A vascular affair

In this thesis, 3 topics regarding the vascular system are discussed. First, a vessel-on-a-chip method is used to study the process of leukocyte transendothelial migration (TEM) in full. In the commonly used methods, the leukocytes encounter plastic after extravasating from the vessels instead of soft tissue. In the vessel-on-a-chip however, these cells encounter a physiological extracellular matrix. Using this state-of-the-art method, we were able to show that different leukocytes employ different methods of migration, something that previously could not be studied in vitro. In addition, we used this system to characterize neutrophils of a patient lacking the ARPC1B gene. These neutrophils are defective, especially in their migratory behavior. Using the vessel-on-a-chip, we could distinguish between hampered extravasation and diminished subsequent migration. The next topic concerns sprouting angiogenesis. A bead-sprouting assay is optimized for confocal microscopy, allowing the study of the process in much more detail. This assay is then used to study the role of Rab5C during VEGFR2 internalization and subsequent sprouting of the endothelial cells. Lastly, the role of the RhoGEF Trio in endothelial cells is described. Trio is well known for its role during neural growth; however, our group has shown it is an important factor in endothelial cells as well. Especially regarding the barrier function between endothelial cells. We created a vascular-specific, inducible mouse model to study this role in vivo