RISING STARS: Approaches to modeling placental function in preeclampsia in vitro and in vivo.

Modeling preeclampsia remains difficult due to the nature of the disease and the unique characteristics of the human placenta. Members of the Hominidae superfamily have a villous hemochorial placenta that is different in structure from those of other therian mammals, including the mouse hemochorial placenta, making this common animal model less ideal for studying this disease. Human placental tissues delivered from pregnancies complicated by preeclampsia are excellent for assessing the damage the disease causes but cannot answer how or when the disease begins. Symptoms of preeclampsia manifest halfway through pregnancy or later, making it currently impossible to identify preeclampsia in human tissues obtained from an early stage of pregnancy. Many animal and cell culture models recapitulate various aspects of preeclampsia, though none can on its own completely capture the complexity of human preeclampsia. It is particularly difficult to uncover the cause of the disease using models in which the disease is induced in the lab. However, the many ways by which preeclampsia-like features can be induced in a variety of laboratory animals are consistent with the idea that preeclampsia is a two-stage disease, in which a variety of initial insults may lead to placental ischemia, and ultimately systemic symptoms. The recent development of stem cell-based models, organoids, and various coculture systems have brought in vitro systems with human cells ever closer to recapitulating in vivo events that lead to placental ischemia.