Aims: Collagen implants are used for repair of chondral defects. We investigated the behavior of human chondrocytes of either healthy or osteoarthritic joints and ovine chondrocytes and bone marrow stromal cells seeded in a collagen-GAG copolymer matrix comprising collagen type I, II and III. Methods: Cells were seeded on matrices and cultured for 12 hours, 4 days, 1 week, 2, 3, and 4 weeks. We evaluated morphology and biosynthetic activity of the cells by histological analysis, immunhistochemistry, electron microscopy, biochemical assays for glycosaminoglycans and DNA, and expression of collagens by RT-PCR. Results: From 12 h to 3 weeks the histology showed a increasing number of spherical cells, consistent with chondrocytic morphology except in the osteoarthritic-chondrocyte-seeded scaffolds. GAG analysis showed an increasing amount in all cell-types except osteoarthritic ones. Human chondro-cytes from healthy cartilage increased the amount from 0 μg/mg GAG at 12 hours to 0,9 μg/mg at 2 weeks. Ovine bone marrow stromal cells from 0,5 μg/mg GAG at 12 hours to 2,9 μg/mg at 4 weeks. Conclusions: The collagen trilayer matrix may be of value as a vehicle for chondro-cyte implantation harvested from healthy cartilage. This matrix also supports the expression of chondrocytic proteins in ovine bone marrow stromal cells without use of growth factors. However, chondrocytes from osteoarthritic cartilage revealed low bioactivity and can not be recommended for cell transplantation procedures.

Aims: The technique of microfracture for the arthroscopic treatment of articular cartilage (AC) defects has been shown to result in reparative tissue in the defect, however, retrieved tissues have demonstrated þbrocartilagenous material. The objective of this study was to evaluate the tissue types formed in AC defects in an ovine model treated by microfracture with a collagen- GAG-copolymer trilayer matrix consisting of collagen type I, II and III and autologous cultured cells. Methods: Sixteen adult sheep were used in the study following the protocol accepted by the Animal Care Commitee of the University. Two 4.5-mm diameter defects were produced in the medial condyle of the right knee, all AC was removed without penetrating the subchondral bone. In twelve animals microfracture was performed with a curved pick, in four of them without further treatment, in four the defect was covered by the collagen implant alone, and in four by the cell-seeded implant with cultured autologous chondrocytes from the left knee, 4 defects served as controls. After four months the knees were removed, parafþn sections were stained with H & E, Safranin O/fast green, alcian blue, azan, and antibodies to types I and II collagen. Results: All treatment groups showed better þlling of the defects than untreated knees. Histological analysis revealed the biggest amount of hyaline-like tissue in the cell augmented treatment group. Reparative tissue was predominantly þbrocartilage in the other groups. Conclusions: Collagen implants are able to increase the repair of chondral defects in combination with microfracture.