Cytomorphometric analysis and surface ultrastructure of developing decidua

A scanning electron microscopic (SEM) and morphometric analysis of the topographical changes occurring in the uterine luminal epithelial layer in association with decidual tissue (DT) formation in guinea pigs was undertaken in order to elucidate the surface ultrastructural characteristics which occur during the process of endometrial differentiation. Experimentally induced decidua formation was promoted by mechanical stimulation of the antimesometrial luminal surface during the period of maximal uterine sensitivity to stromal differentiation. DT-associated remodeling of the uterine epithelial layer was subsequently examined by light and SE microscopic analysis for apical epithelial and luminal contour alterations associated with decidua growth. Cytological changes in the luminal surface associated with DT induction included sparse microvillus growth from the apical epithelial surface, accompanied by the appearance of prominent apical membrane surface protrusions and endometrial gland openings as compared with non-DT-stimulated control samples. Decidua surface growth was characterized by a short, sparse epithelial microvillus pattern present over a highly contoured luminal uterine surface on which contoured gland openings were both numerous and prominent. These surface modifications contrasted with the flat, non-decidualized luminal surface contour which was covered by distinct, microvilli-laden, apical cell membranes, and defined by prominent intercellular membrane borders. The uterine surface at the time of maximal DT formation (i.e. growth) closely resembled that of a uterine luminal surface undergoing apoptosis and subsequent cellular reabsorption, characterized by disrupted cell surface membranes, sparse microvillus surfaces and prominent epithelial contours reflecting stromal tissue and vasculature involution. These data indicate that the alterations in the uterine luminal surface associated with DT formation are reminiscent of the endometrial changes associated with the initiation of early placentation, and may be used as a model for the analysis of the role of epithelial cell surface modifications associated with the induction and support of interstitial blastocyst implantation and early decidua formation. (C) 2003 Elsevier Science Ltd. All rights reserved.