Exosomal lncRNA ENSSSCG00000049656 regulates porcine oocyte maturation via the ssc-miR-500-3p/EGLN2 axis

Efficient in vitro maturation (IVM) of mammalian oocytes is essential for breeding and genetic improvement of elite lines. However, porcine embryos generally show lower developmental potential than those of other species. Oocyte maturation and early embryonic development occur within a dynamically changing follicular microenvironment, in which hypoxia critically shapes developmental competence. Redox homeostasis in follicles is indispensable for oocyte development, yet how exosome-derived non-coding RNAs modulate oxidative-stress balance in porcine oocytes remains unclear. Here, high-throughput sequencing and bioinformatic analysis identified the long non-coding RNA (lncRNA) ENSSSCG00000049656 (lnc49656). We then characterized its function using dual-luciferase reporter assays, RNA immunoprecipitation (RIP), quantitative real-time PCR (qRT-PCR), and Western blotting (WB). Overexpressing lnc49656 significantly enhanced cumulus expansion, cleavage, and blastocyst formation (p < 0.05). Comparative cultures under different oxygen tensions showed that, under normoxia, lnc49656 overexpression significantly reduced expression of downstream HIF-1 target genes-Vascular Endothelial Growth Factor (VEGF), Lactate Dehydrogenase A (LDHA), and Glucose Transporter 1 (GLUT1) (p < 0.05); inhibiting lnc49656 or overexpressing ssc-miR-500-3p (miR-500) reversed these effects. Mechanistically, lnc49656 sequestered miR-500, thereby relieving miR-500-mediated repression of Egl nine homolog 2 (EGLN2). As a core component of the oxygen-sensing system, EGLN2 hydroxylates hypoxia-inducible factor-1α (HIF-1α) to promote its degradation, thereby affecting redox homeostasis in the follicular microenvironment. Collectively, these findings indicate that the lnc49656/miR-500/EGLN2 axis is a key regulator of hypoxic responses and oxidative-stress balance during porcine oocyte maturation and early embryonic development, offering a new perspective for dissecting the molecular mechanisms of the follicular microenvironment.