Supplementation with C-type natriuretic peptide during pre-in vitro maturation regulates key aspects of cumulus cell physiology in cattle.

The present study evaluated the effect of supplementation of C-type natriuretic peptide (CNP) during the pre-in vitro maturation (IVM) period on proliferation, apoptosis and steroidogenesis in cumulus cell (CCs) surrounding the bovine oocyte. We observed that CNP (200 nM) supplementation for 6 h during pre-IVM promoted proliferation and suppressed apoptosis and increased progesterone (P4) and estrogen (E2) production. CNP also upregulated the expression of genes related to proliferation (CDC42, CCND and PCNA),anti-apoptosis (BCL2) and steroidogenesis (StAR, 3β-HSD, CYP11A1 and CYP19A1) in CCs following cumulus-oocyte complexes (COCs) maturation in vitro, whereas the expression levels of pro-apoptosis (CASPASE-3 and BAX) were downregulated. Importantly, low-input transcriptome analysis revealed that the beneficial effect of CNP on physiological functions of bovine CCs might be mediated by regulating mitochondrial function, antioxidant defense system and lipid metabolism. Specifically, CNP pre-IVM significantly increased mitochondrial content, mitochondrial membrane potential and activity, and the mRNA expression levels of genes related to mitochondria biogenesis in bovine CCs. Moreover, CNP pre-IVM significantly reduced the levels of ROS, lipid droplets and fatty acids content, and increased the mRNA expression levels of genes related to antioxidant and lipid metabolism in bovine CCs. Collectively, our findings indicate that CNP supplementation during pre-IVM regulates key physiological functions in bovine cumulus cells, including proliferation, apoptosis, and steroidogenesis. Furthermore, this pre-IVM culture regimen enhances mitochondrial function, antioxidant capacity, and lipid metabolism.