INDUCTION OF VASCULOGENESIS IN QUAIL BLASTODISC-DERIVED EMBRYOID BODIES

We have previously developed an in vitro culture system in which disso ciated cells from unincubated quail blastodiscs formed in vivo-like bl ood islands consisting of blood and endothelial cells in response to f ibroblast growth factors (FGFs). Here we demonstrate that the same qua il blastodisc cells grown in suspension culture in the presence of bas ic FGF (bFGF) reaggregated and formed three-dimensional spherules (emb ryoid bodies, EBs) which underwent vasculogenesis and hematopoiesis wi thin 3 days. In contrast to murine embryoid bodies, which undergo vasc ulogenesis spontaneously, the formation of vascular structures in quai l blastodisc cultures was absolutely dependent on bFGF. While about 75 % contained blood islands and about 50% formed capillaries in the pres ence of bFGF, only 0.2% of the embryoid bodies formed blood islands in control cultures without bFGF. Vascular channels were gradually encoa ted by primitive smooth muscle cells within 5 days. Ultrastructural ex aminations revealed capillary blood vessels and blood islands indistin guishable from their yolk sac counterparts. Mesodermal tissue was pres ent in cultures both with and without bFGF, but consisted of an avascu lar undifferentiated mesenchyme in control cultures. Since the entire sequence of vasculogenesis from the formation of endothelial cells to their assembly into a vascular plexus is observed in response to the i nducer bFGF, this culture system is a suitable model for studying the molecular events that initiate the emergence of endothelial cells and the formation of a vascular plexus during vasculogenesis. (C) 1994 Aca demic Press, Inc.