Oxidative stress occurs when the production of potentially destructive reactive oxygen species (ROS) exceeds the bodies own natural antioxidant defenses, resulting in cellular damage. Oxidative stress is a common pathology seen in approximately half of all infertile men. ROS, defined as including oxygen ions, free radicals and peroxides are generated by sperm and seminal leukocytes within semen and produce infertility by two key mechanisms. First, they damage the sperm membrane, decreasing sperm motility and its ability to fuse with the oocyte. Second, ROS can alter the sperm DNA, resulting in the passage of defective paternal DNA on to the conceptus. This review will provide an overview of oxidative biochemistry related to sperm health and will identify which men are most at risk of oxidative infertility. Finally, the review will outline methods available for diagnosing oxidative stress and the various treatments available.

The global obesity epidemic has paralleled a decrease in semen quality. Yet, the association between obesity and sperm parameters remains controversial. The purpose of this report was to update the evidence on the association between BMI and sperm count through a systematic review with meta-analysis. A systematic review of available literature (with no language restriction) was performed to investigate the impact of BMI on sperm count. Relevant studies published until June 2012 were identified from a Pubmed and EMBASE search. We also included unpublished data (n = 717 men) obtained from the Infertility Center of Bondy, France. Abstracts of relevant articles were examined and studies that could be included in this review were retrieved. Authors of relevant studies for the meta-analysis were contacted by email and asked to provide standardized data. A total of 21 studies were included in the meta-analysis, resulting in a sample of 13 077 men from the general population and attending fertility clinics. Data were stratified according to the total sperm count as normozoospermia, oligozoospermia and azoospermia. Standardized weighted mean differences in sperm concentration did not differ significantly across BMI categories. There was a J-shaped relationship between BMI categories and risk of oligozoospermia or azoospermia. Compared with men of normal weight, the odds ratio (95% confidence interval) for oligozoospermia or azoospermia was 1.15 (0.93–1.43) for underweight, 1.11 (1.01–1.21) for overweight, 1.28 (1.06–1.55) for obese and 2.04 (1.59–2.62) for morbidly obese men. Overweight and obesity were associated with an increased prevalence of azoospermia or oligozoospermia. The main limitation of this report is that studied populations varied, with men recruited from both the general population and infertile couples. Whether weight normalization could improve sperm parameters should be evaluated further.

Agarwal A, et al. World J Mens Health. 2019 Sep;37(3):296-312. https://doi.org/10.5534/wjmh.190055

In mice, seminal fluid elicits an inflammation-like response in the female genital tract that activates immune adaptations to advance the likelihood of conception and pregnancy. In this study, we examined whether similar changes in leukocyte and cytokine parameters occur in the human cervix in response to the male partner’s seminal fluid. After a period of abstinence in proven-fertile women, duplicate sets of biopsies were taken from the ectocervix in the periovulatory period and again 48 h later, 12 h after unprotected vaginal coitus, vaginal coitus with use of a condom, or no coitus. A substantial influx of CD45⁺ cells mainly comprising CD14⁺ macrophages and CD1a⁺ dendritic cells expressing CD11a and MHC class II was evident in both the stratified epithelium and deeper stromal tissue after coitus. CD3⁺CD8⁺CD45RO⁺ T cells were also abundant and increased after coitus. Leukocyte recruitment did not occur without coitus or with condom-protected coitus. An accompanying increase in CSF2, IL6, IL8, and IL1A expression was detected by quantitative RT-PCR, and microarray analysis showed genes linked with inflammation, immune response, and related pathways are induced by seminal fluid in cervical tissues. We conclude that seminal fluid introduced at intercourse elicits expression of proinflammatory cytokines and chemokines, and a robust recruitment of macrophages, dendritic cells, and memory T cells. The leukocyte and cytokine environment induced in the cervix by seminal fluid appears competent to initiate adaptations in the female immune response that promote fertility. This response is also relevant to transmission of sexually transmitted pathogens and potentially, susceptibility to cervical metaplasia.

A receptive endometrial environment requires adequate immunological tolerance to protect the implanting embryo from maternal immune rejection. Studies in mice implicate CD4+CD25+ T-regulatory (Treg) cells as essential mediators of immune tolerance in pregnancy. The aim of this study was to evaluate the link between Treg cells and fertility in women. Expression of Foxp3, a master regulator of Treg cell differentiation, was quantified in endometrial tissue from women experiencing primary unexplained infertility and normal fertile women. Endometrial biopsies were collected during the mid-secretory phase of the menstrual cycle from women meeting rigorously defined criteria for unexplained infertility after experiencing repeated failed cycles of IVF treatment (infertile, n = 10), or women classified as proven fertile (control, n = 12). Expression of Foxp3 mRNA was reduced approximately two-fold in the tissue of infertile women. In contrast, mRNAs encoding T cell transcription factors T-bet and GATA3, associated with differentiation of Th1 and Th2 CD4+ T cells respectively, were unchanged. Treg cell differentiation is controlled by TGFβ, but the relative abundance in endometrial tissue of TGFβ1, TGFβ2, TGFβ3 mRNAs was not changed in infertile women. Cytokines influencing Th1 and Th2 cell differentiation, including IFNγ, IL-2, IL-4, IL-5, IL-10 and IL-12p40, as well as dendritic cell-regulating cytokines IL-1α, IL-1β, IL-6, LIF, GM-CSF and TNFα were also expressed similarly regardless of fertility status. The finding of reduced endometrial Foxp3 implicates impaired differentiation of uterine T cells into the Treg phenotype as a key determinant of fertility in women. The factors underpinning this aberration in the immune response remain to be identified.