The effects of age on DNA fragmentation, the condensation of chromatin and conventional semen parameters in healthy nonsmoking men exposed to traffic air pollution

Novel insights into necrozoospermia from a single-center study: reference ranges, possible etiology, and impact on male fertility

ABSTARCT

Necrozoospermia is a poorly documented condition with a low incidence, and its definition and clinical significance are unclear. Herein, we provide a reference range for necrozoospermia and discuss its possible etiology and impact on male fertility and assisted reproductive outcomes. We extracted relevant information from 650 Chinese male partners of infertile couples and statistically analyzed sperm vitality. Necrozoospermia was present in 3.4% (22/650) of our study population, and the lower cut-off value for sperm vitality was 75.3%. We compared two methods for assessing sperm vitality (eosin-nigrosin head staining and hypo-osmotic swelling test [HOST]), for which the percentage in the eosin-nigrosin group (mean ± standard deviation [s.d.]: 77.5% ± 10.5%) was significantly higher than that in the HOST group (mean ± s.d.: 58.1% ± 6.7% [5-10 min after incubation] and 55.6% ± 8.2% [25-30 min after incubation]; both P < 0.001). The incidence of necrozoospermia increased with age (odds ratio [OR] = 1.116, 95% confidence interval [CI]: 1.048-1.189, P = 0.001), while the percentage of normal sperm morphology and DNA fragmentation index (DFI) were significantly associated with necrozoospermia, with ORs of 0.691 (95% CI: 0.511-0.935, P = 0.017) and 1.281 (95% CI: 1.180-1.390, P < 0.001), respectively. In the following 6 months, we recruited 166 patients in the nonnecrozoospermia group and 87 patients in the necrozoospermia group to compare intracytoplasmic sperm injection (ICSI) and pregnancy outcomes between the two groups. The necrozoospermia group had a significantly lower normal fertilization rate (74.7% vs 78.2%, P = 0.041; OR = 0.822; 95% CI: 0.682-0.992) than that in the nonnecrozoospermia group. This study presents substantial information on necrozoospermia to establish comprehensive and applicable reference values for sperm vitality for spontaneous conception and artificially assisted reproductive management.

Epidemiology of sperm DNA fragmentation in a retrospective cohort of 1191 men

BACKGROUND

The scientific and clinical communities now recognize that sperm DNA integrity is crucial for successful fertilization, good embryo development, and offspring quality of life. Despite the apparent unanimity, this criterion is rarely evaluated in clinical practice. We evaluated the sperm DNA fragmentation index of nearly 1200 sperm samples and its connections based on the patient's age, body mass index, the season of sperm collection, geographical location, medical history, and addictive behaviors.

METHODS

A cohort of 1503 patients who were referred to the Royan Institute between July 2018 and March 2020 was examined. Only 1191 patient records with demographic data, complete semen analysis, and DNA fragmentation index measurements were included in the final cohort. Documents were classified, incorporated into statistical models, and analyzed.

RESULTS

The results confirmed previous findings that the sperm DNA fragmentation index was significantly higher in aging men. The sperm DNA fragmentation index and high DNA stainability levels were significantly higher in spring and summer samples than in those of other seasons. No correlation was found between semen DNA fragmentation index and patient body mass index, although the study cohort was significantly overweight. Contrary to what might be expected, we observed that the sperm DNA fragmentation index was higher in rural than in urban patients. Intriguingly, epileptic patients exhibited significantly higher sperm DNA fragmentation index levels.

DISCUSSION AND CONCLUSION

Age is the factor that is most strongly associated with sperm DNA fragmentation index levels. Our analysis of 1191 samples indicates that between the ages of 19 and 59, the sperm DNA fragmentation index increases by an average of 2% each year. Intriguingly, from an epidemiological perspective, the warm season (spring/summer) is associated with a higher sperm DNA fragmentation index in the study population, possibly due to the deleterious effect of temperature on sperm quality. Some neurological diseases, such as epilepsy, are associated with decreased sperm DNA integrity. This observation could be related to the iatrogenic effects of associated therapies. In the study cohort, body mass index did not appear to be correlated with the DNA fragmentation index.

Fertility in the aging male: a systematic review

The negative effect of advanced female age on fertility and offspring health is well understood. In comparison, much less is known about the implications of male age on fertility, with many studies showing conflicting results. Nevertheless, increasing evidence suggests that advanced paternal age has negative effects on sperm parameters, reproductive success, and offspring health. Herein, we summarize the current body of knowledge on this controversial topic, with the belief that this review will serve as a resource for the clinicians providing fertility counseling to couples with older male partners.

Necrozoospermia: The tree that hides the forest

BACKGROUND

Necrozoospermia is a condition found in 0.2 to 0.4 % of male infertility cases. The causes of necrozoospermia are multiple: they can be related to testicular and/or post-testicular damage. Additionally, these causes most often involve the production of reactive oxygen species (ROS) and/or sperm DNA fragmentation (SDF) which can reduce the chances of spontaneous pregnancy or affect the outcome of assisted reproductive technologies.

OBJECTIVE

To focus on potential etiologies of necrozoospermia, its diagnosis and its therapeutic management especially before the employment of ICSI.

METHODS

Authors searched PubMed/Medline, Web of Science, Cochrane Library, Google and Institutional websites for medical subheading terms and free text words referred to "necrozoospermia", "sperm vitality", "sperm viability", "sperm DNA fragmentation" and "ICSI".

RESULTS

We identified twelve main etiologies of necrozoospermia responsible for either a decrease of sperm vitality, a mild a moderate or a severe necrozoospermia. In case of a confirmed decreased vitality, a thorough check-up should be conducted and if available, etiological treatment should be proposed. Therapeutic management could also include repeated ejaculations, drug treatments, the use of ICSI with ejaculated or surgically extracted spermatozoa in case of a non-treatable necrozoospermia.

DISCUSSION AND CONCLUSION

The potential causes of necrozoospermia should be investigated because many of them could be corrected, thus avoiding the use of ICSI. Moreover, if ICSI procedure remains necessary, the therapeutic management of necrozoospermia could also improve the chances of success by reducing oxidative stress and/or sperm DNA fragmentation. This article is protected by copyright. All rights reserved.

Semen quality and sperm DNA integrity in city policemen exposed to polluted air in an urban industrial agglomeration

BACKGROUND

We examined sperm quality in a cohort of city policemen in Ostrava at the end of a period with high concentrations of air pollutants (winter) and in the same cohort at the end of a relatively low exposure period (summer).

METHODS

The study group was comprised of 54 nonsmoking city policemen living and working in Ostrava, Czech Republic. Average daily air-pollutant concentrations recorded by stationary monitoring for 90 days preceding the collection of semen samples were evaluated for different city districts of Ostrava. Standard semen parameters were assessed according to the guidelines of the World Health Organization (2010). The parameters were semen volume, sperm concentration, sperm morphology, sperm motility, acrosome reaction and sperm plasma membrane integrity. Sperm DNA damage was analysed by the sperm chromatin structure assay (SCSA). Sperm motion characteristics were determined by Computer Assisted Semen Analysis (CASA).

RESULTS

The concentrations of all monitored pollutants (particulate matter, sulphur dioxide, nitrogen oxides, carbon monoxide, benzo[a]pyrene, benzene) were significantly increased during winter (p < 0.001), except for ozone, the concentration of which was significantly higher during summer. Sperm volume, concentration, % vitality, % sperm morphology (normal form) and % acrosome-intact sperm did not differ significantly between the monitoring periods. The percentages of total motility and progressive motility were significantly higher in March, i.e. at the end of winter (p = 0.001). However, CASA testing showed differences in sperm motion kinetics between spring and autumn samples. In the spring samples, we found a significantly lower % of straightness (p = 0.044) and the length of straight-line path (p = 0.01), while linearity and straight-line velocity were near the borderline value (p = 0.064; p = 0.054, respectively). As compared to summer, high exposure to air pollution during winter significantly increased the extent of sperm chromatin integrity damage (median 22.6 vs. 18.6%) (p = 0.003) and the proportion of immature spermatozoa (median 11.2 vs. 9.9%, p = 0.001). Sperm DNA damage negatively correlated with total motility and progressive motility (r = -0.611, -0.299; p < 0.001). The negative correlation with vitality, normal morphology and acrosome-intact sperm (r = -0.522, -0.550 and -0.511, respectively) was also significant (p < 0.001).

CONCLUSION

The examination of the same cohort of city policemen at the end of a period of high air pollution and at the end of relatively low exposure reduced the effects of age, different lifestyles, different occupational exposures, localities and genetic polymorphism on sperm quality impairment associated with air pollution. This study did not demonstrate impaired standard semen parameters in association with exposure. It was shown that sperm chromatin damage and the percentage of immature sperm were highly sensitive to air pollution.