back pain(EuroDISC study)

Autologous cultureexpanded discderived chondrocytes

Percutaneousinjection 12 weeksfollowingmicrodiscectomy

(i) Patients receiving celltransplantation had reducedback pain at 2 years(ii) Increased MRI T2 signalof treated and adjacent discs

(i) 1

Orozco et al[22]

10 patients with lowback pain andradiological evidenceof degenerative discdisease

Autologous MSCs Percutaneousinjection

(i) Clinical improvement inback pain leg pain anddisability(ii) Increased MRI T2 signal(iii) Disc height not recovered

(i) 3

Yoshikawa etal [23]

2 patients with backpain and sciatica withradiological evidenceof lumbar canalstenosis and discdisease

Autologous bonemarrow MSCs

Percutaneousinjection withincollagen sponge

(i) Increased MRI T2 signal(ii) Less instability(iii) Clinical improvement inboth patients

(i) 3

HSCs haematopoietic precursor stem cells MSCs mesenchymal stem cells

models due to a lower incidence of disc degeneration [67 68]Other important considerations are the quadruped posture ofmost animals and differences in disc shape and compositionwhich lead to biomechanical differences [69 70] Inherentdifficulties in measuring pain and functional outcomes areimportant constraints In addition to the abovementionedbiological factors there are economic and ethical constraintsto consider when selecting an animal model [69 70]

Methods of degeneration induction typically involve adisc injury such as chemical or mechanical nucleotomy oranother disc lesion which triggers a degenerative cascadewithin the insulted disc [25 33 37 43 49 71 72] Althoughthis may not be how degeneration typically starts in thehuman it allows for the generation of a reproducible modelbearing similarities to the human condition which can thenbe used to assess disc repair [67 68] Conjecture regarding


the ideal animal model should not be a hindrance to theprogression of regenerative medicine [67 68] The perfectanimal model of lumbar disc degenerationmay not exist andthe authors cited in this review support the use of validatedreproducible models which can demonstrate the efficacy ofcell based treatments It is important however to interpretthe results of such studies in the context of the animal modelused

By far the majority of studies identified in this reviewused smaller animal models such as the rodent There areseveral limitations to the use of such small animal modelsThe small disc dimensions in these animals are such that thevery small cell volumes or scaffolds that are implanted aredisproportionate to the volumes and construct specificationsthat are required in humans The distance from the adjacentvertebral body or nutritional source is much closer thanin humans Moreover these animals are nonchondrodys-trophoid species meaning that their notochordal cell popu-lation persists throughout life [73] This differs from humansand chondrodystrophoid animals such as the sheep whichare prone to disc degeneration following the disappearance oftheir notochordal cell population in early life [74] Thereforein studies performed in the smaller nonchondrodystrophoidanimals the validity of results must be questioned as onecannot be sure whether the resident notochordal cells exertany regenerative effects instead of or in combination withthe transplanted cells Treatments demonstrating efficacyin smaller animals should have safety and efficacy profilesdemonstrated in larger chondrodystrophoid animal modelswith an aim for translation into human clinical trials whereappropriate [73]

42 Disc Chondrocyte Transplantation The concept of trans-planting healthy chondrocytes into a degenerate disc in orderto replace the depleted and senescent resident cell populationappears a sensible approach to disc repair Intervertebraldisc chondrocytes such as NP cells have been successfullyisolated from intervertebral disc tissue culture expanded andused as a means to treat disc degeneration 12 of 14 basicscience studies andone clinical study identified in this reviewreported favourable outcomes following the transplantationof such cells into degenerate discs Improved gross mor-phological and histological assessments as well as increasedproteoglycan content of the NP are relatively consistentfindings in the disc following chondrocyte transplantationMoreover preservation of disc height and increased MRI T2signal point further to reconstitution of the disc extracellularmatrix Whether such preclinical outcomes correlate withclinically significant and durable improvements in humanshas been only studied limitedly The largest clinical trial todate the EuroDISC study by Meisel et al [75] demonstratedthat clinical outcomes improved at 2 years

Logically it would appear that disc cells are ideal to useas cell based disc treatments however there are numerouslimitations and impracticalities with the use of these cellsclinically the least of which not being that they must beharvested from disc tissue Treatment is limited to patientsrequiring disc surgery otherwise patients not undergoing

disc surgery would require harvesting of cells from an adja-cent disc which would likely and inappropriately acceleratedegeneration at that level [73] In addition the expenseexpertise and process of isolating expanding and storingdisc cells under GMP (GoodManufacturing Practice) condi-tions will exclude such therapy from being available to mostspinal surgery centres [76] Moreover disc cells obtainedfrom sequestered or prolapsed disc fragments which aredamaged discs whose cells may be effected by the degener-ative process may be inadequate for cartilage regenerationbecause of the heterogeneity of the tissue collected and lowviability of the cells contained within these tissues [77]

The use of allogeneic chondrocytes either obtained fromsurgical or from cadaveric donors would potentially over-come the hurdles associated with the use of autologousdisc cells Although Nomura et al [34] reported successwith the use of allogeneic NP cells in the rabbit with noevidence of immune or inflammatory response the safety andefficacy of allogeneic transplantation of disc chondrocytesin the treatment of human disc degeneration has not beendetermined to date Despite these limitations the use of discchondrocytes to treat disc degeneration is under investigationand is providing important insights into cell-based discregeneration strategies as well as an understanding of discpathology [75]

43 Transplantation of MSCs MPCs and Other Stem CellsMSCs show exciting promise for disc repair and othertissue engineering strategies MSCs can be isolated fromnumerous tissues including bone marrow adipose tissueand synovium [78ndash80] are reported to be nonimmunogenic[81 82] and unlike ESCs lack the potential to undergomalignant transformation following transplantation [83]MSCs possess the capacity for self-renewal thus maintainingtheir undifferentiated phenotype in multiple subcultures butwhen exposed to the appropriate stimuli they can undergodifferentiation into cells of the mesenchymal lineage such aschondrocytes osteocytes tenocytes and adipose cells MSCscan be isolated from bonemarrow aspirates by their ability toadhere to plastic culture plates a technique that allows themto be separated frommost of the other cellular components ofthe marrow that do not adhere However these cells consistof a heterogeneous population of cells including mixedMSC clones at various stages of differentiation together withcontaminantmononuclear cells and fibroblasts Neverthelessit is evident from perspective of this review that MSCsisolated in such a fashion have the ability to repair damageddiscs at least partially

The earliest uncommitted clonogenic populations of bonemarrow stromal cells designated mesenchymal progenitorcells (MPCs) can be distinguished by their expression ofspecific cell surface antigens including STRO-1 VCAM-1(CD106) STRO-3 (tissue nonspecific alkaline phosphatase)STRO-4 (HSP-90b) and CD146 [84ndash86] By using magneticbeads coupled to antibodies to these specific antigens it ispossible to immunoselect particular clones from mixed cellpopulations MPCs isolated in this manner when expandedin culture can generate cell banks of purified cells from


a single donor which retain extensive proliferative capacityand differentiation potential [85 87 88] MPCs can be usedin an allogeneic fashion [89 90] They have been producedso they can be used as ldquoan off-the-shelf productrdquo and aretherefore well suited to the treatment of large numbers ofpatients without the requirement for expensive GMP cellculturing capabilities at each and every treatment site Asallogeneic cells are taken from a young healthy donor theyare not subject to age related changes or other effects basedon the protoplasm of the patient that can occur with the useof autologous cells [89]

Allogeneic MPCs have been demonstrated to reconsti-tute the disc extracellular matrix when injected into thedegenerate ovine nucleus pulposus Three months follow-ing the administration of the matrix degrading enzymechondroitinase-ABC to ovine discs animals injected withMPCs with a hyaluronic acid cell carrier demonstratedincreased disc height higher T2 MRI signal and improvedhistological grading scores with restoration of the extracel-lular matrix when compared with controls [40] Our groupis conducting further preclinical trials utilising such MPCsin ovine degeneration models utilising a range of cell dosesand cell carriers [89 90] Human allogeneic MPCs isolatedusing the same methods are currently under investigation inhuman clinical trials for the treatment of back pain due todegenerative disc disease [21]

MPCs or MSCs isolated from tissues are more accessiblethan intervertebral discs and appear to be the more practicalalternative to disc cells for the treatment of disc disease Forthese therapies to translate into clinical trials it is importantthat they possess similar or greater efficacy than that ofdisc cell transplantation Feng et al [91] demonstrated thatautologous MSCs and NPCs were comparable in terms ofmaintaining disc height and MRI T2 signal production ofproteoglycans (PGs) and expression of aggrecan and collagenII in a rabbit model Allon et al [63] similarly demonstratedcomparable outcomes between allogeneicNP cells andMSCsalthough MSCs had a lower survival time within the ratdisc This may have been due to less retention of the cellscompared with bilaminar coculture pellets of MSCs andNPCs which were far more efficacious than either cell typewhen used alone Acosta et al [62] reported that allogeneicarticular nondisc chondrocytes were far superior to MSCsin a porcine model however the poor viabilities and lackof regenerative potential demonstrated by their allogeneicbone marrow MSCs are not consistent with that of many ofthe other published MSC studies These MSCs were derivedfrom a different species however the authors do not believethis was the cause of its poor efficacy Furthermore althoughtheseMSCs were shown to have chondrogenic differentiationpotential they were not characterized

Once the safety and efficacy of intradiscal stem celltherapies are established optimisation of the therapeuticintervention will need to be performed Such optimisationwill maximise the therapeutic and regenerative power thatcan be harnessed by these cells What is the ideal cell doseto administer What is the ideal cell carrier with which toadminister the cells Do repeated doses provide increasedclinical benefit Does the treatment provide benefit in

the longer termAnswering these questions should be a focusof future research

44 Cell Viability and the Maintenance of Cells within theDisc Several studies reported very poor results with regardto the retainment of cells within the disc Omlor et al [49]reported only 9 of transplanted MSCs remaining in thedisc 3 days after injection Bertram et al [25] found that90 of cells leaked out when injected in aqueous formhowever this was reduced to 50 by coadministration witha fibrin glue Vadala et al [57] found no evidence of GFPlabelled MSCs in the disc at 9 weeks and concluded that theleakage of cells contributed to the development of peripheralosteophytes Certainly these results require further studies tofind methods that lead to greater retainment of cells withinthe discs space To have some cell leakagemay be unavoidableand perhaps highlights that only a portion of the transplantedcells need to engraft in the disc to impart benefit Despitethe above negative findings the overwhelming majority ofstudies identified in this review that assessed survival of cellsreported more favourable results Transplanted NP cells werereported to be viable within the disc from 8 weeks to 8months whilst reported survival of MSCs ranged from 2 to24 weeks following injection

The issues of cell leakage and survival need to be consid-ered when calculating the ideal cell dose to administer Cellnumber considerations were not however discussed in themajority of studies Serigano et al [54] identified that theoptimal dose of autologous MSCs in the canine was 1 times 106cells From our grouprsquos own work using allogeneic MPCs inan ovine model of disc degeneration we found that an evenlower dose of 01 times 106 cells was the most efficacious [40] Alow dose of cells appears to bemore beneficial due to the poornutritional supply of the NP which contributes to a ceilingeffect above which increased cell numbers cannot surviveandmay in fact be deleterious due to an accumulation of deadcells and waste products [40]

For transplanted cells to repair degenerate discs theymust be retained within the disc long enough to exertan effect either by differentiation into chondrocytic cellswhich engraft within the disc or by the release of solublefactors that stimulate endogenous disc cells in a paracrinefashion If cells leak out soon after implantation their efficacywill be reduced or even abolished leading to a negativeresponse Another important consideration after ensuringthat cells remain within the disc is their survival in thishostile environment The avascular low glucose low oxygentension low pH and nutrient starved disc environment aresome of the hostile factors transplanted cell must overcomein order for cells to survive following transplantation Forthese reasons numerous studies identified in this reviewspecifically addressed this by assessing cell viability andsurvival within the disc but with conflicting results

45 Mechanism of Action of Transplanted Cells There aretwo predominant mechanisms by which transplanted cellsare likely to impart their regenerative effects Firstly thecells can survive and proliferate in the target disc acting as


chondrocyte-like disc cells These transplanted cells produceproteoglycan and collagen extracellular matrix componentsthereby correcting deficiencies and restoring disc structureand function Essentially these new healthy cells rescue thedegenerate disc by replacing the depleted functional chon-drocyte population This is the likely mechanism of actionof transplanted disc chondrocytes which already have achondrocytic phenotype However for undifferentiated stemcells such as MSCs or MPCs the transplanted cells must firstundergo chondrogenic differentiation within the disc if theyare to assume a matrix producing phenotype Henrikssonet al [42] demonstrated that human MSCs transplanted intothe porcine disc differentiated into cells representing discchondrocytes expressing aggrecan collagen II and SOX-9These transplanted cells produced disc matrix and the levelof matrix produced and cellular differentiation was increasedwith coadministration with a hydrogel carrier Sakai et al[52] Wei et al [58] and Yang et al [60] all reported sitedependent differentiation of autologous MSCs toward NPphenotype whilst Murrell et al [48] demonstrated differenti-ation of olfactory neurosphere derived stem cells toward aNPphenotype It is likely that factors released from resident disccells as well as contact with matrix components stimulatethe transplanted MSCs to undergo site-specific differentia-tion Sobajima et al [56] demonstrated synergism betweenNPCs and MSCs with MSCs increasing PG productionwhen cocultured with NPCs Certainly there is evidencefor chondrogenic differentiation following transplantation ofMSCs however this is unlikely to be their sole mechanism ofaction

The second potential mechanism of action is a paracrineeffect as transplanted cells can also act by releasing solubletrophic factors which ldquokick startrdquo or stimulate resident disccells to produce disc matrix MSCs and MPCs secrete anti-inflammatory cytokines and growth factors that aremembersof the Transforming Growth Factor (TGF) family [92] Thesefactors enhance NP cell synthesis of newmatrix and suppresscatabolic events triggered by mechanically mediated discinjury Miyamoto et al [92] demonstrated upregulation ofCol2A1 (collagen type II) and downregulation of matrixdegrading enzymes (TIMP-1 2 MMP-2 3 and 13) andinflammatory cytokines (TNF120572 IL-3) in endogenous rabbitNP cells following coculture with humanMSCs In additionMSCs can stimulate the endogenous NP progenitors toproliferate or prevent them from undergoing apoptosis Yanget al [60] reported inhibition of disc cell apoptosis and discmatrix repair by transplanting autologous MSCs addingfurther weight to the paracrine theory of mechanism ofaction

Besides their regenerative properties cellular therapieshave another potential treatment pathway The clinical ben-efits demonstrated in trials such as reduction of pain areunlikely solely attributable to the restoration of disc structureand mechanical function Pain reduction is likely due to thepotent immune-modulatory and anti-inflammatory proper-ties that the transplanted cells possess such as the regulationof Tumour Necrosis Factor 120572 (TNF120572) and other cytokinesinvolved in the pain process

46 Translation into the ClinicThesuccess of preclinical stud-ies has led to several recent small clinical trials publication ofwhich also shows promising results Yoshikawa et al [23] firstreported alleviation of both back and radicular symptomsfollowing percutaneous administration of autologous MSCsin two elderly patients with degenerative disc disease [23]Orozco et al reported a study of 10 patients with chroniclow back pain and degenerative disc disease treated withintradiscal administration of autologous MSCs [22] 90of participants reported clinical benefit with significantdecreases in pain and disability and improvement in qualityof lifeThese studies were noncontrolled and nonrandomisedutilising a small number of heterogeneous patients whichdetracts from the rigour of the successful results reportedAn FDAof theUSA approved phase-2 randomised controlledclinical trial investigating the percutaneous image-guidedintradiscal administration of allogeneic MPCs for the treat-ment of single level discogenic back pain in 100 patients hasnow completed recruitment [93] Results from this study areeagerly awaited as they will provide important data regardingthe clinical benefit of stem cell therapies to treat disc disease

5 Conclusion

Numerous studies have demonstrated success using cell-based therapies to treat disc disease and these successes arein the early stages of translation into the clinic Althoughnot widely available it is likely that stem cell therapies willbecome a treatment option for somepatientswith disc diseasein the near future Percutaneous stem cell mediated discregeneration may bridge the gap between the two currentalternatives for patients with low back pain inadequate painmanagement at one end and invasive surgery at the otherStem cell therapies to treat degenerative spinal conditionsmay not be the ldquomiracle curerdquo that so many patients hope forThey are however likely to become part of the armamentar-ium that physicians can utilise to manage these patients

The economics of cell-based therapies will need to bedetermined Costs of current spinal treatments are enormousand increasing For stem cell therapies to be utilised on a largescale allogeneic administration of ldquooff-the-shelf rdquo stem cellssuch as MPCs is required We consider the autologous routenot viable for pragmatic and economic reasons The costsof cellular therapies will need to be weighed up against costsavings in terms of increased work productivity and avoid-ance of more invasive and expensive procedures Whetheror not patients health insurance institutions and publichealth providers will absorb the increased direct costs ofcell-based therapies is yet to be established Nonetheless thepromising results of studies so far should provide excitementto clinicians that manage patients burdened by this complexdisease This review provides a summation of the currentlandscape These cell-based biological therapies are for thefirst time attempting to not only provide improvements insymptoms but also attempt to restore biological structure andfunction of the disc


Disclosure

Professor Peter Ghosh andDr TonyGoldschlager are consul-tants toMesoblast LtdDrDavidOehme received scholarshipfunding from the Neurosurgical Society of Australasia (2012)and the Royal Australasian College of Surgeons (2013)

Conflict of Interests

Dr Tony Goldschlager and Professor Graham Jenkin havereceived institutional support through a sponsored researchagreement fromMesoblast Ltd Support from a grant throughthe Victorian Government infrastructure support schemewas also received Professor Peter Ghosh is a consultant toMesoblast Limited AProf Tony Goldschlager is a consultantto Mesoblast Ltd and Member of their Scientific AdvisoryBoard

Authorsrsquo Contribution

The corresponding author Dr David Oehme has had fullaccess to all the data in the study and takes full responsibilityfor the integrity of the data and the accuracy of the dataanalysis as well as the decision to submit for publication Allauthors have contributed to the development of the paper andare in agreement with the results and discussion presented

References

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[2] S Dagenais A C Tricco and S Haldeman ldquoSynthesis of rec-ommendations for the assessment andmanagement of low backpain from recent clinical practice guidelinesrdquo Spine Journal vol10 no 6 pp 514ndash529 2010

[3] G B J Andersson ldquoEpidemiological features of chronic low-back painrdquoThe Lancet vol 354 no 9178 pp 581ndash585 1999

[4] G E Hicks N Morone and D K Weiner ldquoDegenerativelumbar disc and facet disease in older adults prevalence andclinical correlatesrdquo Spine vol 34 no 12 pp 1301ndash1306 2009

[5] J Takatalo J Karppinen J Niinimaki et al ldquoDoes lumbar discdegeneration on magnetic resonance imaging associate withlow back symptom severity in young Finnish adultsrdquo Spine vol36 no 25 pp 2180ndash2189 2011

[6] M W van Tulder W J J Assendelft B W Koes and L MBouter ldquoSpinal radiographic findings and nonspecific low backpain a systematic review of observational studiesrdquo Spine vol22 no 4 pp 427ndash434 1997

[7] E I T de Schepper J Damen J B J van Meurs et al ldquoTheassociation between lumbar disc degeneration and low backpain the influence of age gender and individual radiographicfeaturesrdquo Spine vol 35 no 5 pp 531ndash536 2010

[8] J Takatalo J Karppinen J Niinimaki et al ldquoDoes lumbar discdegeneration on magnetic resonance imaging associate withlow back symptom severity in young finnish adultsrdquo Spine vol36 no 25 pp 2180ndash2189 2011

[9] K LuomaH Riihimaki R Luukkonen R Raininko E Viikari-Juntura and A Lamminen ldquoLow back pain in relation to

lumbar disc degenerationrdquo Spine vol 25 no 4 pp 487ndash4922000

[10] H Brisby ldquoPathology and possible mechanisms of nervoussystem response to disc degenerationrdquo The Journal of Bone ampJoint SurgerymdashAmerican Volume vol 88 supplement 2 pp 68ndash71 2006

[11] V Haughton ldquoMedical imaging of intervertebral disc degener-ation current status of imagingrdquo Spine vol 29 no 23 pp 2751ndash2756 2004

[12] V Haughton ldquoImaging intervertebral disc degenerationrdquo Jour-nal of Bone and Joint Surgery Series A vol 88 no 2 pp 15ndash202006

[13] S Roberts H Evans J Trivedi and J Menage ldquoHistology andpathology of the human intervertebral discrdquoThe Journal of Boneand Joint SurgerymdashAmerican Volume vol 88 no 2 pp 10ndash142006

[14] J Melrose S M Smith C B Little R J Moore B Vernon-Roberts and R D Fraser ldquoRecent advances in annular pathobi-ology provide insights into rim-lesion mediated intervertebraldisc degeneration and potential new approaches to annularrepair strategiesrdquo European Spine Journal vol 17 no 9 pp 1131ndash1148 2008

[15] H J Meisel V Siodla T Ganey Y Minkus W C Hutton andO J Alasevic ldquoClinical experience in cell-based therapeuticsdisc chondrocyte transplantation a treatment for degeneratedor damaged intervertebral discrdquo Biomolecular Engineering vol24 no 1 pp 5ndash21 2007

[16] M K Chelberg G M Banks D F Geiger and T R OegemaJr ldquoIdentification of heterogeneous cell populations in normalhuman intervertebral discrdquo Journal of Anatomy vol 186 part 1pp 43ndash53 1995

[17] G Paesold A G Nerlich and N Boos ldquoBiological treatmentstrategies for disc degeneration potentials and shortcomingsrdquoEuropean Spine Journal vol 16 no 4 pp 447ndash468 2007

[18] H E Gruber and E N Hanley Jr ldquoAnalysis of aging anddegeneration of the human intervertebral disc comparison ofsurgical specimens with normal controlsrdquo Spine vol 23 no 7pp 751ndash757 1998

[19] S Ozaki T Muro S Ito and M Mizushima ldquoNeovasculariza-tion of the outermost area of herniated lumbar intervertebraldiscsrdquo Journal of Orthopaedic Science vol 4 no 4 pp 286ndash2921999

[20] R R Pai B Drsquosa C V Raghuveer and A Kamath ldquoNeo-vascularization of nucleus pulposus a diagnostic feature ofintervertebral disc prolapserdquo Spine vol 24 no 8 pp 739ndash7411999

[21] NIH Safety and Preliminary Efficacy Study of MesenchymalPrecursor Cells (MPCs) in Subjects with Chronic DiscogenicLumbar Back Pain 2012 httpsclinicaltrialsgovct2showNCT01290367term=mesenchymal+precursor+cellsamprank=7

[22] L Orozco R Soler C Morera M Alberca A Sanchez and JGarcıa-Sancho ldquoIntervertebral disc repair by autologous mes-enchymal bone marrow cells a pilot studyrdquo Transplantationvol 92 no 7 pp 822ndash828 2011

[23] T Yoshikawa Y Ueda K Miyazaki M Koizumi and YTakakura ldquoDisc regeneration therapy usingmarrowmesenchy-mal cell transplantation a report of two case studiesrdquo Spine vol35 no 11 pp E475ndashE480 2010

[24] H J Meisel T Ganey W C Hutton J Libera Y MinkusandO Alasevic ldquoClinical experience in cell-based therapeuticsintervention and outcomerdquo European Spine Journal vol 15 no3 pp S397ndashS405 2006


[25] H Bertram M Kroeber H Wang et al ldquoMatrix-assisted celltransfer for intervertebral disc cell therapyrdquo Biochemical andBiophysical Research Communications vol 331 no 4 pp 1185ndash1192 2005

[26] T Ganey J Libera V Moos et al ldquoDisc chondrocyte trans-plantation in a canine model a treatment for degenerated ordamaged intervertebral discrdquo Spine vol 28 no 23 pp 2609ndash2620 2003

[27] M Gorensek C Joksimovic N Kregar-Velikonja et alldquoNucleus pulposus repair with cultured autologous elasticcartilage derived chondrocytesrdquo Cellular and Molecular BiologyLetters vol 9 no 2 pp 363ndash373 2004

[28] H E Gruber T L Johnson K Leslie et al ldquoAutologousintervertebral disc cell implantation amodel usingPsammomysobesus the sand ratrdquo Spine vol 27 no 15 pp 1626ndash1633 2002

[29] B Huang Y Zhuang C-Q Li L-T Liu and Y Zhou ldquoRegen-eration of the intervertebral disc with nucleus pulposuscell-seeded collagen IIhyaluronanchondroitin-6-sulfate tri-copolymer constructs in a rabbit disc degeneration modelrdquoSpine vol 36 no 26 pp 2252ndash2259 2011

[30] C Hohaus T M Ganey Y Minkus and H J Meisel ldquoCelltransplantation in lumbar spine disc degeneration diseaserdquoEuropean Spine Journal vol 17 supplement 4 pp S492ndashS5032008

[31] T Iwashina J Mochida D Sakai et al ldquoFeasibility of using ahuman nucleus pulposus cell line as a cell source in cell trans-plantation therapy for intervertebral disc degenerationrdquo Spinevol 31 no 11 pp 1177ndash1186 2006

[32] K D K Luk D K Ruan D S Lu and Z Q Fei ldquoFresh frozenintervertebral disc allografting in a bipedal animal modelrdquoSpine vol 28 no 9 pp 864ndash870 2003

[33] K Nishimura and J Mochida ldquoPercutaneous reinsertion of thenucleus pulposus an experimental studyrdquo Spine vol 23 no 14pp 1531ndash1539 1998

[34] T Nomura J Mochida M Okuma K Nishimura and KSakabe ldquoNucleus pulposus allograft retards intervertebral discdegenerationrdquo Clinical Orthopaedics and Related Research no389 pp 94ndash101 2001

[35] M Okuma J Mochida K Nishimura K Sakabe and K SeikildquoReinsertion of stimulated nucleus pulposus cells retards inter-vertebral disc degeneration an in vitro and in vivo experimentalstudyrdquo Journal of Orthopaedic Research vol 18 no 6 pp 988ndash997 2000

[36] D-K Ruan H Xin C Zhang et al ldquoExperimental interver-tebral disc regeneration with tissue-engineered composite in acaninemodelrdquoTissue Engineering Part A vol 16 no 7 pp 2381ndash2389 2010

[37] M Sato T Asazuma M Ishihara T Kikuchi M Kikuchi andK Fujikawa ldquoAn experimental study of the regeneration of theintervertebral disc with an allograft of cultured annulus fibrosuscells using a tissue-engineeringmethodrdquo Spine vol 28 no 6 pp548ndash553 2003

[38] G Crevensten A J L Walsh D Ananthakrishnan et alldquoIntervertebral disc cell therapy for regeneration mesenchymalstem cell implantation in rat intervertebral discsrdquo Annals ofBiomedical Engineering vol 32 no 3 pp 430ndash434 2004

[39] T Ganey W C Hutton T Moseley M Hedrick and H-JMeisel ldquoIntervertebral disc repair using adipose tissue-derivedstem and regenerative cells experiments in a canine modelrdquoSpine vol 34 no 21 pp 2297ndash2304 2009

[40] P Ghosh RMoore B Vernon-Roberts et al ldquoImmunoselectedSTRO-3+ mesenchymal precursor cells and restoration of the

extracellular matrix of degenerate intervertebral discs labora-tory investigationrdquo Journal of Neurosurgery Spine vol 16 no 5pp 479ndash488 2012

[41] H T Hee H D Ismail C T Lim J C H Goh andH KWongldquoEffects of implantation of bone marrow mesenchymal stemcells disc distraction and combined therapy on reversingdegeneration of the intervertebral discrdquo The Journal of Bone ampJoint SurgerymdashBritish Volume vol 92 no 5 pp 726ndash736 2010

[42] H BHenriksson T SvanvikM Jonsson et al ldquoTransplantationof human mesenchymal stems cells into intervertebral discs ina xenogeneic porcine modelrdquo Spine vol 34 no 2 pp 141ndash1482009

[43] A Hiyama J Mochida T Iwashina et al ldquoTransplantation ofmesenchymal stem cells in a canine disc degeneration modelrdquoJournal of Orthopaedic Research vol 26 no 5 pp 589ndash6002008

[44] G Ho V Y L Leung K M C Cheung and D Chan ldquoEffectof severity of intervertebral disc injury on mesenchymal stemcell-based regenerationrdquoConnective Tissue Research vol 49 no1 pp 15ndash21 2008

[45] J H Jeong E S Jin J K Min et al ldquoHuman mesenchymalstem cells implantation into the degenerated coccygeal disc ofthe ratrdquo Cytotechnology vol 59 no 1 pp 55ndash64 2009

[46] J H Jeong J H Lee E S Jin J K Min S R Jeon andK H Choi ldquoRegeneration of intervertebral discs in a ratdisc degeneration model by implanted adipose-tissue-derivedstromal cellsrdquo Acta Neurochirurgica vol 152 no 10 pp 1771ndash1777 2010

[47] T Miyamoto T Muneta T Tabuchi et al ldquoIntradiscal trans-plantation of synovial mesenchymal stem cells prevents inter-vertebral disc degeneration through suppression of matrixmetalloproteinase-related genes in nucleus pulposus cells inrabbitsrdquo Arthritis Research and Therapy vol 12 no 6 articleR206 2010

[48] W Murrell E Sanford L Anderberg B Cavanagh and AMackay-Sim ldquoOlfactory stem cells can be induced to expresschondrogenic phenotype in a rat intervertebral disc injurymodelrdquo Spine Journal vol 9 no 7 pp 585ndash594 2009

[49] G W Omlor H Bertram K Kleinschmidt et al ldquoMethods tomonitor distribution and metabolic activity of mesenchymalstem cells following in vivo injection into nucleotomizedporcine intervertebral discsrdquo European Spine Journal vol 19 no4 pp 601ndash612 2010

[50] J D Prologo A Pirasteh N Tenley et al ldquoPercutaneous image-guided delivery for the transplantation of mesenchymal stemcells in the setting of degenerated intervertebral discsrdquo Journalof Vascular and Interventional Radiology vol 23 no 8 pp1084e6ndash1088e6 2012

[51] D Sakai J Mochida Y Yamamoto et al ldquoTransplantationof mesenchymal stem cells embedded in Atelocollagen gel tothe intervertebral disc a potential therapeutic model for discdegenerationrdquo Biomaterials vol 24 no 20 pp 3531ndash3541 2003

[52] D Sakai J Mochida T Iwashina et al ldquoDifferentiation ofmesenchymal stem cells transplanted to a rabbit degenerativedisc model potential and limitations for stem cell therapy indisc regenerationrdquo Spine vol 30 no 21 pp 2379ndash2387 2005

[53] D Sakai J Mochida T Iwashina et al ldquoRegenerative effects oftransplanting mesenchymal stem cells embedded in atelocolla-gen to the degenerated intervertebral discrdquo Biomaterials vol 27no 3 pp 335ndash345 2006

[54] K Serigano D Sakai A Hiyama F Tamura M Tanaka andJ Mochida ldquoEffect of cell number on mesenchymal stem cell


transplantation in a canine disc degenerationmodelrdquo Journal ofOrthopaedic Research vol 28 no 10 pp 1267ndash1275 2010

[55] H Sheikh K Zakharian R P De La Torre et al ldquoIn vivo inter-vertebral disc regeneration using stemcell-derived chondropro-genitors laboratory investigationrdquo Journal of NeurosurgerySpine vol 10 no 3 pp 265ndash272 2009

[56] S Sobajima G Vadala A Shimer J S Kim L G Gilbertsonand J D Kang ldquoFeasibility of a stem cell therapy for interverte-bral disc degenerationrdquo Spine Journal vol 8 no 6 pp 888ndash8962008

[57] G Vadala G SowaMHubert L G Gilbertson V Denaro andJ D Kang ldquoMesenchymal stem cells injection in degeneratedintervertebral disc cell leakage may induce osteophyte forma-tionrdquo Journal of Tissue Engineering and Regenerative Medicinevol 6 no 5 pp 348ndash355 2012

[58] A Wei H Tao S A Chung H Brisby D D Ma and A DDiwan ldquoThe fate of transplanted xenogeneic bone marrow-derived stem cells in rat intervertebral discsrdquo Journal ofOrthopaedic Research vol 27 no 3 pp 374ndash379 2009

[59] F Yang V Y L Leung K D K Luk D Chan and K MC Cheung ldquoMesenchymal stem cells arrest intervertebral discdegeneration through chondrocytic differentiation and stimu-lation of endogenous cellsrdquoMolecularTherapy vol 17 no 11 pp1959ndash1966 2009

[60] H Yang J Wu J Liu et al ldquoTransplanted mesenchymal stemcells with pure fibrinous gelatin-transforming growth factor-1205731 decrease rabbit intervertebral disc degenerationrdquo The SpineJournal vol 10 no 9 pp 802ndash810 2010

[61] Y-G Zhang X Guo P Xu L-L Kang and J Li ldquoBone mes-enchymal stem cells transplanted into rabbit intervertebral discscan increase proteoglycansrdquo Clinical Orthopaedics and RelatedResearch no 430 pp 219ndash226 2005

[62] F L Acosta Jr L Metz H D Adkisson et al ldquoPorcine interver-tebral disc repair using allogeneic juvenile articular chondro-cytes ormesenchymal stem cellsrdquoTissue Engineering Part A vol17 no 23-24 pp 3045ndash3055 2011

[63] A A Allon N Aurouer B B Yoo E C Liebenberg Z Buserand J C Lotz ldquoStructured coculture of stem cells and disc cellsprevent disc degeneration in a rat modelrdquo Spine Journal vol 10no 12 pp 1089ndash1097 2010

[64] G Feng X Zhao H Liu et al ldquoTransplantation of mesenchy-mal stem cells and nucleus pulposus cells in a degenerativedisc model in rabbits a comparison of 2 cell types as potentialcandidates for disc regenerationrdquo Journal of Neurosurgery Spinevol 14 no 3 pp 322ndash329 2011

[65] S M W Haufe and A R Mork ldquoIntradiscal injection ofhematopoietic stem cells in an attempt to rejuvenate theintervertebral discsrdquo Stem Cells and Development vol 15 no 1pp 136ndash137 2006

[66] G Feng X Zhao H Liu et al ldquoTransplantation of mesenchy-mal stem cells and nucleus pulposus cells in a degenerativedisc model in rabbits a comparison of 2 cell types as potentialcandidates for disc regeneration Laboratory investigationrdquoJournal of Neurosurgery Spine vol 14 no 3 pp 322ndash329 2011

[67] P Ghosh T K F Taylor and K G Braund ldquoVariation of theglycosaminoglycans of the intervertebral disc with ageing IINon-chondrodystrophoid breedrdquoGerontology vol 23 no 2 pp99ndash109 1977

[68] P Ghosh T K F Taylor K G Braund and L H Larsen ldquoAcomparative chemical and histochemical study of the chon-drodystrophoid and nonchondrodystrophoid canine interver-tebral discrdquo Veterinary Pathology vol 13 no 6 pp 414ndash4271976

[69] G D OrsquoConnell E J Vresilovic andDM Elliott ldquoComparisonof animals used in disc research to human lumbar disc geome-tryrdquo Spine vol 32 no 3 pp 328ndash333 2007

[70] K Singh K Masuda and H S An ldquoAnimal models for humandisc degenerationrdquo Spine Journal vol 5 no 6 supplement pp267Sndash279S 2005

[71] PA Revell EDamien LDi SilvioNGurav C Longinotti andL Ambrosio ldquoTissue engineered intervertebral disc repair inthe pig using injectable polymersrdquo Journal of Materials ScienceMaterials in Medicine vol 18 no 2 pp 303ndash308 2007

[72] H-J Wilke F Heuer C Neidlinger-Wilke and L Claes ldquoIs acollagen scaffold for a tissue engineered nucleus replacementcapable of restoring disc height and stability in an animalmodelrdquo European Spine Journal vol 15 supplement 3 ppS433ndashS438 2006

[73] MAlini SM Eisenstein K Ito et al ldquoAre animalmodels usefulfor studying human disc disordersdegenerationrdquo EuropeanSpine Journal vol 17 no 1 pp 2ndash19 2008

[74] S R S BibbyDA Jones R B Lee J Yu and J PGUrban ldquoThepathophysiology of the intervertebral discrdquo Joint Bone Spinevol 68 no 6 pp 537ndash542 2001

[75] H J Meisel V Siodla T Ganey Y Minkus W C Hutton andO J Alasevic ldquoClinical experience in cell-based therapeuticsdisc chondrocyte transplantation A treatment for degeneratedor damaged intervertebral discrdquo Biomolecular Engineering vol24 no 1 pp 5ndash21 2007

[76] T Goldschlager G Jenkin P Ghosh A Zannettino and J VRosenfeld ldquoPotential applications for using stem cells in spinesurgeryrdquo Current Stem Cell Research and Therapy vol 5 no 4pp 345ndash355 2010

[77] A A Hegewald M Endres A Abbushi et al ldquoAdequacy ofherniated disc tissue as a cell source for nucleus pulposusregeneration laboratory investigationrdquo Journal of NeurosurgerySpine vol 14 no 2 pp 273ndash280 2011

[78] J Dennis and A Caplan ldquoBone marrow mesenchymal stemcellsrdquo in StemCell Handbook p 108 Humana Press Albany NYUSA 2003

[79] P A Zuk M Zhu P Ashjian et al ldquoHuman adipose tissue is asource of multipotent stem cellsrdquoMolecular Biology of the Cellvol 13 no 12 pp 4279ndash4295 2002

[80] Y Sakaguchi I Sekiya K Yagishita and T Muneta ldquoCompar-ison of human stem cells derived from various mesenchymaltissues superiority of synovium as a cell sourcerdquo Arthritis andRheumatism vol 52 no 8 pp 2521ndash2529 2005

[81] I Rasmusson O Ringden B Sundberg and K Le BlancldquoMesenchymal stem cells inhibit the formation of cytotoxicT lymphocytes but not activated cytotoxic T lymphocytes ornatural killer cellsrdquoTransplantation vol 76 no 8 pp 1208ndash12132003

[82] K le Blanc F Frassoni L Ball et al ldquoMesenchymal stemcells fortreatment of steroid-resistant severe acute graft-versus-hostdisease a phase II studyrdquoTheLancet vol 371 no 9624 pp 1579ndash1586 2008

[83] M E Bernardo N Zaffaroni F Novara et al ldquoHuman bonemarrow-derivedmesenchymal stem cells do not undergo trans-formation after long-term in vitro culture and do not exhibit


telomere maintenance mechanismsrdquo Cancer Research vol 67no 19 pp 9142ndash9149 2007

[84] S Shi and S Gronthos ldquoPerivascular niche of postnatal mes-enchymal stem cells in human bone marrow and dental pulprdquoJournal of Bone andMineral Research vol 18 no 4 pp 696ndash7042003

[85] S Gronthos R McCarty K Mrozik et al ldquoHeat shock protein-90 beta is expressed at the surface of multipotential mesenchy-mal precursor cells generation of a novel monoclonal antibodySTRO-4 with specificity for mesenchymal precursor cells fromhuman and ovine tissuesrdquo Stem Cells and Development vol 18no 9 pp 1253ndash1261 2009

[86] P Ghosh J Wu S Shimmon A CW Zannettino S Gronthosand S Itescu ldquoPentosan polysulfate promotes proliferation andchondrogenic differentiation of adult human bone marrow-derived mesenchymal precursor cellsrdquo Arthritis Research andTherapy vol 12 no 1 article R28 2010

[87] S Gronthos S Fitter P Diamond P J Simmons S Itescu andA C W Zannettino ldquoA novel monoclonal antibody (STRO-3)identifies an isoform of tissue nonspecific alkaline phosphataseexpressed by multipotent bone marrow stromal stem cellsrdquoStem Cells and Development vol 16 no 6 pp 953ndash963 2007

[88] A C W Zannettino S Paton A Kortesidis F Khor SItescu and S Gronthos ldquoHuman multipotential mesenchy-malstromal stem cells are derived from a discrete subpopula-tion of STRO-1119887119903119894119892ℎ119905CD34minusCD45minusglycophorin-A-bone mar-row cellsrdquo Haematologica vol 92 no 12 pp 1707ndash1708 2007

[89] T Goldschlager D Oehme P Ghosh A Zannettino J VRosenfeld and G Jenkin ldquoCurrent and future applications forstem cell therapies in spine surgeryrdquo Current Stem Cell ResearchandTherapy vol 8 no 5 pp 381ndash393 2013

[90] D Oehme T Goldschlager J V Rosenfeld P Ghosh and GJenkin ldquoThe role of stem cell therapies in degenerative lumbarspine disease a reviewrdquo Neurosurgical Review 2015

[91] R Q Feng L Y Du and Z Q Guo ldquoIn vitro cultivation anddifferentiation of fetal liver stem cells frommicerdquo Cell Researchvol 15 no 5 pp 401ndash405 2005

[92] H Miyamoto M Doita K Nishida T Yamamoto M Sumiand M Kurosaka ldquoEffects of cyclic mechanical stress on theproduction of inflammatory agents by nucleus pulposus andanulus fibrosus derived cells in vitrordquo Spine vol 31 no 1 pp4ndash9 2006

[93] NIH Safety and Preliminary Efficacy Study of MesenchymalPrecursor Cells (MPCs) in Subjects with Chronic DiscogenicLumbar Back Pain ClinicalTrailsGov 2011 httpwwwclini-caltrialsgovct2showNCT01290367term=back+pain+stem+cellamprank=1

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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International Journal of

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Zoology


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GenomicsInternational Journal of


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BioinformaticsAdvances in

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Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



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ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Genetics Research International


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Virolog y

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Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


fibrosis (AF) which consists of concentrically lamellated col-lagen fibres Thin hyaline cartilage endplates attach the discto the adjacent vertebral bodies and disc nutrition passesthrough these end plates to the predominantly avascular IVD[13 14] The IVD functions to facilitate movement and flexi-bility of the vertebral column whilst also having the ability torecover from deformation following axial loadingThe nativecell population of the disc represents approximately 1 of thedisc tissue but is pivotal in maintaining disc metabolism [1315] Cells of the NP and inner AF demonstrate chondrocyticmorphologywhilst cells in the outer AF aremore fibroblastic-like [16 17]

The causes of disc degeneration are complex and mul-tifactorial including genetic nutritional and mechanicalinfluences [17] An imbalance between extracellular matrixdegradation and synthesis results in progressive collapseand mechanical failure of the disc An overall decrease inresident disc cell number and function and cellular responsesto nutritional deficiencies leads to alterations in both thecartilaginous and proteoglycan matrix components of thedisc [13 18] The loss of the pivotal water binding proteogly-can component leads to dehydration of the NP impactingthe discs ability to adequately distribute and recover frommechanical loading As degeneration progresses neovascu-larisation with concurrent neoinnervation can occur withinthe degenerative AF and extend to within the NP [10 19 20]this pathological ingrowth of nerve fibres and vessels has beenlinked to the mechanical back pain experienced by patientswith disc disease [10] Endplate changes occur with thinningcalcification and alterations in vascularity as nutritionallydeprived discs attempt to increase their nutrient supplyThis creates a hostile environment that is a major challengeto maintain cell viability of both native cells or cells thatare implanted in regenerative therapies Moreover changeswithin the adjacent vertebral bodies and endplates occurincluding sclerosis and subchondral bone microfracture [13]

Whilst the degenerative cascade is well understood lowback pain can be a source of frustration for patients and clin-icians due to difficulties in identifying the pain generator anda lack of treatment options available to successfully manageall patients Initial treatments include conservative therapiessuch as analgesics physical therapies and psychological painmanagement strategiesWhen these nonoperative treatmentsfail surgical interventions such as lumbar fusion or total discarthroplasty are commonly performedThese treatments areoften successful however they do not address the underlyingcause and despite these interventions some patients remainwith chronic pain and disability

Substantial progress has occurred in the fields of regen-erative medicine tissue engineering and stem cell therapieswith the aim of treating and reversing disc degeneration aswell as augmenting and enhancing current treatments Clini-cal trials have commenced utilising cell-based biological ther-apies to treat many common diseases including those affect-ing the musculoskeletal system and in particular degener-ative discopathies Culture expanded disc chondrocytes andmesenchymal stem cells isolated from bonemarrow or othersources are the two cell types most commonly used byresearchers to biologically repair the degenerate disc Other

types of stem or progenitor cells used in either an autologousor allogeneic fashion have also been investigated in studiesSeveral small clinical trials have recently been published withanother larger randomised phase-2 trial currently underway[21ndash24]

This paper will comprehensively review the current statusof basic science studies as well as preclinical and clinicaltrials utilising cell-based therapies to repair the degenerateintervertebral disc Significant positive and negative findingsof trials published to date will be highlighted and therelative benefits and limitations of various cell types andtreatment strategies will be discussed Animal models ofdisc degeneration and the applicability of these models tothe human condition will also be addressed Knowledge ofwhat has been achieved to date as well as the limitations ofthese achievements is important to guide future trials as thisexciting field of regenerative medicine translates toward theclinic

2 Methods

We performed a literature search using theMEDLINE onlineelectronic database between 1950 and 2013 Google Scholarand the Cochrane Database The following keywords werequeried in combination with intervertebral disc stem cellmesenchymal stem cell progenitor cell nucleus pulposus celldisc chondrocyte disc regeneration and tissue engineeringThesearch was limited to articles published in English Studiesutilising either stem cells progenitor cells or intervertebraldisc chondrocytes to regenerate the intervertebral disc wereincluded in the analysis The indexes of suitable articles werereviewed for further relevant published studies Publicationscomprised of in vitro work only were excluded Studies werethen grouped into one of the following four categories foranalysis (1) studies utilising chondrocyte transplantationobtained from intervertebral disc tissue or other cartilagesources (2) studies utilising stem and progenitor cell trans-plantation including mesenchymal stem cells (MSCs) andother cell types obtained from noncartilaginous tissues (3)studies comparing chondrocyte and stem cell transplanta-tion and (4) human clinical trials utilising any form ofcell-based therapy to repair degenerative discs includingchondrocytes and stem cell therapies The flow diagram forour search is outlined in Figure 1

3 Results

31 Studies Utilising Intervertebral Disc or Chondrocyte (orChondrocyte-Like) Cell Transplantation There were 14 stud-ies identified assessing the ability of disc derived and nondiscderived chondrocytes to regenerate IVDs as shown inTable 1

311 Animal Models Utilised 214 studies utilised a rodentanimalmodel (rat) [28 33] whilst 1214 studies utilised largeranimal models (rabbit canine or monkey) [15 25ndash27 29ndash32 34] 1214 studies utilised nucleotomy as the method ofinducing degeneration one study used a laser to damagethe disc and in the remaining study a total discectomy wasperformed It should be noted that the amount of nuclear



Author Animalmodel

Degenerationmodel

Cellstransplanted




AutologousNPCs
























XenogeneicHumanNPCs




Totaldiscectomy

















Table 1 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted















(n = 42)



(n = 22)

(n = 62)

(n = 62) (n = 16)

(n = 4)(n = 3)

(n = 46)

(n = 25)(n = 14)

other sources




disc therapy


MSCs



transplantation



















4 Discussion




Author Animalmodel

Degenerationmodel

Cellstransplanted



MSCs




nucleotomy










marrow MSCs





Human MSCs




MSCs
















Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted













nucleotomy













NP aspiration





NP aspiration









Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



Author Animalmodel

Degenerationmodel

Cellstransplanted




AutologousNPCs
























XenogeneicHumanNPCs




Totaldiscectomy

















Table 1 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted















(n = 42)



(n = 22)

(n = 62)

(n = 62) (n = 16)

(n = 4)(n = 3)

(n = 46)

(n = 25)(n = 14)

other sources




disc therapy


MSCs



transplantation



















4 Discussion




Author Animalmodel

Degenerationmodel

Cellstransplanted



MSCs




nucleotomy










marrow MSCs





Human MSCs




MSCs
















Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted













nucleotomy













NP aspiration





NP aspiration









Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


Table 1 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted















(n = 42)



(n = 22)

(n = 62)

(n = 62) (n = 16)

(n = 4)(n = 3)

(n = 46)

(n = 25)(n = 14)

other sources




disc therapy


MSCs



transplantation



















4 Discussion




Author Animalmodel

Degenerationmodel

Cellstransplanted



MSCs




nucleotomy










marrow MSCs





Human MSCs




MSCs
















Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted













nucleotomy













NP aspiration





NP aspiration









Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology













4 Discussion




Author Animalmodel

Degenerationmodel

Cellstransplanted



MSCs




nucleotomy










marrow MSCs





Human MSCs




MSCs
















Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted













nucleotomy













NP aspiration





NP aspiration









Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



Author Animalmodel

Degenerationmodel

Cellstransplanted



MSCs




nucleotomy










marrow MSCs





Human MSCs




MSCs
















Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted













nucleotomy













NP aspiration





NP aspiration









Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted













nucleotomy













NP aspiration





NP aspiration









Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


Table 2 Continued

Author Animalmodel

Degenerationmodel

Cellstransplanted






MSCs























Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



Author Animalmodel


















evidence

Haufe et al[65]





(i) 3

Meisel et al[15]





(i) 1

Orozco et al[22]




(i) 3

Yoshikawa etal [23]





(i) 3




























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

























5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology
















5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology






5 Conclusion




Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


Disclosure






References












































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



















































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



















































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




















Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

Documents

Review Article Cell-Based Therapies Used to Treat Lumbar ... · Cell-Based Therapies Used to Treat Lumbar Degenerative Disc Disease: A Systematic Review of Animal Studies and Human