Figure 3

First trimester villous explants after 7 days in serum-free conditioned medium from first trimester placental fibroblasts. (b) is an enlargement of the boxed area in (a) showing streaming-type migration by trophoblast, with cells adopting a bipolar morphology oriented in the direction of migration. (c) shows a control experiment in which unconditioned medium was added daily. Tissue is on the right, with collagen gel to the left and a dense multilayered sheet of phase-bright cytotrophoblast in between.