ABSTRACT
Nascent blood vessel development in angiogenesis is a complex process involving cellular response to biochemical growth factors, degradation of the surrounding matrix, and coordinated migration of multiple endothelial cells up a growth factor gradient. Mechanistic understanding and quantitative modeling of the dominant dynamics involved in nascent vessel development will enable new strategies for regulating vessel growth rate and geometry, and may have implications in controlling development of complete vascular networks both in vitro and in vivo. In this work, we investigate the dynamics of nascent vessel development in 3D microfluidic assays, and formulate a quantitative process model based on our experimental characterization. We begin by developing a new microfluidic assay consisting of a collagen gel scaffold with features to reduce assay-to-assay variability and increase experimental throughput. The new assay yields a multitude of time-lapse and time-point growth data that reveal important dynamics involved in nascent vessel development, including dynamics of cell migration and the evolution of the vessel boundary as the matrix is degraded. A key experimental finding is that there is an inverse relationship between nascent vessel elongation rate and diameter under diverse biochemical conditions. This finding is supported by immunofluorescent staining and biochemical inhibition studies, which give insight into the dominant mechanisms determining nascent vessel diameter. Based on our experimental characterization, we formulate a simple quantitative model that predicts experimentally observed vessel diameters, and supports our understanding of the relevant dynamics. We are currently attempting to control nascent vessel growth rate and diameter based on our quantitative model, and by using a growth factor gradient as a control input.