Differential effects of the type of iron chelator on the absolute number of hematopoietic peripheral progenitors in patients with β-thalassemia major

[Deferoxamine promotes recovery of bone marrow hematopoietic function in mice exposed to a sublethal dose of X-ray irradiation]

OBJECTIVE

To evaluate the effect of deferoxamine (DFO) on bone marrow hematopoietic function in C57 mice exposed to a sublethal dose of X-ray irradiation.

METHODS

C57 mice exposed to a sublethal dose (5.4 Gy, 1.0 Gy/min) of total body X-ray irradiation (TBI) were treated with subcutaneous injection of 100 mg/kg DFO, with normal saline as the control, on a daily basis for 10 and 20 consecutive days. Body weight changes of the mice were monitored every 3 days. Five mice were selected from each group at 10 and 20 days for examination of blood cell counts, bone marrow nucleated cell counts, percentage of bone marrow CD34+ cells, bone marrow pathology, and expressions of cleaved PARP-1, cleaved caspase-3, VEGF, GPX4, and SLC7A11 in the nucleated cells.

RESULTS

The body weight of the mice decreased significantly on day 3 in TBI and DFO groups (P<0.05), and to the lowest on day 6 in TBI group (P<0.01). Blood cell counts and bone marrow nucleated cell counts of the mice were significantly decreased at 10 and 20 days following TBI (P<0.01). On day 10 following TBI, the mice showed significantly decreased nucleated cells and the presence of adipocytes in the bone marrow, where increased expressions of cleaved PARP-1 and cleaved caspase-3 and lowered expressions of GPX4 and SLC7A11 were detected in the nucleated cells (P<0.05). In the mice exposed to TBI, treatment with DFO significantly increased CD34+ cell percentage (P<0.001), decreased the expressions of cleaved PARP-1 and cleaved caspase-3, and increased the expressions of GPX4, SLC7A11 and VEGF in the bone marrow nucleated cells (P<0.05). DFO treatment significantly increased blood cell counts and bone marrow nucleated cells in mice at 20 days following TBI (P<0.05).

CONCLUSION

DFO improves bone marrow hematopoiesis in mice with sublethal-dose TBI by inhibiting apoptosis and ferroptosis of bone marrow nucleated cells and promoting VEGF expression and CD34+ cell proliferation.

In vivo HSC transduction in rhesus macaques with an HDAd5/3+ vector targeting desmoglein 2 and transiently overexpressing cxcr4

We developed a new in vivo hematopoietic stem cell (HSC) gene therapy approach that involves only IV injections and does not require myeloablation/conditioning and HSC transplantation. In this approach, HSCs are mobilized from the bone marrow into the peripheral bloodstream and transduced with IV injected helper-dependent adenovirus (HDAd) vectors. A fraction of transduced HSCs returns to the bone marrow and persists there long term. Here, we report desmoglein 2 (DSG2) as a new receptor that can be used for in vivo HSC transduction. HDAd5/3+ vectors were developed that use DSG2 as a high-affinity attachment receptor, and in vivo HSC transduction and safety after IV injection of an HDAd5/3+ vector expressing green fluorescent protein (GFP) in granulocyte colony-stimulating factor/AMD3100 (plerixafor)-mobilized rhesus macaques were studied. Unlike previously used CD46-targeting HDAd5/35++ vectors, HDAd5/3+ virions were not sequestered by rhesus erythrocytes and therefore mediated ∼10-fold higher GFP marking rates in primitive HSCs (CD34+/CD45RA-/CD90+ cells) in the bone marrow at day 7 after vector injection. To further increase the return of in vivo transduced, mobilized HSCs to the bone marrow, we transiently expressed cxcr4 in mobilized HSCs from the HDAd5/3+ vector. In vivo transduction with an HDAd5/3+GFP/cxcr4 vector at a low dose of 0.4 × 1012 viral particles/kg resulted in up to 7% of GFP-positive CD34+/CD45RA-/CD90+ cells in the bone marrow. This transduction rate is a solid basis for in vivo base or prime editing in combination with natural or drug-induced expansion of edited HSCs. Furthermore, our study provides new insights into HSC biology and trafficking after mobilization in nonhuman primates.

Unique molecular and functional features of extramedullary hematopoietic stem and progenitor cell reservoirs in humans

Rare hematopoietic stem and progenitor cell (HSPC) pools outside the bone marrow (BM) contribute to blood production in stress and disease but remain ill-defined. Although nonmobilized peripheral blood (PB) is routinely sampled for clinical management, the diagnosis and monitoring potential of PB HSPCs remain untapped, as no healthy PB HSPC baseline has been reported. Here we comprehensively delineate human extramedullary HSPC compartments comparing spleen, PB, and mobilized PB to BM using single-cell RNA-sequencing and/or functional assays. We uncovered HSPC features shared by extramedullary tissues and others unique to PB. First, in contrast to actively dividing BM HSPCs, we found no evidence of substantial ongoing hematopoiesis in extramedullary tissues at steady state but report increased splenic HSPC proliferative output during stress erythropoiesis. Second, extramedullary hematopoietic stem cells/multipotent progenitors (HSCs/MPPs) from spleen, PB, and mobilized PB share a common transcriptional signature and increased abundance of lineage-primed subsets compared with BM. Third, healthy PB HSPCs display a unique bias toward erythroid-megakaryocytic differentiation. At the HSC/MPP level, this is functionally imparted by a subset of phenotypic CD71+ HSCs/MPPs, exclusively producing erythrocytes and megakaryocytes, highly abundant in PB but rare in other adult tissues. Finally, the unique erythroid-megakaryocytic-skewing of PB is perturbed with age in essential thrombocythemia and β-thalassemia. Collectively, we identify extramedullary lineage-primed HSPC reservoirs that are nonproliferative in situ and report involvement of splenic HSPCs during demand-adapted hematopoiesis. Our data also establish aberrant composition and function of circulating HSPCs as potential clinical indicators of BM dysfunction.

The effect of deferasirox on endocrine complications in children with thalassemia

Endocrine system dysfunctions are the significant complications of excessive iron overload in beta thalassemia patients. The aim of this study was to evaluate the long-term effect of chelation with deferasirox on endocrine complications. The study group consisted of children with beta thalassemia who had been evaluated for the growth and pubertal development, bone metabolism, thyroid/parathyroid functions, glucose metabolism dysfunctions in the department of pediatric hematology of Ankara Dışkapı Child Health and Diseases Hematology Oncology Training And Research Hospital between 2009-2011 and reevaluated after deferasirox chelation therapy in 2018. Thirty-one transfusion dependent beta-thalassemia patients were enrolled for the study. Seventeen (54.8%) patients were male and the mean age was 16.9 ± 3.8 (9-23) years. Splenectomy was performed in 11 patients (35.5%). In the initial evaluation, 26 patients (84%) received deferoxamine and/or deferiprone and five (17%) patients received deferasirox as a chelator; in the final evaluation all patients were receiving deferasirox. The mean duration of deferasirox treatment was 5.9 ± 2.02 years (1-10 years). Of the 26 patients who had endocrine complications between 2009-2011, 18 were recovered. In the final evaluation, eight patients (25%) developed new endocrinopathies. The frequency of endocrine complications seen before the deferasirox treatment (83%) was higher than the frequency of complications while receiving deferasirox treatment (25.8%) (p < 0,05). In this study, it was determined that both existing endocrine abnormalities were reduced and recent developed problems were less likely with long-term deferasirox treatment in thalassemia patients.

Suitability of small diagnostic peripheral-blood samples for cell-therapy studies

BACKGROUND AIMS

Primary hematopoietic stem and progenitor cells (HSPCs) are key components of cell-based therapies for blood disorders and are thus the authentic substrate for related research. We propose that ubiquitous small-volume diagnostic samples represent a readily available and as yet untapped resource of primary patient-derived cells for cell- and gene-therapy studies.

METHODS

In the present study we compare isolation and storage methods for HSPCs from normal and thalassemic small-volume blood samples, considering genotype, density-gradient versus lysis-based cell isolation and cryostorage media with different serum contents. Downstream analyses include viability, recovery, differentiation in semi-solid media and performance in liquid cultures and viral transductions.

RESULTS

We demonstrate that HSPCs isolated either by ammonium-chloride potassium (ACK)-based lysis or by gradient isolation are suitable for functional analyses in clonogenic assays, high-level HSPC expansion and efficient lentiviral transduction. For cryostorage of cells, gradient isolation is superior to ACK lysis, and cryostorage in freezing media containing 50% fetal bovine serum demonstrated good results across all tested criteria. For assays on freshly isolated cells, ACK lysis performed similar to, and for thalassemic samples better than, gradient isolation, at a fraction of the cost and hands-on time. All isolation and storage methods show considerable variation within sample groups, but this is particularly acute for density gradient isolation of thalassemic samples.

DISCUSSION

This study demonstrates the suitability of small-volume blood samples for storage and preclinical studies, opening up the research field of HSPC and gene therapy to any blood diagnostic laboratory with corresponding bioethics approval for experimental use of surplus material.

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.

Iron overload and chelation therapy in myelodysplastic syndromes

Iron overload remains a concern in MDS patients especially those requiring recurrent blood transfusions. The consequence of iron overload may be more relevant in patients with low and intermediate-1 risk MDS who may survive long enough to experience such manifestations. It is a matter of debate whether this overload has time to yield organ damage, but it is quite evident that cellular damage and DNA genotoxic effect are induced. Iron overload may play a critical role in exacerbating pre-existing morbidity or even unmask silent ones. Under these circumstances, iron chelation therapy could play an integral role in the management of these patients. This review entails an in depth analysis of iron overload in MDS patients; its pathophysiology, effect on survival, associated risks and diagnostic options. It also discusses management options in relation to chelation therapy used in MDS patients and the impact it has on survival, hematologic response and organ function.

Ineffective erythropoiesis in β -thalassemia

In humans, β-thalassemia dyserythropoiesis is characterized by expansion of early erythroid precursors and erythroid progenitors and then ineffective erythropoiesis. This ineffective erythropoiesis is defined as a suboptimal production of mature erythrocytes originating from a proliferating pool of immature erythroblasts. It is characterized by (1) accelerated erythroid differentiation, (2) maturation blockade at the polychromatophilic stage, and (3) death of erythroid precursors. Despite extensive knowledge of molecular defects causing β-thalassemia, less is known about the mechanisms responsible for ineffective erythropoiesis. In this paper, we will focus on the underlying mechanisms leading to premature death of thalassemic erythroid precursors in the bone marrow.