Cellular turnover of the hematopoietic system is supported by a small population of cells termed hematopoietic stem cells(HSCs). The mechanisms underlying the proliferation and differentiation of HSCs are incompletely understood. To study the cell kinetics of HSCs, the AC133+ cells, a subpopulation of hematopoietic stem and progenitor cells were first exposed to an expansion-promoting liquid medium, then grown in presence of either of the lineage specific cytokines EPO or G-CSF. The cells cultured for 14 days in liquid medium containing EPO were amplified 831-fold, and 98.2% of the resulting cells were erythroid. A similar culture exposed to G-CSF for 14 days grew 1350-fold, and 97.4% of progeny cells were myeloid. When the EPO-stimulated population was re-cultured with G-CSF, erythroid cells decreased gradually and myeloid cells developed, constituting 95.2% of the culture after 14 days; cell number grew 5075-fold over the primary inoculum. Conversely, reculture of the G-CSF-stimulated population with EPO resulted in 81.4% erythroid cells and 15.8% granulocytes after 14 days; cell number grew 4083-fold. When primary colonies were grown on semisolid medium containing EPO or G-CSF, then individually replated on medium containing the other cytokine, some secondary colonies showed self-renewal potential after 14 days and could be induced to develop into a different lineage. Analyses of cell surface antigens and receptors by single-cell RT?PCR and in situ hybridization showed that asymmetric cell divisions were occurring. CD34 and Notch1, EPO-R or CD13 were expressed within the same cells even after 28 days of culture. Our results indicate that progenitor cells co-express genes from different lineage pathways before commitment and that cytokines influence lineage commitment.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Intramural Research (Z01)
Project #
1Z01DK027008-04
Application #
6535211
Study Section
Medicinal Chemistry B Study Section (MCHB)
Project Start
Project End
Budget Start
Budget End
Support Year
4
Fiscal Year
2001
Total Cost
Indirect Cost
Name
U.S. National Inst Diabetes/Digst/Kidney
Department
Type
DUNS #
City
State
Country
United States
Zip Code