Abstract
Human embryonic stem cells provide a unique tool to study early events occurring in the development of human embryonic hematopoiesis, and their totipotent capability indicates a potent clinical application based on the cellular therapy and the evaluation of drug effects on hematopoietic and blood cells. To achieve efficient production of hematopoietic cells from human embryonic stem cells, we attempted to reproduce the circumstance surrounding embryonic hematopoietic cells in vitro. Since fetal liver is the predominant source of hematopoietic and blood cells in mammalian embryogenesis, we established stromal cells from mouse fetal liver at days 14 to 15 of gestation. In the co-culture of human embryonic stem cells with the established stromal cells, a number of hematopoietic progenitors were generated at around day 14 of co-culture, and this hematopoietic activity was highly enriched in the cobble stone-like cells under the stromal layer. Most of the cobble stone-like cells collected expressed CD34 and contained a variety of hematopoietic colony-forming cells, especially multilineage colony-forming cells, at a high frequency. The multipotential hematopoietic progenitors in the cobble stone-like cells produced all types of mature blood cells, including adult type hemoglobin-synthesizing erythrocytes and tryptase and chymase-bouble positive mast cells in the suspension cultiue with a cytokine cocktail. The developed co-culture system of human embryonic stem cells should offer a novel source for hematopoietic and blood cells applicable to cellular therapies and drug screening.
Mesenchymal Stromal Cells Derived from Human Embryonic Stem Cells, Fetal Limb and Bone Marrow Share a Common Phenotype but Are Transcriptionally and Biologically Different
