Villous explant culture: characterization and evaluation of a model to study trophoblast invasion.

The mechanisms that control invasion of cytotrophoblast (CTB) cells into the maternal decidua and myometrium with transformation of the maternal spiral arteries are not fully understood, but oxygen is thought to be a key factor. We carried out a semiquantitative evaluation of an explant culture model for use in the study of trophoblast proliferation and invasion. Explants of human villous tissue (6-9 weeks of gestation) cultured on Matrigel in both standard culture conditions (18% O2) and in a low oxygen environment (2% O2) produced regions of outgrowth, of cytotrophoblast cells from villous tips and migration of cells into the Matrigel. The number of sites of outgrowth and migration, area of outgrowth, and extent of migration of cells into the Matrigel tended to increase throughout the culture period (144 h) but varied between explants from the same placenta and those from different placentas. There were no significant differences in the number of sites of outgrowth or migration scores in explants cultured in a low oxygen environment compared to those cultured in standard conditions. This study highlights the importance of careful validation, design and interpretation of experiments using in vitro culture systems, particularly those investigating the regulatory role of oxygen.