Differential expression of the integrin subunits in human fetal membranes

Abstract

The distribution of the α1, α3-α6, β3 and β4 integrin subunits in fetal membranes at term was examined using an indirect immunofluorescence technique and confocal laser scanning microscopy. In the amniotic epithelium, β4 integrin (α6β4) exhibited distinct basal localization, whereas β1 integrins (α3β1 α5β1) were localized basolaterally. This finding suggests that integrins, especially α6β4 which is a structural component of the hemidesmosomes, may function as basement membrane receptors. Integrins localized laterally may play a role in cell-cell interactions. β1 (α1β1, α5β1) integrins are probably involved in cell-matrix interactions in the connective tissue layers which are rich in collagens and fibronectin. Cytotrophoblasts, located predominantly towards the chorionic basement membrane, mainly expressed α6β4, while those located predominantly in the vicinity of decidua expressed α5β1 α3β1 and α1β1 Decidual cells expressed α3β1 and α1β1 whereas α1, α5, α6, β1 and β4 were expressed in blood vessels. This pattern of integrin expression reflects the reported difference in composition of the extracellular matrix at these locations and obviates an important role for α5β1 at the chorio-decidual interface. The differential integrin expression at the cell-basement membrane interfaces demonstrated in this study (at amniotic epithelium, cytotrophoblasts, decidual cells and blood vessels) indicated a differential recognition of basement membranes by these cells. β4 may have a specialized function at the blood vessels, and possibly in cytotrophoblasts, that is distinct from its role in hemidesmosome-mediated attachment. This study suggests that integrins may be involved in cell-matrix and cell-cell adhesions in fetal membranes and may therefore be important for maintaining their normal structural and functional integrity.