T3 peptide, a fragment of tumstatin, stimulates proliferation and migration of cardiac fibroblasts through activation of Akt signaling pathway.

Proliferation and migration of cardiac fibroblasts are important in early stage of wound-healing after myocardial infarction. The effects of tumstatin, a cleaved fragment of collagen type IV α3 chain, on these functions of cardiac fibroblasts have not been clarified. In this study, we examined it by using T3 peptide, an active fragment of tumstatin. Cardiac fibroblasts were isolated from ventricles of adult male Wistar rats. Proliferation was examined by a cell counting assay. Boyden chamber assay was performed to examine migration. Expression and phosphorylation of proteins were determined by Western blotting. T3 peptide (300 ng/ml, 24 h) significantly increased proliferation and migration of cardiac fibroblasts. T3 peptide (300 ng/ml, 30 min) significantly increased Akt (Ser473) phosphorylation. LY294002 (10 μM, 30 min pretreatment), a phosphoinositide 3-kinase (PI3K)/Akt inhibitor, significantly inhibited the T3 peptide-induced proliferation, migration, and activation of Akt signaling pathway in cardiac fibroblasts. Cilengitide, an inhibitor of integrin αvβ3/αvβ5, suppressed Akt phosphorylation and proliferation of cardiac fibroblasts. Expression of tumstatin decreased in the infarcted area of rat model of myocardial infarction. We for the first time demonstrated that T3 peptide stimulates proliferation and migration at least partly through the activation of PI3K/Akt signaling pathway via binding integrin αvβ3/αvβ5 in adult rat cardiac fibroblasts. These results indicate that tumstatin promotes the initial stage of wound-healing through activation of cardiac fibroblasts after myocardial infarction.