Part B: Directed Differentiation of Human Embryonic Stem Cells into Endothelial Cells

Human embryonic stem (ES) cells have virtually unlimited self-renewal capacity and developmental potential, giving them great promise to impact the future of cell based therapies and tissue engineering. Harnessing the ability to drive controlled differentiation of human ES cells to a given cell type is now at the forefront of biomedical research. Of particular importance to this developing technology, is the generation of endothelial cells. Such cells line all blood vessels and serve the vital role of transporting blood throughout the body, allowing all cells access to gas and metabolic exchange. Vascularization of tissues is therefore fundamentally required for the viability of complex organisms, such as humans. The clinical importance of blood vessels is unmistakable when considering human ailments, such as ischemia, cardiovascular disease and tumour angiogenesis. Not only can engineered endothelial cells be used directly to treat vascular disease and ischemic tissue in vivo, but they can be used indirectly to test anti-angiogenic drugs or study ex vivo the effects of specific gene mutations. In addition, they are also paramount to the successful cultivation, integration and survival of transplanted or engineered tissues. In this chapter, we will review the fundamental characteristics of the EC and outline three protocols for inducing human ES cells to differentiate into endothelial cells, based on a combination of special culture conditions, selection and EC amplification. Overall, these methods allow the generation of highly enriched populations of human endothelial cells, which can be used for further culture, analysis and functional assays.