An ovine in vitro model for chondrocyte-based scaffold-assisted cartilage grafts

Michaela Endres,Undine Freymann,Marcus Stoffel,Raimund W Kinne,Katja Neumann,Bei Zhou,Christian Kaps,David Pretzel

doi:10.1186/1749-799x-7-37

Abstract

BackgroundScaffold-assisted autologous chondrocyte implantation is an effective clinical procedure for cartilage repair. From the regulatory point of view, the ovine model is one of the suggested large animal models for pre-clinical studies. The aim of our study was to evaluate the in vitro re-differentiation capacity of expanded ovine chondrocytes in biomechanically characterized polyglycolic acid (PGA)/fibrin biomaterials for scaffold-assisted cartilage repair.MethodsOvine chondrocytes harvested from adult articular cartilage were expanded in monolayer and re-assembled three-dimensionally in PGA-fibrin scaffolds. De- and re-differentiation of ovine chondrocytes in PGA-fibrin scaffolds was assessed by histological and immuno-histochemical staining as well as by real-time gene expression analysis of typical cartilage marker molecules and the matrix-remodelling enzymes matrix metalloproteinases (MMP) -1, -2 and −13 as well as their inhibitors. PGA scaffolds characteristics including degradation and stiffness were analysed by electron microscopy and biomechanical testing.ResultsHistological, immuno-histochemical and gene expression analysis showed that dedifferentiated chondrocytes re-differentiate in PGA-fibrin scaffolds and form a cartilaginous matrix. Re-differentiation was accompanied by the induction of type II collagen and aggrecan, while MMP expression decreased in prolonged tissue culture. Electron microscopy and biomechanical tests revealed that the non-woven PGA scaffold shows a textile structure with high tensile strength of 3.6 N/mm2 and a stiffness of up to 0.44 N/mm2, when combined with gel-like fibrin.ConclusionThese data suggest that PGA-fibrin is suited as a mechanically stable support structure for scaffold-assisted chondrocyte grafts, initiating chondrogenic re-differentiation of expanded chondrocytes.

Highlights

Scaffold-assisted autologous chondrocyte implantation is an effective clinical procedure for cartilage repair
There is no significant evidence that the autologous chondrocyte implantation (ACI) procedure is superior to other cartilage repair techniques in the treatment of full-thickness articular cartilage defects [8,14]
Viable cells as assessed by trypan blue dye exclusion were seeded into cell culture flasks with an initial density of 2x105 cells/cm2 in RPMI 1640 supplemented with 10% FBS and penicillin/ streptomycin

Summary

Introduction

Scaffold-assisted autologous chondrocyte implantation is an effective clinical procedure for cartilage repair. The aim of our study was to evaluate the in vitro re-differentiation capacity of expanded ovine chondrocytes in biomechanically characterized polyglycolic acid (PGA)/fibrin biomaterials for scaffold-assisted cartilage repair. Applied cartilage repair procedures comprise debridement, bone marrow stimulating techniques like drilling or microfracturing, osteochondral autograft transfer and autologous chondrocyte implantation (ACI) [5,6,7,8,9]. In ACI, a small cartilage biopsy is harvested from the less weight-bearing area of the articular cartilage. There is no significant evidence that the ACI procedure is superior to other cartilage repair techniques in the treatment of full-thickness articular cartilage defects [8,14]. ACI is regarded as a second line treatment for small and a first line treatment for defects larger than 2 to 4 cm2 [15]

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