T9.3 Decidual cell surface and secreted factors regulate extravillous trophoblast function: important implications in placental development

Abstract

Integrins are heterodimeric glycoproteins acting as membrane receptors for extracellular matrix components. The specificity of these receptors towards one particular matrix glycoprotein depends on the type of α and β subunit combination. Since integrins are involved in the migratory behaviour of cells and since cytotrophoblastic cells are constitutively invasive, we undertook to immunolocalize the α2, α5 and α6 integrin subunits in normal and hydatidiform molar trophoblast, in an implantation site as well as in decidualized and non-decidualized endometrium. α6 positivity was confined to villous cytotrophoblast and was clearly polarized towards the basement membrane. Extravillous cytotrophoblastic cells were α6-negative but became α5-positive. In contrast to normal trophoblast, villous cytotrophoblast from hydatidiform molar tissue was α5-positive. We conclude that the expression of a α5 integrin subunit on cytotropholastic cell surfaces is correlated with the appearance of an invasive phenotype. α6 and α2 integrin subunits were both localized on the surface and glandular epithelium of the endometrium and their expression was increased during the secretory phase but became low or undetectable after decidualization. In contrast, α5 subunit positivity was weak in the same epithelia during the first half of the cycle but disappeared after ovulation. Stromal cell α5 positivity was present throughout the cycle but increased dramatically in decidualized endometria. We conclude that the α5 integrin subunit which disappears from the epithelium at the end of the cycle might allow migration of the epithelial cells and repair of the endometrium after menses. We also wonder if α5 positivity is part of a change in the stromal cell phenotype induced by decidualization.