Chondrogenic phenotype of perichondrium-derived chondroprogenitor cells is influenced by transforming growth factor-beta 1

Our laboratory has developed a method for the repair of osteochondral defects by implanting cultured perichondrial cells attached to a biodegradable polylactic acid scaffold. The success of this approach depends in part on the proliferative characteristics and the phenotype of the implanted cells. Transforming growth factor-beta 1 has been reported to influence these parameters in several mesenchymal-derived tissues in vitro and in vivo. The chondrocytic phenotype is marked by an enhanced expression of the collagen type-II gene. In this study, cultures grown from explants of rabbit rib perichondrium were exposed to exogenously added transforming growth factor-beta 1 at concentrations of 0.1-10 ng/ml of media. Cell proliferation and collagen gene expression were measured. The expression of types I and II collagen genes was analyzed by Northern blot and reverse transcriptase-polymerase chain reaction. The exogenous addition of transforming growth factor-beta 1 at a concentration of 0.1-10 ng/ml resulted in tritiated thymidine uptake by perichondrial cells, with optimum proliferative effects at 0.1 ng/ml. Transforming growth factor-beta 1 added at concentrations of 0.1 and 0.5 ng/ml significantly upregulated the expression of type-II collagen mRNAs. The results suggest that, when the chondrocytic phenotype is defined by markedly enhanced type-II collagen gene expression, the chondrocytic phenotype of explant cultures of perichondrium-derived cells is enhanced by the exogenous addition of transforming growth factor-beta 1.