ABSTRACT
BACKGROUND: Our previous studies demonstrated that cardiac stem cells (CSCs) transplantation could improve cardiac function in rats with myocardial infarction (MI). However, the overall survival and cardiac differentiation of CSCs were low. OBJECTIVE: To investigate the effect of hypoxia preconditioning on CSCs proliferation and cardiogenic differentiation and the role of hypoxia induced factor-1alpha (HIF-1α)/apelin/putative receptor protein related to the angiotensin receptor AT1 (APJ) pathway in the procedure. METHODS: Cells cultured in vitro experienced exposure to hypoxia (1% O2) for 24 hours. Cardiogenic differentiation was induced by using 5-azacytidine for another 24 hours. Then, cells were cultured in normal condition for 2 weeks. Normoxia (20% O2) was used as a negative control during the whole process. Cell proliferation was detected using MTS method and expressions of HIF-1α, apelin, cTnT and APJ were detected using western blot assay after 24 hours of preconditioning and 2 weeks after the induction of differentiation; the percentage of cTnT-positive cardiomyocyte-like cells was observed by immunofluorescence staining. RESULTS AND CONCLUSION: Compared with the normoxia group, the hypoxia group presented a higher proliferation rate and a higher absorbance value at 490 nm (P < 0.01); the protein expressions of HIF-1α, apelin and APJ were all enhanced after hypoxia exposure for 24 hours and 2 weeks after the induction of differentiation (P < 0.01); the percentage of cTnT-positive cells was greatly increased in the hypoxia group (P < 0.01), and the expression of cTnT was also significantly intensified (P < 0.01). To conclude, hypoxia preconditioning could promote the proliferation and cardiogenic differentiation of CSCs, and the activation of HIF-1α/Apelin/APJ pathway might be involved in this process.