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

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

Congreso; LXI Reunión Anual de la Sociedad Argentina de Investigación Clínica, LXIV Reunión de la Sociedad Argentina de Inmunología y XLVIII Reunión de la Sociedad Argentina de Farmacología Experimental; 2016

Sociedad Argentina de Investigación Clínica, Sociedad Argentina de Inmunología y Sociedad Argentina de Fisiología Experimental

During early pregnancy, the myometrium undergoes a notable increase in proliferation, which is critical for implantation. Alterations of myometrial morphogenesis during development may lead to reproductive anomalies at adulthood. In previous studies we found that neonatal exposure to the pesticide endosulfan alters the expression of the morphoregulatory genes Hoxa10 and Wnt7a in the myometrium of prepubertal rats, and induces implantation failures at adulthood. This study investigates the long-term effects of neonatal exposure to endosulfan on myometrium differentiation during the peri-implantation period (gestational day 5, GD5). Newborn female rats were treated by s.c. injections every 48 h from postnatal day 1 (PND1) to PND7 with corn oil (vehicle), diethylstilbestrol 0.2 μg/Kg/day (DES, endocrine disruptor control) and endosulfan 600 μg/Kg/day (Endo600). On PND90, females were mated and on GD5 the uteri were obtained, fixed and paraffin-embedded. The thickness of circular (cM) and longitudinal (lM) myometrium, as well as, the relative area occupied by blood vessels were evaluated in hematoxylin-eosin stained sections. Protein expression of Ki-67 (as a cell proliferation marker), Wnt7a, and Hoxa10 were evaluated in the myometrium by immunohistochemistry. DES treatment increased the thickness of the cM and the relative area occupied by blood vessels, and enlarged intercellular spaces, suggesting the presence of edema. Contrarily, Endo600 group showed a decrease in the thickness of cM and lM, in association with lower cell proliferation. The treatment with endosulfan decreased the expression of Hoxa10 in the lM, and downregulated Wnt7a in both myometrial layers. Endosulfan-induced Hoxa10 and Wnt7a deregulation in the myometrium 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 the endosulfan-induced implantation failures.