[Effect and related mechanism of miRNA-21 on hydrogen peroxide-induced C-kit(+) cardiac stem cells apoptosis]

Objective: To explored the effect and related mechanism of miRNA-21 on hydrogen peroxide-induced C-kit(+) cardiac stem cells apoptosis. Methods: C-kit(+) cardiac stem cells were isolated from SD rats by the methods of enzyme digestion and magnetic bead. Cells were divided into the following experimental groups: (1) negative control mimics (NCM)group: cells were transfected with negative control miRNA-21 mimics for 48 hours; (2)mimics group: cells were transfected with miRNA-21 mimics for 48 hours; (3) NCM+ H(2)O(2) group: negative control miRNA-21 mimics were transfected into cells for 48 hours and then treated with 100 μmol H(2)O(2) for 2 hours; (4)mimics+ H(2)O(2) group: miRNA-21 mimics were transfected into cells for 48 hours and then treated with 100 μmol H(2)O(2) for 2 hours. mRNA of miRNA-21 was detected by RT-PCR. The apoptosis rate of C-kit(+) cardiac stem cells was determined using the annexin V-FITC/PI staining assay. Western blot was employed to measure the expression of apoptosis related proteins(Caspase-3, Bax, and Bcl-2). Results: (1) Compared with the NCM group, the mRNA expression level of miRNA-21 was significantly up-regulated in mimics group, while obviously down-regulated in NCM+ H(2)O(2) group(all P<0.05). Compared with the mimics group, the mRNA expression levels of miRNA-21 in mimics+ H(2)O(2) group was significantly downregulated (P<0.05), but remarkably upregulated compared with the NCM+ H(2)O(2) group(P<0.05). (2) Flow cytometry results indicated that the early apoptosis rates were similar between the NCM group and mimics group ((4.57±3.45)% vs. (5.13±3.21)%, P>0.05). Compared with the NCM group, the early apoptosis rates were remarkably increased ((79.07±5.75)% vs.(4.57±3.45)%, P<0.05) in NCM+ H(2)O(2) group. Compared with the mimics group, the early apoptosis was significantly up-regulated in the mimics+ H(2)O(2) group ((30.27±1.36)% vs.(5.13±3.21)%, P<0.05), which were further down-regulated in mimics+ H(2)O(2) group compared with the NCM+ H(2)O(2) group ((30.27±1.36)% vs.(79.07±5.75)%, P<0.05). (3) Western blot results showed similar protein expression of Caspase-3, Bax and Bcl-2 between NCM group and mimics group(all P>0.05). Compared with the NCM group, the Caspase-3 and Bax protein expression was significantly increased in NCM+ H(2)O(2) group (all P<0.05), but the protein expression level of Bcl-2 was similar between the 2 groups(P>0.05). The Caspase-3 and Bax protein expression was markedly decreased, while Bcl-2 apparently increased in the mimics+ H(2)O(2) group compared with the NCM+ H(2)O(2) group(all P<0.05). Conclusion: Overexpression of miRNA-21 protects the C-kit(+) cardiac stem cells from apoptosis caused by oxidative stress through downregulating proapoptotic and upregulating the antiapoptotic proteins.