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

Cyclosporine Combined with Levamisole for Lower-Risk Myelodysplastic Syndromes

Clinical and experimental evidence suggests an immune-mediated pathophysiology in subjects with lower-risk myelodysplastic syndromes (MDS) in whom immunosuppressive therapy may be effective. The novel immunosuppressive strategy of cyclosporine A (CsA) alternately combined with levamisole (LMS; CsA + LMS regimen) can dramatically improve the response rate and survival in aplastic anemia from those of our previous study. Herein, we retrospectively analyzed the data of 89 lower-risk MDS patients who received the CsA + LMS regimen. A total of 63 patients (70.8%) achieved either complete remission or hematological improvement at 4 months. Overall, 51, 41 and 19 patients had erythroid, platelet and neutrophil responses, respectively. Following the CsA + LMS regimen, 6 patients progressed to more advanced MDS at a median interval of 5 months (range, 3-42 months). The estimated 24-month progression-free survival was 82.2% (95% CI, 72.84-91.56) for all patients. Within the median follow-up of 18.5 months (range, 7.0-61.0), 6 patients died. In conclusion, the CsA + LMS regimen alleviated cytopenias and improved survival and freedom from evolution, suggesting that it could be reserved as an alternative choice for lower-risk MDS.

Impaired differentiation and apoptosis of hematopoietic precursors in a mouse model of myelodysplastic syndrome

Expression of a NUP98-HOXD13 (NHD13) fusion gene, initially identified in a patient with myelodysplastic syndrome, leads to a highly penetrant myelodysplastic syndrome in mice that recapitulates all of the key features of the human disease. Expansion of undifferentiated lineage negative (lin(neg)) hematopoietic precursors that express NHD13 was markedly inhibited (30-fold) in vitro. Decreased expansion was accompanied by decreased production of terminally differentiated cells, indicating impaired differentiation of NHD13 precursors. Rather than differentiate, the majority (80%) of NHD13 lin(neg) precursors underwent apoptotic cell death when induced to differentiate. These findings demonstrate that NHD13 lin(neg) cells provide a tractable in vitro system for studies of myelodysplastic syndrome.

Cytogenetic biclonality in a child with hypocellular primary myelodysplastic syndrome

A 13-year-old boy with hypocellular primary myelodysplastic syndrome, classified as refractory cytopenia, underwent umbilical cord blood transplantation. Cytogenetic analysis revealed two rare biclonal chromosomal aberrations, del(17)(p12) and del(11)(q23). Cytogenetic analysis was a valuable tool in diagnosis, in clinical decision-making, and in treatment and follow-up. To our knowledge, this is the first reported case of cytogenetic biclonality involving chromosomes 17 and 11.

Hematopoietic changes during progression from Fanconi anemia into acute myeloid leukemia: case report and brief review of the literature

Fanconi anemia (FA) is a rare autosomal recessive disorder characterized by bone marrow (BM) failure and a wide array of physical abnormalities. Around 9% of FA patients develop acute myeloid leukemia (AML), which makes FA a good genetic model to study leukemogenesis. To date, however, no information exists on the functional integrity of the hematopoietic system of FA patients during the period in which they develop AML. Herein, we report on the characterization of hematopoietic progenitor cells from a pediatric FA patient that developed AML. Our results show that significant changes occurred in the hematopoietic system of the patient from the time he presented with FA to the time he developed AML. Such changes included marrow cellularity, frequency of CD34(+) cells and CFC, as well as proliferation potential of progenitor cells in liquid cultures supplemented with recombinant cytokines. Interestingly, no significant changes in the karyotype of marrow cells were observed, indicating that progression from FA into AML may proceed without major chromosomal alterations (i.e. translocations and/or deletions). This study represents one of the first steps towards the cellular characterization of the hematopoietic system in FA patients that develop AML.

Low IPSS score and bone marrow hypocellularity in MDS patients predict hematological responses to antithymocyte globulin

Immunosuppressive therapy has been shown to induce sustained hematological responses in a subset of patients with myelodysplastic syndromes (MDS). In particular, antithymocyte globulin (ATG), a polyclonal immunoglobulin induces hematological responses in up to 60% of MDS patients. We report herein on the results of a retrospective multicenter study on the use of ATG in the treatment of 96 patients with MDS. Patients were evaluated for duration of response to ATG, as well as survival after administration of ATG. The median age of the cohort was 54.7 years (range: 19-75 years), with a median follow-up of 33.8 months (range: 0.8-133 months). A total of 40 patients (42%) achieved a hematological response, of which 30 patients (75%) had a durable hematological response lasting a median duration of 31.5 months (range: 6-92 months). On multivariate analysis, both low International Prognostic Scoring System (IPSS) and bone marrow (BM) hypocellularity were independent predictive factors for improved response to ATG (IPSS Int-2/high: odds ratio (OR) 0.08, P=0.018 and BM normo/hypercellularity: OR 0.49, P=0.012). In addition, IPSS was the sole predictor of overall survival, with Int-2/high risk patients having a significantly poorer survival outcome (OR 0.08, P<0.01). In conclusion, this study identifies BM hypocellularity and a low IPSS as important factors predicting response to ATG.

Quantitative analysis of bone marrow CD34 cells in aplastic anemia and hypoplastic myelodysplastic syndromes

Aplastic anemia (AA) and hypoplastic myelodysplastic syndromes (hMDS) are often difficult to distinguish. However, an accurate diagnosis is important because the prognosis and treatment of these diseases may differ. CD34+ hematopoietic progenitors are central to the pathogenesis of both disorders; they are the targets of the autoimmune attack in AA and neoplastic transformation in MDS. The aim of this study was to assess whether bone marrow CD34+ cell numbers could be used in differentiating between AA and hMDS. The percentage of bone marrow CD34+ cells was normal or increased (mean -3.5+0.5%, range 1-7%) in 15 of 35 patients studied, and low (mean -0.13 +/- 0.02%, range 0.02-0.36%) in 20 of 35 patients. All patients with a normal or increased percentage of CD34+ cells were ultimately diagnosed with hMDS based on the detection of clonal cytogenetic abnormalities or progression to refractory anemia with excess blasts/acute myeloid leukemia. All patients with low marrow CD34+ cell numbers met standard clinical criteria for AA and have not demonstrated neoplastic transformation with follow-up. Quantification of marrow CD34+ cells may serve as an important tool for distinguishing between AA and hMDS.

Mesenchymal stem cells in myelodysplastic syndromes: phenotypic and cytogenetic characterization

Bone marrow-derived mesenchymal stem cells (MSC) have been defined as primitive, undifferentiated cells, capable of self-renewal and with the ability to give rise to different cell lineages, including adipocytes, osteocytes, fibroblasts, chondrocytes, and myoblasts. MSC are key components of the hematopoietic microenvironment. Several studies, including some from our own group, suggest that important quantitative and functional alterations are present in the stroma of patients with myelodysplasia (MDS). However, in most of such studies the stroma has been analyzed as a complex network of different cell types and molecules, thus it has been difficult to identify and characterize the cell(s) type(s) that is (are) altered in MDS. In the present study, we have focused on the biological characterization of MSC from MDS. As a first approach, we have quantified their numbers in bone marrow, and have worked on their phenotypic (morphology and immunophenotype) and cytogenetic properties. MSC were obtained by a negative selection procedure and cultured in a MSC liquid culture medium. In terms of morphology, as well as the expression of certain cell markers, no differences were observed between MSC from MDS patients and those derived from normal marrow. In both cases, MSC expressed CD29, CD90, CD105 and Prolyl-4-hydroxylase; in contrast, they did not express CD14, CD34, CD68, or alkaline phosphatase. Interestingly, in five out of nine MDS patients, MSC developed in culture showed cytogenetic abnormalities, usually involving the loss of chromosomal material. All those five cases also showed cytogenetic abnormalities in their hematopoietic cells. Interestingly, in some cases there was a complete lack of overlap between the karyotypes of hematopoietic cells and MSC. To the best of our knowledge, the present study is the first in which a pure population of MSC from MDS patients is analyzed in terms of their whole karyotype and demonstrates that in a significant proportion of patients, MSC are cytogenetically abnormal. Although the reason of this is still unclear, such alterations may have an impact on the physiology of these cells. Further studies are needed to assess the functional integrity of MDS-derived MSC.

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.

Distinctive gene expression profiles of CD34 cells from patients with myelodysplastic syndrome characterized by specific chromosomal abnormalities

Aneuploidy, especially monosomy 7 and trisomy 8, is a frequent cytogenetic abnormality in the myelodysplastic syndromes (MDSs). Patients with monosomy 7 and trisomy 8 have distinctly different clinical courses, responses to therapy, and survival probabilities. To determine disease-specific molecular characteristics, we analyzed the gene expression pattern in purified CD34 hematopoietic progenitor cells obtained from MDS patients with monosomy 7 and trisomy 8 using Affymetrix GeneChips. Two methods were employed: standard hybridization and a small-sample RNA amplification protocol for the limited amounts of RNA available from individual cases; results were comparable between these 2 techniques. Microarray data were confirmed by gene amplification and flow cytometry using individual patient samples. Genes related to hematopoietic progenitor cell proliferation and blood cell function were dysregulated in CD34 cells of both monosomy 7 and trisomy 8 MDS. In trisomy 8, up-regulated genes were primarily involved in immune and inflammatory responses, and down-regulated genes have been implicated in apoptosis inhibition. CD34 cells in monosomy 7 showed up-regulation of genes inducing leukemia transformation and tumorigenesis and apoptosis and down-regulation of genes controlling cell growth and differentiation. These results imply distinct molecular mechanisms for monosomy 7 and trisomy 8 MDS and implicate specific pathogenic pathways.

Impaired generation of bone marrow CD34-derived dendritic cells with low peripheral blood subsets in patients with myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a stem cell disorder characterized by ineffective haematopoiesis and blood cytopenias. The present study investigated the potential of bone marrow CD34(+) progenitors in MDS patients to proliferate and differentiate into dendritic cells (DCs) in a cytokine-supplemented liquid culture system and analysed the status of blood DC subsets in these patients. CD34(+) progenitors had low potential to generate DCs in vitro, as the number of DCs obtained from one CD34(+) cell was significantly lower compared with controls (median value 0.2 vs. 4, P = 0.003). In patients, the survival and proliferation of CD34(+) cells in culture was not correlated to the degree of apoptosis. Phenotypically and functionally CD34(+)-derived DCs were similar in MDS patients and normal subjects. The percentage of both circulating DC subsets in patients was extremely diminished compared with controls (myeloid DC: 0.10 +/- 0.10% vs. 0.35 +/- 0.13%, P < 0.001; plasmacytoid DC: 0.11 +/- 0.10% vs. 0.37 +/- 0.14%, P < 0.001). In cases with the 5q deletion both CD34-derived DCs and blood DCs harboured the cytogenetic abnormality. Our results indicate that, in MDS, the production of DCs is affected by the neoplastic process resulting in ineffective 'dendritopoiesis' with low blood DC precursor numbers. This quantitative DC defect probably contributes to the poor immune response against infectious agents and to the escape of the malignant clone from immune recognition with disease progression towards acute leukaemia.

Severe functional alterations in vitro in CD34(+) cell subpopulations from patients with chronic myeloid leukemia

Chronic myeloid leukemia (CML) arises from the malignant transformation of a hematopoietic stem cell (HSC) that gives rise to functionally defective progeny, including primitive and relatively mature progenitor cells (HPC). Both HSC and HPC are comprised within the population of CD34(+) cells, normally present in bone marrow (BM). In the present study, we have separated two different subpopulations of CD34(+) cells from CML marrow: Population I, enriched for CD34(+) Lin(-) cells; and Population II, enriched for CD34(+) CD36(-) CD38(-) CD45RA(-) Lin(-) cells, and assessed their progenitor cell content as well as their capacity to proliferate and expand in response to a combination of hematopoietic cytokines in serum- and stroma-free long-term liquid cultures. The absolute cell numbers recovered in Population I from normal and CML samples were similar; in contrast, we found that Population II from CML was amplified four-fold, as compared to normal. In spite of this latter observation, no significant differences were observed in terms of the absolute number of CFC when comparing Populations I and II from CML patients and normal subjects. Interestingly, the proliferation and expansion potentials of CML cells were clearly deficient as compared to their normal counterparts. Indeed, in cultures of Population I cells the maximum fold increase in total and progenitor cell numbers corresponded to 30 and 8%, respectively, of those observed in cultures of normal marrow-derived Population I cells. Such functional deficiencies were even more evident in Population II cells in which the maximum fold increase in total and progenitor cell numbers corresponded to 3 and 0.5%, respectively, of the levels found in cultures of Population II cells from normal marrow. The present study demonstrates that bone marrow-derived CD34(+) cells from CML patients possess functional abnormalities, clearly evident in the in vitro system used by us. Among the two CML subpopulations studied here, the more immature one (Population II; enriched for CD34(+) CD36(-) CD38(-) CD45RA(-) Lin(-) cells) was the one that showed the most severe abnormalities, as compared to its relatively more mature counterpart (Population I; enriched for CD34(+) Lin(-) cells).

Lingering biologic dilemmas about the status of the progenitor cells in myelodysplasia

Myelodysplastic syndromes (MDS) are considered to be stem cell disorders. High incidence of intramedullary apoptosis has been associated with the peripheral cytopenia and refractory anemia in these disorders. The investigations on the cell of origin in the bone marrow have invariably been hampered by a poor yield of CD34+ cells from these marrows. Interestingly, even though limited in number, these studies raised more questions and dilemmas than providing answers. While the enigma surrounding the clonality of these marrows continues, the controversies regarding incidence of apoptosis, proliferation, and potential of clonogenic expansion may be closer to a settlement. The present review proposes a model depicting interplay between extraneous apoptogenic factors and intracellular apoptosis-susceptibility determinants that contributes significantly toward the progression of MDS and how a shift in dynamics of this interplay may provide grounds to accumulate additional mutations with a probable block in differentiation eventually leading to a leukemic transformation.