Presence of Integrin alpha(IIb)beta 3 in early gestation human trophoblasts: possible involvement of fibrin as a matrix ligand.
BACKGROUND
Various integrins are expressed on trophoblast membrane and participate in placenta anchoring, cell adhesion , migration and vascular development. Although integrin alpha IIb beta 3 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.


METHODS
Trophoblasts were isolated and cultured from early term placentas (9-13 weeks of gestation). The presence of alpha IIb beta 3 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.


RESULTS
Expression of alpha IIb protein in trophoblasts decreased with time in culture and was more prominent when cells were cultured on fibrin as compared to fibronectin. Presence of alpha IIb 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 alpha IIb, but only by 10% to fibronectin, suggesting fibrin as a ligand for trophoblast alpha IIb beta 3.


CONCLUSIONS
Our finding demonstrate the transient presence and participation of alpha IIb beta 3 in the orchestrated adhesion molecules of trophblasts and villi. The increased adhesion and expression of alpha IIb in trophoblasts on fibrin suggest its involvement as a ligand in the extracellular milieu of the early fetal placenta.
Snir
Ayelet
A
Thrombosis and Hemostasis Unit, Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus P.O.B 9602, Haifa, 31096, Israel.
Brenner
Benjamin
B
Paz
Baram
B
Lanir
Naomi
N
D002478:Cells, Cultured; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000378:metabolism*; D005260:Female; D005337:Fibrin / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007150:Immunohistochemistry; D008024:Ligands; D010920:Placenta / Q000166:cytology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011247:Pregnancy; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism*
D016326:Extracellular Matrix Proteins; D008024:Ligands; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005337:Fibrin