7406 Developmental Programming: Impact Of Prenatal Exposure To A Real-Life Environmental Chemical Mixture Via Biosolids On Ovarian Follicle Populations In Prepubertal Sheep

Abstract Disclosure: K.M. Halloran: None. J.N. Ciarelli: None. Y. Zhou: None. M. Bellingham: None. R.G. Lea: None. N.P. Evans: None. K.D. Sinclair: None. P. Smith: None. V. Padmanabhan: None. Establishment of the fetal ovarian follicular reserve is a determinant of lifelong fertility. Environmental chemicals (ECs) are implicated in perturbation of early follicle development which may negatively impact adult reproductive function. Considering humans are exposed to a complex cocktail of ECs that may have additive, synergistic and/or antagonistic effects, real-life exposure models are needed to assess the impact of mixtures of ECs on ovarian reserve. Biosolids contain a complex mixture of ECs and earlier studies have shown that grazing pregnant sheep on biosolids-treated pastures (BTP) did not influence the ovarian follicular pool of fetal day 110 lambs. In contrast, an increased proportion of healthy primordial and reduced proportion of healthy transitory follicles, without an impact on their cortical density, was observed in late gestation fetuses (day 140). Collectively this suggests that in BTP sheep, while establishment of an ovarian reserve is not affected its depletion across the reproductive life span may be affected. In this study we tested the hypothesis that prenatal biosolid exposure would affect follicular depletion and negatively impact ovarian reserve in postnatal lambs. Ewes were grazed on pastures treated with either inorganic fertilizer (control; C) or biosolids (BTP) beginning a month before mating and throughout gestation until birth. After birth, ewes and lambs were moved to C pastures. Female lambs (10 C and 11 BTP) were euthanized at 8 weeks of age. Ovarian follicles were classified by stage (primordial, transitory, primary, preantral, and antral) and health status. The impact of exposure to mixture of ECs on follicular cortical density (n/mm2), distribution, health status, and activation rate were assessed. Anti-müllerian hormone (AMH) expression, which correlates with the number of growing follicles, was quantified by immunohistochemical staining. BTP lambs had reduced density (P=0.07) and proportion (P=0.001) of primordial follicles. Activation rate was increased in the BTP group (P=0.01). The density of unhealthy follicles was reduced in the primordial (P=0.04) and transitory (P=0.09) stages, but increased in preantral (P=0.02) and antral (P=0.09) stages. The percentage of unhealthy follicles was reduced in transitory (P=0.09), but increased in preantral (P=0.01) and antral (P=0.07) stages. Consistent with this, increased AMH staining intensity was evident in transitory plus primary follicles (P<0.05). Collectively these results provide evidence that lambs born to BTP ewes have a reduced ovarian follicular pool, increased follicular activation, and increased unhealthy activated follicles at 8 weeks of age. These findings demonstrate the detrimental effects of ECs in biosolids on ovarian health leading to premature depletion of follicular pool and raise concerns regarding the quality of activated follicles. Funding: NIH R01 ES030374 Presentation: 6/1/2024