An In Vitro Model of Trophoblast Invasion of Spiral Arteries

Extravillous trophoblasts invade the uterine wall (interstitial invasion) and the spiral arteries (endovascular invasion), replacing the cells of the vessel wall and creating a high-flow, low-resistance vessel. We describe a model to allow the interactions between the invading trophoblast cells and the cells of the spiral artery to be directly examined. Unmodified (non-placental bed) spiral arteries are obtained from uterine biopsies at Caesarean section. Fluorescently labeled trophoblasts (either primary first-trimester extravillous trophoblasts or an extravillous trophoblast cell line) are seeded on top of artery segments embedded in fibrin gels (to study interstitial invasion) or perfused into the lumen of arteries (to study endovascular invasion). Trophoblasts are incubated with the vessels for different periods prior to cryosectioning. Both interstitial and endovascular interactions/invasion can be detected and immunohistochemical analyses carried out. This novel method is useful in an area where in vitro studies have been hampered by the lack of suitable models directly examining cellular interactions during invasion.