Differential Expression and Localization of Integrins and CD44 in the Membrane Domains of Human Uterine Epithelial Cells During the Menstrual Cycle

Abstract

Human uterine epithelium displays a distinctly polarized organization with basal, lateral, and apical plasma membrane domains. Although nonadhesive throughout most of the menstrual cycle, uterine epithelial cells allow attachment of trophoblast cells to their apical pole during embryo implantation. Development of the receptive state might involve expression of cell adhesion molecules and/or redistribution of such molecules with respect to their localization at the basal, lateral, and apical membrane domains of cells. Expression and distribution of alpha 1-, alpha 3-, alpha 5-, alpha 6-, beta one-, beta 3- and beta 4-integrin subunits as well as of CD44 were examined in the luminal epithelium of human endometrium by immunohistochemistry in different phases of the menstrual cycle. The luminal epithelium was found to express alpha 1-, alpha 3-, alpha 6-, beta 1-, beta 4-integrin subunits and CD44. alpha l6-Integrin subunits and CD44 displayed cycle dependency. The alpha 6-integrin subunits were detected in the basal membrane domains in all phases. However, in correlation with increasing expression during the secretory phase of cycle, these subunits newly appeared in the lateral membranes of epithelial cells. CD44 showed increased expression in the secretory phase but was always restricted to the lateral membranes. The conspicuous behavior of alpha 6-integrin subunits and CD44 is discussed with respect to its possible functional significance for embryo implantation, and in relation to a hypothesis postulating that steroid-controlled master genes direct the acquisition of the receptive state of the luminal uterine epithelium by changing elements of the apicobasal polarity of these cells.