Directed Differentiation of Specialized Endothelial Cells

Vascular endothelial cell (EC) or endothelial progenitor cells (EPC) derived from stem cells could potentially lead to a variety of clinically relevant therapeutic applications including building new blood vessels in both in damaged heart and skeletal muscle, lining small diameter vascular grafts for reduced thrombosis, or in the development of a variety of tissue-engineered materials that will need a vasculature for receiving an adequate blood supply. These cells are also valuable as target for screening for new anti-angiogenic and anti-thormobogenic molecules. However, EC exhibit a variety of functionally distinct subphenotypes. These include the arterial and venous EC, as well as sprouting “tip” and “stalk”, and the lesser understood “phalanx” EC in a sprouting blood vessel. The studies proposed in this grant application explore this potential (and limitations) for directing the fate of EC subphenotypes using biochemical and physical signaling, as well as, examine the molecular mechanisms underlying the specification of these EC subphenotypes. To date, we have been able to generate EC subphenotypes, called tip and stalk EC, consistent with highly angiogenic EC. These are the most relavant EC subphenotype for developing anti-angiogenic strategies associated with tumor progression, as well as, the best EC subphenotype to be used in repairing ischemia in the heart and/or limbs.

Endothelial cells (EC) exhibit a wide range of functionally distinct subphenotypes including: arterial, venous, as well as the lesser understood “tip”, “stalk”, and “phalanx” EC. The arterial-specific phalanx EC are perhaps most desirable as delivery vehicles for lining the lumens of small diameter vascular grafts in order to minimize thrombosis/arteriosclerosis while the proangiogenic tip/stalk EC would generate the most robust cells for ischemic transplantation and for screening antiangiogenic compounds. This project focused on the in vitro derivation of these distinct subpopulations of EC so that they can be tailored, as needed, for studying disease or repair. From these studies, human ESC and iPS cells have been successfully derived into endothelial cells. Data indicates that tip/stalk and phalanx endothelial cells can be generated and isolated from human ESC. Moreover, the mechanical signal from shear stress does aid in differentiation of endothlelial cells from vascular progenitor cells. However, stability of these subphenotypes has not yet been established.