Role of Collagen in Retinoic Acid-induced Differentiation and Down-regulation of TGF-β Receptors in Rat Preosteoblastic RCT-1 Cells

Abstract

Retinoic acid induces differentiation of preosteoblastic cells. We have demonstrated that osteoblastic differentiation and down-regulation of transforming growth factor (TGF)-β receptors requires the interaction of type I collagen with α2β1 integrin (J Biol Chem 271: 3938-3944, 1996). The purpose of this study was to clarify the role of collagen in retinoic acid-induced differentiation and down-regulation of TGF-β receptors using preosteoblastic RCT-1 cells. Retinoic acid enhanced the expression of alkaline phosphatase and type I collagen, and reduced TGF-β receptors in these cells. Inhibiting collagen synthesis abolished these changes. Because TGF-β inhibits osteoblastic differentiation, the changes described here may contribute to the osteoblastic differentiation by retinoic acid.