Macrophage inflammatory protein-1 alpha mediated growth inhibition in a haemopoietic stem cell line is associated with inositol 1,4,5 triphosphate generation

Molecular signatures of self-renewal, differentiation, and lineage choice in multipotential hemopoietic progenitor cells in vitro

The molecular mechanisms governing self-renewal, differentiation, and lineage specification remain unknown. Transcriptional profiling is likely to provide insight into these processes but, as yet, has been confined to "static" molecular profiles of stem and progenitors cells. We now provide a comprehensive, statistically robust, and "dynamic" analysis of multipotent hemopoietic progenitor cells undergoing self-renewal in response to interleukin-3 (IL-3) and multilineage differentiation in response to lineage-affiliated cytokines. Cells undergoing IL-3-dependent proliferative self-renewal displayed striking complexity, including expression of genes associated with different lineage programs, suggesting a highly responsive compartment poised to rapidly execute intrinsically or extrinsically initiated cell fate decisions. A remarkable general feature of early differentiation was a resolution of complexity through the downregulation of gene expression. Although effector genes characteristic of mature cells were upregulated late, coincident with morphological changes, lineage-specific changes in gene expression were observed prior to this, identifying genes which may provide early harbingers of unilineage commitment. Of particular interest were genes that displayed differential behavior irrespective of the lineage elaborated, many of which were rapidly downregulated within 4 to 8 h after exposure to a differentiation cue. These are likely to include genes important in self-renewal, the maintenance of multipotentiality, or the negative regulation of differentiation per se.

Retroviral transfer and expression of human MDR-1 in a murine haemopoietic stem cell line does not alter factor dependence, growth or differentiation characteristics

In view of the recent report of a myeloproliferative syndrome in mice that had received an MDR-1-transduced haemopoietic graft, we have investigated the potential effects of MDR-1 expression on primitive haemopoietic cell growth and differentiation. Retroviral gene transfer was used to achieve exogenous expression of either MDR-1 or truncated nerve growth factor receptor (tNGFR) in the multipotent murine haemopoietic progenitor cell line, FDCP-mix. Following gene transfer, clonal lines were derived and FACS analysis confirmed appropriate expression of each transgene. MDR-1 (but not tNGFR) expression was associated with verapamil-sensitive rhodamine efflux and resistance to killing by etoposide. When growth factor responsiveness, proliferative capacity and differentiation capacity were examined, MDR-1 expressing FDCP-mix cells exhibited a normal phenotype and mimicked the response of tNGFR-expressing or untransduced FDCP-mix cells. Thus, in the model system we have used, MDR-1 does not perturb haemopoietic cell growth and development and our data do not support a myeloproliferative role for MDR-1.

Transforming growth factor-beta 1 induces apoptosis independently of p53 and selectively reduces expression of Bcl-2 in multipotent hematopoietic cells

Transforming growth factor-beta1 (TGF-beta1) can inhibit cell proliferation or induce apoptosis in multipotent hematopoietic cells. To study the mechanisms of TGF-beta1 action on primitive hematopoietic cells, we used the interleukin-3 (IL-3)-dependent, multipotent FDCP-Mix cell line. TGF-beta1-mediated growth inhibition was observed in high concentrations of IL-3, while at lower IL-3 concentrations TGF-beta1 induced apoptosis. The proapoptotic effects of TGF-beta1 occur via a p53-independent pathway, since p53(null) FDCP-Mix demonstrated the same responses to TGF-beta1. IL-3 has been suggested to enhance survival via an increase in (antiapoptotic) Bcl-x(L) expression. In FDCP-Mix cells, neither IL-3 nor TGF-beta1 induced any change in Bcl-x(L) protein levels or the proapoptotic proteins Bad or Bax. However, TGF-beta1 had a major effect on Bcl-2 levels, reducing them in the presence of high and low concentrations of IL-3. Overexpression of Bcl-2 in FDCP-Mix cells rescued them from TGF-beta1-induced apoptosis but was incapable of inhibiting TGF-beta1-mediated growth arrest. We conclude that TGF-beta1-induced cell death is independent of p53 and inhibited by Bcl-2, with no effect on Bcl-x(L). The significance of these results for stem cell survival in bone marrow are discussed.

Distinct biological effects of macrophage inflammatory protein-1alpha and stroma-derived factor-1alpha on CD34+ hemopoietic cells

Chemokines are important regulators of both hemopoietic progenitor cell (HPC) proliferation and adhesion to extracellular matrix molecules. Here, we compared the biological effects of the CC chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) with those of the CXC chemokine stroma-derived factor-1alpha (SDF-1alpha) on immunomagnetically purified CD34+ cells from leukapheresis products (LP CD34+). In particular, studies on chemokine-induced alterations of LP CD34+ cell attachment to fibronectin-coated plastic surfaces, proliferation of these cells in colony-forming cell (CFC) assays and intracellular calcium mobilization were performed. MIP-1alpha but not SDF-1alpha was found to increase the adhesion of LP CD34+ cells to fibronectin in a dose-dependent manner. Both chemokines elicited growth-suppressive effects on LP CD34+ cells in CFC assays. While MIP-1alpha reduced the number of granulomonocytic (CFC-GM) and erythroid (BFU-E) colonies to the same extent, SDF-1alpha showed a significantly greater inhibitory effect on CFC-GM than BFU-E. Finally, we demonstrated that SDF-1alpha but not MIP-1alpha triggers increases in intracellular calcium in LP CD34+ cells. The SDF-1alpha-induced calcium response was rapid and concentration-dependent, with a maximal stimulation observed at > or = 15 ng/ml. In conclusion, our data suggest distinct biological properties of SDF-1alpha and MIP-1alpha in terms of modulation of LP CD34+ cell adhesion to fibronectin and intracellular calcium levels. However, comparable growth-suppressive effects on HPC proliferation were observed, indicating that this feature may be independent of chemokine-induced calcium responses.

Expression of Macrophage Inflammatory Protein-1 Receptors in Human CD34+ Hematopoietic Cells and Their Modulation by Tumor Necrosis Factor- and Interferon-γ

Macrophage inflammatory protein-1 (MIP-1) can stimulate growth inhibitory and potent chemotactic functions in hematopoietic cells. To investigate whether the action of MIP-1 may be regulated at the cellular receptor level, we studied the expression and modulation of MIP-1 receptors on CD34+ cells isolated from normal bone marrow (NBM), umbilical cord blood (CB), and leukapheresis products (LP). Expression of MIP-1 receptors on CD34+cells was analyzed by two-color flow cytometry using a biotinylated MIP-1 molecule. The mean percentage of LP CD34+ cells expressing the MIP-1 receptors was 67.7 ± 7.2% (mean ± SEM; n = 22) as compared with 89.9 ± 2.6% (n = 10) and 74.69 ± 7.04% (n = 10) in CB and NBM, respectively (P = .4). The expression of the MIP-1 receptor subtypes on LP CD34+ cells was studied by indirect immunofluorescence using specific antibodies for the detection of CCR-1, CCR-4, and CCR-5. Microscopical examination revealed a characteristic staining of the cytoplasmic cell membrane for all three receptor subtypes. Detailed analysis of two LP samples showed that 65.8%, 4.4%, and 30.5% of CD34+ cells express CCR-1, CCR-4, and CCR-5, respectively. Culture of LP CD34+ cells for 24 to 36 hours in the presence of tumor necrosis factor- (TNF-) and interferon-γ (IFN-γ) resulted in a significant increase in MIP-1 receptor expression. TNF- induced MIP-1 receptor upregulation in a time- and concentration-dependent manner. Our results suggest that inhibitory cytokines produced by the bone marrow microenvironment are likely to be involved in the regulation of MIP-1 receptor expression on hematopoietic cells.

© 1998 by The American Society of Hematology.

Expression of Macrophage Inflammatory Protein-1 Receptors in Human CD34+ Hematopoietic Cells and Their Modulation by Tumor Necrosis Factor- and Interferon-γ

Macrophage inflammatory protein-1 (MIP-1) can stimulate growth inhibitory and potent chemotactic functions in hematopoietic cells. To investigate whether the action of MIP-1 may be regulated at the cellular receptor level, we studied the expression and modulation of MIP-1 receptors on CD34+ cells isolated from normal bone marrow (NBM), umbilical cord blood (CB), and leukapheresis products (LP). Expression of MIP-1 receptors on CD34+cells was analyzed by two-color flow cytometry using a biotinylated MIP-1 molecule. The mean percentage of LP CD34+ cells expressing the MIP-1 receptors was 67.7 ± 7.2% (mean ± SEM; n = 22) as compared with 89.9 ± 2.6% (n = 10) and 74.69 ± 7.04% (n = 10) in CB and NBM, respectively (P = .4). The expression of the MIP-1 receptor subtypes on LP CD34+ cells was studied by indirect immunofluorescence using specific antibodies for the detection of CCR-1, CCR-4, and CCR-5. Microscopical examination revealed a characteristic staining of the cytoplasmic cell membrane for all three receptor subtypes. Detailed analysis of two LP samples showed that 65.8%, 4.4%, and 30.5% of CD34+ cells express CCR-1, CCR-4, and CCR-5, respectively. Culture of LP CD34+ cells for 24 to 36 hours in the presence of tumor necrosis factor- (TNF-) and interferon-γ (IFN-γ) resulted in a significant increase in MIP-1 receptor expression. TNF- induced MIP-1 receptor upregulation in a time- and concentration-dependent manner. Our results suggest that inhibitory cytokines produced by the bone marrow microenvironment are likely to be involved in the regulation of MIP-1 receptor expression on hematopoietic cells.

© 1998 by The American Society of Hematology.