ESA-SRB-AOTA 2019

Prematuration culture with c-type natriuretic peptide improves cumulus function and oocyte quality during minimal stimulation IVM in mice (#195)

Dulama Richani 1 , Yiqing Zhao 1 2 , Xiuhua Liao 1 3 , Adriana E Krysta 1 , Michael J Bertoldo 1 4 , Anne Poljak 5 , Robert B Gilchrist 1
  1. Fertility & Research Centre, School of Women’s and Children’s Health, University of New South Wales Sydney, Kensington, New South Wales, Australia
  2. Reproductive Medicine Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
  3. Reproductive Medicine Center, Fujian Provincial Maternity and Children’s Hospital, Fuzhou, China
  4. Laboratory for Ageing Research, School of Medical Sciences, University of New South Wales Sydney, Kensington, New South Wales, Australia
  5. Bioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical Centre, University of New South Wales Sydney, Kensington, NSW, Australia

Oocyte in vitro maturation (IVM) is an attractive reproductive technology as it brings significant benefits to patients, however it is not practiced widely due to lower success rates than IVF. Oocyte pre-IVM using c-type natriuretic peptide (CNP) is an innovative new IVM system currently undergoing clinical evaluation. This study aimed to determine temporal effects of CNP-mediated pre-IVM on cumulus cell function and oocyte developmental competence in mildly-stimulated mice. Immature cumulus oocyte complexes (COCs) derived from mildly stimulated (23h PMSG) 28-day old mice were cultured for 0-24h in pre-IVM medium (CNP+E2+FSH+insulin), prior to IVM/IVF. Subsequent embryo development and quality post-IVM/IVF was assessed. Day-6 blastocyst rate increased incrementally with increasing pre-IVM duration: 40.6±2.0%, 45.8±1.2%, 52.2±3.5%, 53.3±5.9% and 59.9±2.5% for 0, 2, 6, 12 and 24h pre-IVM, respectively (P<0.01). DNA content/COC, a measure of cumulus cell proliferation, was significantly higher in 24h pre-IVM group compared to 0, 2, and 6, but not the 12h, pre-IVM groups (P<0.001). Pre-IVM for 24h significantly increased cumulus expansion and mRNA expression of matrix genes Has2 and Tnfaip6 relative to no pre-IVM control (P<0.01). Cumulus-oocyte gap-junctional communication (GJC) was maintained throughout 24h pre-IVM (P<0.0001), and GJC loss was slowed during the subsequent IVM phase, whilst meiotic resumption was accelerated (P<0.05). Pre-IVM increased COC ATP and ADP content (P<0.05), but not AMP, ATP/ADP and energy charge. In conclusion, this study demonstrates that CNP-mediated pre-IVM improves the quality of IVM oocytes in a temporally-dependent manner and significantly influences cumulus cell function including increased cell proliferation, cumulus expansion, and prolonged cumulus-oocyte GJC. To identify the protein signatures reflecting enhanced COC developmental competence endowed by CNP pre-IVM, investigation into the oocyte and cumulus cell proteomes using tandem mass spectrometry is currently underway.