Multigenerational effects of maternal cigarette smoke exposure during pregnancy on sperm counts of F1 and F2 male offspring

Inter- and trans-generational impacts of environmental exposures on the germline resolved at the single-cell level

Reproduction is a remarkably intricate process involving the interaction of multiple cell types and organ systems unfolding over long periods of time and that culminates with the production of gametes. The initiation of germ cell development takes place during embryogenesis but only completes decades later in humans. The complexity inherent to reproduction and its study has long hampered our ability to decipher how environmental agents disrupt this process. Single-cell approaches provide an opportunity for a deeper understanding of the action of toxicants on germline function and analyze how the response to their exposure is differentially distributed across tissues and cell types. In addition to single-cell RNA sequencing, other single-cell or nucleus level approaches such as ATAC-sequencing and multi-omics have expanded the strategies that can be implemented in reproductive toxicological studies to include epigenomic and the nuclear transcriptomic data. Here we will discuss the current state of single-cell technologies and how they can best be utilized to advance reproductive toxicological studies. We will then discuss case studies in two model organisms (Caenorhabditis elegans and mouse) studying different environmental exposures (alcohol and e-cigarettes respectively) to highlight the value of single-cell and single-nucleus approaches for reproductive biology and reproductive toxicology.

Epigenetic programming of TBX2/CX43 mediates lower sperm quality in male offspring induced by prenatal dexamethasone exposure

Decreased sperm quality is the main cause of male infertility. Studies have found that prenatal dexamethasone exposure (PDE) decreases sperm quality in male offspring after birth, but the mechanism is unclear. Wistar pregnant rats were subcutaneously injected with 0.1, 0.2 and 0.4 mg/kg.d dexamethasone at gestational day 9-20. The testes and sperm of first-generation (F1) offspring were collected, and F1 offspring were mated with wild-type female rats to obtain F2. Compared with the control group, F1 offspring in PDE group had lower sperm count and motility after birth, and the deformity rate increased. F2 fetal rats' body length and weight decreased, and the intrauterine growth retardation rate increased. Meanwhile, PDE decreased the expression of connexin 43 (CX43) in offspring testes, while T-box transcription factor 2 (TBX2) promoter region histone 3 lysine 9 acetylation (H3K9ac) level and its expression were increased. Traced back to F1 fetus testes, PDE increased the expression of glucocorticoid receptor (GR) and P300, activated GR protein into the nucleus, and made GR act on the TBX2 promoter region. Further, a series of Sertoli cell interventions confirmed that dexamethasone promoted GR to recruit P300, increased the H3K9ac level of TBX2 promoter region and its expression, and inhibited the expression of CX43. This study confirmed that PDE decreased sperm quality of male offspring, which is related to the epigenetic programming of TBX2/CX43 in the Sertoli cells, provided a theoretical and experimental basis for guiding the rational use of drugs during pregnancy.

Fetal exposure to maternal cigarette smoking and male reproductive function in young adulthood

Maternal smoking during pregnancy constitutes a potential, major risk factor for adult male reproductive function. In the hitherto largest longitudinal cohort, we examined biomarkers of reproductive function according to maternal smoking during the first trimester and investigated whether associations were mitigated by smoking cessation prior to the fetal masculinization programming window. Associations between exposure to maternal smoking and semen characteristics, testicular volume and reproductive hormones were assessed among 984 young men from the Fetal Programming of Semen Quality (FEPOS) cohort. Maternal smoking was assessed through interview data and measured plasma cotinine levels during pregnancy. We applied negative binomial, logistic and linear regression models to estimate differences in outcomes according to levels of maternal smoking. Sons of light smokers (≤ 10 cigarettes/day) had a 19% (95% CI - 29%, - 6%) lower sperm concentration and a 24% (95% CI - 35%, - 11%) lower total sperm count than sons of non-smokers. These estimates were 38% (95% CI - 52%, - 22%) and 33% (95% CI - 51%, - 8%), respectively, for sons of heavy smokers (> 10 cigarettes/day). The latter group also had a 25% (95% CI 1%, 54%) higher follitropin level. Similarly, sons exposed to maternal cotinine levels of  > 10 ng/mL had lower sperm concentration and total sperm count. Smoking cessation prior to gestational week seven was not associated with a higher reproductive capacity. We observed substantial and consistent exposure-response associations, providing strong support for the hypothesis that maternal smoking impairs male reproductive function. This association persisted regardless of smoking cessation in early pregnancy.

Temporal Trend of Conventional Sperm Parameters in a Sicilian Population in the Decade 2011-2020

Objective: To evaluate the changes of conventional sperm parameters in men who referred to an andrology reference center in Catania (Eastern Sicily, Italy) in the decade 2011–2020. Methods: For this purpose, we selected–retrospectively and randomly–the reports of 1409 semen analyses performed according to the 2010 WHO criteria. Data on sperm concentration, total sperm count, progressive sperm motility, and percentage of normal forms were analyzed using linear regression of the raw and logarithmic-transformed data. The sperm parameters were subsequently pooled in two five-year periods (2011–2015 and 2016–2020) and compared with each other. Finally, the influence of the city of residence was assessed on five-year pooled data. Main results: A slight but non-significant decline of total sperm count (−2.26 million/year; p = 0.065) and the percentage of spermatozoa with normal morphology (−0.08%/year; p = 0.057) was observed. In contrast, a significant increase of progressive sperm motility (+0.28%/year; p = 0.008) over time was found. The total sperm count of the quinquennium 2016–2020 was significantly lower. and an upward trend of progressive sperm motility was found. compared to the years 2011–2015. No changes in sperm concentration and morphology occurred in the years 2011–2015 vs. 2016–2020. Sperm conventional parameters did not differ when the five-year pooled data were analyzed according to the town of residence. Conclusions: Divergent trends of total sperm count and progressive sperm motility over time were found in patients from Eastern Sicily. This may point out the need of assessing whether a time-dependent change of biofunctional sperm parameters occurs to really understand the trend of sperm quality over time.