Transforming growth factor β1 stimulates type II collagen expression in cultured periosteum-derived cells

Abstract

Chondrogenesis can occur during a bone repair process, which is related to several growth factors. Transforming growth factor β₁, (TGF-β₁,) downregulates the expression of type II collagen by chondrocytes in vitro, but injection of TGF-β₁, into the periosteum in vivo increases type II collagen mRNA levels and initiates chondrogenesis.⁽¹⁾ We examined the effect of TGF-β₁, on collagen gene expression in a bovine periosteum-derived cell culture system to evaluate its direct effect on the periosteum. Cultured cells expressed alkaline phosphatase and collagen proα₁,(I) and proα₁(II) mRNAs. A low level of type II collagen synthesis was demonstrated by immunoprecipitation. TGF-β₁, had no effect on periosteal cell proliferation. Expression of collagen proα₁(I) mRNA did not change with TGF-β₁, treatment, but alkaline phosphatase mRNA showed a dose-dependent decrease. Expression of collagen proα₁(II) mRNA was stimulated 2.7-fold by TGF-β₁. TGF-β₁, also caused a 2.6-fold increase in type II collagen synthesis by immunoprecipitation. These findings indicate that TGF-β₁ is an enhancer of the expression of the chondrocyte phenotype of the periosteal cells and suggest that TGF-β₁, is important in initiating and promoting cartilage formation in vivo.