The common environmental toxicant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or, commonly, dioxin) is a known endocrine disruptor that has been linked to the development of endometriosis in experimental models. Using a murine model, we previously demonstrated that in utero TCDD exposure promotes the transgenerational development of an "endometriosis-like" uterine phenotype consisting of reduced responsiveness to progesterone, subfertility and an increased risk of preterm birth. Since adenomyosis is frequently observed as a comorbidity in women with endometriosis, herein, we sought to determine the incidence of adenomyosis in non-pregnant mice with a history of direct or indirect TCDD exposure. Using histologic assessment and immunohistochemical staining, we analyzed murine uteri for adenomyosis, microvessel density and expression of estrogen receptors alpha and beta (ESR1 and ESR2). Our studies revealed that unexposed control mice did not exhibit adenomyosis while this disease was frequently observed in mice with a history of early life TCDD exposure. A transgenerational impact of developmental TCDD exposure was demonstrated since a subset of mice with only an indirect exposure (F3) also exhibited adenomyosis. Microvessel density within the uterus was significantly higher in all groups of TCDD exposed mice compared to control animals, with density correlated to the severity of disease. Both ESR1 and ESR2 protein exhibited alterations in expression in experimental mice compared to controls. Similar to women with endometriosis, we observed a significant reduction in the ratio of Esr1/Esr2 mRNA in all F1 mice compared to controls. Although this retrospective study was not designed to specifically address mechanisms associated with development of adenomyosis, our data suggest that developmental TCDD exposure permanently alters adult steroid responses which may contribute to the transgenerational development of adenomyosis.

Preterm birth (PTB), parturition prior to 37 weeks gestation, is the leading cause of neonatal mortality. The causes of spontaneous PTB are poorly understood; however, recent studies suggest that this condition may arise as a consequence of the parental fetal environment. Specifically, we previously demonstrated that developmental exposure of male mice (F1 animals) to the environmental endocrine disruptor 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was associated with reduced sperm quantity/quality in adulthood and control female partners frequently delivered preterm. Reproductive defects persisted in the F2 and F3 descendants, and spontaneous PTB was common. Reproductive changes in the F3 males, the first generation without direct TCDD exposure, suggest the occurrence of epigenetic alterations in the sperm, which have the potential to impact placental development. Herein, we conducted an epigenetic microarray analysis of control and F1 male-derived placentae, which identified 2171 differentially methylated regions, including the progesterone receptor (Pgr) and insulin-like growth factor (Igf2). To assess if Pgr and Igf2 DNA methylation changes were present in sperm and persist in future generations, we assessed methylation and expression of these genes in F1/F3 sperm and F3-derived placentae. Although alterations in methylation and gene expression were observed, in most tissues, only Pgr reached statistical significance. Despite the modest gene expression changes in Igf2, offspring of F1 and F3 males consistently exhibited IUGR. Taken together, our data indicate that paternal developmental TCDD exposure is associated with transgenerational placental dysfunction, suggesting epigenetic modifications within the sperm have occurred. An evaluation of additional genes and alternative epigenetic mechanisms is warranted.