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Demasculinization by environmental endocrine-disrupting chemicals (EDCs) is observed in many animal species but less evident in humans. Rodent studies with gestational exposure to either the fungicide vinclozolin or the insecticide methoxychlor demonstrate impaired male fertility with abnormal DNA methylation patterns in spermatozoa. Once established, these epigenetic changes may be permanent and thus paternally passed to subsequent generations. Conclusive evidence of a similar phenomenon in humans has not been established, but several observations bring up the possibility. Some, but not all, studies show an increase in male genital abnormalities after prenatal EDC exposure. Other studies demonstrate sperm abnormalities in males with EDC contact, although it is unclear as to whether this is due to prenatal or postnatal exposure. Although not examined in males with EDC exposure, one study shows gamete DNA methylation abnormalities in males with severe oligospermia. A subsequent study failed to corroborate these findings. The use of assisted reproductive techniques including intracytoplasmic sperm injection has removed natural selection barriers thus enabling reproduction in males that would otherwise be sterile. This review explores the hypothesis that prenatal EDC exposure results in transgenerational male reproductive abnormalities propagated by the use of assisted reproductive technologies. [ABSTRACT FROM AUTHOR]

: BACKGROUND Although stress is known to disturb natural fertility through the inhibition of the hypothalamic–pituitary–gonadal (HPG) axis, the impact of stress on infertile women who receive exogenous gonadal hormones is not well defined. This is probably due to lack of experimental models for evaluating the impacts of stress through an ovarian-independent pathway. The objective of this study was to investigate the possible impact of stress on uterine receptivity, independent of HPG axis dysfunction, using a mouse implantation model maintained with hormone supplementation. : METHODS Blastocysts from donor mice were transferred into the uterine lumen of ovariectomized (OVX) Balb/c female recipient mice following supplementation with estradiol and progesterone. The recipients were divided into two groups: those exposed (stress group) or not exposed (control group) to intermittent sonic exposure prior to embryo transfer (ET). The number of implantation sites (IS) was compared between these groups. Microarray analysis was performed to elucidate stress-induced molecular alterations in uteri during the implantation period. Sequential gene expression of leukemia inhibitory factor (Lif), an estradiol-inducible gene, was also analyzed using real-time PCR. : RESULTS A non-mating OVX model with satisfactory implantation rates was established. The number of IS in the stress group (n = 20) was significantly less than that in the control group (n = 18) (Mann–Whitney test, P = 0.0375). Implantation-related genes and ovarian-hormone-responsive genes were repressed in the stress group despite ovarian hormone supplementation. The expression of Lif was suppressed in the stress group. : CONCLUSIONS Stress can cause decreased uterine receptivity through an ovarian-independent pathway. [ABSTRACT FROM AUTHOR]