Murine hematopoietic stem cells committed to macrophage/dendritic cell formation: Stimulation by Flk2-ligand with enhancement by regulators using the gp130 receptor chain

Abstract

The stimulation by Flk2-ligand (FL) of blast colony formation by murine bone marrow cells was selectively potentiated by the addition of regulators sharing in common the gp130 signaling receptor-leukemia inhibitory factor (LIF), oncostatin M, interleukin 11, or interleukin 6. Recloning of blast colony cells indicated that the majority were progenitor cells committed exclusively to macrophage formation and responding selectively to proliferative stimulation by macrophage colony-stimulating factor. Reculture of blast colony cells initiated by FL plus LIF in cultures containing granulocyte͞macrophage colony-stimulating factor plus tumor necrosis factor ␣ indicated that at least some of the cells were capable of maturation to dendritic cells. The cells forming blast colonies in response to FL plus LIF were unrelated to those forming blast colonies in response to stimulation by stem cell factor and appear to be a distinct subset of mature hematopoietic stem cells.Hematopoietic stem cells can be separated from other murine bone marrow cells by fluorescence-activated cell sorting as a morphologically uniform population, but the population appears to be heterogeneous based on varying proliferative and differentiative potentials. The least mature stem cells exhibit long-term repopulating capacity in vivo and a capacity for self-renewal (1). The most mature stem cells exhibit no capacity for self-renewal but, when stimulated in vitro by stem cell factor (SCF), can form blast colonies composed of progenitor cells committed to differentiation in a number of lineages (2). This action of SCF is strongly enhanced by the addition of colony-stimulating factors (CSFs) or interleukin 6 (IL-6) (3, 4).Flk2-ligand (FL), the ligand for the Flt3͞Flk2 receptor displayed on immature hematopoietic cells, has a relatively weak proliferative action in cultures of marrow cells to stimulate the formation of blast colonies and small numbers of predominantly granulocytic colonies (5). Combinations of FL with other growth factors exhibit enhanced activity in stimulating the proliferation of stem cells to generate progenitor cells and more differentiated progeny (6, 7). Administration of FL to mice increased the formation of dendritic cells (8). In its actions, FL therefore exhibits some features in common with SCF but does differ in other aspects.Leukemia inhibitory factor (LIF) is a pleiotropic factor that can suppress self-generation and induce differentiation in cells of the murine myeloid leukemic cell line, M1 (9). When acting alone in semisolid cultures of murine bone marrow cells, LIF has no observable proliferative action on any hematopoietic population (10).In an analysis of synergistic interactions exhibited by combinations of various growth factors in semisolid cultures of mouse bone marrow cells, it was noted that LIF enhanced colony formation stimulated by FL. The present experiments have analyzed this intriguing example of potentiation of a weak stimulus by addition of a factor with no overt activity and have extended the o...

Two distinct types of murine blast colony-forming cells are multipotential hematopoietic precursors

“…As reported previously (14), in most experiments, the numbers were approximately additive. This implied that most of the cells forming blast colonies when stimulated by SCFϩIL-6 were different from those forming colonies when stimulated by FLϩIL-6 but that some overlap was likely between the two populations.…”

“…In contrast, blast colonies stimulated to develop by the combination of Flt3-ligand (FL) ϩ IL-6 are more commonly composed of dispersed cells (Fig. 1B) (14). The cells in both types of colonies have similar morphologies of undifferentiated blast cells ( Fig.…”

“…In more recent years, two different types of blast colonies have been shown to be formed in semisolid agar cultures by murine adult bone marrow cells responding either to stimulation by stem cell factor plus G-CSF or IL-6 (13) or by Flt3 ligand plus a cytokine using the GP130 receptor (14). In view of the potential value of using blast colony-forming cells to reveal the mechanisms responsible for lineage commitment, it is important to establish whether these two types of blast colony-forming cells are identical or distinct, whether they can self-generate, how they relate to ancestral cells including CFU-S, and the range of lineage-committed progeny that is able to be generated by them.…”

Regulation of Extrathymic T Cell Development and Turnover by Oncostatin M

“…Because of their abundant expression of MHC class I and class II molecules and their specific chemokine and cytokine expression profile, dendritic cells seem to have a unique ability to control the homing of postthymic T cells and to provide the continuous TCR ligation required for the survival of naive and memory T cells in the periphery (72,(75)(76)(77). Interestingly, OM and Flt3 ligand act synergistically to enhance the in vitro proliferation of hemopoietic stem cells committed to macrophage/dendritic cell formation (78). Therefore, it will be of great interest to evaluate the influence of OM on the number, phenotype, and function of dendritic cells in vivo.…”

Imbalanced gp130-Dependent Signaling in Macrophages Alters Macrophage Colony-Stimulating Factor Responsiveness via Regulation of c-fms Expression

“…Furthermore, IL-6 promotes the formation of macrophages in cultures containing granulocyte-M-CSF (17,27) and has also been shown to enhance the expansion of primitive macrophage-committed (pre-CFU-M) progenitors (26). These observations suggest differences in the transcriptional programming of immature and committed (i.e., CFU-M) hematopoietic progenitors to respond to gp130 signaling, with the latter primed for inhibition by IL-6 family cytokines.…”