Proliferation and differentiation of myelodysplastic CD34+ cells

Analysis of hematopoietic progenitor cells in patients with myelodysplastic syndromes according to their cytogenetic abnormalities

The present work analyzes the hematopoietic progenitor cells (HPC) in myelodysplastic syndrome (MDS) patients using both an immunophenotypical and a functional approaches in order to know whether they are similar in patients with or without cytogenetic abnormalities. Among CD34+ HPC, the proportion of myeloid committed progenitors was higher in patients with an abnormal karyotype. Ninety MDS patients were studied. Patients with abnormal karyotype showed a similar platting efficiency than patients with normal cytogenetics. Trisomy 8 and 5q- showed a significant higher P.E. than patients with normal karyotype or monosomy 7. We observed that when the most immature HPC were studied, the total number of granulo-monocytic colonies produced by LTBMC was higher in the normal karyotype group. In summary, the present study shows that in MDS the HPC are impaired; this impairment is deeper in patients with abnormal karyotype.

Effects of cyclosporine on hematopoietic and immune functions in patients with hypoplastic myelodysplasia: in vitro and in vivo studies

BACKGROUND

Immunosuppression may benefit some patients with hypoplastic myelodysplasia (HMDS) and refractory anemia (RA), but its mechanism of action is still obscure.

METHODS

Using flow cytometry, we studied Fas-receptor (Fas-R), Fas-ligand (Fas-L), and interferon-gamma (IFN-gamma) expression in CD34(+) cells and lymphocytes obtained from 11 HMDS and 20 RA patients. In colony assays and long-term cultures, the effects of Fas triggering, IFN-gamma blockade, or cyclosporine(CsA) on the growth of hematopoietic progenitors (colony-forming cells [CFC]) were determined. The effects of CsA at daily doses of 1-3 mg/kg for at least 3 months in HMDS patients were also studied.

RESULTS

In basal conditions, committed and immature progenitor cells were found decreased in myelodysplastic (MDS) patients. No significant differences between HMDS and RA patients were detected. IFN-gamma-expressing CD4(+) cells were significantly increased in HMDS patients, whereas intracytoplasmic Fas-L expression was only borderline elevated in CD3(+) MDS cells. Increased numbers of CD34(+) cells expressing Fas-R were found in HMDS and RA patients. CFC and secondary CFC showed higher susceptibility to Fas-L-mediated inhibition and the blockade of IFN-gamma improved marrow primary, but not secondary, CFC growth. CsA added in vitro to patient's lymphocytes significantly decreased the number of IFN-gamma-expressing CD4(+) cells, but not Fas-L production. These effects were associated with increased colony formation. Similar to IFN-gammablockade, production of secondary CFC was not enhanced by CsA. Administration of CsA to patients resulted in prolonged partial hematologic improvement in 8 of 11 HMDS patients.

CONCLUSIONS

Increased frequency of IFN-gamma producing CD4(+) cells supports the involvement of lymphocyte-mediated suppression of hematopoiesis in the development of cytopenia in MDS patients. The ability of CsA to decrease in vitro IFN-gamma production may improve hematopoietic function, explaining the beneficial effect of this agent in HMDS patients.

Comparative analysis of the in vitro proliferation and expansion of hematopoietic progenitors from patients with aplastic anemia and myelodysplasia

Aplastic anemia (AA) and myelodysplasia (MDS) show great similarities in their biology. To date, however, it is still unclear to what extent hematopoietic progenitor cells (HPCs) from AA and MDS share biological properties and what the functional differences are between them. In trying to address this issue, in the present study we have analyzed, in a comparative manner, the proliferation and expansion capacities of bone marrow (BM) progenitor cells from AA and MDS in response to recombinant cytokines. BM samples from normal subjects (NBM) and patients with AA and MDS were enriched for HPC by immunomagnetic-based negative selection. Selected cells were cultured in the absence (control) or in the presence of early-acting cytokines (Mix I), or early-, intermediate- and late-acting cytokines (Mix II). Proliferation and expansion were assessed periodically. In NBM and MDS cultures apoptosis was also determined. In NBM cultures, Mix I induced a nine-fold increase in total cell numbers and a 3.6-fold increase in colony-forming cell (CFC) numbers. In Mix II-supplemented cultures, total cells were increased 643-fold, and CFC 12.4-fold. In AA cultures, no proliferation or expansion were observed in Mix I-supplemented cultures, whereas only a four-fold increase in total cell numbers was observed in the presence of Mix II. In MDS cultures, a 12-fold increase in total cells and a 2.9-fold increase in CFC were observed in the presence of Mix I; on the other hand, Mix II induced a 224-fold increase in total cells and a 5.9-fold increase in CFC. Apoptosis was reduced in cytokine-supplemented cultures from NBM. In contrast, Mix II induced a significant increase in the rate of apoptosis in MDS cultures. Our results demonstrate that, as compared to their normal counterparts, AA and MDS progenitors are deficient in their proliferation and expansion potentials. Such a deficiency is clearly more pronounced in AA cells, which seem to be unable to respond to several cytokines. MDS progenitors, on the other hand, are capable to proliferate and expand in response to cytokines; however, their rate of apoptosis is increased by intermediate- and late-acting cytokines, so that the overall proliferation and expansion are significantly lower than those of normal progenitor cells.

In vitro characterization of hematopoietic microenvironment cells from patients with myelodysplastic syndrome

In vitro studies on the functional integrity of the hematopoietic microenvironment in myelodysplasia have been controversial. Although some of them suggest that such a microenvironment is functionally normal, there is increasing evidence indicating that there are alterations in the function of microenvironment (adherent) cell layers from myelodysplastic syndromes (MDS) marrow. Adherent cell layers developed in vitro, however, consist of a mixture of different cell types-mostly fibroblasts and macrophages-thus, it is not clear which cell type(s) is(are) functionally abnormal in this disorder. In order to address this issue, in the present study, we first assessed some functional properties of MDS-derived adherent cell layers, as a whole, and then we analyzed those same functional properties after separating these cells into two different populations: a fibroblast-enriched cell layer and a macrophage-enriched cell layer. When whole adherent layers from MDS patients were analyzed, no significant differences were observed, as compared to their normal counterparts, in terms of morphology and total cell number. A major difference, however, was observed when analyzing the production of the cytokines interleukin-6 (IL-6) and tumor necrosis factor (TNF-alpha). Indeed, adherent layers from MDS patients produced higher levels of these cytokines (2- and 22-fold, respectively), as compared to normal layers. When fibroblast- and macrophage-enriched cell layers were analyzed, a higher apoptotic index was observed in those derived from MDS marrow (4% of TUNEL-positive cells in normal fibroblast layers versus 27% in MDS-derived fibroblast layers; 7% of TUNEL-positive cells in normal macrophage layers versus 24% in MDS macrophage layers). Macrophages from MDS marrow produced significantly higher levels of TNF-alpha (nine-fold) than their normal counterparts. MDS-derived fibroblasts, on the other hand, produced higher levels of IL-6 (nine-fold), as compared to normal fibroblasts. Surprisingly, whereas normal fibroblasts showed a discrete production of TNF-alpha, we found a very high production of this cytokine in cultures of fibroblasts from MDS patients. In summary, in the present study we have demonstrated that, at least in vitro, both fibroblasts and macrophages from MDS bone marrow (BM) are functionally abnormal. Such abnormalities include an increased apoptotic index, as well as a high production of both IL-6 and TNF-alpha.

Successful establishment of long-term bone marrow cultures in 103 patients with myelodysplastic syndromes

We used bone marrow biopsies instead of mononuclear cells to maintain long-term cultures from 103 patients belonging to all five sub-categories of myelodysplastic syndromes (MDS), as well as 12 normal controls. By week 4, 30-50% confluency was reached and could be maintained for up to 12 weeks with 100% confluency. The four prominent cells were fibroblasts, macrophages, endothelial cells and adipocytes. Immunohistochemical and electron microscopic studies provided lineage confirmation. Normal hematopoiesis was well supported by MDS stroma. Neither the FAB nor cytogenetics was co-related with the potency of growth. MDS stroma appears to be both morphologically and functionally normal.

Haematological response of patients with myelodysplastic syndrome to antithymocyte globulin is associated with a loss of lymphocyte-mediated inhibition of CFU-GM and alterations in T-cell receptor Vbeta profiles

We have demonstrated that 44% of myelodysplastic syndrome (MDS) patients with cytopenia have a haematological response to antithymocyte globulin (ATG). Three ATG responders and two non-responders with refractory anaemia were further studied for lymphocyte-mediated inhibition of bone marrow using a standard CFU-GM assay. In responders, peripheral blood lymphocytes (PBL) added at a 5:1 ratio suppressed CFU-GM by 54+/-9% (P=0.04) and was reversed by ATG treatment. Pre-treatment marrow depleted of CD3 lymphocytes, increased CFU-GM by 32% (P=0.02) in an ATG responder, but not in a non-responder. CD3 lymphocytes from 6-month post-treatment marrow did not inhibit pre-treatment CFU-GM, indicating ATG had affected the T cells. Pre-treatment marrow depleted of CD8 lymphocytes, increased CFU-GM by 60% (P=0.01) and 49% (P=0.03) in two ATG responders, but not in a non-responder. Inhibition required cell-cell interaction through MHCI. TCRVbeta families, analysed by SSCP, changed from clonal to polyclonal in one ATG responder after 6 months, but clones persisted in a non-responder. These results indicate patients with refractory anaemia who respond to ATG have CD8 T-cell clones that mediate MHCI-restricted suppression of CFU-GM which are replaced by polyclonal T cells that do not suppress CFU-GM after ATG treatment.