Hematopoietic progenitor cells in the blood and bone marrow in various hematologic disorders

Long-term outcomes of 172 children with severe aplastic anemia treated with rabbit antithymocyte globulin and cyclosporine

This study retrospectively analyzed the clinical outcome of 172 children with newly diagnosed severe aplastic anemia (SAA) between January 2008 and April 2018, who received rabbit antithymocyte globulin (ATG) and cyclosporine (CsA) as first-line treatment. The median age at diagnosis was 5 years (range, 1-14). The overall response rates were 22.7%, 45.3%, and 61% at 40 days, 3 months, and 6 months, respectively, after rabbit ATG. In multivariate analysis, mild disease severity was the only predictor of favorable response at 6 months (P = 0.006). In the present study, median follow-up period was 63 months (range, 1-135). The 5-year overall survival (OS) and failure-free survival (FFS) rates were 90.5% and 70.4%. Multivariate analysis showed that erythroid burst-forming units (BFU-E) > 2/10⁵ bone marrow mononuclear cell (BMMNC) (P = 0.037) and time interval before IST ≤ 30 days (P = 0.017) were independent positive predictors for OS, meanwhile BFU-E > 2/10⁵BMMNC (P = 0.029) was the only favorable prognostic factor for FFS.

Erythropoiesis In Vitro-A Research and Therapeutic Tool in Thalassemia

Thalassemia (thal) is a hereditary chronic hemolytic anemia due to a partial or complete deficiency in the production of globin chains, in most cases, α or β, which compose, together with the iron-containing porphyrins (hemes), the hemoglobin molecules in red blood cells (RBC). The major clinical symptom of β-thal is severe chronic anemia—a decrease in RBC number and their hemoglobin content. In spite of the improvement in therapy, thal still severely affects the quality of life of the patients and their families and imposes a substantial financial burden on the community. These considerations position β-thal, among other hemoglobinopathies, as a major health and social problem that deserves increased efforts in research and its clinical application. These efforts are based on clinical studies, experiments in animal models and the use of erythroid cells grown in culture. The latter include immortal cell lines and cultures initiated by erythroid progenitor and stem cells derived from the blood and RBC producing (erythropoietic) sites of normal and thal donors, embryonic stem cells, and recently, "induced pluripotent stem cells" generated by manipulation of differentiated somatic cells. The present review summarizes the use of erythroid cultures, their technological aspects and their contribution to the research and its clinical application in thal. The former includes deciphering of the normal and pathological biology of the erythroid cell development, and the latter—their role in developing innovative therapeutics—drugs and methods of gene therapy, as well as providing an alternative source of RBC that may complement or substitute blood transfusions.

Hematopoietic peripheral circulating blood stem cells as an independent marker of good transfusion management in patients with β-thalassemia: results from a preliminary study

BACKGROUND

Beyond hemoglobin (Hb) levels and performance status, further surrogate markers of appropriate transfusion management should improve the quality of thalassemia care. We investigated the levels of peripheral circulating CD34+ stem cells as an independent marker of appropriate hematopoietic balance in patients with thalassemia.

STUDY DESIGN AND METHODS

Peripheral circulating CD34+ stem cells, colony-forming unitgranulocyte, erythrocyte, macrophage, magakaryocyte (CF-GEMM), colony-forming unitgranulocyte/macrophage (CFU-GM), and erythroidburst-forming units (BFU-E) were assayed, according to standard procedures. Patients with thalassemia major (TM) and thalassemia intermedia (TI) were tested and compared to healthy controls. Demographic and clinical data were recorded.

RESULTS

Overall, 56 patients with TM (median age, 35 years; range, 13-52 years) and 13 with TI (median age, 44 years; range, 27-67 years) were evaluated. Annual red blood cell (RBC) transfusion requirements ranged from 10 to 65 units in all patients except four nontransfused cases. A significant increase in peripheral circulating stem cells was observed in patients, in comparison with healthy controls. Nontransfused patients showed the mean highest levels of stem cells (CD34, 32.5 ± 14.8/μL; BFU-E, 41.3 ± 22.8/mL; CFU-GM, 19.6 ± 5.6/mL; CFU-GEMM, 9.0 ± 6.1/mL). CD34+ cell count was 6.9 ± 4.5/μL in TM (p = 0.014) and 11.8 ± 14.8/μL (p = 0.051) in TI. Furthermore, only in patients with TI was a significant increase in CFU-GEMM (3.0 ± 4.8 vs. 0.75 ± 2.05/mL, p = 0.0001) observed. At multivariate analysis, peripheral circulating CD34+ stem cells did not correlate with age, sex, smoking habit, number of RBCs units transfused, Hb levels, iron chelation therapy, history of splenectomy, and hypothyroidism.

CONCLUSION

Circulating peripheral CD34 + stem cells are increased in β-thalassemia, in particular in nontransfused patients, compared to healthy controls.

Diagnostic and prognostic value of colony formation of hematopoietic progenitor cells in myeloid malignancies

Hematopoietic progenitor cells are capable of forming colonies of mature blood cells in semisolid media in response to specific growth factors. Colony assays have been extensively used for many years to study normal and malignant hematopoiesis in vitro. In fact, these assays have provided an excellent research tool for investigating growth and differentiation of progenitor cells in response to positive and negative regulators of hematopoiesis. However, apart from their role in basic research, colony assays are also widely used in routine clinical practice in the diagnosis of various hematologic disorders, such as aplastic anemia, myelodysplastic syndromes and myeloproliferative disorders. This review summarizes our current knowledge on the diagnostic value and prognostic significance of the growth of progenitor cells in peripheral blood and bone marrow in patients with myeloid malignancies.

Semi-solid colony growth in acute myeloid leukemia and its relation to cytogenetic risk groups

The prognostic significance of in vitro growth characteristics of leukemic blast cells in acute myeloid leukemia (AML) is well established in the literature. This review focuses on semi-solid colony growth from bone marrow mononuclear cells (BMMCs) of 322 newly diagnosed patients with AML in relation to the three established cytogenetic risk groups. The median numbers of colonies derived from cytokine-stimulated BMMCs significantly differed between patients with favorable karyotypes (2/10(6)), intermediate cytogenetics (12/10(6)) and unfavorable abnormalities (51.5/10(6)). Colony growth in the absence of stimulatory cytokines was assessed in 113 patients. Individuals with unfavorable karyotypes exhibited significantly more often partial or full autonomous growth in vitro when compared to the intermediate and favorable prognostic group. Median stimulated colony growth of patients who entered complete remission (CR) was 9/10(6) BMMCs compared with 63 in patients with no response. Both, cytokine-stimulated as well as autonomous colony formation, significantly discriminated between patients regarding survival. However, multiple regression analysis revealed cytogenetic risk groups as the most important predictor for achieving CR, with colony growth adding no additional prognostic information. In conclusion, semi-solid colony growth predicts response to treatment and survival in AML but is clearly related to karyotypic abnormalities.

New insights into paroxysmal nocturnal hemoglobinuria

The characteristic, defining defect in paroxysmal nocturnal hemoglobinuria is the somatic mutation of the PIG-A gene (essential to the biosynthesis of the glycosylphosphatidylinositol moiety that affixes a number of proteins to the cellular surface) in hematopoietic cells. These cells thus lack the proteins usually held in place by this anchor. The absence of these proteins is the most reliable diagnostic criterion of the disease and is responsible for many of the clinical manifestations of PNH. The current hypothesis explaining the disorder suggests that there are two components: (1) hematopoietic stem cells with the characteristic defect are present in the marrow of many if not all normal individuals in very small numbers; (2) some aplastogenic influence suppresses the normal stem cells but does not suppress the defective stem cells, thus allowing the proportion of these cells to increase. Current research attempts to substantiate this hypothesis and design therapy consistent with the hypothesis. Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired stem cell disorder characterized by intravascular hemolysis, hypercoagulability, and relative bone marrow failure [1]. It is characterized by a somatic mutation in the gene encoding the alpha1-6-N-acetylglucosaminyltransferase necessary for the formation of the glycosylphosphatidylinositol (GPI) anchor that binds certain proteins to the membrane surface (Fig. 1) [2,3*]. Whereas many of the manifestations can be accounted for by the absence of these proteins on the cells of the hematopoietic system, it is not entirely clear whether this defect is sufficient to make the disease manifest. In this paper, the author reviews recent clinical observations and relates them to the underlying pathophysiology of the disease.