Open Access Open Badges Research article

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

Michaela Endres12, Katja Neumann1, Bei Zhou3, Undine Freymann1, David Pretzel4, Marcus Stoffel3, Raimund W Kinne4 and Christian Kaps1*

Author Affiliations

1 TransTissue Technologies GmbH, Charitéplatz 1, Berlin, 10117, Germany

2 Tissue Engineering Laboratory, Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin, 10117, Germany

3 Institute of General Mechanics, RWTH Aachen, Templergraben 64, Aachen, 52062, Germany

4 Experimental Rheumatology Unit, Department of Orthopedics, University Hospital Jena, Waldkrankenhaus, Rudolf Elle, Klosterlausnitzer Str. 81, Eisenberg, 07607, Germany

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Journal of Orthopaedic Surgery and Research 2012, 7:37  doi:10.1186/1749-799X-7-37

Published: 9 November 2012



Scaffold-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.


Ovine 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.


Histological, 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.


These 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.

Cartilage grafts; Chondrocytes; In vitro model; Scaffolds; Fibrin; Polyglycolic acid; Tissue engineering; Regenerative medicine; Differentiation; Biomechanics