APEX1 deficiency impairs oocytes quality by disrupting mitophagy and activating ferroptosis in diminished ovarian reserve

Diminished ovarian reserve (DOR) is pathological condition characterized by reduced oocyte quantity and quality. Due to the complex etiology and limited therapeutic options, clarifying the underlying molecular mechanisms is critical. Oxidative stress has emerged as a pivotal contributor to DOR pathogenesis, disrupting essential cellular pathways, particularly by compromising protective mitophagy and promoting destructive ferroptosis. Identifying central molecular regulators that mitigate these oxidative stress-linked processes offers promising therapeutic potential for preserving ovarian reserve. The redox-sensitive transcriptional co-activator and DNA repair protein Apurinic/apyrimidinic endonuclease 1 (APEX1) represents a compelling candidate, given its established functions in maintaining genomic integrity and regulating cellular stress responses. Human granulosa cells (hGCs) were isolated from follicular fluids obtained during oocyte retrieval for quantification of APEX1 expression. siRNA was transfected into human ovarian granulosa-like tumor cell line (KGN cells) to assess the impact on proliferation, apoptosis, mitochondrial function, mitophagy, and ferroptosis, using CCK-8 assay, Annexin V-FITC/PI flow cytometry, JC-1 and DCFH-DA staining, and Western blotting. In vivo, APEX1 was overexpressed in mouse ovaries via in situ microinjection of adeno-associated virus (AAV), followed by cyclophosphamide (CTX) exposure to induce ovarian injury. Ovarian reserve, oocyte quality, and iron homeostasis was evaluated by histopathological staining (H&E), follicle counting, superovulation assays, and live-cell fluorescence imaging. APEX1 expression was downregulated in granulosa cells of DOR patients, correlating positively with AMH and negatively with age. In KGN cells, APEX1 knockdown induced apoptosis, suppressed proliferation, and disrupted mitochondrial dysfunction, accompanied by impaired mitophagic flux and ferroptotic activation. APEX1 overexpression ameliorated follicular atresia, restored mitophagic activity, alleviated ferroptosis, preserved mitochondrial homeostasis, and improved oocyte quality in mice. Collectively, APEX1 exerts its protective effects by coordinating mitophagy and inhibiting ferroptosis, thereby sustaining cellular homeostasis and oocyte quality. These results highlight APEX1 as a potential diagnostic biomarker and therapeutic target, offering mechanistic insights in DOR.