Figure 1.

Morphology of trophoblast cells. (A) Primary undifferentiated cytotrophoblasts (CTB) were cultured as described in Materials and Methods. After 24 h cultivation cells show characteristics of mononucleated epithelial cells with well-demarcated cell borders and large nuclei as highlighted by the red arrows; and (B) after 3 days of cultivation CTB fused to form multinucleated entities representing a syncytium (STB) as indicated by the red arrows. STB appear as a single continuous layer without cell borders. Bright field images were captured at 10× magnification. Trophoblasts were isolated from a healthy human placenta at term.