Oral Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2014

C-Type natriuretic peptide stimulates the resumption of meiosis in porcine COCs via cGMP-dependant but PKG-independent mechanism. (#34)

Ryan D Rose 1 , Satoshi Sugimura 2 , Hannah M Brown 1 , Jeremy G Thompson 1 , Robert B Gilchrist 3
  1. Robinson Research Institute, School of Paediatrics & Reproductive Health, University of Adelaide, Adelaide, SA, Australia
  2. Institute of Agriculture, Department of Biological Production , Tokyo University of Agriculture and Technology, Tokyo, Japan
  3. School of Women’s & Children’s Health, Discipline of Obstetrics & Gynaecology, University of New South Wales, Sydney, NSW, Australia

Research conducted in recent years has led to great advances in our understanding of the participation of cGMP in meiosis. It is clear that increased intra-oocyte concentrations of cGMP inhibit meiosis in mouse models. Like cAMP, cGMP may also have a meiotic stimulatory function, possibly via cGMP/PKG.
Abattoir derived gilt porcine ovaries were collected, antral follicles aspirated and oocytes collected and cultured in TCM-199 + 3mg/mL BSA. Natriuretic peptide receptor 2 (NPR2) mRNA expression was 2 fold higher in cumulus cells compared to granulosa cells. After 24h of culture CNP increased the proportion of oocytes that resumed meiosis compared to control (main effect. Both 100nM CNP and 1µM 8pCPTcGMP (cGMP analogue) significantly reduced oocyte-cumulus gap junction communication (GJC), as measured by dye transfer, from 12h by 1.7- and 1.85-fold respectively, compared to control (P<0.05). CNP or 8pCPTcGMP significantly increased ERK1/2 phosphorylation (western blot), 2.6- and 3.1-fold respectively, above control (P<0.05). This increase was not affected by PKA or PKG inhibitors, H89 and Rp-8pCPTcGMP, but was eliminated by 10µM AG1478 a selective EGF receptor inhibitor. Neither CNP nor 8pCPTcGMP had any effect on phosphorylation of cAMP-response binding protein (CREB) nor did they affect mRNA expression of EGF-like peptides at 2h culture, compared to control.
0>0>These results demonstrate that CNP stimulates the phosphorylation of ERK1/2, via a cGMP-dependant mechanism requiring EGFR signalling in porcine COCs. This subsequently leads to decreased oocyte-cumulus GJC and the resumption of meiosis. To date, research suggests CNP stimulation of cGMP inhibits meiosis. This is the first study to suggest CNP assists in the resumption of meiosis and the possible mechanism with in the cumulus oocyte complex.