Figure 2

First trimester villous explants after (a) 3 and (b) 5 days of culture on a collagen gel support in serum-free medium with daily medium change. (c) shows an enlargement of the boxed area in (b). In (d) the medium was left unchanged for 5 days. (e) shows an enlargement of the boxed area in (d). Note that both explants show elongated bipolar cytotrophoblasts at the periphery. However when the medium is unchanged, cells detach from the edge of the outgrowing sheet and migration is more extensive.