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

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Abstract
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 Kogenous; addition of transforming growth factor‐beta 1.