MicroRNA-101 protects cardiac fibroblasts from hypoxia-induced apoptosis via inhibition of the TGF-β signaling pathway.

Cardiac fibroblasts (CFs) are the most numerous cells in the heart and are recognized primarily for their ability to maintain both the structural integrity and the physiological functions of the heart. The transforming growth factor beta (TGF-β) signaling pathway is reportedly involved in the modulation of CF functions, including apoptosis. Recent studies have indicated that microRNA-101 (miR-101) attenuates the TGF-β signaling pathway, either by inhibiting the expression of TGFβ1 or by targeting transforming growth factor-β receptor type I (TGFβRI). The present study aimed to determine whether miR-101 protects CFs from hypoxia-induced apoptosis and to investigate the mechanisms underlying its protective effects. The CCK-8 test, electron microscopy and TUNEL assay results demonstrated that miR-101a/b significantly inhibited hypoxia-induced CF apoptosis. The results of Western blotting, quantitative RT-PCR and immunofluorescence assays indicated that miR-101a dramatically inhibited the hypoxia-induced up-regulation of both TGFβRI and p-Smad 3 but not TGFβ1 in CFs. Additionally, miR-101a significantly reversed the hypoxia-induced up-regulation of Bax and Caspase-3, the down-regulation of Bcl-2 and the activation of Caspase-3 in CFs. Moreover, miR-101a markedly inhibited the intracellular Ca(2+) ([Ca(2+)]i) overload caused by hypoxia. Taken together, our results suggest that miR-101a protects CFs against hypoxia-induced apoptosis by inhibiting the TGF-β signaling pathway, which may be a potential therapeutic target for heart injury.