Fig. 1

Formation of human cystic embryoid bodies.

(A) Time scale of hEBs development. Shown from left to right is a gradual growth and transformation with time of simple, densely packed hEBs into cystic hEBs. To induce formation of EBs, ES cells were transferred to plastic Petri dishes to allow their aggregation and grown in culture medium lacking leukemia inhibitor factor (LIF) and basic fibroblast growth factor (bFGF). Shown from I to IV are EBs from 3, 7, 10 and 14 days, respectively, after their transfer to Petri dishes. I: simple EB; II & III: cavitated EB; IV: cystic EB. Scale bar, 200 µm. (B) Morphological differentiation. Shown are 5 µm paraffin-embedded sections of 20-day-old EBs stained with hematoxylin and eosin (H&E; I-III), in different magnifications. I: ×5; scale bar, 400 µm. II: ×20; scale bar, 100 µm. III: ×40; scale bar, 50 µm. Note in the enlarged EB, a single cell layer of endodermal-like cells in the periphery and epithelial cells surrounding a lumen in the center.