. Morphological and molecular analysis of myometrial differentiation during early pregnancy in rats neonatally exposed to endosulfan

ALARCÓN R; VARAYOUD J; MUÑOZ-DE-TORO M; LUQUE EH; MILESI MM

Congreso; SAIC 2016; 2016

During early pregnancy, the myometrium undergoes a notableincrease in proliferation, which is critical for implantation. Alterationsof myometrial morphogenesis during development may leadto reproductive anomalies at adulthood. In previous studies wefound that neonatal exposure to the pesticide endosulfan altersthe expression of the morphoregulatory genes Hoxa10 and Wnt7ain the myometrium of prepubertal rats, and induces implantationfailures at adulthood. This study investigates the long-term effectsof neonatal exposure to endosulfan on myometrium differentiationduring the peri-implantation period (gestational day 5, GD5). Newbornfemale rats were treated by s.c. injections every 48 h frompostnatal day 1 (PND1) to PND7 with corn oil (vehicle), diethyl stilbestrol0.2 μg/Kg/day (DES, endocrine disruptor control) and endosulfan600 μg/Kg/day (Endo600). On PND90, females were matedand on GD5 the uteri were obtained, fixed and paraffin-embedded.The thickness of circular (cM) and longitudinal (lM) myometrium, aswell as, the relative area occupied by blood vessels were evaluatedin hematoxylin-eosin stained sections. Protein expression of Ki-67 (as a cell proliferation marker), Wnt7a, and Hoxa10 were evaluatedin the myometrium by immunohistochemistry. DES treatmentincreased the thickness of the cM and the relative area occupiedby blood vessels, and enlarged intercellular spaces, suggesting thepresence of edema. Contrarily, Endo600 group showed a decreasein the thickness of cM and lM, in association with lower cell proliferation.The treatment with endosulfan decreased the expressionof Hoxa10 in the lM, and downregulated Wnt7a in both myometriallayers. Endosulfan-induced Hoxa10 and Wnt7a deregulation in themyometrium might be responsible for the lower proliferation rate,which might be in turn the cause of lower myometrial thickness.These morphological and molecular changes could promote theendosulfan-induced implantation failures.