Expression of betaglycan in pregnant tissues throughout gestation

Background: Betaglycan is a membrane-anchored proteoglycan involved in mediating the passage of transforming growth factor-beta (TGF-beta), inhibin and activin activities into cells. TGF-beta and inhibin-related proteins are growth factors that are expressed by several tissues and in pregnancy. They have a function in modulating the growth, differentiation and invasion of the placental trophoblast. Objective: To evaluate whether betaglycan is expressed by intrauterine tissues throughout gestation. Design and methods: Expression of betaglycan mRNA and protein was evaluated (by RT-PCR and immunohistochemistry, respectively) in trophoblast, decidua and fetal membranes collected during the first (n = 6 elective terminations of pregnancy, between 8 and 12 gestational weeks) and third (n = 6 elective caesarean sections, between 39 and 40 weeks) trimesters of pregnancy. Results: Betaglycan mRNA was expressed by all gestational tissues, independently of gestational age. Immunoreactive protein was found in decidual cells and in some chorionic, but not epithelial, amniotic cells. With respect to the placental localization, syncytiotrophoblast, but not cytotrophoblast, cells were intensively stained both in the placental bed and in the villous trophoblast, and in some cells within the stroma of terminal villi, of the first and third trimesters of pregnancy Immunoreactive betaglycan was demonstrated in the endothelial cells of decidual vessels in both the first and third trimesters of pregnancy, whereas endothelial cells of fetal blood vessels in the villous were clearly represented only in first trimester samples, not in those of term placenta. Conclusions: Betaglycan mRNA and peptide are expressed by the trophoblast, the decidua and the fetal membranes, but the localization of the peptide in vessel walls is dependent on gestational age.