Quantitative Imaging-Based Examination of Pericytes Controlling Endothelial Growth Dynamics and Angiogenesis.

Microvascular endothelial cell-mural cell interactions are instrumental in modulating both physiological and pathologic angiogenesis. Pericyte-endothelial cell communication through direct physical associations and secreted effectors comprises a bidirectional signal array that regulates vascular maturation and integrity. As endothelial cell proliferation, migration, and morphogenesis are key elements of vascular growth and remodeling during angiogenesis, we have developed novel preclinical systems for studying the roles of endothelial-mural cell dynamics on cell cycle entry and angiogenic activity in vitro. These coculture models not only enable evaluation of endothelial cell-pericyte "cross talk" but also allow for the quantitative analysis of both heterotypic contact-dependent and contact-independent cell cycle progression in either cell population, as well as angiogenic sprouting in three-dimensional vascular networks. Cells actively proliferating in two-dimensional assays can be labeled via incorporation of 5-ethynyl-2'-deoxyuridine (EdU) into their DNA. Additionally, each cell population can be vitally labeled with a variety of cell-specific and/or membrane-permeant lipophilic dyes prior to coculture, such as DiO, or through immunofluorescence of mural or endothelial cell-specific markers after cellular fixation and/or permeabilization. Ultimately, this experimental approach can be used to investigate cellular contact-dependent and soluble mechanisms mediating mural-endothelial cell interactions, which may be instrumental in microvascular development and remodeling in vivo.