MURINE HEMATOPOIETIC STEM AND PROGENITOR CELLS .1. ENRICHMENT AND BIOLOGIC CHARACTERIZATION

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(hl). 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(hl) 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. (C) 1995 by The American Society of Hematology.