Further studies of lectin binding by villous and extravillous trophoblast in normal and pathological pregnancy

Examination of human pregnancy tissues with a panel of lectins provides the opportunity to probe different aspects of carbohydrate structure. Nine biotinylated lectins [concanavalin A (con A), wheat germ agglutin (WGA), Lens culinaris A (LCH-A), Pisum sativum (PSA), Phaseolus vulgaris (PHA-E and PHA-L), Ulex europaeus 1 (UEA1), Griffonia simplicifolia (GSI and GSII)] were used to investigate the lectin binding of human trophoblast in normal, tubal, and molar pregnancy. All lectins except UEA1 bound to normal villous syncytiotrophoblast. Binding of lectins to extravillous trophoblast was more restricted than to villous trophoblast, occurring predominantly with con A, PHA-E, PHA-L, WGA, GSI, and GSII. LCH-A reacted with cyto-trophoblastic columns but not with interstitial or endovascular trophoblast. Con A and GSII were the only lectins that bound to trophoblastic giant cells. GSI and GSII bound preferentially to extravillous trophoblast, showing only focal reactivity with villous trophoblast. Lectin binding in ectopic pregnancy was similar to that in normal first-trimester intrauterine pregnancy. Reactivity in molar pregnancy also generally mirrored that observed in normal pregnancy; however, reactivity of GSII with villous trophoblast was more consistent than that observed in normal pregnancy, and GSI showed uniform binding to proliferating syncytial areas. Thus, lectin binding studies allow definition of surface carbohydrates, which may play a role in the controlled trophoblast proliferation and invasion that occurs in normal pregnancy.