Apoptosis assay
Apoptotic cells in NC, miR-210 mimic and miR-210 inhibitor groups were quantified using the Annexin V-FITC apoptosis detection kit (Beyotime Institute of Biotechnology, Jiangsu, China). Both the attached cells and cells in the supernatant were collected from the above four groups and fixed with 2% paraformaldehyde. They were washed twice with cold phosphate-buffered saline (PBS) and resuspended in 100 μl of the annexin-binding buffer. Then, H9C2 cells were incubated with 2.5 μl of Annexin V for 15 min and analysed using an EPICS XL flow cytometer (Beckman-Coulter, Fullerton, USA). Apoptotic cells were defined as the cells that belonged to the right quadrant (right top + right bottom) in flow cytometry plots. The experiment was independently repeated three times, and an average apoptotic rate was calculated.