Francine Goulet, Ph.D., pht Nanomedical Biological Device in Development for Torn ACL Replacement.

INTRODUCTION

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 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 shocks

Langer R, et al. 1993

Therapeutic options Synthetic prostheses Carbone dacron LAD Allograft Autograft Synthetic prostheses Carbone dacron LAD Allograft Autograft

Option used often 1/3 patellar tendon + patella and tibia fragments

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

ACL : complex features Histological content: Fibroblasts Collagen fibers Proteoglycans Elastin….. Ultrastructure: Fibrocartilage Sharpey’s fibers Vascular network Nervous receptors

ACL: 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: N 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: N

« 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 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 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.

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

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

MATERIAL AND METHODS

Characterization of the collagen scaffolds

ACL collagen scaffold cultured without tension © F.G./LOEX

ACL collagen scaffold subjected to tension © F.G./LOEX

Before grafting Native ACL Periodicity: 67 nm Collagen fibers alignment © F.G./LOEX

Average cross section of 100 mm 2 Scaffold structure Force /resistance to rupture (N) Site of rupture 1 layer of hydrated collagen (gel) (+ 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 N (+ 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