The development of immunodeficient mouse xenograft models has greatly facilitated the investigation of some human hematopoietic malignancies, but application of this approach to the myelodysplastic syndromes (MDSs) has proven difficult. We now show that cells from most MDS patients (including all subtypes) repopulate nonobese diabetic-severe combined immunodeficient (scid)/scid-2 microglobulin null (NOD/SCID-2m ؊/؊ ) mice at least transiently and produce abnormal differentiation patterns in this model. Normal marrow transplants initially produce predominantly erythroid cells and later predominantly B-lymphoid cells in these mice, whereas most MDS samples produced predominantly granulopoietic cells. In 4 of 4 MDS cases, the regenerated cells showed the same clonal markers (trisomy 8, n ؍ 3; and 5q؊, n ؍ 1) as the original sample and, in one instance, regenerated trisomy 8 ؉ B-lymphoid as well as myeloid cells were identified. Interestingly, the enhanced growth of normal marrow obtained in NOD/SCID-2m ؊/؊ mice engineered to produce human interleukin-3, granulocyte-macrophage colony-stimulating factor, and Steel factor was seen only with 1 of 7 MDS samples. These findings support the concept that human MDS originates in a transplantable multilineage hematopoietic stem cell whose genetic alteration may affect patterns of differentiation and responsiveness to hematopoietic growth factors.
Apoptosis has been implicated in the pathogenesis of marrow failure in MDS and the coexistence of marrow hypercellularity along with blood cytopenias was seen as evidence of extreme cell death of mainly mature cells in the marrow (ineffective hematopoiesis). We investigated apoptosis in 53 patients with MDS, by using single-step DNA extraction and gel electrophoresis and then by separating fresh marrow mononuclear cells in CD34+ and CD34 − populations and in situ single cell evaluation of the process. We also studied the expression of apoptosis-related genes, in total and separated mononuclear marrow cells and correlated the findings with clinical and laboratory characteristics. Patients with apoptosis had increased marrow cellularity, longer overall survival and a longer period for transformation to AML. In 'good' prognosis MDS patients, total mononuclear marrow cells, as well as isolated populations of CD34+ and CD34 − cells showed significant degrees of apoptosis; in 'poor' prognosis cases, however, apoptosis was evident only in a large percentage of CD34 + marrow cells and not in total or CD34 − cells. Absence of expression of both c-myc and p53 in total marrow cells was associated with significant degrees of apoptosis and in isolated CD34+ and CD34 − marrow cells the phenomenon was inversely correlated with the level of bcl-2 expression. In conclusion, marrow apoptosis is detected in both CD34+ and CD34 − cells in early MDS and seems to be restricted to CD34+ cells in advanced MDS cases.
In this study, we describe the successful use of a gene transfer approach to demonstrate the ability of forced BCR-ABL expression to deregulate the growth and differentiation of primitive naïve human hematopoietic cells after their transplantation into immunodeficient mice. Human CD34 þ cord blood cells were exposed to an MSCV retrovirus containing a BCR-ABL-IRES-GFP (P210) cassette and then injected immediately into sublethally irradiated nonobese diabetic-severe combined immunodeficiency (NOD/SCID) or NOD/SCID-b2microglobulin À/À mice. P210-and control-transduced (GFP þ ) human hematopoietic cells were produced in the bone marrow of the mice at similar levels until termination of the experiments 5-6 months later. However, the P210-transduced cells produced a markedly different spectrum of progeny, with an increased ratio of myeloid to B-lymphoid cells and a frequently prolonged increase in erythroid and megakaryocytic cells. After 5 months, several of the mice transplanted with P210-transduced cells developed an increased WBC count and/or splenomegaly due to an expansion of the human GFP þ population. These findings demonstrate that forced expression of BCR-ABL in primitive transplantable human hematopoietic cells is sufficient to cause a rapid and persistent deregulation of their growth and differentiation in vivo with occasional evidence after several months of progression to an early stage of disease.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.