Human embryonic stem cells maintained in the absence of mouse embryonic fibroblasts or conditioned media are capable of hematopoietic development

To date, hematopoietic development of human embryonic stem cells (hESCs) has been limited to cell lines cultured in the presence of either mouse embryonic fibroblasts (MEFs) or MEF-conditioned media (MEF-CM). Anonymous xenogenic factors from MEFs or MEF-CM complicate studies of hESC self-renewal and also raise concerns for the potential clinical applications of generating primitive hematopoietic cells from hESC lines maintained under these ambiguous conditions. Here, we demonstrate that hESCs can be cultured over 30 passages in defined conditions in the absence of MEFs or MEF-CM using only serum replacement (SR) media and high concentrations of basic fibroblast growth factor (SR-bFGF). Similar to hESCs cultured in MEF-CM, hESCs cultured in SR-bFGF sustained characteristics of undifferentiated hESCs, proliferative potential, normal karyotype, in vitro and in vivo 3 germ-layer specification and gave rise to hemogenic-endothelial precursors required for subsequent primitive hematopoietic development. Our report demonstrates that anonymous factors produced by feeder cells are not necessary for hESC maintenance and subsequent hematopoietic specification, thereby providing a defined system for studies of hESC self-renewal and hESC-derived hematopoiesis. (c) 2005 by The American Society of Hematology.