Differential regulation of biglycan and decorin synthesis by connective tissue growth factor in cultured vascular endothelial cells

It is possible that connective tissue growth factor (CTGF) serves as either an independent regulator or a downstream effector of transforming growth factor-β (TGF-β) on the proteoglycan synthesis in vascular endothelial cells. Since TGF-β regulates endothelial proteoglycan synthesis in a cell density-dependent manner, dense and sparse cultures of bovine aortic endothelial cells were metabolically labeled with [ ³⁵S]sulfate or ³⁵S-labeled amino acids in the presence of CTGF, and the labeled proteoglycans were characterized by biochemical techniques. The results indicate that CTGF suppresses the synthesis of biglycan but newly induced that of decorin in the cells when the cell density is low; in addition, no change was observed in the hydrodynamic size and the glycosaminoglycan chain length of these two small chondroitin/dermatan sulfate proteoglycans. The regulation of endothelial proteoglycan synthesis by CTGF is completely different from that by TGF-β, suggesting that CTGF is not a downstream effector of TGF-β but an independent regulator in vascular endothelial cells with respect to the proteoglycan synthesis.