Trophoblastic invasion in vitro and in vivo: similarities and differences.

BACKGROUND The basic mechanisms of trophoblast invasion are not completely understood. This may be due to the lack of suitable in vitro models which enable experimental modulation of this complex process. In the present study, a three-dimensional co-culture model is used for comparing two factors considered to be implicated in the regulation of trophoblast invasion, the expression of HLA-G and apoptosis, in vitro and in vivo. METHODS Tissue fragments from human first trimester decidua parietalis were put in close contact with spheroids of AC-1M59 trophoblast/choriocarcinoma hybrid cells as a model of the invasive trophoblast. Cryostat sections from these co-cultures were immunohistochemically stained and compared with first trimester placentation sites in vivo. RESULTS Only the invasive trophoblast-derived cells showed an intensive staining for HLA-G, whereas the cells on the periphery of the confrontation culture exhibited only a weak staining. A similar staining pattern was found in vivo. Both in vitro and in vivo CD45(+) apoptotic leukocytes were frequently detected in close proximity to the invasive trophoblastic cells. CONCLUSIONS In this co-culture system, key factors considered to be implicated in trophoblast invasion in vivo can also be demonstrated in vitro. Therefore, it may help in finding strategies for the management of diseases associated with deficient trophoblast invasion.