P-701 Human embryos diagnosed as mosaic and aneuploid after preimplantation genetic testing for aneuploidy are associated with increased levels of apoptosis in trophectoderm cells

Abstract Study question Are there cell lineage-related differences in the apoptotic rates of human blastocysts classified as euploid, mosaic and aneuploid after preimplantation genetic testing for aneuploidy (PGT-A)? Summary answer In blastocysts, apoptosis is more frequent trophectoderm (TE) cells associated with presence uniform chromosomal alterations. What known already Embryos diagnosed PGT-A can develop into healthy infants. However, reason why these embryos achieve reproductive competence needs further research. One hypothesis that are negatively selected during embryo development through competition mechanisms, such or differential proliferation. While mechanisms have been demonstrated mouse embryos, which occurs frequently inner mass (ICM), evidence scarce. fact, only one previous study has shown an association between mosaicism increased levels apoptosis, was TE cells. design, size, duration Prospective cohort performing colocalization cell-lineage expression markers by immunofluorescence (IF). A total 53 vitrified a diagnosis on day 5 (D5) 6 (D6) were analysed: n = 13 euploid (n 11 D5; 2 D6), 22 16 18 7 D6). All donated research purposes. Participants/materials, setting, methods Following warming re-expansion, fixed 4% paraformaldehyde, processed IF imaged confocal microscopy. Primary antibodies: 1:80 goat anti-human Nanog (AF1997, R&D-Systems), 1:100 Gata3 (MAB6330, R&D-Systems) 1:1000 rabbit Caspase-3 (NB10056113, Novus Biologicals). 165 μM DAPI used nuclei staining. Total cells: DAPI+ TE: Gata3+ ICM: Gata3-/Nanog+ Incidence apoptosis: % Caspase-3+ (per embryo). Data analysed using Chi-square ANOVA (p < 0.05 significant). Main results role chance number similar among (59.2±20.6 78.5±0.7 (49.6±15 58.8±16.9 D6) (48.6±14.2 59.6±23.5 (P > 0.05). evidenced establishment ICM lineages blastocyst stage: while proportion Nanog+ decreased from 38.2% (755/1979) D5 to 20.3% (188/927) D6 0.0001), 77.8% (1540/1979) 83.1% (770/927) 0.01). The persistence status embryo, significantly higher Gata3+/Nanog+ found (27.9%=149/534 4.6%=19/417 compared (13.1%=104/794 3.4%=12/353 (9.7%=63/651 0%=0/157 incidence (45.9%±16.1 49%±15.1 (44.1%±19.6 43%±16.8 (26.6%±16.6 17.5%±14.8 Conversely, much less (2.2%±7.7), no groups Limitations, reasons caution This descriptive, single-centre limited sample size. karyotype concordance not tested. Wider implications findings Our demonstrate common particularly abnormalities support its mechanism eliminate may indeed be related potential embryos. Trial registration Not applicable