Preconception paternal alcohol exposure decreases IVF embryo survival and pregnancy success rates in a mouse model

Abstract

Increasingly, couples struggling with fertility turn to assisted reproductive techniques, including in vitro fertilization (IVF), to have children. Despite the demonstrated influence of periconception male health and lifestyle choices on offspring development, studies examining IVF success rates and child health outcomes remain exclusively focused on maternal factors. Using a physiologically relevant mouse model, we tested the hypothesis that chronic paternal preconception alcohol intake adversely affects IVF success and negatively impacts IVF offspring fetoplacental growth. Using a voluntary, binge-like mouse model, we exposed sexually mature C57BL/6J males to three preconception treatments (0% (Control), 6% EtOH or 10% EtOH) for six weeks, isolated and cryopreserved caudal sperm from treated males, and then used these samples to fertilise oocytes before assessing IVF embryo developmental outcomes. We found that preconception paternal alcohol use reduced IVF embryo survival and pregnancy success rates in a dose-dependent manner, with the pregnancy success rate of the 10% EtOH treatment falling to half those of the Controls. Mechanistically, we found that preconception paternal alcohol exposure disrupts embryonic gene expression, including Fgf4 and Egfr, two critical regulators of trophectoderm stem cell growth and placental patterning, with lasting impacts on the histological organization of the late-term placenta. The changes in placental histoarchitecture were accompanied by altered regulation of pathways controlling mitochondrial function, oxidative phosphorylation and some imprinted genes. Our studies indicate that male alcohol use may significantly impede IVF success rates, increasing the couple's financial burden and emotional stress, and highlights the need to expand prepregnancy messaging to emphasize the reproductive dangers of alcohol use by both parents.

Alterations in sperm RNAs persist after alcohol cessation and correlate with epididymal mitochondrial dysfunction

“…16,17 Using a mouse model, our group has demonstrated that chronic preconception paternal alcohol exposures induce dose-dependent changes in placental patterning, defects in craniofacial development, and long-term effects on postnatal glucose homeostasis. [31][32][33][34][35][36][37][38][39][40] In these previous studies, we did not observe any differences in sperm count, morphology, or offspring litter size. [31][32][33]35,37,39 However, using an in vitro fertilization (IVF) system to model the impacts of paternal alcohol use on early embryonic development, we observed that chronic ethanol exposures reduce embryo development and pregnancy success rates in a dose-dependent manner.…”

“…These observations suggest that epididymides of active drinkers exhibit alterations in processes related to mitochondrial dysfunction, oxidative phosphorylation, and the generalized stress response but that these differences revert after the cessation of alcohol use. Notably, we previously identified differential expression of genetic pathways regulating oxidative phosphorylation and mitochondrial function in the early embryo and placentae of offspring derived from alcohol-exposed males, 35,38 suggesting this transcriptional signature may transmit to the early offspring through sperm.…”

“…63 Previously, we observed dose-dependent reductions in IVF embryo survival and pregnancy success rates, with the pregnancy success rate of the 10% EtOH treatment falling to half those of controls. 38 Therefore, we isolated mitochondrial DNA from a selection of the cryopreserved sperm samples we used in these previous experiments and compared mtDNAcn between the control and 6% treatments. Consistent with clinical observations, we also identified a significant increase in mtDNAcn in cryopreserved samples derived from the 6% treatment group compared to the controls (Figure 4A).…”

“…[31][32][33]35,37,39 However, using an in vitro fertilization (IVF) system to model the impacts of paternal alcohol use on early embryonic development, we observed that chronic ethanol exposures reduce embryo development and pregnancy success rates in a dose-dependent manner. 38 These intergenerational effects on fertility and offspring development correlate with alcoholinduced alterations in sperm-inherited noncoding RNAs and histone structure but do not associate with any significant changes in DNA methylation. 31,33,36 Significantly, the Homanics group has also identified alcohol-induced changes in sperm noncoding RNAs using a vapor chamber exposure model, reinforcing the assertion that paternal ethanol exposures affect sperm small noncoding RNA abundance.…”

“…Beginning on postnatal day 90, we individually caged males and initiated the control and ethanol (EtOH) treatments using a prolonged version of the drinking in the dark model. 47 Using published methods, 37,38 we exposed males to control (water alone), 6% or 10% weeks of constant EtOH exposure using CO 2 asphyxiation followed by cervical dislocation. For Cohort 2, we ceased the control and EtOH treatments and left the mice undisturbed for an additional 4 weeks before sacrifice using CO 2 asphyxiation and cervical dislocation, followed by tissue collection and sperm isolation.…”