Chondrocytes produce many types of ECM to maintain elasticity and plasticity in articular cartilage of revolute joints. Both transforming growth factor β (TGF-β) and bone morphogenetic proteins (BMPs) induce extracellular matrix proteins such as type IIα1 collagen and aggrecan during chondrogenic differentiation in vitro. However, differences in the matrix gene expression pattern by the stimulation of TGF-βs and BMPs remains unclear. In the present study, we created a customized PCR-based ECM array to investigate the pattern of ECM expression genes in the chondrocyte progenitor cell line ATDC5, that was stimulated by TGF-βs or BMPs. Fibronectin (Fn) expression was drastically induced after TGF-β stimulation, but not BMP-4. Epidermal growth factor receptor (Egfr) gene was also significantly activated in TGF-β1-induced chondrogenic differentiation as compared to BMP-4-mediated differentiation. Furthermore, EGFR-knockdown assay of the cells showed decreasing Fn expression during TGF-β1-induced chondrogenic differentiation. These data indicated that Egfr gene activation by TGF-β is involved in the differences in the expression of cellular matrix genes such as Fn, as compared to the expression pattern induced by BMPs.

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