Murine hematopoietic stem and progenitor cells: I. Enrichment and biologic characterization

Abstract

Murine bone marrow cells were fractionated by fluorescence-activated cell sorting into Rh123(lo) Lin- c-kit+ Ly6A+, Rh123(hi) Lin c-kit+ Ly6A+, and Lin c-kit+ Ly6A- populations within which most, if not all, of the hematopoetic activities of the marrow resided. The Rh123(lo) Lin c-kit+ Ly6A+ cells, which consist exclusively of small- or medium-sized lymphocyte- like cells, are highly enriched for long-term hematopoietic in vivo repopulating cells. The enrichment factor for these cells from the marrow was estimated as 2,000-fold. The Rh123(hi) Lin c-kit+ Ly6A+ cells, although also highly enriched for day-12 spleen colony-forming units, were relatively depleted of long-term in vivo repopulation capacity. Most, if not all Lin c- kit+ Ly6A- cells were Rh123(hi). In contrast to both Rh123(lo) and Rh123(hi) Lin c-kit+ Ly6A+ stem cell populations, the Lin c-kit+ Ly6A- cells can be stimulated to proliferate in vitro in the presence of single cytokines, which is a characteristic of committed progenitor cells. No marked synergistic interactions between individual cytokines were observed with this cell population. Both Rh123(hi) Lin c-kit+ Ly6A+ mature stem cell and Lin- c-kit+ Ly6A- progenitor cell populations displayed in vivo repopulation kinetics resembling those of the putative short-term hematopoietic repopulating cells.