Fibronectin and laminin in the early human placenta.

The distribution of fibronectin and laminin was investigated in early intrauterine and ectopic tubal pregnancy using a standard immunoperoxidase technique on paraffin-embedded tissues. Localization of both fibronectin and laminin appeared identical in intrauterine and in ectopic pregnancy. Fibronectin was demonstrated in chorionic villous stroma, in the distal cytotrophoblast cell columns, in infiltrating mononuclear extravillous trophoblast and in endovascular trophoblast. Villous trophoblast and multinucleate interstitial trophoblast did not label. Extracellular fibronectin was demonstrated amidst sheets of infiltrating extravillous trophoblast. Laminin distribution was similar to that described for fibronectin but laminin was also present in the basement membrane of villous cytotrophoblast. Both fibronectin and laminin showed a pericellular distribution around decidual stromal cells. This study demonstrates further heterogeneity of human trophoblast populations. The presence of fibronectin in infiltrating extravillous trophoblast, endovascular trophoblast and in the distal columns may enhance trophoblast adhesion to maternal tissues and facilitate trophoblast migration.