In vitro model for developmental progression from vasculogenesis to angiogenesis with a murine endothelial precursor cell line, MFLM-4

In the embryo, vascular networks are developed through both vasculogenesis, the assembly of vessels from endothelial progenitor cells or hemangioblast s, and angiogenesis, the sprouting of vessels from preexisting capillaries. Cell culture models using endothelial cells (EC) and various extracellular matrix components have been useful in understanding the cellular and molec ular factors involved in angiogenesis. However, there are few models of vas culogenesis. Using a murine endothelial precursor cell line, MFLM-4, derive d from e14.5 lung mesenchyme, we have developed a culture system that not o nly recapitulates many of the characteristics of vasculogenesis but also pr ogresses into angiogenesis. By 8 h, MFLM-4 cultured on the basement membran e preparation Matrigel invade the matrix, coalesce, and assemble into large clusters of cells resembling blood islands. During vascular development, b lood islands are the focal areas for coalescence of endothelial precursors. For MFLM-4, this phase of in vitro vasculogenic clustering does not requir e proliferation. If proliferation is not blocked, MFLM-4 progresses into an angiogenic phase with the clusters forming multicell angiogenic sprouts. T hrough 3 days of culture, lumens form within the clusters, adjacent cluster s are connected with tube-like structures, and eventually an extensive netw ork or plexus of clusters connected by capillary-like tubes is formed. MFLM -4 cultured on Matrigel provides an in vitro system for analysis of the mul tistage, concurrent processes of vasculogenesis and angiogenesis. (C) 2000 Academic Press.