ISOLATION AND BIOLOGICAL CHARACTERIZATION OF 2 CLASSES OF BLAST-CELL COLONY-FORMING CELLS FROM NORMAL MURINE MARROW

In this study, a primitive progenitor cell, the blast-cell colony-form ing cell (BC-CFC), which is thought by some to be equivalent to the he matopoietic stem cell (HSC), those cells capable of long-term marrow r epopulation, has been isolated from normal murine marrow. The cell sep aration method we employed has, as its final step, the purification of marrow cells based on their ability to take up (bright) or exclude (d ull) the mitochondrial dye, Rhodamine (Rho)-123. Rho-bright and Rho-du ll cells are enriched for multipotential progenitor cells or for HSC, respectively. It was found that Rho-bright cells contain more BC-CH: t han Rho-dull cells (310 +/- 50 v 120 +/- 40 per 10(5) purified cells, respectively). However, the BC-CFC that copurified with the Rho-bright and the Rho-dull cells were different in terms of replating efficienc y and response to interleukin-3 (IL-3) and stem cell factor (SCF). In fact, on replating, the blast-cell colonies cultured from the Rho-dull population give rise to many more secondary colonies and had a greate r replating efficiency than those obtained from Rho-bright cells (repl ating efficiency: 29.0 +/- 6.3 v 19.5 +/- 3.7, respectively, P<.01). F urthermore, while the same numbers of blast-cell colonies were detecte d in culture of Rho-bright cells stimulated with IL-3 alone or in comb ination with SCF, blast-cell colonies were generated in cultures of Rh o-dull cells only in the presence of both IL-3 and SCF. After 5 days i n suspension culture stimulated with IL-3 and SCF, Rho-dull cells gene rated BC-CFC whose replating potential was similar to the replating po tential of BC-CFC contained in the Rho-bright population. These result s indicate that BC-CFC contained in the Rho-bright and -dull populatio ns are qualitatively different. Because the Rho-dull population contai ns HSC, the results indicate that few, if any, BC-CFC are HSC. (C) 199 6 by The American Society of Hematology.