Effect of Early Life Exposure to Atrazine on Uterine Maturation in Neonatal Piglets

The bioavailability of endocrine disrupting chemicals (EDCs) in the environment is a rising concern due to their known effects on offspring development. Amongst EDCs relevant to livestock species, atrazine, a widely used herbicide, is often detected at moderate levels in drinking water. Previous studies have linked Atrazine exposure with abnormal steroidogenesis and perturbations in estrogen synthesis and metabolism. Successful establishment and maintenance of pregnancy in swine depends on the formation of functional uterine glands, which develop shortly after birth in an estrogen-dependent manner. This study aimed to investigate whether perinatal atrazine exposure programs postnatal uterine maturation, which could compromise gilt fertility. We hypothesized that perinatal atrazine exposure negatively programs early stages of uterine maturation that are critical for morphogenesis of the glandular epithelium (GE), a process known as adenogenesis. To test this hypothesis, we assessed uterine morphology of female piglets exposed to Atrazine via maternal drinking water. Seven pregnant sows were provided access to water containing either environmental levels of Atrazine [20 mg/L; (TRT, n = 3)] or vehicle control (CTRL, n = 3) from gestation day 28 through farrowing and 10 days of lactation. Female piglets (n = 19; TRT = 7, CTRL = 12) were weighed at postnatal day 0 (PND0) and PND10. Uteri were collected at PND10 for histological processing and stained for hematoxylin and eosin. Cross-sections were imaged at low magnification for morphometric quantification using ImageJ. Measured outcomes included uterine height (along the mesometrial axis), uterine width, cross-sectional area (mean height/width) and myometrial height. Morphological assessments included the quantification of nascent GE buds (indicative of adenogenesis onset) and number of GE cross-sections within the endometrial stroma. Dependent variables were normally distributed, and statistical analyses were conducted using glmmTMB of R. Data are presented as least-squares means±SE. Body weight tended to be greater at both PND0 (P = 0.08) and PND10 (P = 0.06) for CTRL (PND0 = 1.77±0.06 kg; PND10 = 4.02±0.11 kg) compared to TRT (PND0 = 1.60±0.08 kg; PND10 = 3.66±0.15 kg) piglets. Although uterine width, myometrial height and cross-sectional area did not differ between groups, uterine height tended to be greater (P = 0.07) for CRTL piglets (34.8±2.77 mm) than in TRT (26.1±3.92 mm). While the progression of adenogenesis did not differ between groups based on the number of tubular and/or coiled GE cross-sections observed within the stromal compartment (P = 0.3), CTRL piglets exhibited a greater number of nascent GE buds within the luminal compartment (39.1±1.85) compared to TRT (31.6±2.42)(P = 0.01), suggesting a delay in the onset of glandular morphogenesis. Summarizing, these results suggest that perinatal exposure to Atrazine may delay overall growth, as well as postnatal uterine gland development of female piglets, which could pose long-term consequences on reproductive function and fertility of adult females.