Problem:  Invasion of trophoblast differs between implantation and subsequent placentation. Here we present double tissue co-culture in vitro models for trophoblast invasion.

Material and Methods:  Pieces of decidua parietalis (6-12 weeks gestation) were confronted directly with villous explants (direct confrontation) or after separate preculture for 72h (indirect confrontation). For “indirect confrontation” decidua pieces re-epithelialized during preculture (constant agitation). All confrontations were harvested after 72h and were processed for immunohistochemistry.

Results:  During indirect confrontation immunohistochemical staining for HLA-G and cytokeratin 7 revealed trophoblast migration on top of the decidual epithelium and little invasion into the decidual stroma. During direct confrontation, the same staining revealed strong invasion of extravillous trophoblasts into decidual stroma.

Conclusion:  Trophoblasts confronted to decidual epithelium seem to be less invasive than trophoblasts confronted to the decidual stroma directly. These model systems will be further used to investigate mechanisms underlying the interactions between trophoblasts and decidual epithelium/stroma.