Oral Presentation ESA-SRB-NZSE-CaSR 2026 in conjunction with ENSA

Proteomic insights into the mechanisms driving oocyte quality in the context of hormonal stimulation and clinical IVM systems (143812)

Emily R Frost 1 , Ananya Vuyyuru 1 , Anne Poljak 2 , Bettina P Mihalas 1 , Lindsay E Wu 3 , Robert B Gilchrist 1
  1. Fertility & Research Centre, Discipline of Women’s Health, School of Clinical Medicine, 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

Background:
Within the ovarian follicle, mammalian oocytes may acquire the ability to support successful fertilisation and embryonic development, termed oocyte developmental competence. The specific molecular mechanisms that constitute developmental competence remain unknown, limiting our capacity to assess or enhance oocyte quality both in research and in clinical assisted reproduction. A novel oocyte in vitro maturation system (CAPA-IVM) provides the oocyte with extended time in vitro to acquire developmental competence, with improved success rates in mice and humans.

Methods:
C57Bl/6J mice were used to obtain cumulus-oocyte complexes (COCs) in various germinal vesicle (GV) states [Unstimulated, 23hr PMSG stimulated, CAPA pre-IVM and 46hr PMSG stimulated] and mature (MII) oocytes matured in vivo or by IVM. Mass spectrometry was performed on pooled oocyte and cumulus cells (n=4), with orthogonal validation of protein targets using immunocytochemistry (n=3, 5-15 COCs per replicate).

Results:
Differential expression and pattern analysis collectively revealed a signature of proteins that were consistently differentially expressed between in vivo and IVM matured oocytes, and between GV oocytes receiving various hormonal stimulation treatments (log2FC of ± 1 and a p-value ≤ 0.05). In MII oocytes, EIF2A (protein abundance PA 6.64FC p=3.56E-16; fluorescence intensity FI 1.36-fold p=0.0025) and RPL24 (PA 1.09FC p=0.0003; FI 1.29-fold p=0.0003) were elevated in vivo, linking aberrant translation to IVM. IVM cumulus cells showed dysregulation in their ability to detoxify reactive oxygen species and regulate serine biosynthesis, with FDX1 decreased (PA 1.88FC p=2.98E-11, FI 5.83-fold p <0.0001) and PHGDH elevated (PA 1.61FC p=9.26742E-09, FI 1.81-fold p=0.0023). In GV COCs, proteomics identified 1528 oocyte and 2939 cumulus proteins respectively, with validation underway to uncover key developmental competence proteins earlier in folliculogenesis.

Conclusions:
Together these findings suggest that profiling the proteome in cumulus cells and oocytes under different physiological states provides insight into the mechanisms underpinning oocyte quality in clinically relevant protocols.