Fig 1.

Comparison of in vivo placental structure to placenta explant model. (A) Structure and orientation of fetus and placenta in uterus at ∼6 weeks of gestation. Fetal structures are represented in shades of blue and purple while maternal structures are in shades of red. Maternal structures: MY, myometrium; SA, spiral arteries; DD, decidua (uterine lining during pregnancy); IVS, intervillous space filled with maternal blood. Fetal structures: VT, villous tree; CP, chorionic plate; UC, umbilical cord; AF, amniotic fluid. (B) Close-up view of the maternal-fetal interface as indicated by the inset in panel A. Maternal blood surrounds the villous tree composed of anchoring villi (AV) and floating villi (FV), which are covered by a syncytiotrophoblast (SYN) that is underlaid by subsyncytial cytotrophoblasts (sCTB) and a basement membrane. The sCTB layer grows increasingly discontinuous in later trimesters. Gas and nutrient exchange with the maternal blood occurs across the syncytiotrophoblast to supply fetal capillaries (not shown) in the villous stroma (STR). At the uterine wall, extravillous cytotrophoblasts (EVT) anchor the villous tree in the decidua. Some invade the decidua and move away from the tip to remodel maternal spiral arteries (not shown), with altered gene expression patterns as they move. (C) Six-week placental explant anchored in Matrigel. Bar, 1 mm. (D) Cartoon representation of the relevant structures shown in panel C. B. Mem, basement membrane.