Sunday - Grand 7 - Basic, Translational, and Clinical ......2/27/2010 6 Hemodynamic and vascular biology interactions: a challenge and an opportunityOptimize Upstream Hemodynamics

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Disclosures

•Off Label use: Vascugel, PRT 201, Trinam, Optiflow

• /•Consultant/Advisory Board: Bioconnect, Pervasis, Proteon

•Grant/Research Support: Bioconnect, Proteon

Prabir Roy-Chaudhury MD, PhD, FACPUniversity of Cincinnati and Cincinnati VA Medical Center

Recent Contributions to our Understanding of Vascular Biology

Outline•Pathology and Pathogenesis of dialysis access dysfunction

•Interactions between hemodynamics yand vascular biology (AV fistula maturation)

•Message for the future!!

A message for the present!!•Current therapies for dialysis access stenosis (multiple angioplasties) are not very effective

Don’t worry, I’ll find a good site soon!!

y

•Lack of understanding about the actual mechanismsinvolved in dialysis access stenosis

Clinical presentation of dialysis access stenosis

Artery

Vein Vein

A

G

Courtesy Tom Vesely AVF AVG

Artery

ArteryV

•Perianastomotic stenosis

•AVF non maturation and late AVF stenoses

• Stenosis at the graft‐vein anastomosis

•Graft thrombosis

Venous neointimal hyperplasia is made up of myofibroblasts

SMA Vim Des

SMCs + ‐ +

Myofib + + ‐

Fib. ‐ + ‐

Roy-Chaudhury et al. AJKD 2007

• Migrated in from the media and perhaps the adventitia

• Response to hemodynamic stress, surgical injury and in some cases angioplasty injury

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Dialysis access stenosis is a balance between expansive remodeling and neointimal hyperplasia

Original lumen size

Final lumen size

Significant Neointimal Hyperplasia +Expansive Remodeling

100% 200%100%

100%

Minimal Neointimal Hyperplasia +Negative Remodeling

25%

Adapted from Mike Conte

Mature AVF

AVF maturationfailure

In an ideal world!!!

Creation of an AVF

Increased Flow

Increased endothelial production of NO

Inhibits neointimalhyperplasia

Expansive oroutward remodeling

Successful AV fistula maturation

Hemodynamic and vascular biology interactions

Upstream Hemodynamics

AVFNon‐maturation

Downstream Vascular Biology

AVF Creation

MatureAVF

Flow patterns determine endothelial cell characteristics

Static Laminar Turbulent

Davies et al. PNAS 1986

Polygonal Stellate SICK!!

Shear Stress is the most important hemodynamic factor which influences vascular remodeling

• Viscous drag of blood on the cells lining the vessel wall

• Directly proportional to velocity of flow and inversely proportional to fourth power of the radius

• Non laminar flow with oscillatory shear (LOW)

• Laminar flow with laminar shear (HIGH)

Flow patterns and shear stress influence endothelial function

• Endothelial activation

• Increased Oxidative Stress

• Inflammatory gene profile (VCAM-1)

• Endothelial quiescence

• Minimal Oxidative Stress

• Non-Inflammatory gene profile (Nitric oxide)

AVF

Inward remodeling

Neointimal hyperplasia

AVF

Expansive remodeling

No neointimal hyperplasia

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Flow Patterns, shear stress rates and cellular responses

Laminar Flowand Laminar Shear Stress

Non Laminar Flow andOscillatory Shear Stress

Happy Endothelial Cells!

Unhappy EndothelialCells!

Shear stress induced mechanotransduction

Laminar or Oscillatory Shear

Calculating a hemodynamic shear stress profile in AVFs AV Fistula Model (CT Angiography)

3D Mesh Framework

Proximal Artery

AV Anastomosis

Proximal Vein

AV Fistula Model: (Flow and Pressure Analysis)

Flow Pressure

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3D Wall Shear Stress Profile

Proximal Artery

AV Anastomosis

Proximal Vein

Proximal Artery

AV anastomosis

AV Fistula Model Development (Shear Stress Analysis)

Low Shear Stress

Krishnamoorthy et al. Kidney International 2008

anastomosis

Proximal Vein


Proximal veinProximal artery

AV anast.

42d Histology

Different patterns ofshear on opposite walls


Anatomical configuration influences shear stress profiles

StraightCurved


Blood flow is greater in the curved configuration

CurvedStraight

p < 0.05

FLOW

C S

Diameter is greater in the curved configuration

CurvedStraight

FLOW

p < 0.05

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Anatomy, Shear and Stenosis!

Ideal anatomical configuration for AVFs and PTFE grafts

Optimize flow patterns and shear stress in AVFs and PTFE grafts

Reduction of AVF and PTFEgraft stenosis

Intrinsic Endothelial (dys)function

•Hemodynamic forces can influence endothelial response

•What about the quality of the baseline endothelial cell and how does this influence its response to shear stress alterations??

ESRD and CKD are states of massive endothelial dysfunction!!

8

12

16

0

4

Healthy Controls

HTN CAD CKD‐5

•Uremia

•Oxidative stress

• Inflammation •Reduction in flow mediated dilation (marker of endothelial function) Kopel et al. F‐PO1696, ASN 2009

Uremic mice have a 2-3 fold increase in the magnitude of AV fistula stenosis

AV anastomosisChoi et al.

JASN. 2008

CKDNon-uremic

Neointimal Volume

Non-uremic CKD

X 2-3

What does this really mean??

A MouseI tIs notA Man!

Uremia and oxidative stress can result in neointimal hyperplasia independent of hemodynamics

Media % Stenosis 46.6 ± 9.3

I/M Area Ratio

0.24 ± 0.07

Lee et al. ASN 2009, FC-297

NeointimaRatio

Average IM Thickness

0.34 ± 0.12

Maximal IM Thickness

1.16 ± 0.30

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Hemodynamic and vascular biology interactions: a challenge and an opportunity

Optimize UpstreamHemodynamics

AVF d AVG Minimize Dialysis

OptimizeDownstream Biology

AVF and AVG Creation

Minimize DialysisAccess Dysfunction

in 2010‐2020

Traditional

GV anastomosis

Venous segment

VascugelFig 4a: Cell (endothelial) Optiflow

Optimizing upstream hemodynamics and downstream vascular biology

TRINAM Gene Therapy Vein

Artery

Anastomosis

PRT‐201: PROTEON

• Advances in molecular pathogenesis

• Huge clinical problem

• Growing population

It was the best of times…

It was the worst of times…

We Live in Exciting Times for Dialysis Access Stenosis!!

• Advances in biomaterials and delivery technology

g p p

• Elderly and clinically complex patients

• No effective therapies

SOLUTION

We can do better!!

Come back here Arnold; Stacey isn’t needling today!!

Multidisciplinary Collaborators

Vascular

Surgery(Munda and

Rudich)

Radiology(Choe)

Vascular Stenosis

Cardiology(Weintraub)

Pharmacy(Desai)

Chemistry(Meyerhoff)

Engineering(Banerjee)

Pathology(Arend)

Cincinnati Dialysis Access Program (CAP)

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Optimizing upstream hemodynamics and downstream biology using LOCAL

therapy

Upstream Hemodynamics

Downstream Biology

•DEVICE: Anastomotic conduit (Optiflow)

•CELL therapy (Vascugel)

•DRUG therapy (Elastase)

•GENE therapy (VEGF‐D)

Dialysis access grafts and fistulae could be the ideal clinical model for testing out novel

LOCAL therapies for neointimal hyperplasia

•Superficially located•A f j i•Away from major anatomic structures

•Easy repeated access to patients and their grafts and fistulae

•Aggressive clinical course

Optimizing Upstream Hemodynamics:Shielding the peri-anastomotic area (Bioconnect)

Conduit Artery

Flanges

Vein

Roy-Chaudhury et al. ASN 2009, PO-1575

• Sutureless anastomotic conduit

• Shields the peri-anastomotic region

Optimizing Upstream Hemodynamics (Optiflow)

•10 patients•100% technical successsuccess

•90% primary patency at 42d

•Phase II study starting in Europe


• Rationale behind this approach is that the endothelial cell is not just a lining cell but also a cell that produces a slew

Optimizing downstream biology with CELL therapy: perivascular endothelial

cell loaded gel foam wraps

Edelman and Nugent J Vasc Res 2003

pof beneficial mediators

• Just need to deliver ECs to a site near the region of stenosis and the beneficial mediators will do the rest!

Perivascular endothelial cell implants (Vascugel) for AV Fistulae

Venous segment

Courtesy Pervasis Therapeutics

AV anastomosis

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Perivascular endothelial cell implants (Vascugel) in diabetic patients

Implants

A t

Vein

AVF

Vascugel

Primary patency

(n 25)Artery

Implants

Vein Artery Roy-Chaudhury et al. ASN 2009, PO-1576

AVG Placebop = 0.0054

(n=25)

(n=11)

•Recombinant elastase

•Applied to the adventitia

Optimizing downstream biology with DRUG therapy: perivascular elastase administration

(Proteon)Pre‐Treatment

Media

•Destroys the elastin in the vessel wall

•Results in a permanent increase in vessel calibre

Post‐Treatment

Adventitia

Adventitia

Media

Vein

Artery

Pre‐Treatment

Perivascular Elastase (PRT-201) Administration

Vein

Artery

Post‐Treatment

Fistula First and Catheter Last!!

Biodegradable Collar

Optimizing downstream biology with GENE therapy: perivascular VEGF-D (Ark)

• VEGF-D adenoviral vectors stimulate the production of NO

• Good safety data from a Phase II study

• First patient in the Phase III study was enrolled in Cincinnati last week!

• Advances in molecular pathogenesis

• Huge clinical problem

• Growing population

It was the best of times…

It was the worst of times…

We Live in Exciting Times for Dialysis Access Stenosis!!

• Advances in biomaterials and delivery technology

g p p

• Elderly and clinically complex patients

• No effective therapies

SOLUTION

We can do better!!

Come back here Arnold; Stacey isn’t needling today!!

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Multidisciplinary Collaborators

Vascular

Surgery(Munda and

Rudich)

Radiology(Choe)

Vascular Stenosis

Cardiology(Weintraub)

Pharmacy(Desai)

Chemistry(Meyerhoff)

Engineering(Banerjee)

Pathology(Arend)


Optimizing downstream biology: novel perivascular administration devices Shear Stress Rates and Flow Patterns

• Shear stress rate is the difference in velocity between the boundary layer and the center of the lumen

Laminar Flow and High Shear Stress

Vascular DilatationMinimal Neointimal Hyperplasia

Non Laminar Flow and Low Shear Stress

Vascular ConstrictionMore Neointimal Hyperplasia

Endothelial cells are used to laminar flowProduce GOOD mediators

ECs are not used to non laminar flowProduce BAD mediators

Shear stress induced mechanotransduction Uremic interactions that influence AVF stenosis

Oxidative stress

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Putting it all together: a challenge and an opportunity!!

• Combination of suboptimal shear stress profiles and an increase in oxidative stress which is responsible for the endothelial dysfunction and aggressive access stenosis in hemodialysisaggressive access stenosis in hemodialysis patients

• Optimization of hemodynamic shear stress profiles together with interventions to reduce both local and systemic oxidative stress could result in novel therapies for all forms of dialysis access stenosis

3D Flow Patterns

Proximal ArteryProximal Artery

AV Anastomosis

Proximal Vein

Hemodynamic and vascular biology interactions: a challenge and an opportunity

OscillatoryShear

AVF

EndothelialDysfunction

AVF Creation

AVFNon-maturation

Perivascular Endothelial Cell Wrapsin a Pig AV Fistula model

Artery


Vein

Wrap

Perivascular Endothelial Cell Implants Reduce Neointimal Hyperplasia

Control Wrap Endothelial Wrap


Phase II human study has just been completed by Pervasis Therapeutics

Pervasis Vascugel Wrap Study

• Phase II study has just been completed in the US

• 31 AV fistula patients;

Sponge #1

Sponge #2V

A

31 AV fistula patients; 34 AV graft patients

• 2:1 randomization

• Primarily a technical feasibility/safety study

Sponge #1

Sponge #2

V

G

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Perivascular Endothelial Cell Wraps in Dialysis Access Patients (AV Grafts)

GV anastomosis

Courtesy PervasisTherapeutics

Venous segment

Vascugel has a Good Safety Profile

4

6

8

10

12

f Sub

ject

s

PlaceboVascugel

0

2

4

Interventions Wound Infections

Thrombosis Interventions Wound Infections

Thrombosis

2 weeks 4 weeks

Perc

ent o

f

FDA submission for a Phase III study in progress

VEGF-D “GENE” therapy (Trinam; Ark Therapeutics)

Biodegradable Collar

• VEGF-D adenoviral vectors will deliver VEGF-D to the vessel wall

• Stimulate the production of nitric oxide and prostacyclin

• Inhibit venous stenosis at the GVA with minimal systemic toxicity

• Good safety data from a Phase II study

• Phase III study is being initiated

Linkages between WSS and IM thickening in AVF

Curved

Straight

Bullfrog Micro-Infusion System Perivascular injection

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Flow patterns determine cellular characteristics

Disturbed Flow Laminar Flow

Increased elongationindex with laminar flow

Atherosclerosis prone regions have lower shear stress and less NO production

AR AP

Atherosclerosis Resistant

ARHigh Shear =More NO

Atherosclerosis ProneAP

Low Shear =Less NO

Green nuclei =β Gal linked to an eNOS promoter

Won et al. Am J Path 2007

Nitric Oxide Synthesis by Cultured Endothelial Cells Nitric Oxide Synthesis by Cultured Endothelial Cells Is Modulated by Flow ConditionsIs Modulated by Flow ConditionsNoris M et al., Circulation Res, 1995

Low Shear Stress or Static Condition

Laminar Flow Secondary Flows or Turbulence

Physiological vascular tone

regulation

Impaired vascular tone regulation

Endothelin NO Endothelin NO

SMC

EC

Vasoconstriction and cell proliferation

Endothelin NO

Tailor therapies to the biologicalcourse of vascular stenosis

• Endovascular device such as the “Adventa” micro‐infusion catheter (Mercator‐Med)

Sheathed needle

Optimizing downstream biology: novel perivascular administration devices

Drug A initially followed byDrug B at 6 monthly intervals

Extruded needle

Heme Oxygenase -/- mice have more aggressive AV fistula stenosis

HO-1 +/+

HO-1 -/-

Juncos et al.Kid Int. 2008

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Physiological shear stress Vs. Low and Oscillating shear stress Physiological shear stress Vs. Low and Oscillating shear stress Duration of hemodialysis correlates with pre-existing medial venous thickness

Normal Vein Uremic VeinFeinfeld et al. AJKD 1999

Optimizing downstream biology: perivascular elastase administration

Pre‐Treatment Post‐Treatment

Adventitia

Media

Adventitia

Media

•Recombinant elastase

•Applied to the adventitia


•Destroys the elastin in the vessel wall

•Results in a permanent increase in vessel calibre


•Topically applied

•2 5ml over 10 min

Vein

•2.5ml over 10 min

• Irrigation with saline 1 min after treatment

Artery

Anastomosis


Proximal veinProximal artery

AV anast.

2d Macrophages42d Histology

Different patterns ofshear on opposite walls

Krishnamoorthy et al. Kidney International 2008Rao et al. ASN 2009, PO-1563

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Shear stress to macrophages to stenosis

Inflammatory (macrophage) response (2d)

Chemokines and cytokines (2d‐7d)

Intima‐media thickening (42d)

3D Flow Patterns

Proximal ArteryProximal Artery

AV Anastomosis

Proximal Vein

AVF creation using the Optiflow Device



•Topically applied

•2 5ml over 10 min

Vein

•2.5ml over 10 min

• Irrigation with saline 1 min after treatment

Artery

Anastomosis

Perivascular endothelial cell implants (Vascugel) in diabetic patients

Implants

A t

Vein

AVFVascugel

Placebo

p = 0.054

Unassisted primary patency

Artery

Implants

Vein Artery Roy-Chaudhury et al. ASN 2009, PO-1576

AVG


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Flow patterns and shear stress influence endothelial function

• Non laminar flow with oscillatory shear (LOW)

• Endothelial activation

• Increased Oxidative Stress

• Inflammatory gene profile (VCAM-1)

• Laminar flow with laminar shear (HIGH)

• Endothelial quiescence

• Minimal Oxidative Stress

• Non-Inflammatory gene profile (Nitric oxide)


Optimizing Upstream Hemodynamics:Shielding the peri-anastomotic area (Bioconnect)

Conduit

Artery

Vein

Flanges Vein


Artery

• Sutureless anastomotic conduit

• Shields the peri-anastomotic region

• Optimize hemodynamic shear by altering the anastomotic angle

Technology can change existing clinical paradigms

•AVF >>>AVG >>>>>>TDC•TDC that has no infection and no thrombosis

•TDC > AVF >>> AVG

Technology can change existing clinical paradigms

•Anti‐infective coatings •Anti‐thrombotic coatingsg

•Optimizing hemodynamics to reduce thrombosis

Venous neointimal hyperplasia is characterized by significant angiogenesis

Roy-Chaudhury et al. Kidney Int. 2001

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Perigraft macrophages play a role in venous neointimal hyperplasia

Graft

Roy-Chaudhury et al. Kidney Int. 2001

Shear Stress is the most important hemodynamic factor which influences vascular remodeling

• Viscous drag of blood on the cells lining the vessel wall

• Directly proportional to velocity of flow and inversely proportional to fourth powerproportional to fourth power of the radius

• Increase in shear due to an increased velocity of blood flow after AVF creation results in venous dilation in order to return shear to baseline levels

Neointimal Hyperplasia is a Response to Vascular Injury!!

SMC and EC Injury

Adapted from Robbins Pathology

Vascular Injury in the Setting of Hemodialysis Vascular Access Dysfunction

Hemodynamics Dialysis Needles

Surgical injury Angioplasty

•Get away from the “one size fits all” paradigm

A Message for the Future!!

size fits all paradigm •Stratify patients based on

biological and clinical parameters

Individualize Vascular Access Care

•Offer them the dialysis access that is best suited for them

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• 25 yr old with good vessels and good endothelial function = AVF

• 50 yr old with average veins and moderate endothelial function = AVF “plus”

• 70 yr old with poor veins and poor endothelial function =

Individualize Vascular Access Care

y p pGraft “plus”

• 80 yr old with poor veins, poor endothelial function and multiple co-morbidities = Catheter “plus”

“plus” = better anatomical configuration, local anti-proliferativedrug therapy, anti-infective coatings, local enhancement of

endothelial function

Anatomical configuration influences shear stress profiles

StraightCurved


Blood flow is greater in the curved configuration

CurvedStraight

p < 0.05

FLOW

C S

Diameter is greater in the curved configuration

CurvedStraight

FLOW

p < 0.05

Anatomy, Shear and Stenosis!

Ideal anatomical configuration for AVFs and PTFE grafts

Optimize flow patterns and shear stress in AVFs and PTFE grafts

Reduction of AVF and PTFEgraft stenosis

Patients with pre-existing arterial IMT on histology have a poorer AVF survival

(Kim et al.)• Demonstrated pre‐existing radial artery intima‐media thickening (IMT) prior

IMT < 500μm

thickening (IMT) prior to AVF creation

• Primary patency of AVFs at 1 year was decreased in patients with a radial IMT > 500 microns!

Kim et al. J Korean Med Sci 2006

IMT > 500μm

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Optimizing upstream hemodynamics and downstream biology using LOCAL

therapyConduit

Venous

segment

Flanges

AV anastomosis


Pharmacologic intervention to enhance maturation and prevent dysfunction of

AV access Anatole Besarab MD, FACPDirector of Clinical Research

Division of Nephrology and HypertensionHenry Ford Hospital

Professor of MedicineWayne state University school of Medicine

Detroit, MI

Venous stenosis and dysfunction

• The process that leads to dysfunction is neointimal hyperplasia (NIH) of the vein– Within the perianastamotic area of AVF

At the graft vein anastamosis of synthetic bypass grafts– At the graft vein anastamosis of synthetic bypass grafts

• Few effective therapies

Pathogenesis

Endothelial Injury

PlateletActivation

Integrins and Thrombin

Recruitment of Cells

Wall Thickening And Stenosis

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HealingHealing

We understand this

Why here?

Neointimal Hyperplasia AVF

AngioplastyAngioplasty

StenosisStenosis

Wrist AVF

Why here?

Why here?

Vein NIH at the graft-vein anastomosis

P RP R--CC

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Is turbulence and shear stress on endothelium part of the equation?

Neointimal Hyperplasia

• Histology– Myofibroblasts (from adventitia?) – Lots of extracellular matrix in bypass grafts– Proinflammatory cells (giant cells)y (g )– Neovasculature within the expanding neointima

• Biochemistry– Growth factors– Matrix enzymes– Cytokines

The intraluminal milieu: A complex place with lots of activity

The vessel wall : A complex place with lots of

activity.

Vascular smooth muscle cells (VSMC)

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Summary• What do we know about intimal hyperplasia?

• Quite a bit

• Is it complex ? • You betchum

• Have we tried therapies? • Yes

• Have they worked? • Depends

• Do we have new therapies in the pipe line?

• Maybe

• Will we succeed • Eventually (I hope)

Processes to control

•• The response to injury (new surgical techniques)The response to injury (new surgical techniques)

•• Shear stress (can we modify the design) Shear stress (can we modify the design)

•• VSMC phenotypic transformation influenced by a host of VSMC phenotypic transformation influenced by a host of mediators:mediators:

NO E d th liNO E d th li 11NO, Endothelin NO, Endothelin ‐‐11

Integrins (VCAMIntegrins (VCAM‐‐1 and MCP1 and MCP‐‐1 , NF1 , NF‐‐κκB)B)proteases (MMPproteases (MMP‐‐2), plasmin, PAI2), plasmin, PAI‐‐11

Growth factors: bFGF, PFGF, Ang II, TGFGrowth factors: bFGF, PFGF, Ang II, TGFβTNF‐α induction of MCP‐1, VCAM‐1, MMP‐9 (blocked by clusterin)

Neointimal Hyperplasiamagnitude of the response

PCNA indices as high as 20%. Even avascular areas of lesion have indices 5 PCNA indices as high as 20%. Even avascular areas of lesion have indices 5 x those of coronary artery lesions.x those of coronary artery lesions.Cell counts: 42% ECs, 49% VSMCs, 6% Macrophages, 5% inflammatory.Cell counts: 42% ECs, 49% VSMCs, 6% Macrophages, 5% inflammatory.No correlation between proliferation and age of graft.No correlation between proliferation and age of graft.Immunostaining shows PDGF, TGFImmunostaining shows PDGF, TGF‐‐b, thrombinb, thrombing ,g , ,,The process is aggressive even in AVF.The process is aggressive even in AVF.11

Restenotic lesion after PTA have even higher PNCA than primary lesions.Restenotic lesion after PTA have even higher PNCA than primary lesions.22

CKD accelerates NIH which can be blocked by bone morphometric CKD accelerates NIH which can be blocked by bone morphometric proteinprotein‐‐7.7.33

1. Chaudhury et al. AJKD 2007:50: 782-90 2. Ghang et al. AJKD 2004 43:74-843 Kakubo et al. JASN 2009; 20: 1236-45

Therapeutic ConsiderationsRedundancy

Multiple growth factors; multiple intracellular signaling Multiple growth factors; multiple intracellular signaling pathwayspathways. . – Need multiple drugs or must affect multiple steps.

–Blockade of a single pathway inadequate; promising results inBlockade of a single pathway inadequate; promising results in animals not recapitulated in clinical trials.

Must target those components shared by many Must target those components shared by many regulatory molecules rather than a specific growth regulatory molecules rather than a specific growth factors or their receptorsfactors or their receptors

Therapeutic ConsiderationsOption 1 ‐ Growth factors

•• Blockade of growth factorsBlockade of growth factors

–– PDGF, bFGF antibodiesPDGF, bFGF antibodies

–– Trapidil (PDGF receptor blockade)Trapidil (PDGF receptor blockade)

–– ACE inhibitorsACE inhibitors

C l i Ch l Bl kC l i Ch l Bl k Where?Where?–– Calcium Channel BlockersCalcium Channel Blockers

–– Heparin/heparansHeparin/heparans

–– Protein Kinase inhibitors.Protein Kinase inhibitors.

–– MisoprotolMisoprotol

–– Antiplatelet drugsAntiplatelet drugs

•• Blockade of integrins: IIb/IIIa, Blockade of integrins: IIb/IIIa, ααVVββ33–– Suramin Suramin ‐‐ blocks multiple growth factors.blocks multiple growth factors.

Where?Where?-- Systemic vs. LocalSystemic vs. LocalHow Long?How Long?-- hr. vs. dayshr. vs. days

Blockade of VSMC ProliferationBlockade of VSMC Proliferation–– Heparin, heparans, heparin fragmentsHeparin, heparans, heparin fragments–– HMG CoA Reductase Inhibitors (statins).HMG CoA Reductase Inhibitors (statins).–– Chimeric Drugs that kill proliferating cells.Chimeric Drugs that kill proliferating cells.–– Interferon Interferon γγ (cells can resume their proliferating ability). (cells can resume their proliferating ability). AntiAnti sense oligonucleotides directed against cell regulatory genes: PCNAsense oligonucleotides directed against cell regulatory genes: PCNA

Therapeutic ConsiderationsOption 2: Effector Cells

–– AntiAnti‐‐sense oligonucleotides directed against cell regulatory genes: PCNA, sense oligonucleotides directed against cell regulatory genes: PCNA, CC‐‐Myb, Cdc2, Myb, Cdc2,

–– AntiAnti‐‐sense oligonucleotides directed against transcription factors: E2F.sense oligonucleotides directed against transcription factors: E2F.–– Rapamycin (inhibition of cell cycle kinases)Rapamycin (inhibition of cell cycle kinases)–– Radiation (brachytherapy within 48 hr of construction.).Radiation (brachytherapy within 48 hr of construction.).–– Increase apoptosis by gene manipulation.Increase apoptosis by gene manipulation.Blockade of effector cellsBlockade of effector cells

–– inflammatory cells: antiinflammatory cells: anti‐‐CD4+ antibody x 10dCD4+ antibody x 10d

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•• Blockade of Advential/VSMC MigrationBlockade of Advential/VSMC Migration–– Heparin, heparansHeparin, heparans–– Blockade of integrins: IIb/IIIa, aVb3 (cellBlockade of integrins: IIb/IIIa, aVb3 (cell--matrix matrix

interactions)interactions)

Therapeutic ConsiderationsOption 3: Blockade of VSMC

•• GpenGRGDSPCAGpenGRGDSPCA•• Prevent ProliferationPrevent Proliferation•• Blockade of phenotypic expressionBlockade of phenotypic expression

–– transcription of genestranscription of genes•• Increase ECM degradation Increase ECM degradation

–– NO synthaseNO synthase–– NO donor drugs.NO donor drugs.

What have we tried?

Only 2 RCT have been performed with adequate power

DAC‐NIH (National Institute of Health) AVF study

– Effect of Clopidrogel on prevention of early failure rate (AVF thrombosis) I CKD and ESRD patients.

– Primary Outcome: 30% reduction in early failure rate assessed at 6 weeks. S d O t f ti lit ( bl t f 8 12 di l i– Secondary Outcome: functionality (able to use for 8‐12 dialysis treatments in a month and obtain a blood flow of 300 ml/min)

– Timeline: randomization over 51 months with 6 month minimum follow‐up

– Sample size = 1284 patients for two sided α= 0.05 and β=0.85– Lens‐Demets spending function for determining efficacy or futility

Clopidrogel and early failure of AVF

• 1036 enrolled (not 1284); 877 randomized. Enrollment stopped after an interim analysis for efficacy.

• AVF thrombosis in 12.2% of clopidrogel compared to 19.5% of control based on physical examination at 6 p yweeks.

• Suitability not different between the two groups: 40.5% control, vs 39.2% in clopidrogel group.

Dember LM et al JAMA 2008; 299: 2164-2171

DAC‐NIH (National Institute of Health) Graft study

– Effect of Aggrenox (200 mg persantine + 81 mg ASA) BID on primary unassisted patency in virgin grafts.

– Primary Outcome: 25% improvement in primary unassisted patency assessed at one year.

– Secondary OutcomesTi t it l f ft• Time to site loss of graft

• Time to death• Composite using both

– Sample size = 1056 patients for two sided α= 0.05 and β=0.85.

– Lens‐Demets spending function for determining efficacy or futility.

Effect of dipyridamole plus aspirin on hemodialysis graft patency

• At 13 centers in the United States, 649 patients were randomly assigned to receive dipyridamole plus aspirin or placebo

• Primary unassisted patency at 1 year was 23% (95% y p y y (CI, 18% to 28%) in the placebo group and 28% (95% CI, 23% to 34%) in the dipyridamole‐aspirin group, an absolute difference of 5 percentage points that yielded hazard ratio of 0.82 ( 95% CI, 0.68 to 0.98; P=0.03 )

Dixon B et al N Engl J Med. 2009 May 21;360(21):2191-201.

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hOther options

Therapies tried in small series or animal studies

• Preconditioning of endothelial cells to improve endothelial cell retention (little human data)

• External beam radiation (works in pigs but BRAVO was a disappointment in man)

• Cryotherapy in recurrent venous anastamotic lesions of grafts (clinical small pilot study)

• Chymase inhibitor (blocks Ang II formation in tissues and of latent TGF‐β1 to active form (animals only)

• Sirolimus –loading of grafts (sheep)• Trinam (EG004), a vascular endothelial growth factor (VEGF) inhibits

VSMC migration and proliferation (? Via NO and Prostacyclin)‐ Study designed 2001 ? Completed

• Perivascular delivery of antiproliferative drugs at time of surgical construction (paclitaxel vascular wrap or nanoparticles, dipyridamole in microspheres for continuous local release to 35 days.

We have a long way to go !

• Need the NIH to fund research on NIH.• Funding of smaller (underpowered if necessary) interventions whose size effects are large in animal feasibility studies.y

• Better data on permanence of the initial effects.• Delivery methods: initial as well as with interventions.

Stenosis Leads to ThrombosisStenosis Leads to Thrombosis

60-65%

Severe Stenosis

Stenosis with Thrombus

Why does one lesion produce thrombosis and the other does not? Cross sectional residual lumen is the same! P RP R--CC

Bharat Sachdeva [email protected] Professor MedicineAssociate Program DirectorDepartment of Medicine / NephrologyLSUHSC Shreveport

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Why new?

Improve Primary and Secondary PatencyReduce Complications

Intimal hyperplasiaInfectionsInfectionsPseudo aneurysmsBleeding after needle punctureEarly access for Hemodialysis

Manufacturer GraftFibril Length μm

Thickness (mm) Support Wrap/

Coating

Atrium Advanta VS 60/20 Std: .6Thin: .4

++

--

Atrium Advanta VXT 60/20 Std: .6Thin: .4

++

++

Atrium Advanta SST 60/20 .25 Midbody ++Bard IMPRA Std 20/30 .6 + +Bard IMPRA Thin 20/30 .4 + +Bard IMPRA Carboflo 20/30 6/ 4 + +Bard IMPRA Carboflo 20/30 .6/.4 + +Bard Venoflo w/carbon 20/30 .6 - -

Boston Sc Excel 20/30 Std .6Thin .5

++

++

Edwards Life Sc Lifespan 20/30 StdThin

++

++

WL Gore Standard 10/20 .6 + +WL Gore Thin 10/20 .4 + +WL Gore Stretch 10/20 .6 + ++WL Gore Diastat 10/20 .8

Vascutek PTFE Seal 10/20 Std .6Thin .4

++

++

Vectra Vascular Access Graft

Tri-layered graft (segmented polyetherurethaneurea / siloxane containing a surface modifying additive)Self-sealing properties allowing early cannulationSolid non-permeable middlelayer that allows the graft wall to seal rapidly after a needle removal

Vectra Graft

Glickman et al, 2001Design

Prospective, randomized 12 month comparison of Vectra vs. ePTFE AV grafts142 patients in 5 centersp

ResultsPrimary patency of 51% at 6 months and 44% at 12 monthsfor Vectra vs. 59% and 43% respectively for ePTFESecondary patency of 85% at 6 months and 74% at 12 months for Vectra vs.. 86% and 79% respectively for ePTFE

No statistical significance between two groups

J Vasc Surg 34:465-472, 2001

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Vectra Graft

53.9% Vectra grafts cannulated within 9 days vs.. 0% ePTFE80 7% homeostasis within 5 minutes in Vectra80.7% homeostasis within 5 minutes in Vectra grafts vs.. 26.8% in ePTFEHigher incidence of kinking events in Vectra group (10 vs.. 0 events for ePTFE)

J Vasc Surg 34:465-472, 2001

Vectra GraftAdvantages

Immediate access after implantation Avoid need for catheter

Rapid hemostasis

Surgical learning curve

Patch angioplasty may be complex

Slow tissue incorporationRapid hemostasis

Excellent for interposition graft

Disadvantages

Slow tissue incorporation

Unable to use Doppler ultrasound to image

Kinking of graft / Axial graft elongation

J Vasc Surg 34:465-472, 2001

GORE PROPATEN® Vascular Graft

Heparin molecules are bonded to the luminal surface of the graft

Heparin is a polysaccharide anticoagulant with a long history of clinical use1

Heparin has a potent antiproliferative effect on vascular smooth muscle cells2smooth muscle cells2

A proprietary end-point attachment mechanism is utilized to bond heparin molecules to the graft surface

1 Circulation 2001;103(24):2994-3018.2 Nature 1977;265(5595):625-626.

Proprietary End-Point Covalent Bonding

Bioactive siteHeparinmolecule

End-point covalent bond

Graft surface

Propaten®Prospective, non-randomized, single-center study comparing 4 – 7 mm GORE PROPATEN® Vascular Graft to 4 – 7 mm non-heparin bonded ePTFE graft.

GORE PROPATEN® Vascular Grafts were generally preferred for difficult, high risk patientsp , g p

GORE PROPATEN® Vascular Graft n = 83Non-heparin bonded graft n = 67

Enrollment: January 1, 2007 – November 1, 2008

Abstract presented at the 35th Annual VEITH Symposium; November 19-23, 2008; New York, NY

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Propaten®

1 Yr Clot free survival 78% vs. 58% for control

Dr Ross in a single center study reportedConsec ti e implants in high risk patients ithConsecutive implants in high-risk patients with compromised veins or low flow state6 Months primary patency 77%

34th Annual VEITH Symposium ; November 14 –18, 2007; New York, NY.

Peripheral Arterial disease

350 patients who underwent a lower-limb bypass procedure that used either a heparin-bonded ePTFE graft (n=240) or an ASV graft (n=110)

Type of Graft Saphenous vein ePTFE-Heparin1 yr (2yr) primary

patencyAbove knee

femoropopliteal91% (80%) 92% (83%)

Below-knee femoropopliteal

72% (72%) 92% (83%)

Femorocrural grafts

69% (64%) 79% (69%)

J Vasc Surg 49, 1210-16, 2009

Other studies

Yarn wrapped graft (EXCEL) failed to show improved survival. Surg Today. 2004;34(5):409-12.

Angle of graft vein anastomosis may play a role in attenuating the compliance mismatch problem J VASC SURG 1994;19:1067–73

Antisense oligonucleotides (ODNs) prevent NIH in arterial injury modelsinjury models. Cardiovasc Res 2000; 45: 783–787

Intravascular adenovirus-mediated VEGF-C gene transfer reduced NH in balloon-denuded rabbit aorta. Circulation 2000; 102: 2262–2268

β-adrenergic receptor kinase, an inhibitor of G-protein signaling, significantly reduced NH in porcine model. Circulation 2005; 111: 1679–1684

Drugs to decrease NIHLocal drug delivery

coating of the graft with the drugplacing a drug-coated stent intravascularly i j ti th d i t th

Rapamycin: RAVEL1, SIRIUS2,3 trials, No clinical trials in AV access Paclitaxel-eluting wrap placed around the anastomosis: inhibit NIHinjecting the drug into the

vascular wall at the anastomosisplacing a drug depot perivascularly (polymer gel/ impermeable wrap)

anastomosis: inhibit NIH formation in sheep4 and porcine5 AV ePTFE graft modelsImatinib mesylate: PDGF Inhibitor shown to has also been demonstrated in animal models of arterial proliferative diseases6

1. N Engl J Med 2002; 346: 1773–17802. Circulation 2005; 111: 1040–10443. J Am Coll Cardiol 2007; 50: 1299–13044. J Vasc Surg 2007; 45: 1029–1037; discussion 1037–1028

5. Nephrol Dial Transplant 2006; 21: 2425–2431.6. Cardiovasc Drugs Ther 1999; 13: 159–168

Shear Stress and Stenosis

vorticesturbulent flow

Annals of Vascular SurgeryVolume 21, Issue 5, September-October 2007, Pages 611-617

stagnation

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Shear Stress and Stenosis

Recirculation and NIH

Annals of Vascular SurgeryVolume 21, Issue 5, September-October 2007, Pages 611-617

SwirlGraft™

Helical geometry of the SwirlGraft™ produces swirling and mixing flowWall shear is minimized and stagnation eliminated

http://www.tayflow.com/index.asp

20 Patient study 2006The 6-month primary patency rate was 57.9% ±11.4

Angiographic evidence of reduction of helical geometryafter implantation!

Eur J Vasc Endovasc Surg 33, 472 - 475 (2007)

Bovine Mesenteric Vein Procol®

Harvested bovine mesenteric veinGlutaraldehyde Crosslinking and Gamma radiation

Resistant to host rejection and degredationMaintain viscoelastic compliance similar to saphenous vein

Elastic mismatch is improved by use of Bovine graftsMajor Limitations

lower overall mechanical strength difficulty repair when comparedto synthetic grafts

Bovine Mesenteric Vein Procol®

Multicenter prospective studyPrimary 35.6% MVB vs 28.4% synthetic grafts66%-61% Secondary patency at 12 and 24 months in bovine graftsI t l C t l 34% d 18%Internal Control 34% and 18% Higher Interventional rate with synthetic graftsLower thrombosis rate 0.78 events/yr vs. 1.3 events /yr for synthetic graftsLower Infections 0.05 events/yr vs. 0.20 events/yr

Cryopreserved Femoral vein

Cryopreserved vessel allograft Cellular elements removed using antigen reduction technologyImmunologically invisible preventing hostImmunologically invisible preventing host sensitization and rejectionConsidered for in situ replacement of infected arterio venous grafts

J Vasc Surg 36:464-468, 2002

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Biopsy and graft engineeringEndothelial, smooth muscle and fibroblasts are taken from a dialysis patientSheets of living fibroblasts grown from cells extracted from patientSheets are wrapped around a stainless steelSheets are wrapped around a stainless steel mandrel (4.8 mm diameter) Maturation phase of 10 weeks in cultureVessel is taken off the mandrelInner plies devitalized by air-dryingEndothelial cells are seeded into the lumen

The lancet Vol 373 April 25, 2009

Bioengineered grafts10 patients Argentina and PolandAll had a previous Hemodialysis access failureComposite graft length of 14–40 cmPatients were followed up:

physical examinations during dialysis visitsp ys ca e a a o s du g d a ys s s sintermittent Doppler ultrasoundintravascular ultra soundAngiographyCT angiography

During the safety phase (>3 Months) of the study, successful vascular grafts were not punctured


Outcome

Graft aneurysm, Noted to have rejection

Patient withdrew

Time in Months

Graft thrombosed, low blood flows

TransplantedDied with a functioning graft

Graft Dilated, Removed


Lifeline® Graft

68 patient-months of graft patency0.015 interventions per patient-monthNo Infections noted in graftsE l t f ti t i t th t iEnrolment of patients into the arteriovenous shunt study and for leg vascular bypass with both allogeneic and autologous tissue-engineered vascular grafts


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J Thorac Cardiovasc Surg 2008;135:1237-46

Graft implanted 55 rabbits

Scaffold: Nonresorbable polycarbonate-siloxane polyurethane

Compliance, burst strength, and suturabilityMicrostructure: Resorbable bovine hide-derived collagen and hyaluronic acidcollagen and hyaluronic acid

Cell attachment and proliferationPrevent leakage of fluid through the porous macrostructure

Heparin added to both the macrostructure and microstructure (H graft)Sirolimus added to the macrostructure (HS Graft), Control (C) had neither drug


6 month follow upPatency rate was 100% in the H, HS, and C grafts

50% ePTFE occluded at 6 months

None of the H or HS grafts had any stenosis or thrombus

Neointima formation was inhibited in the HS graft compared with the H or C graft at 6 months (123 ± 126 mm vs. 206 ±158 mm or 202 ± 67 mm P < .05)

Marked neocapillary formation 6 months after surgery

The graft macrostructure was unchanged according to the biomechanical evaluation in the H and HS grafts


Development of biological Grafts

A completely biological tissue-engineered human blood vessel. FASEB J. 12, 47–56 (1998)

In vivo biostability of a poly(carbonateurea) urethane graft. Biomaterials 24, 2549–2557A (2003)

Cellular engineering of conduits for coronary and lower limb bypass surgery: role of cell attachment peptides and pre-conditioning in optimising smooth muscle cells (SMC) adherence to compliant poly(carbonateurea) urethaneadherence to compliant poly(carbonateurea) urethane scaffolds. Eur. J. Vasc. Endovasc. Surg. 27, 608–616 (2004)

Novel bioengineered small-caliber vascular graft incorporating heparin and sirolimus: Excellent 6-month patency. J Thorac Cardiovasc Surg 2008;135:1237-46

Tissue engineering of a hybrid bypass graft for coronary and lower limb bypass surgery. FASEB J. 22, 2084–2089 (2008)

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