L26/P-151 Exploring morphometric and morphodynamic profiles of rescued germinal vesicle (GV) oocytes: a pilot study in the clinical setting

Le résumé fourni par la source

Abstract Study question Which morphometric and morphodynamic features are associated with germinal vesicle (GV) oocyte rescue to metaphase-II (rMII) stage and subsequent developmental competence to blastocyst? Summary answer Larger GV-oocyte size and faster GV breakdown (GVBD) timing are associated with higher rescue rate. Larger rMII-oocyte size is also associated with higher blastulation rate. What is known already Immature oocytes retrieved during ovarian stimulation are discarded because of their reduced developmental competence. In some IVF cycles, the proportion of immature oocytes might exceed the expected rate of approximately 20%, raising interest in rescue in vitro maturation (rescue-IVM), particularly in patients with poor reproductive prognosis. Although studies suggest that GV-rescue may increase the number of oocytes available for treatment, its clinical value remains unclear. In addition, rescue-IVM is still debated due to heterogeneous laboratory practices and the absence of cumulus-cells during IVM, which may impair oocyte competence. However, time-lapse technology hold promises for predicting the developmental potential of GV-oocytes. Study design, size, duration Retrospective study (2017–2024) analysing GV-rescue in 20 women (35.4±2.7 years) undergoing ICSI, obtaining ≤6 MII-oocytes, <80% maturity relative to ≥ 14-mm follicles at trigger, and ≥4 GV-oocytes. GV-oocytes (N = 93) were cultured in EmbryoScope for ≤24 hours and, if rescued, inseminated and cultured to blastocyst. GV-oocytes’ morphometrics were tested for associations with rescue and blastulation. rMII oocytes’ morphometrics and fertilization dynamics were tested for associations with blastulation and compared to sibling-MII (N = 58). Participants/materials, setting, methods Cumulus-oocyte-complexes were cultured for 4hours before denudation. GV-oocytes reaching rMII within 24hours were inseminated ≤4hours from first polar-body (PB1) extrusion with the same ejaculate produced the day before. Morphometrics (zona-pellucida [ZP] thickness, areas of oocytes, GV and PBs) and morphodynamics (maturation: GVBD and PB1 extrusion; fertilization: PB2 extrusion, cytoplasmic-wave emergence, PN-appearance, juxtaposition and fading, cytoplasmic-halo and cleavage; preimplantation-development: 2cell to blastocyst timings including developmental anomalies [e.g., multinucleation, fragmentation, direct-cleavage]) were manually annotated (EmbryoViewer/ImageJ). Main results and the role of chance 46 (49.5%) GV-oocytes remained arrested or progressed the MI stage, while 47 (50.5%) reached rMII. Successfully rescued GV-oocytes versus arrested/MI showed larger area (9128±767µm² versus 8590±820µm²; p = 0.002) and ZP-thickness (19±3µm versus 17±3µm; p = 0.015). They also showed lower prevalence of cytoplasmic granularity (33% versus 68%; p = 0.018). When compared to the 12 GV-oocytes resuming meiosis but arresting at MI stage, successfully rescued GV-oocytes showed faster GVBD timing (6±5hours versus 16±9; p < 0.001). rMII were smaller than sibling-MII (area: 8775±820µm² versus 9752±1030µm², p < 0.001). The only different fertilization timing was a shorter cytoplasmic halo appearance (8±2hours versus 10±3hours; p = 0.003). rMII blastulation rate was 19% (N = 9/47) versus 67% for sibling-MII (N = 39/58; p < 0.001). Only rMII-oocyte area was associated with blastulation rate (developmentally-competent 9285±840µm² versus arrested 8655±778µm²; p = 0.037). Meiosis progression (or rescue) and fertilization timings were instead similar between developmentally-competent and incompetent rMII. Among embryos that progressed to the blastocyst stage, no differences were observed between rMII- and sibling MII-derived embryos across all morphometric and morphodynamic features analyzed. Limitations, reasons for caution The design is retrospective at a private IVF center. The sample size is limited because GV-rescue cannot still be considered standard clinical practice and our inclusion criteria were very strict. Nevertheless, these data are valuable as they were produced in a clinical setting. Wider implications of the findings GV-rescue represents a patient-centred strategy that measurably increases cumulative success in cycles with limited mature oocyte yield. Emerging AI-tools integrated with time-lapse monitoring can support the development of predictive models of GV-oocytes’ competence, assisting decision-making regarding rescue-IVM. Our preliminary data support further studies to this end. Trial registration number No

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.