Mitotic activity in chondrocyte transplantation from the in vitro phase to the in vivo phase

The transplantation of devitalized allogenic matrices vehiculating autologous chondrocytes, previously isoled and seeded on them could be a solution to the problem of repairing lesions of the joint cartilage. For the matrix/cell "composite" to be "graftable" the cells must continue to duplicate and produce cartilaginous matrix even after transport in vivo. The present study analyzes the mitotic activity of chondrocytes planted on devitalized allogenic cartilage and grafted in living animals. Chondrocytes of joint cartilage of lambs were isolated enzymatically and then seeded in vitro on devitalized allogenic cartilaginous matrices for 3 weeks. At the end of the co-culture period, these matrix/chondrocyte composites were transplanted in subcutaneous pockets of athymic mice. The experimental and control samples were evaluated subsequent to explantation by histological study and incorporation of tritiated thymidine. The results obtained revealed an important decrease in the values for the incorporation of thymidine beginning from experimental time 0 (pre-implant evaluation) up to day 28 after implantation, followed by a mild increase at the experimental time of 42 days. This study demonstrated the tendency of articular chondrocytes cultivated in vitro and subsequently transplanted in vivo on a support of devitalized allogenic cartilaginous matrix to modify mitotic activity from very high values for the first experimental times, typical of the in vitro phases of cellular expansion, to very low values, more similar to the behavior of articular chondrocytes in vivo.