miR-27b-3p Exacerbates VCD-Induced KGN Cell Injury by Targeting PAPPA to Suppress IGF-1 Release and Inhibit the PI3K/AKT Pathway

Background/Objectives: While currently termed premature ovarian insufficiency (POI), premature ovarian failure (POF) remains a prominent driver of female infertility with a molecular pathogenesis that is still lacking comprehensive clarification. In in vitro studies, the pathology of POI is commonly simulated through a well-characterized model involving VCD (4-vinylcyclohexene diepoxide)-mediated cytotoxicity within KGN-derived human granulosa cells. However, the key regulatory molecular networks involved in this process are still poorly characterized. Although microRNAs (miRNAs) have emerged as critical regulators in ovarian function decline, the specific role and underlying mechanism of miR-27b-3p in POI remain elusive. Methods: A VCD-induced KGN cell injury model was established by treating cells with 1.0 mM VCD for 24 h. Cell viability, apoptosis rate, and miR-27b-3p expression were assessed by CCK-8 assay, flow cytometry, and RT-qPCR, respectively. Overexpression and targeted suppression of miR-27b-3p were achieved by introducing its specific mimics and inhibitors, respectively. Target identification was conducted via bioinformatic prediction, EdU incorporation, Western blot, and dual-luciferase reporter assays. Functional rescue experiments were carried out by co-transfection with a PAPPA-overexpressing plasmid (oe-PAPPA). IGF-1 secretion was quantified by ELISA, and phosphorylation of IGF1R and AKT was analyzed by Western blot to determine whether miR-27b-3p modulates cellular phenotypes via the PAPPA–IGF-1–PI3K/AKT axis. Exogenous IGF-1 supplementation was further applied to confirm pathway dependence. Results: VCD treatment dose-dependently restrained cellular growth and stimulated apoptotic pathways in KGN cells; paralleling these phenotypic changes, miR-27b-3p abundance was remarkably increased. Ectopic expression of miR-27b-3p exacerbated VCD-induced growth inhibition and apoptosis, whereas its inhibition conferred cytoprotective effects. Through the integration of computational predictions and dual-luciferase reporter systems, PAPPA was definitively established as a direct downstream target of miR-27b-3p. miR-27b-3p negatively regulated both PAPPA mRNA and protein levels, thereby impairing PAPPA-mediated cleavage of IGF-binding proteins (e.g., IGFBP4) and subsequent release of free IGF-1. This led to reduced IGF-1 secretion and significantly diminished phosphorylation of IGF1R and AKT. Remarkably, PAPPA overexpression effectively reversed the detrimental effects of miR-27b-3p, and exogenous IGF-1 supplementation similarly attenuated miR-27b-3p–mediated proliferation arrest and pro-apoptotic phenotypes. Conclusions: This study uncovers a novel pathogenic mechanism whereby miR-27b-3p exacerbates VCD-induced granulosa cell injury by directly targeting PAPPA, suppressing IGF-1 release, and consequently inhibiting the PI3K/AKT pro-survival signaling pathway. A novel perspective on the fundamental basis of POI is established by this research, which further posits therapeutic manipulation of the miR-27b-3p/PAPPA/IGF-1 module as a prospective treatment for disrupted ovarian function.