Transplantation of autologous rabbit BM-derived mesenchymal stromal cells embedded in hyaluronic acid gel sponge into osteochondral defects of the knee

Background Mesenchymal stromal cells ( MSC) have the potential to differentiate into distinct mesenchymal tissues including cartilage, suggesting that these cells are an attractive cell source for cartilage tissue engineering approaches. Various methods, such as using hyaluronan-based materials, have been employed to improve transplantation for repair. Our objective was to study the effects of autologous transplantation of rabbit MSC with hyaluronic acid gel sponges into full-thickness osteochondral defects of the knee. Methods Rabbit BM-derived MSC were cultured and expanded with fibroblast growth factor ( FGF). Specimens were harvested at 4 and 12 weeks after implantation, examined histologically for morphologic features, and stained immunohistochemically for type II collagen and CD44. Results The regenerated area after autologous transplantation of hyaluronic acid gel sponge loaded with MSC into the osteochondral defect at 12 weeks after surgery showed well-repaired cartilage tissue, resembling the articular cartilage of the surrounding structure, of which the histologic score was significantly better than that of the untreated osteochondral defect. In the regenerated cartilage, type II collagen was found in the pericellular matrix of regenerative chondrocytes, while CD44 expression in the regenerative tissue could not be revealed. Discussion These data suggest that the autologous transplantation of MSC embedded in hyaluronan-based material may support chondrogenic differentiation and be useful for osteochondral defect repair.