WHO laboratory manual for the examination and processing of human semen

Reactive oxygen species

BACKGROUND: Sperm DNA damage is common amongst infertile men and may adversely impact natural reproduction, IUI-assisted reproduction and to a lesser degree IVF pregnancy. The aim of this study was to examine the influence of sperm DNA damage on the risk of spontaneous pregnancy loss after IVF and ICSI. METHODS: We conducted a systematic review and meta-analysis of studies on sperm DNA damage and pregnancy loss after an IVF and/ or ICSI pregnancy. RESULTS: Two by two tables were constructed and odds ratios (ORs) were derived from 11 estimates of pregnancy loss (five IVF and six ICSI studies from seven reports). These 11 studies involved 1549 cycles of treatment (808 IVF and 741 ICSI cycles) with 640 pregnancies (345 IVF and 295 ICSI) and 122 pregnancy losses. The combined OR of 2.48 (95% CI 1.52, 4.04, P< 0.0001) indicates that sperm DNA damage is predictive of pregnancy loss after IVF and ICSI. CONCLUSIONS: In conclusion, sperm DNA damage is associated with a significantly increased risk of pregnancy loss after IVF and ICSI. These data provide a clinical indication for the evaluation of sperm DNA damage prior to IVF or ICSI and a rationale for further investigating the association between sperm DNA damage and pregnancy loss.

Sperm DNA damage is associated with an increased risk of pregnancy loss after IVF and ICSI: systematic review and meta-analysis

DNA damage in the male germ line has been linked with a variety of adverse clinical outcomes including impaired fertility, an increased incidence of miscarriage and an enhanced risk of disease in the offspring. The origins of this DNA damage could, in principle, involve: (i) abortive apoptosis initiated post meiotically when the ability to drive this process to completion is in decline (ii) unresolved strand breaks created during spermiogenesis to relieve the torsional stresses associated with chromatin remodelling and (iii) oxidative stress. In this article, we present a two-step hypothesis for the origins of DNA damage in human spermatozoa that highlights the significance of oxidative stress acting on vulnerable, poorly protaminated cells generated as a result of defective spermiogenesis. We further propose that these defective cells are characterized by several hallmarks of 'dysmaturity' including the retention of excess residual cytoplasm, persistent nuclear histones, poor zona binding and disrupted chaperone content. The oxidative stress experienced by these cells may originate from infiltrating leukocytes or, possibly, the entry of spermatozoa into an apoptosis-like cascade characterized by the mitochondrial generation of reactive oxygen species. This oxidative stress may be exacerbated by a decline in local antioxidant protection, particularly during epididymal maturation. Finally, if oxidative stress is a major cause of sperm DNA damage then antioxidants should have an important therapeutic role to play in the clinical management of male infertility. Carefully controlled studies are now needed to critically examine this possibility.

On the possible origins of DNA damage in human spermatozoa

DNA damage in the male germ line has been associated with poor semen quality, low fertilization rates, impaired preimplantation development, increased abortion and an elevated incidence of disease in the offspring, including childhood cancer. The causes of this DNA damage are still uncertain but the major candidates are oxidative stress and aberrant apoptosis. The weight of evidence currently favours the former and, in keeping with this conclusion, positive results have been reported for antioxidant therapy both in vivo and in vitro. Resolving the causes of DNA damage in the male germ line will be essential if we are to prevent the generation of genetically damaged human embryos, particularly in the context of assisted conception therapy.

DNA damage to spermatozoa has impacts on fertilization and pregnancy

Influence of deoxyribonucleic acid damage on fertilization and pregnancy

Despite the ever-increasing knowledge of the fertilization process, there is still a need for better understanding of the causes of sperm DNA fragmentation and its impact on fertilization and pregnancy. For this reason, human sperm DNA fragmentation was investigated by means of the terminal deoxynucleotidyl transferase-mediated dUDP nick-end labelling (TUNEL) assay and the production of reactive oxygen species (ROS) in the ejaculate and in the spermatozoa themselves. These data were correlated with fertilization and pregnancy data from IVF and intracytoplasmic sperm injection (ICSI) patients. Sperm DNA fragmentation did not correlate with fertilization rate, but there was a significantly reduced pregnancy rate in IVF patients inseminated with TUNEL-positive spermatozoa. ICSI patients exhibited the same tendency. This implies that spermatozoa with damaged DNA are able to fertilize an oocyte, but at the time the paternal genome is switched on, further development stops. The determination of ROS in the ejaculate and the percentage of ROS-producing spermatozoa revealed markedly stronger correlations between sperm functions (i.e. motility) and the percentage of ROS-producing spermatozoa. The influence of seminal leukocytes, known to produce large amounts of oxidants, on sperm DNA fragmentation should not be neglected.

https://www.rbmojournal.com/article/S1472-6483(10)61893-7/pdf

DNA fragmentation of spermatozoa and assisted reproduction technology.

The presence of excess leucocytes in the semen has been associated with male infertility. According to the WHO, concentrations of more than 106 leucocytes ml-1 are considered as leucocytospermia, indicating genital tract infections. Up to now, no consensus has been achieved on how leucocytes should be quantified in semen. Using the peroxidase staining and monoclonal antibodies to CD15, CD45 and CD68, we found significant differences between the detection methods. Only 47.4% of the semen samples that were assessed as leucocytospermic by CD45 were identified as such by peroxidase staining. The concentration of peroxidase-positive cells was significantly correlated with polymorphonuclear granulocyte (PMN) elastase (P < 0.0001). However, a negative correlation of peroxidase-positive cells with the sperm concentration was only found in oligozoospermic patients (P < 0.0001). Moreover, the slightly positive correlation with normal sperm morphology seems to be applicable only in cases of oligozoospermia. Significant negative correlation of the number of peroxidase-positive cells were found for both maximal inducible acrosome reaction (P = 0.0219) and the inducibility of acrosome reaction (P = 0.0370), indicating a rather deleterious effect of leucocytes on this important sperm function. Concerning the result in the in vitro fertilization programme, none of the examined parameters (PMN elastase, concentration of round cells and peroxidase-positive cells) showed a correlation with either fertilization or pregnancy. This result seems to be reasonable as severely damaged spermatozoa and leucocytes are eliminated from the ejaculate by different sperm separation methods. Interestingly, a significant negative correlation of the TUNEL assay as a measure of sperm DNA fragmentation was found only with pregnancy (P = 0.006) but not with fertilization. As DNA fragmentation can also be caused by ROS that are generated by leucocytes, this causality should not be neglected.

Marjam Hajimohammad

Papers

Influence of deoxyribonucleic acid damage on fertilization and pregnancy

DNA fragmentation of spermatozoa and assisted reproduction technology.

Urogenital inflammation: changes of leucocytes and ROS.