Normal labor associated with changes in uterine heparan sulfate proteoglycan expression and localization

Hypothesis: Proteoglycans are well‐known modulators of intercellular communication and signaling. Remodeling of the proteoglycans in the human uterus occurs throughout pregnancy, and during labor. We therefore hypothesize that heparan sulfate proteoglycans (HSPGs) play an important role in establishing normal labor. In this study HSPGs were characterized and localized in human uterine tissue. Methods: Uterine biopsies were obtained from four nonpregnant women, four women during elective cesarean section and four during emergency cesarean section. The biopsies were extracted using 4 m guanidinium hydrochloride (GuHCL). HSPGs were then purified by repeated ion‐exchange chromatography on dehydroepiandrosterone (DEAE)‐cellulose after digestion with chondroitinase ABC and finally precipitated with Alcian blue. HSPGs were identified by agarose gel electrophoresis and Western blotting. Controlled degradation of the heparan sulfate (HS) side‐chains was performed using heparitinase or deglycosylation with trifluoromethanesulfonic acid (TFMS). The resulting core proteins were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and visualized by Coomassie staining. HSPGs were localized in uterine tissue by immunohistochemistry. Results: SDS–PAGE after deglycosylation indicated the presence of multiple distinct core proteins tentatively identified as syndecans 1–4 and glypican 1. Western blots confirmed the presence of these proteoglycans and also perlecan. Immunohistochemistry revealed that the HSPGs were localized mainly in the smooth muscle with few in the extracellular matrix (ECM). Syndecan 3, the dominant proteoglycan, showed the most pronounced changes during pregnancy and labor. Conclusion: For the first time several heparan sulfate proteoglycans have been identified and localized in the human uterus and shown to vary in expression during pregnancy and labor. Syndecan 3 had the most outstanding features in this respect.