Granulosa cell mevalonate pathway abnormalities contribute to oocyte meiotic defects and aneuploidy

With aging, abnormalities during oocyte meiosis become more prevalent. However, the mechanisms of aging-related oocyte aneuploidy are not fully understood. Here we performed Hi-C and SMART-seq of oocytes from young and old mice and reveal decreases in chromosome condensation and disrupted meiosis-associated gene expression in metaphase I oocytes from aged mice. Further transcriptomic analysis showed that meiotic maturation in young oocytes was correlated with robust increases in mevalonate (MVA) pathway gene expression in oocyte-surrounding granulosa cells (GCs), which was largely downregulated in aged GCs. Inhibition of MVA metabolism in GCs by statins resulted in marked meiotic defects and aneuploidy in young cumulus-oocyte complexes. Correspondingly, supplementation with the MVA isoprenoid geranylgeraniol ameliorated oocyte meiotic defects and aneuploidy in aged mice. Mechanically, we showed that geranylgeraniol activated LHR/EGF signaling in aged GCs and enhanced the meiosis-associated gene expression in oocytes. Collectively, we demonstrate that the MVA pathway in GCs is a critical regulator of meiotic maturation and euploidy in oocytes, and age-associated MVA pathway abnormalities contribute to oocyte meiotic defects and aneuploidy.