Isolation and Characterization of CD34-Low/Negative Mouse Hematopoietic Stem Cells

摘要

We have previously reported that, in adult mouse bone marrow, CD34~(low/-) c_Kit~+ Sca-1~+ lineage markers negative (Lin~-) (CD34~-KSL) cells represent hematopoietic stem cells with long-term marrow repopulating ability whereas CD34~+ c-Kit~+ Sca-1~+ Lin~- (CD34~+KSL) cells are progenitors with short-term reconstitution capacity. To characterize these two populations of cells further, relative expression of various genes was examined by RT-PCR. In CD34KSL cells, most cytokine receptor genes were not expressed with the exception of IL2Ry and AIC-2B. In contrast, expression of all cytokine receptor genes examined except IL-2Ralpha, IL-7Ralpha, and IL9Ralpha chains were found in CD34~+KSL cells. Cell cycle studies revealed only 3% of CD34~-KSL cells and 26% of CD34~+KSL cells are dividing at a given time. Long-term BrdU administration study demonstrated, however, that majority of CD34~-KSL cells contribute to hemopoiesis by dividing very slowly. Furthermore, analysis of aged mice revealed more than tenfold increase in absolute number of CD34~-KSL cells. Those CD34~-KSL cells in aged mice appeared to include HPP-CFC at an equivalent frequency with those in younger mice. These data support our previous notion that CD34~-KSL cells are at higher rank in hematopoietic hierarchy than CD34~+KSL cells. In addition, our results provide important clues for cell therapy and gene therapy targeting hematopoietic stem cells.