Studies on hematopoiesis have focused on the function and composition of human bone marrow stroma. Stroma function gives hematopoietic stem cells the microenvironment appropriate for self-renewal and/or prompt differentiation into hematopoietic progenitor cells, then into terminal specialized cells. Human bone marrow stroma has been dissected into hematopoietic and nonhematopoietic components. The former includes hematopoietic-derived cells, mainly macrophages, while the latter, still poorly characterized, is composed mainly of endothelial and mesenchymal stem cells and their derivatives (adipocytes, chondrocytes, cells of the osteogenic lineage). Isolation of bone marrow mesenchymal stem cells has made available a population of adherent cells, belonging to the non-hematopoietic stroma, which are morphologically and phenotypically homogeneous. This review will focus on: (i) definition of bone marrow stroma and mesenchymal stem cells; (ii) methods of mesenchymal stem cell isolation, morphological and phenotypic characterization; (iii) mesenchymal stem cell functional and differentiation properties and (iv) therapeutic applications of mesenchymal stem cells.

We conclude that the expression of Tdt or CD7 is associated with an unfavorable outcome and that the combination of both defines a clinical subset with a poorer prognosis due to the significantly higher association with MDR phenotype, and 'poor prognostic' chromosomal abnormalities.

Nineteen transfusion-dependent beta-thalassemia major patients were included in the study. Six of these patients underwent chelation therapy with desferrioxamine by subcutaneous infusion (50 mg/kg/12 hr) and 13 received intravenous infusion (50 mg/kg/6 hr or 100 mg/kg/24 hr). BUN, creatinine, creatinine clearance, beta 2-microglobulin, urinary beta 2-microglobulin and urinary growth hormone excretion were evaluated during desferrioxamine treatment. Thirteen out of nineteen patients presented tubular damage indicated by increased excretion of urinary beta 2-microglobulin. 85% (11 of 13) of these patients showed more serious tubular damage, as demonstrated by concurrent increased urinary growth hormone excretion. Moreover, a positive correlation between urinary growth hormone excretion and urinary beta 2-microglobulin was observed (P < 0.05).

We compared the immunophenotypic and karyotypic features of 25 cases of minimally differentiated acute myeloid leukemia (AML-M0) with those of 247 cases comprising all AML French-American-British (FAB) classification. Myeloperoxidase (MPO) was detectable with a specific monoclonal antibody in all cases of AML-M0, whereas CD13 and CD33 were both negative in 4 of the 25 cases. Thus, anti-MPO reliably detects minimal myeloid differentiation in AML-M0. CD34 and terminal deoxynucleotidyl transferase (TdT) were more frequently expressed in AML-M0 (96% and 68% of the cases, respectively) than in the other FAB subsets (P &lt; . 001 for both). By contrast, GP-170 and CD7 were less frequently expressed in AML-M0 than in FAB classes such as M1, M4, and M5 (P = .02 and .003, respectively). A total of 80% of AML-M0 cases carried lymphoid markers (including TdT), and 48% showed a coordinate positivity for two or more of them. CD2, CD5, CD10, and CD19 were expressed in a similar fashion among the different FAB groups, whereas CD4 expression was significantly more frequent in AML-M0, AML-M4, and AML-M5 (P = .014). AML-M0 was characterized by a more frequent occurrence of complex karyotypes. In addition, approximately 20% of cases had TdT positivity, complex karyotypes, and anomalies of chromosome 5 and/or 7, a pattern not observed in the other FAB subsets. Finally, 80% of anomalies of chromosome 5 and/or 7 in AML-M0 were comprised within complex karyotypes, whereas only 13% of the remaining FAB cases carried this feature. In summary, AML-M0 frequently expresses immunophenotypic and karyotypic aspects that are likely to identify a “stem cell” pattern.

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