Expression and role of sugar chains in human placenta

Aim: The presence of carbohydrates in different cell types in human placenta suggests their major role in maternal-fetal exchanges, intercellular adhesion, cellular metabolism, proliferation and branching of the villous vessels. Although studies on glycoconjugates distribution in human placenta have been already performed, progress toward their physiological function in placenta development are missing. In this study we investigated the sugar chain expression, role and control mechanism of core-1 O-glycans and N-glycans in human placenta. Methods: paraffin fixed sections from first trimester human placenta were processed for lectin histochemistry using Peanut agglutinin (PNA) directed to core-1 O-glycans (Galβ1–3 GalNAc) and Concanavalin A (ConA) directed to pentasaccharidic core of N-glycans (-D-Man and D-Glc). HTR8 trophoblast cells were incubated under low (3%) or standard (20%) oxygen tension and levels of Galβ1–3 GalNAc disaccharide and N-glycans were measured by FACS. Cultures were exposed to PNA and ConA lectins and assayed for cell viability and proliferation. Results: ConA staining was widely distributed in all cellular elements of the villi, the PNA staining was restricted to villous cytotrophoblast. Galβ1–3 GalNAc disaccharide expression level was significantly increased (5-fold) at 3% of oxygen, N-glycans expression was not influenced by oxygen tensions. The treatment of cell cultures with PNA lectin resulted in a significant increase in cell proliferation as compared to control untreated or ConA- treated cultures. Conclusions: These data suggest that post-translational modifications such as specific glycosylation are modulated by low oxygen tension and play a major role in determining trophoblast differentiation.