Fibronectin-mediated adhesion rescues cell cycle arrest induced by fibroblast growth factor-1 by decreased expression of p21(cip/waf) in human chondrocytes.

In chondrocytes, fibroblast growth factors (FGFs) inhibit chondrocytes proliferation by upregulation of the cell cycle inhibitor p21(cip/waf). In this report, we first investigated the roles of fibronectin (FN)-mediated cell adhesion in the modulation of FGF-1's antiproliferative function in chondrocytes. In this study, we found that FN-mediated signaling could rescue cell cycle arrest induced by FGF-1 in primary human chondrocytes. This prevention of cell cycle arrest induced by FGF-1 was due to the suppression of the cell cycle inhibitor p21(cip/waf) expression on adhesion to FN and its downstream activation of signaling pathways. Finally, we showed that this rescue induced by FN-mediated adhesion is dependent on the extracellular regulated kinase (ERK) signaling pathway. Taken together, these studies support that, despite FGF-FGF receptor's growth-inhibitory function, the FN-mediated signaling can collaborate to compensate for its negative effect on chondrocytes proliferation, providing evidence for cross talk between signals emerging from these cell surface molecules in chondrocyte.