The distribution of laminins and fibronectins is modulated during extravillous trophoblastic cell differentiation and decidual cell response to invasion in the human placenta.

We studied the distribution of laminin (Ln) alpha1-alpha3, beta1-beta3, and gamma1 chains, and of the extradomain-A (EDA) and EDB and the oncofetal epitope of fibronectin (Onc-Fn) in extravillous trophoblastic cells and decidua in the human placenta by immunohistochemistry. We found that the transition from villous to extravillous trophoblast was accompanied by emergence of immunoreactivity for EDA-, EDB-, and Onc-Fn among the cells. Furthermore, whereas the villous trophoblastic basement membrane (BM) contains Ln alpha1, alpha2, beta1, beta2, and gamma1 chains, immunoreactivity for Ln alpha1, beta1, and gamma1, but not for Ln alpha2 and beta2 chains, was detected in association with extravillous trophoblastic cells. Interestingly, although immunoreactivity for the Ln alpha1, alpha2, beta1, beta2, and gamma1 chains was detected in all decidual cell BMs, EDB-Fn and Onc-Fn were detected only in decidua that had been invaded by the trophoblast. In summary, our results describe distinct changes in the distribution of Ln and Fn isoforms during the differentiation of villous trophoblast into extravillous trophoblastic cells. Furthermore, EDB- and Onc-Fn are preferentially found in decidua that has been invaded by the trophoblast, indicating that the deposition of these Fn isoforms reflects a decidual cell response to invasion.