Directing Angiogenesis Cellular Responses to Gradients in vitro
Abstract: Blood vessels are essential for the delivery of nutrients and oxygen to tissues, as well as for the removal of waste products. Patients with tumors, wounds or diabetes all have active angiogenesis, formation and remodeling of blood vessels, a process that is initiated and manipulated by gradients of secreted signaling proteins.This thesis describes the development of new microfluidic in vitro assays where directed migration of single endothelial cells and three dimensional vascular structures can be monitored in real time. Combining these assays with live imaging microscopy we have studied the behavior of endothelial cells in gradients of proangiogenic factors as well as directed sprouting in embryonic kidneys and stem cell cultures.With the 2D assay we have quantified endothelial cell chemotaxis towards FGF2, VEGFA165 and VEGFA121 and we also demonstrate that constant levels of VEGFA165, but not of FGF2, are able to reduce chemokinesis of endothelial cells.In the 3D migration chamber we have studied directed endothelial cell sprouting in mouse embryonic kidneys and embryoid bodies in response to VEGFA gradients. In both models directed angiogenesis is detected towards increasing levels of growth factor.Using the microarray technique on differentiating embryonic stem cells we have been able to identify the gene exoc3l2 as potentially involved in angiogenesis and endothelial cell migration and we present evidence that ExoC3l2 is associated with the exocyst complex; an important regulator of cell polarity. We have also shown that siRNA mediated gene silencing of exoc3l2 results in impaired VEGFR2 phosphorylation as well as loss of directionality in response to a VEGFA gradient.
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