MiR-23a represses CELF1 to modulate buffalo granulosa cell apoptosis and steroidogenesis via the PI3K/AKT pathway

MicroRNAs (miRNAs) are critical regulators of mammalian follicle development. Our previous work showed that miR-23a expression was significantly higher in buffalo oocytes at metaphase II (MII) than at the germinal vesicle (GV) stage, implying a role in oocyte maturation. Here, we investigated the function and mechanism of miR-23a in buffalo granulosa cells (GCs). GCs cultured in vitro were transfected with miR-23a mimics or inhibitor. The miR-23a mimic markedly increased apoptosis, reduced estradiol (E2) release, elevated progesterone (P4) secretion, and suppressed the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway, whereas the inhibitor exerted the opposite effects. Dual-luciferase and rescue assays revealed that miR-23a directly targets CUG triplet repeat-binding protein 1 (CELF1). Overexpression of CELF1 reversed the pro-apoptotic effect of miR-23a, restored proliferation, normalized E2 and P4 production, and re-activated PI3K/AKT signaling. Thus, miR-23a targeted CELF1 to inhibit the PI3K/AKT pathway, promoting apoptosis, suppressing proliferation and modulating steroidogenesis in buffalo GCs, thereby controlling follicular homeostasis.