Figure 7.

Vasculogenesis of metanephric mesenchymal (MM) cells grown in three-dimensional (3D) culture in sea sponges. A–I: MM cells proliferate in 3D sea sponge scaffolds in response to vascular endothelial growth factor (VEGF)-A (B) and platelet-derived growth factor B chain (PDGF-BB) (C–I) relative to diluent controls (A). However, only PDGF-BB stimulates vascular profiles characterized by large cyst-like structures with lumens lined with VEGF receptor 2 (Flk-1) + MM cells and a network of arborized cells (C–E). G: By electron microscopy, MM cells incubated with diluent show long attenuated capillary-like profiles often with lumens. H: The arborized MM cells after incubation with PDGF-BB show cytoplasmic extensions and numerous vacuoles proposed by others to be a mode of capillary lumen formation. I: Profiles of cyst-like structures show long attenuated cells with microvilli at the surface projecting into the lumen above several layers of attenuated cells similar in appearance to vascular smooth muscle cells. J and K: Three-dimensional (3D) co-culture of MM and ureteric bud (UB) cells in sea sponges in vitro (J) and in implants in vivo (K) leads to epithelialization of UB cells and organization and arborization of surrounding MM cells. Data are expressed as means ± SEM. n = 3 independent experiments. ^∗P < 0.05 versus diluent control. Original magnification: ×20 (A, J, K); ×10 (B–E); ×5,000 (G–I).