Differences in trophoblast invasion in extrauterine and intrauterine pregnancy

If trophoblast invasion in ectopic pregnancy is compared with intrauterine pregnancy similarities can be observed concerning the expression of human leukocyte antigen (HLA)-G in extravillous trophoblast cells and concerning the proteases which are involved in the remodelling of the extracellular matrix (MT1-MMP, MT2-MMP, MMP-1, TIMP-2) and which are also located in extravillous trophoblast cells. The same is true for the cytokines involved in implantation (LIF, TGFbeta, interferons, EGF). However, NK cells which are typical for intrauterine pregnancy are absent. Ectopic pregnancies can be divided into viable tubal pregnancies and tubal abortions. In viable tubal pregnancies trophoblast invasion is enhanced compared to intrauterine pregnancy and to tubal abortion. It is characteristic for those cases that the strict discrimination between the proliferative and the invasive phenotype of trophoblast typical for intrauterine pregnancies is abolished. So proliferative and invasive zone are overlapping with earlier apolar matrix secretion and expedited switch towards invasion-associated integrin expression.