VLCs have the capacity to generate functional blood vessels in vivo. (A) CFSE-labeled VLCs injected in Matrigel plugs into immunodeficient mice assembled into tomato lectin–perfusioned, Cy3-labeled blood vessels within 2 weeks. Combined image of CFSE-labeled cells and counterstaining with DAPI (4′,6-Diamidino-2-phenylindole) is also shown (magnification, × 200). CD45^-VE-cadherin⁺ cells (ECs) also form functional neovessels, whereas CD45⁺VE-cadherin^- cells (leukocytes) sorted from the same specimen remain as individual cells and do not partake in the formation of blood vessels assembled by host cells in the periphery of the Matrigel plugs (arrows). (B) VLCs cultured on fibronectin-coated plates in endothelial cell growth media developed cytoplasmic projections and intercellular junctions after 2 weeks. (Magnification, × 200.) (C) Capillaries in human tumors harbored CD45⁺ cells coexpressing the endothelial marker VE-cadherin. (Magnification, × 200.)