50 Generation of Precursors and Primitive Human Hematopoietic Cells from Human ESC Lines

Establishment of pluripotent human embryonic stem cell (hESC) lines has given rise to new opportunities for regenerative-based medicine. The use of hESC lines is further complicated by the now recognized differences in murine embryonic stem cells (mESCs) versus hESCs. Although it is difficult to accept, based on the developmental similarities between the species, hESCs, unlike mESCs, possess distinct growth and differentiation requirements. Accordingly, not all previous work from mESC studies is directly applicable to understanding hESCs. This is especially important in regard to differences in methodologies used to proliferate or differentiate hESCs or to assay pluripotency by chimera formation. Accordingly, applicability of ESCs to stem cell therapies requires the fundamental study of hESCs. Reconstitution of cellular components of the hematopoietic system has immense utility in several areas of clinical medicine and it describes the functional property of mammalian hematopoietic stem cells (HSCs). The only conclusive way to assay HSCs is by repopulation of the entire hematopoietic system in conditioned recipients. Fundamental investigations into lineage relationship among hESC progeny will lead to insights by which procedures and technology can be developed that will allow the generation of transplantable human HSCs from ESCs.