(282b) Local Mechanical Signals Influence Endothelial Cell Behavior During 3D Vasculogenesis in Vitro

Endothelial cell morphogenesis depends on both chemical and mechanical signaling through the extracellular matrix (ECM). Various ECM components and soluble factors have been shown to promote or inhibit the process of spontaneous tube formation in vitro; however, separating mechanical and chemical influences on this process remains a challenge. To isolate the impact of local mechanical signaling through the ECM on global vasculogenesis in vitro, we vary cell interaction distances and impose mechanical constraints in 3D, HUVEC-seeded collagen matrices while using anti-VEGF antibodies to block VEGF signaling. Mechanically constrained boundaries alter the effective mechanics of the matrix without changing the chemistry of the ECM and allow us to define the mechanical length scale over which ECs can communicate through the matrix to form connections. Using fluorescence confocal microscopy, we characterize the variety of multi-cellular behaviors observed in 3D using cluster analysis and percolation theory, and we summarize our observations with a cell behavior ?state diagram' that is a function of initial cell spacing and mechanical confinement. We report that a critical, initial cell-separation distance is required for the formation of a connected multi-cellular structure. In addition, adhesive boundaries screen the long range interactions between cells and direct the cells towards this boundary to create a planar vascular plexus with open lumens. This study leads us towards micromechanical methods with which to direct vasculogenesis in vitro for future studies on the mechanisms of angiogenesis in development and disease.