Fig. 3. miR-9 prevents cardiomyocyte apoptosis in response to H₂O₂.

a Downregulation of miR-9 level in MI mice heart (n = 8). **P < 0.01 by Student’s t-test. Data are presented as mean ± SEM. b Elevation of miR-9 level in NRVMs treated with 200 μM H₂O₂ for 4 h (n = 8). **P < 0.01 by Student’s t-test. Data are presented as mean ± SEM. NRVMs were transfected with NC (negative control), miR-9, AMO-9, or miR-9 + AMO-9 for 24 h, then treated with H₂O₂ (200 μM) for 4 h. c Restoration of cell viability by miR-9 in NRVMs treated with 200 μM H₂O₂ for 4 h, determined MTT assay (n = 6). **P < 0.01 by one-way ANOVA analysis with Tukey’s multiple comparison test. Data are presented as mean ± SEM. d Representative images of TUNEL staining of NRVMs for DNA defragmentation showing the apoptotic cells (scale bar: 60 μm). e Statistical results of TUNEL-positive cells per field indicating the suppression of H₂O₂-induced cell apoptosis by miR-9 (n = 6). **P < 0.01 by one-way ANOVA analysis with Tukey’s multiple comparison test. Data are presented as mean ± SEM. f Abolishment of H₂O₂-induced expression upregulation of Bax by miR-9 overexpression (n = 6). *P < 0.05, **P < 0.01 by one-way ANOVA analysis with Tukey’s multiple comparison test. Data are presented as mean ± SEM. g Abolishment of H₂O₂-induced expression downregulation of Bcl-2 by miR-9 overexpression (n = 6). **P < 0.01 by one-way ANOVA analysis with Tukey’s multiple comparison test. Data are presented as mean ± SEM. h Decrease of cleaved-caspase-3 (C-Casp3) by miR-9 in the presence of H₂O₂ (n = 4). *P < 0.05 by one-way ANOVA analysis with Tukey’s multiple comparison test. Data are presented as mean ± SEM. i Upper panels show representative fluorescent images of JC-1 monomeric mitochondria showing green fluorescence and JC-1 aggregated mitochondria from Control, H₂O₂, H₂O₂ + NC, H₂O₂ + miR-9, and H₂O₂ + miR-9 + AMO-9 groups (scale bar: 60 μm). j Reduction of H₂O₂-induced JC-1 staining by miR-9 overexpression (n = 5). **P < 0.01 by one-way ANOVA analysis with Tukey’s multiple comparison test. Data are presented as mean ± SEM.