Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

A proteomic signature of mouse oocyte developmental competence gained from in vivo and in vitro systems (#164)

Emily R Frost 1 , Dulama Richani 1 , Anne Poljak 2 , Xuihua Liao 1 , Amelia Brown 1 , Joelene Greasby 1 , Bettina P Mihalas 1 , Irene E Sucquart 1 , Kaushiki Kadam 1 , Lindsay E Wu 3 , Robert B Gilchrist 1
  1. Fertility & Research Centre, University of New South Wales, Sydney, NSW, Australia
  2. Bioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW, Australia
  3. School of Biomedical Sciences, University of New South Wales, Sydney, NSW, Australia

Within the ovarian follicle, mammalian oocytes acquire the necessary molecular machinery for successful fertilisation and embryonic development. In the absence of the follicle, oocytes matured in vitro (IVM) using traditional IVM show compromised developmental competence, resulting in poorer outcomes for patients. A novel in vitro system (CAPA-IVM) using c-type natriuretic peptide provides the oocyte with extended time to develop, with improved success rates. In this study, we compared cumulus-oocyte complexes (COCs) matured in vivo, or in vitro during CAPA-IVM and traditional IVM. Mature oocytes underwent IVF to assess developmental competence. Day-6 blastocyst rates were decreased in the two in vitro groups (CAPA-IVM 50.3±5.9% and IVM 37.1±5.0%), compared with in vivo developed oocytes (84.3%±5.0%; p<0.01). Proteomic analyses of oocytes and cumulus cells (CCs) from both immature and mature oocytes were performed across all groups. Heatmap and differential expression analysis revealed a subset of proteins that were consistently altered in both IVM groups compared to in vivo (27 proteins in oocytes and 125 proteins in CCs). In oocytes, the 27 proteins were associated with biological pathways including ribosome biogenesis, microRNA processing and intermediate filament organisation. In CCs, dysregulation of transcription factors and extracellular matrix pathways are associated with the 125 proteins changed in both IVM systems. This suggests that the IVM systems are insufficient at the regulation of these processes compared with those occurring in vivo. However, histones and proteins involved in DNA damage response are consistently expressed between in vivo COCs and CAPA COCs, when compared with IVM COCs. Together these findings suggest that while CAPA-IVM ameliorates some of the deficiencies of underdeveloped COCs, there are key components of oocyte developmental competence that need to be further supported in vitro. Profiling the proteome in CCs and oocytes under different physiological states provides some insight into the mechanisms that establish oocyte quality.