Presence of Integrin alpha(IIb)beta3 in early gestation human trophoblasts : Possible involvement of fibrin as a matrix ligand

IntroductionVarious integrins are expressed on trophoblast membrane and participate in placenta anchoring, cell adhesion , migration and vascular development. Although integrin αIIbβ3 is known to be associated mainly with megakaryocytes and platelets, here we show for the first time its presence in human trophoblasts and in ex-vivo placental villi.MethodsTrophoblasts were isolated and cultured from early term placentas (9-13 weeks of gestation). The presence of αIIbβ3 integrin was demonstrated in the cells by means of immunofluorescence , flow cytometry and Western blot analysis and in villous placentas by immunohistochemistry. Interaction of trophoblasts with fibronectin and fibrin was evaluated by adhesion assays.ResultsExpression of αIIb protein in trophoblasts decreased with time in culture and was more prominent when cells were cultured on fibrin as compared to fibronectin. Presence of αIIb on villous trophoblasts was documented in placenta sections of 8 and 15 weeks of gestation but not in term placentas.Trophoblasts adhesion to fibrin was reduced by 45% in the presence of blocking antibodies for αIIb, but only by 10% to fibronectin, suggesting fibrin as a ligand for trophoblast αIIbβ3.ConclusionsOur finding demonstrate the transient presence and participation of αIIbβ3 in the orchestrated adhesion molecules of trophblasts and villi. The increased adhesion and expression of αIIb in trophoblasts on fibrin suggest its involvement as a ligand in the extracellular milieu of the early fetal placenta.