Distinct post-insemination dynamics between fresh and frozen-derived gametes using testicular sperm

Abstract

PurposeTo evaluate differences in post-insemination events between fresh and frozen-derived gametes when testicular sperm extraction (TESE) is used.MethodA retrospective cohort study including 980 oocytes retrieved across 72 cycles from 30 couples, between January 2017 and September 2023. Gamete sources were fresh (fresh-TESE) or frozen-thawed-TESE (frozen-TESE) from the same patients with non-obstructive azoospermia (NOA), and fresh or vitrified (frozen) oocytes from the same female partner. Following insemination by TESE-sperm, embryos were cultured in a time-lapse (TL) incubator. Resulting blastocysts underwent trophectoderm (TE) biopsy for preimplantation genetic testing for aneuploidy (PGT-A) by next-generation sequencing (NGS). Fertilization, usable blastocysts, and euploidy rates were recorded, and morphokinetic key parameters were annotated.ResultsOocyte/sperm dyads using frozen-TESE showed an association with lower fertilization (OR 0.64, 95% CI 0.45-0.89, P = 0.008) and lower blastulation/MII (OR 0.53, 95% CI 0.37-0.77, P = 0.001), but similar blastulation/2PN (OR 0.69, 95% CI 0.45-1.07, P = 0.09). After accounting for female age, euploidy per tested blastocyst was similar whether fresh or frozen-TESE was used, but frozen oocyte use showed no association with these outcomes. The use of frozen dyads was associated with longer duration of 2PN after tPNa to tPNf: in frozen-TESE, 2.10 h longer (95% CI 0.55-3.64, P = 0.008) and in vitrified oocytes, 2.34 h longer (95% CI 0.31-4.36, P = 0.024). Slight morphokinetic differences between fresh and frozen-TESE were observed during subsequent developmental stages.ConclusionsSynchronizing fresh-TESE with oocyte retrieval, when possible, appears safer to maximize fertilization rates. Regardless of the gamete type, frozen-sourced sperm or oocyte impact 2PN-lag time, possibly indicating nuclear repair mechanisms post-freezing, requiring further investigation.