CHAPTER 18 Hematopoiesis from Human Embryonic Stem Cells

Hematopoiesis provides a well-defined system for studying molecular and cellular processes that control growth and development. The hematopoietic system consists of a heterogeneous array of cells ranging from rare primitive hematopoietic stem cells to large numbers of mature cells. Studies from amphibians, chicks, fish, and mammals show that blood cell emergence is established through waves of distinct hematopoietic compartments arising from distinct anatomical sites. In many of these animal embryogenesis models, initial emergence of blood cells is recognized in the extra embryonic yolk sac which principally sustains primitive erythropoiesis. The induction and support of these various hematopoietic compartments during human embryoid body (EB) development is influenced by different cytokines and growth factors. The use of cytokines, including SCF, FIt3L, IL-3, IL-6, G-CSF, VEGF, and the ventral mesoderm inducer BMP-4, have been shown to promote the differentiation of a highly enriched hematopoietic progenitor population that possess a CD45+CD34+ phenotype similar to the first definitive hematopoietic cell detected within the wall of the dorsal aorta of human embryos. This chapter provides techniques commonly employed by laboratory to differentiate phenotypically and functionally assay the hematopoietic cells derived from human EBs.