Francine Goulet, Ph.D., phtFrancine Goulet, Ph.D., pht

Nanomedical Biological Device in Development for Torn ACL Replacement.

Nanomedical Biological Device in Development for Torn ACL Replacement.

INTRODUCTIONINTRODUCTION

Ligaments, including ACL, extend between adjacent bone structures and serve a primary function of providing appropriate stability to the joints, especially when subjected to loads in tension or upon torsional movement.

Type I collagen can be regenerated after tissue injury.

However, the anterior cruciate ligament (ACL) has little ability to heal itself.

ACL REPLACEMENTACL REPLACEMENT

100, 000 total ruptures / yr (USA)

50,000 reconstructive surgeries / yr (USA)

100, 000 total ruptures / yr (USA)

50,000 reconstructive surgeries / yr (USA)

Repeated shocksRepeated shocks

Langer R, et al. 1993

Therapeutic optionsTherapeutic options

• Synthetic prosthesesCarbonedacronLAD

• Allograft

• Autograft

• Synthetic prosthesesCarbonedacronLAD

• Allograft

• Autograft

Option used oftenOption used often

1/3 patellar tendon + patella and tibia fragments1/3 patellar tendon + patella and tibia fragments

Clinical drawbacksClinical drawbacks

•Knee joint fibrosis•Patellar impegement•Anterior knee pain•Patellar fracture•Patellar tendon’s rupture•Quads weaknesses

ACL : complex features ACL : complex features

Histological content:•Fibroblasts•Collagen fibers•Proteoglycans•Elastin…..

Ultrastructure:•Fibrocartilage•Sharpey’s fibers•Vascular network•Nervous receptors

ACL: Knee stabilizerACL: Knee stabilizer

•Average length: 32 mm•Average diameter: 11 mm•Diam. at its insertions: 23 mm (femoral) and 30 mm (tibial)

•Functional limits: -Max. elongation: 6% (about 2 mm)-Max. load: 1730 N (390 pds)

-Walking: 169 N-Intensive sport: 400-500N

•Average length: 32 mm•Average diameter: 11 mm•Diam. at its insertions: 23 mm (femoral) and 30 mm (tibial)

•Functional limits: -Max. elongation: 6% (about 2 mm)-Max. load: 1730 N (390 pds)

-Walking: 169 N-Intensive sport: 400-500N

« LIGAMENTISATION » POST-IMPLANTATION« LIGAMENTISATION » POST-IMPLANTATION

6 weeks; Vascularisation of the implant

30 weeks: histological and functional recoveries

6 weeks; Vascularisation of the implant

30 weeks: histological and functional recoveries

Questions:Innervation: ?Mechanisms?

Questions:Innervation: ?Mechanisms?

ACL tissue engineeringACL tissue engineering

Tissue engineering seems to be a promising alternative to produce ACL/ligament models:

- for fundamental studies in vitro;

- to develop tissue-emgineered human ACL substitutes

Tissue engineering seems to be a promising alternative to produce ACL/ligament models:

- for fundamental studies in vitro;

- to develop tissue-emgineered human ACL substitutes

ACL tissue engineeringACL tissue engineering

To understand ACL healing and to establish new options for torn ACL replacement, the potential of tissue-engineered collagen scaffolds has to be assessed in vitro and in vivo.

To understand ACL healing and to establish new options for torn ACL replacement, the potential of tissue-engineered collagen scaffolds has to be assessed in vitro and in vivo.

Tissue-engineered ACLTissue-engineered ACL

Appropriate scaffold is needed to provide support and promote cell adhesion, migration and growth, leading to tissue regeneration.

The scaffold must be biocompatible, biodegradable, suitable for cell attachment, and have a three-dimensional, porous structure.

Since collagen is a major structural element in so many tissues and organs, collagen fibers are a logical choice for scaffolds.

Appropriate scaffold is needed to provide support and promote cell adhesion, migration and growth, leading to tissue regeneration.

The scaffold must be biocompatible, biodegradable, suitable for cell attachment, and have a three-dimensional, porous structure.

Since collagen is a major structural element in so many tissues and organs, collagen fibers are a logical choice for scaffolds.

Objective:Objective:Develop a new alternative for torn ACL replacement through the tissue-engineering approach.Develop a new alternative for torn ACL replacement through the tissue-engineering approach.

Hypothesis:Hypothesis:

Based on our expertise with tissue-engineered human epidermal substitutes, we postulated that ACL regeneration can be achieved by providing a biocompatible scaffold that can be colonized, remodeled and renewed by living cells in situ post-grafting.

Based on our expertise with tissue-engineered human epidermal substitutes, we postulated that ACL regeneration can be achieved by providing a biocompatible scaffold that can be colonized, remodeled and renewed by living cells in situ post-grafting.

We tested our collagen-based ACL scaffolds in the goat model…We tested our collagen-based ACL scaffolds in the goat model…We tested our collagen-based ACL scaffolds in the goat model…We tested our collagen-based ACL scaffolds in the goat model…

MATERIAL AND METHODSMATERIAL AND METHODS

Characterization of the collagen scaffolds Characterization of the collagen scaffolds

ACL collagen scaffold cultured without tensionACL collagen scaffold cultured without tension

© F.G./LOEX

ACL collagen scaffold subjected to tensionACL collagen scaffold subjected to tension

© F.G./LOEX

Before graftingBefore grafting Native ACLNative ACLPeriodicity: 67 nmPeriodicity: 67 nm

Collagen fibers alignmentCollagen fibers alignment

© F.G./LOEX

© F.G./LOEX

6.0 9.03.0

Elongation (mm)

Force (N)

1,0

2,0

3,0

0

0.0

bACL rupture assay before graftingbACL rupture assay before grafting

RuptureRupture

6.0 9.03.0

Elongation (mm)

Force (N)

1,0

2,0

3,0

0

0.0

bACL rupture assay before graftingbACL rupture assay before grafting

RuptureRupture

© F.G./LOEX

Average cross section of 100 mm2Average cross section of 100 mm2

Scaffold structure Force /resistance to rupture (N)

Site of rupture

1 layer of hydrated collagen (gel) 0.2-0.5 (+ 5%) Interface bone-collagen

+ 1 layer of lyophilized collagen (rehydrated) 2 (+ 5%) Mid-portion of the scaffold

+ 1 layer of lyophilized collagen (rehydrated)Dipped in 10% glycerol

20 (+ 10%) Mid-portion of the scaffold

+ 2 layers of lyophilized collagen (rehydrated)Dipped in 10% glycerol

40- 50N (+ 10%) Mid-portion of the scaffold

+ 1 layer of lyophilized collagen (rehydrated)around a surgical thread (Maxon 3.0)

> 60N (grafted) Not determined

© F.G./LOEX