Correlations between elevated basal sperm DNA fragmentation and the clinical outcomes in women undergoing IUI

Outcomes comparison of testicular versus ejaculated sperm for intracytoplasmic sperm injection in infertile men with high DNA fragmentation: updated systematic review and meta-analysis

Background

The testicular sperm instead of ejaculated sperm for intracytoplasmic sperm injection (ICSI) in infertile men with high sperm DNA fragmentation (SDF) is a controversial topic. This updated systematic review and meta-analysis aims to evaluate whether couples with high level of SDF will benefit more from intracytoplasmic sperm injection with testicular sperm (Testi-ICSI) as compared to intracytoplasmic sperm injection with ejaculated sperm (Ejac-ICSI).

Methods

A systematic search was conducted according to PRISMA guidelines, using PubMed, Embase, Web of Science and the Cochrane Central Register of Controlled Trials (CENTRAL), encompassing studies from the earliest record until May 2022. We included studies analyzing comparative pregnancy outcomes of testicular versus ejaculated sperm for ICSI in infertile men with high DNA fragmentation. The risks of bias and certainty of evidence were assessed using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework, respectively.

Results

Eleven studies were included. Meta-analysis showed that SDF levels revealed a significant difference association [odds ratio (OR) =-25.81; 95% confidence interval (CI): -34.82, -16.81; I2=94%; P<0.00001] between testicular and ejaculated sperm. Compared with Ejac-ICSI, a non-significant tendency was observed for fertilization rates (FRs) in the Testi-ICSI group (OR =0.87; 95% CI: 0.67, 1.12; I2=81%; P=0.28). However, there was significant difference pointing to better outcomes for Testi-ICSI in clinical pregnancy rates (CPRs) (OR =2.36; 95% CI: 1.71, 3.24; I2=0%; P<0.00001), live birth rates (LBRs) (OR =3.10; 95% CI: 2.13, 4.51; I2=4%; P<0.00001) and miscarriage rates (MRs) (OR =0.28; 95% CI: 0.13, 0.60; I2=0%; P=0.001).

Conclusions

Results of this updated meta-analysis reveal that SDF rates are lower in testicular sperm than in ejaculated sperm and that Testi-ICSI is correlated with better clinical outcomes, including higher CPRs, higher LBRs, and lower MRs in infertile males with high SDF levels. Nevertheless, with the overall low to moderate quality of the studies, further well-designed controlled studies are required.

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.

Is There a Relationship between Sperm DNA Fragmentation and Intra-Uterine Insemination Outcome in Couples with Unexplained or Mild Male Infertility? Results from the ID-Trial

BACKGROUND

Sperm DNA fragmentation has been proposed as a candidate test for the assessment of sperm function on the premise that damage to the sperm chromatin is associated with a detrimental reproductive outcome. The objective of our study was to investigate whether sperm DNA fragmentation testing has a prognostic value, and thus can play a pivotal role in selecting future patients for intra-uterine insemination (IUI) therapy.

METHODS

This was a prospective cohort study conducted in a University Hospital setting. SDF was measured through TUNEL assay on the fresh semen sample presented at diagnosis and at insemination in couples with idiopathic/mild male infertility undergoing natural cycle IUI treatment. The generalized estimating equation (GEE)-model and multivariable model were used to analyze the probability of live birth and clinical pregnancy, respectively. ROC analysis was carried out to determine an SDF cut-off.

RESULTS

There was an inverse relationship between SDF in the ejaculate of the diagnostic semen sample and CP (p = 0.02; OR 0.94 95% CI (0.90, 0.989)) as well as LB (p = 0.04; OR 0.95 95% CI (0.90, 0.9985)). No significant association was found between SDF after gradient and IUI outcome in the diagnostic sample nor between SDF (ejaculate/after gradient) in the IUI samples. The ROC analysis proposed a cutoff of 17.5% as the best compromise between sensitivity and specificity in the diagnostic SDF for live birth; however, the test diagnostics are low, with an AUC of 0.576.

CONCLUSIONS

Overall, this study strengthens the hypothesis of an inverse relationship between SDF and CP/LB. Furthermore, SDF taken together with other clinical characteristics might provide more insight into male reproductive potential and predicting IUI outcome. Couples with SDF ≥ 17.5% in the diagnostic semen sample did not reach live birth. Further research is necessary to establish the diagnostic and prognostic potential of SDF as an add-on test.