Sperm DNA integrity does play a crucial role for embryo development after ICSI, notably when good-quality oocytes from young donors are used

Based on the inconsistent literature published thus far involving infertile patients, whether intracytoplasmic sperm injection (ICSI) allows overcoming total fertilization failure due to sperm DNA fragmentation is still unclear. Related to this, female factors, which may have a significant impact on assisted reproduction outcomes, can mask male infertility. In this scenario, evaluating ICSI outcomes following cycles using healthy donor gametes could shed light on this realm, as it would avoid the influence of (un)known confounding factors present in infertile individuals. The present work, therefore, aimed to address whether single- and double-stranded sperm DNA fragmentation leads to impaired ICSI outcomes in double gamete donation cycles. The study also compared these double-gamete donation cycles to cycles in which only sperm were donated and oocytes were obtained from infertile patients. Two cohorts were included: (a) the Donor-Donor (DD) cohort, which included 27 semen donor samples used in 49 ICSI cycles with young healthy oocyte donors; and (b) the Donor-Infertile (DI) cohort, which involved 34 semen donor samples used in 57 ICSI cycles with oocytes from patients. Single- and double-stranded sperm DNA breaks were determined with alkaline and neutral Comet assays, respectively; ICSI was conducted following standard protocols and embryos were monitored through time-lapse microscopy. In the DD cohort, the percentage of sperm with high overall DNA damage correlated with fertilization rates (Rs = - 0.666; P < 0.001) and with the percentage of blastocysts per injected oocyte (Rs = - 0.414; P = 0.040). In addition, sperm DNA damage delayed the first embryo division (Rs = 0.421; P = 0.036), and development from the 8-cell to the morula stage (Rs = 0.424; P = 0.034). In contrast, double-stranded DNA breaks had no effect in this cohort. As far as the DI cohort is concerned, while overall sperm DNA damage was not found to be correlated to fertilization or blastocyst rates, pronuclei formation following ICSI was delayed when the incidence of double-stranded DNA breaks was high (Rs = 0.485; P = 0.005). In conclusion, this study, which is the first involving double donation cycles (i.e., a donor-donor cohort), supports that sperm DNA damage has a detrimental impact on fertilization rates after ICSI, and delays embryo development. Moreover, the use of oocytes from infertile individuals is suggested to hide the male-factor effect.

Do donor spermatozoa improve reproductive outcomes after oocyte donation failure? A retrospective analysis of cumulative live birth rates per donor oocyte consumed

RESEARCH QUESTION

Do donor spermatozoa improve IVF outcomes after first oocyte donation failure?

DESIGN

Retrospective, multicentre study including couples undergoing oocyte donation cycles using autologous or donor spermatozoa after a failed first attempt. Male partners were further characterized as normozoospermic or oligoasthenoteratospermic, i.e. fewer than 5 million motile progressive spermatozoa in the ejaculate. The main outcomes measured were live birth rate (LBR) per embryo transfer, LBR per number of embryos transferred, and cumulative LBR (CLBR) considering oocytes consumed in the previous donation cycles.

RESULTS

Analysis comprised 6065 cycles of oocyte donation failure; among these, subgroup analyses by sperm quality comprised 4113 cycles with severe male factor and 1150 cycles with suboptimal/normal spermatozoa. Sperm replacement in the first cycle after failure increased LBR per embryo transfer (OR 2.21, 95% CI 1.7-2.8, P < 0.001) and per number of embryos transferred (OR 2.46, 95% CI 1.9-3.1, P < 0.001) for normospermic and oligoasthenoteratospermic men. Replacement by the third cycle after failure was less beneficial (LBR per embryo transfer: OR 1.35, 95% CI 0.9-2.1, P = 0.16; LBR per embryos transferred: OR 1.33, 95% CI 0.9-2.0, P = 0.186). Kaplan-Meier curves of CLBR per oocyte fertilized with autologous or donor spermatozoa were statistically different (P < 0.001) and demonstrate how each additional oocyte may affect success based on sperm source (donor/autologous).

CONCLUSIONS

Donor spermatozoa improved outcomes when used after an initial failed oocyte donation cycle. The CLBR curves can be used to determine the cumulative chances of live birth using either autologous or donor spermatozoa, providing guidance on when to replace spermatozoa.