miR-204 restoration decreases [Ca²⁺]_i and depolarizes mitochondrial membrane potential. (A–C) Analysis of [Ca²⁺]_i (Fluo3-AM) and cell proliferation (PCNA nuclear localization) of PASMCs from PAH and control (Ctrl) patients. miR-204 antagomir (Inh) and mimics, VIVIT (NFAT competitor peptide), and PP2 (Src inhibitor) compared with PP3, its negative control, STAT3 siRNA, SHP2 siRNA, and appropriate controls for each treatment were added as indicated (n = 50–150 cells/patient in three PAH and five control patients). (D–F) Analysis of the mitochondrial membrane potential (ΔΨ_m; TMRM) and serum starvation–induced apoptosis (TUNEL staining) of PASMCs from PAH and control patients. miR-204 antagomir (Inh) and mimics, VIVIT (NFAT competitor peptide), PP2 (Src inhibitor), STAT3 siRNA, SHP2 siRNA, and appropriate controls for each treatment were added as indicated (n = 50–150 cells/patient in three PAH and five control patients). F.U., fluorescence unit. Graphs represent means ± SEM (*, P < 0.05; **, P < 0.01; ***, P < 0.001).