| Angiogenesis is the process by which endothelial cells disassemble and grow into functional blood vessels. Endothelial cell migration, assembly, and force generation are key components for initiating angiogenesis and new blood vessel formation. How the local environment, including matrix mechanics and chemical signals, influence these cellular functions is important for understanding and controlling angiogenesis. In this thesis, human umbilical vein endothelial cells (HUVECs) were seeded onto polyacrylamide gels of varying stiffness and treated with bFGF, VEGF, or left untreated and observed over time. The radial distribution function was adapted from its classic function of determining the atomic structure of liquids and gases to determine the structure and extent of cellular networking. Using a microfluidic device, we presented a spatially and temporally stable VEGF gradient to the HUVECs and measured their motility and force generation over time. We showed that HUVECs assemble on soft substrates (E < 1000 Pa) but the addition of growth factors disrupts stable network formation. The radial distribution function is able to quantify the extent of network formation, but it is statistically dependent on the amount of data, or cells, available to analyze in each image. Finally, HUVECs were shown to move chemotactically in a gradient of VEGF and migration is dependent on the local concentration of growth factor. While chemotaxis does not affect cellular force generation, cells on stiffer substrates exert larger traction stresses and force centers polarize with the direction of motion. We have been able to show how altering mechanical and chemical signals affect endothelial cell functions, which improves the understanding of how cells migrate and assemble to form new blood vessels. |
