In this experiment, the suppression of 5 or B1 integrin expres sion resulted in significant reduction of type I and type III procollagen expression, while their suppression Vandetanib did not alter the expression of type II procollagen or aggrecan. An MTT assay confirmed that cell viability was little affected Inhibitors,Modulators,Libraries by the introduction of siRNAs for either integrin gene. We then examined whether the change of cell shape after plating was affected by RNAi for 5 or B1 integrin, and confirmed our previous observation that these integrins were unlikely to be involved in the change of cell mor phology. 5 and B1 integrins form a func tional heterodimer on a cell. These results thus suggest a possibility that 5B1 integrin may promote the induction of type I and type III procollagen expression in dediffe rentiating chondrocytes.

5B1 integrin induces noncartilaginous procollagen gene expression through the activation of PI3K AKT signaling in dedifferentiating chondrocytes When bound to ligands, an integrin heterodimer activates intracellular signaling to induce a cellular response. Inhibitors,Modulators,Libraries We thus next attempted to determine the signal pathway activated by 5B1 integrin and induces the expression of the noncartilaginous procollagens. For this, monolayer cultured chondrocytes were treated with a panel of specific signal inhibitors, and the change in gene expression was evaluated. In this experiment, Wortmannin and LY294002, inhibitors for phosphatidylinositol 3 kinase, were found to reduce the expression of type I and type III procollagen in dedifferentiating chondrocytes, without changing Inhibitors,Modulators,Libraries the ex pression of type II procollagen or aggrecan.

The expression of type I and Inhibitors,Modulators,Libraries type III procollagen was also suppressed by SB202190 and SB203580 that inhibit p38 signaling, but these inhibitors suppressed the expression of type II collagen and aggrecan as well, indicating that p38 signaling Inhibitors,Modulators,Libraries may not be responsible for the induction of type I and type III procollagen expression during dedifferenti ation. Inhibition of c Jun N terminal kinase by SP600125 obviously enhanced type III procollagen expression with out affecting type I procollagen expression. Meanwhile, in hibition of protein kinase C by GF109203X did not cause any significant change in the expression of either gene in vestigated here. From this result, phosphoinositide 3 kinase AKT signaling was considered to be involved in the induction of the noncartilaginous procollagen expression.

To examine this possibility, the experiment was repeated using two specific inhibitors for AKT phosphorylation, and consistent results were obtained. Based upon these results, we evaluated levels of AKT phosphorylation in monolayer cultured chondrocytes at 2 and 7 days after plating, and confirmed that the phos phorylation was in fact promoted during www.selleckchem.com/products/CP-690550.html that period.