Elevated sperm DNA fragmentation does not predict recurrent implantation failure

DNA damage in testicular germ cells and spermatozoa. When and how is it induced? How should we measure it? What does it mean?

This review surveys the causes and consequences of DNA damage in the male germ line from spermatogonial stem cells to fully differentiated spermatozoa. Within the stem cell population, DNA integrity is well maintained as a result of excellent DNA surveillance and repair; however, a progressive increase in background mutation rates does occur with paternal age possibly as a result of aberrant DNA repair as well as replication error. Once a germ cell has committed to spermatogenesis, it responds to genetic damage via a range of DNA repair pathways or, if this process fails, by the induction of apoptosis. When fully-differentiated spermatozoa are stressed, they also activate a truncated intrinsic apoptotic pathway which results in the activation of nucleases in the mitochondria and cytoplasm; however, the physical architecture of these cells prevents these enzymes from translocating to the nucleus to induce DNA fragmentation. Conversely, hydrogen peroxide released from the sperm midpiece during apoptosis is able to penetrate the nucleus and induce DNA damage. The base excision repair pathway responds to such damage by cleaving oxidized bases from the DNA, leaving abasic sites that are alkali-labile and readily detected with the comet assay. As levels of oxidative stress increase and these cells enter the perimortem, topoisomerase integrated into the sperm chromatin becomes activated by SUMOylation. Such activation may initially facilitate DNA repair by reannealing double strand breaks but ultimately prepares the DNA for destruction by nucleases released from the male reproductive tract. The abasic sites and oxidized base lesions found in live spermatozoa are mutagenic and may increase the mutational load carried by the offspring, particularly in the context of assisted conception. A variety of strategies are described for managing patients expressing high levels of DNA damage in their spermatozoa, to reduce the risks such lesions might pose to offspring health.

Association of embryo aneuploidy and sperm DNA damage in unexplained recurrent implantation failure patients under NGS-based PGT-A cycles

PURPOSE

Recurrent implantation failure (RIF) is one of the most common conditions affecting In Vitro Fertilization (IVF)/Intracytoplasmic sperm injection (ICSI) outcomes. Aneuploidy embryos, one of the main types of embryos-related factors, was reported to be a major contributor to RIF. The present study aimed to examine the association between sperm DNA fragmentation index (DFI) and outcomes of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidy (PGT-A) in unexplained RIF patients.

METHODS

This study analyzed 119 couples with unexplained RIF who underwent 119 PGT-A cycles between January, 2017 and March, 2022. The 119 males were divided into 3 groups according to their sperm DFI levels: Group1 (low, DFI ≤ 15%, n = 50), Group2 (medium, 15% < DFI < 30%, n = 41) and Group3 (high, DFI ≥ 30%, n = 28). Sperm DFI was measured by sperm chromatin structure analysis (SCSA) technique. Trophectoderm biopsy on day 5 or 6 were performed with NGS technique. The following outcomes of PGT-A were analyzed and compared: fertilization, good-quality embryos, aneuploidy rate, miscarriage, live birth and newborn defects.

RESULTS

The component of aneuploidy embryos was significantly higher in high DFI group (42.71%) than that of medium group (28.39%) and low group (27.80%). The miscarriage rate of high DFI group (27.27%) and medium group (14.29%) is significantly higher than that of low group (0.00%). No significant differences were found regarding fertility, good-quality embryo rate, pregnancy rate, live birth rate or newborn defects among three groups.

CONCLUSION

The sperm DNA damage is associated with blastocyst aneuploidy and miscarriage rate in unexplained RIF cases. Embryo selection by PGT-A and efforts to decrease sperm DFI before IVF/ICSI treatments should be considered for those male patients with high DFI.

Sperm DNA integrity is critically impacted by male age but does not influence outcomes of artificial insemination by husband in the Chinese infertile couples

The sperm chromatin structure assay (SCSA) is crucial for assessing male fertility. However, the predictive value of the SCSA parameters, including the DNA fragment indices (DFI) and the percentages of high DNA stainability (HDS), for outcomes of artificial insemination by husband (AIH) remains controversial. This study aims to evaluate the correlations between SCSA parameters and male aging as well as other routine semen parameters, and explore their prognostic powers on AIH outcomes of the Chinese infertile couples. A total of 809 AIH cycles were retrospectively analyzed. The results showed that DFI in the age groups < 35 years were significantly lower than that in the age groups ≥ 35 years (P < 0.001). Meanwhile, there was no statistical difference in HDS between the age groups (P = 0.063). DFI and HDS are negatively correlated with most routine semen parameters (all P < 0.05). The chi-square and generalized linear model tests indicated that neither DFI nor HDS influenced the clinical pregnancy rate of AIH. In summary, this study found that aging is a critical factor leading to increased sperm DFI but not HDS. DFI and HDS are negatively correlated with most semen parameters but do not significantly influence AIH outcomes.

A review of the pathophysiology of recurrent implantation failure

Implantation is a critical step in human reproduction. The success of this step is dependent on a competent blastocyst, receptive endometrium, and successful cross talk between the embryonic and maternal interfaces. Recurrent implantation failure is the lack of implantation after the transfer of several embryo transfers. As the success of in vitro fertilization has increased and failures have become more unacceptable for patients and providers, the literature on recurrent implantation failure has increased. While this clinical phenomenon is often encountered, there is not a universally agreed-on definition-something addressed in an earlier portion of this Views and Reviews. Implantation failure can result from several different factors. In this review, we discuss factors including the maternal immune system, genetics of the embryo and parents, anatomic factors, hematologic factors, reproductive tract microbiome, and endocrine milieu, which factors into embryo and endometrial synchrony. These potential causes are at various stages of research and not all have clear implications or immediately apparent treatment.