Role of growth factors in rabbit articular cartilage repair by chondrocytes in agarose

Objective: Novel approaches to intervention in joint diseases consist of th e replacement of diseased cartilage by in vitro engineered, viable cells or graft tissues. Two major obstacles remain to be overcome: (1) Hyaline cart ilage in vitro often loses differentiated traits. (2) Grafts frequently are not integrated satisfactorily into host cartilage and/or the tissue is rem odelled in situ into functionally inferior fibrocartilage. Therefore, we ha ve explored the possibility whether chondrocytes embedded into agarose gels provided better graft tissues in a repair model of full thickness defects in rabbit joint cartilage. Design: Experimental defects of knee joint cartilage was filled with articu lar chondrocytes cultured in agarose gels. Chondrocytes in vitro either rem ained unstimulated or were treated with several growth factors. Repair of t he defects was assessed by histology and was scored between 0 (no healing) and 1 (perfect healing) as judged by the follwing parameters: intensity of proteoglycan staining, organization of the superficial zone, ossification a t the border between repair cartilage and subchondral bone, tidemark format ion in the repaired area, arrangement of chondrocytes, and integration of r epair cartilage into host. Results: Treatment of chondrocyte cultures with bFGF had a stabilizing effe ct on the differentiated state of the cells in implanted grafts whereas bon e morphogenetic proteins stimulated ingrowth of subchondral bone reducing r epair cartilage thickness and preventing normal tide mark formation; TGF-be ta did not significantly affect evaluation parameters in comparison with un treated controls. Conclusion: Growth factor treatment resulted in an ambiguous quality of gra ft development. Only FGF had a clear beneficial effect to the graft tissues after 1 month. Further studies are required to define the precise conditio ns and sequence of growth factor treatment of in vitro engineered cartilage which benefits graft quality. (C) 2001 OsteoArthritis Research Society Int ernational.