Expression of beta 1 integrins in human endometrial stromal and decidual cells

The present study was undertaken to investigate the expression of beta1 integrins in human endometrium and decidua using flow cytometry, immunohistochemistry, and immunoprecipitation. Fluorescence-activated flow cytometry demonstrated the greater expression of the beta 1, alpha 1, alpha 2, and alpha 5 subunits of the beta1 integrin family in cultured stromal cells from the midsecretory phase, than in those of the early proliferative phase. The addition of estradiol (E2) and progesterone (P) to cultured stromal cells in the early proliferative phase increased the expression of beta1 integrins in vitro. The immunohistochemical distribution of beta1 integrins demonstrated predominantly glandular epithelial staining in the proliferative phase, and mesenchymal and glandular staining in the midsecretory phase. Flow cytometry also demonstrated the expression of the beta 1, alpha 1, alpha 2, alpha 3, alpha 5, and alpha 6 subunits of beta 1 integrin family in cultured decidual cells, and the enriched-fraction of prolactin (PRL)-producing decidual cells isolated by Percoll gradients showed high levels of beta 1, integrins expression. Immunohistochemistry confirmed the beta 1 integrin cell surface phenotypes in cultured decidual cells observed by flow cytometry. Autoradiography of immunoprecipitate subjects to SDS-PAGE revealed three major polypeptides with molecular weights of 130 kDa (beta 1 subunit), 165 kDa (alpha 2 subunit), and 210 kDa (alpha 1 subunit) under reducing conditions. In summary, the present study demonstrated that endometrial stromal and decidual cells expressed beta1 integrin subunits at their surfaces. The expression exhibited a variability throughout the menstrual cycles, being predominantly detected in the secretory phase, and was maintained highly in the decidua. Thus, beta 1 integrins in human endometrium and decidua may be important in mediating the organization of extracellular matrix proteins derived from embryos during the early stage of implantation.