Profound morphological changes occur during the comparatively short life span of the placenta (Benirschke and Kaufmann, 2000; Fox, 1997). Most of these can be related directly to functional requirements; establishing support for fetal development and growth, maintaining an immunological barrier and adjusting maternal physiology to meet the demands of pregnancy. Histology and ultrastructure present snapshots of cell and tissue behavior, but not an account of cellular interactions or pathological mechanisms. Appropriate and robust in vitro models are therefore essential in bridging the gap between structure and function, as they can accommodate mechanistic questions and offer scope for the design and testing of possible therapeutic interventions. Models should mimic cell responses in vivo and go at least part way to reflecting physiological events within the placenta. Experimental levels range from tissue perfusion to explant and cell culture. Recently, genomic, transcriptomic, proteomic and computational biology approaches have become available to complement and extend in vitro methodologies. To appreciate how these models have been applied to studying pre-eclampsia, and the scope of the in vitro methods currently available, it is convenient to divide the placenta into structurally and functionally distinct compartments, i.e. the chorionic villus and the placental bed. In turn, we have subdivided these into individual cellular components, namely those of the trophoblast, vasculature and stroma.
Cytotrophoblast and syncytiotrophoblast in primary culture
Cytotrophoblast cells of the human placenta are the precursors of all other trophoblast phenotypes. As such, a variety of methods have been employed for their purification.