Hematopoietic Stem Cell Transplantation in Thalassemia

Beta thalassemia syndromes: New insights

Beta thalassemia (β-thalassemia) syndromes are a heterogeneous group of inherited hemoglobinopathies caused by molecular defects in the beta-globin gene that lead to the impaired synthesis of beta-globin chains of the hemoglobin. The hallmarks of the disease include ineffective erythropoiesis, chronic hemolytic anemia, and iron overload. Clinical presentation ranges from asymptomatic carriers to severe anemia requiring lifelong blood transfusions with subsequent devastating complications. The management of patients with severe β-thalassemia represents a global health problem, particularly in low-income countries. Until recently, management strategies were limited to regular transfusions and iron chelation therapy, with allogeneic hematopoietic stem cell transplantation available only for a subset of patients. Better understanding of the underlying pathophysiological mechanisms of β-thalassemia syndromes and associated clinical phenotypes has paved the way for novel therapeutic options, including pharmacologic enhancers of effective erythropoiesis and gene therapy.

Risk factors for hemorrhagic cystitis in children with severe beta-thalassemia after allogeneic hematopoietic stem cell transplantation

Purpose

To investigate the risk factors for hemorrhagic cystitis (HC) in children with severe beta-thalassemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT).

Methods

The clinical data of 152 children under the age of 15 who underwent allo-HSCT between January 2011 and December 2021 were retrospectively analyzed. The incidence of HC and related variables were evaluated using univariate analysis. Variables with statistical significance (P < 0.05) were included in a multivariable logistic regression model to identify independent risk factors for HC.

Results

Among the 152 children, 42 developed HC, with an incidence rate of 27.63%. The median onset time of HC was 25 days (IQR: 10-38.75 days). Univariate analysis indicated that older transplantation age, elevated pre-transplant serum ferritin levels, cytomegalovirus (CMV) infection, and prolonged neutrophil engraftment time were associated with HC occurrence (P < 0.05). Multivariable logistic regression further confirmed that older transplantation age (OR 1.236, 95% CI: 1.031-1.531, P = 0.033), elevated pre-transplant ferritin levels (OR 1.053, 95% CI: 1.028-1.086, P < 0.01), CMV infection (OR 11.522, 95% CI: 2.912-76.345, P = 0.002), and prolonged neutrophil engraftment time (OR 1.385, 95% CI: 1.109-1.793, P < 0.01) were independent risk factors for HC.

Conclusion

Older transplantation age (>5.95 age years old), elevated pre-transplant serum ferritin levels, CMV infection, and delayed neutrophil engraftment are independent risk factors for HC in children with severe beta-thalassemia after allo-HSCT. Early identification and intervention for these risk factors are crucial in reducing the incidence of HC.

Creating New Cis-Regulatory Elements of HBD to Reactivate Delta-Globin

β-thalassemia and sickle cell disease (SCD) are global monogenic blood system disorders, and reactivated δ-globin is expected to replace missing or abnormal β-globin. With the development of gene editing technology, activating γ-globin for treating β-thalassemia and SCD has been highly successful. However, δ-globin, as another important potential therapeutic target, has few related studies. Gene editing technology introduced cis-acting elements, including NF-Y, KLF1, GATA1, and TAL1, into the regulatory region of HBD, successfully activating the expression of δ-globin. It was confirmed that the activation effect of δ-globin was closely related to the location of the introduced cis-acting elements. In this study, the mutation creates a de novo binding site for KLF1 at -85∼93 bp upstream of the transcription start site of the HBD gene, as well as the site for TAL1 and GATA1 cobinding motifs at -59 to ∼-78 bp, which could effectively activate δ-globin.

Establishment of an α-thalassemia mouse model through fetal liver cell transplantation and analysis of hematological parameters

Clinically, α-thalassemia is stratified into mild, intermediate, and severe forms, differentiated by the degree of anemia severity. Specifically, severe α-thalassemia manifests in homozygous individuals, characterized by a profound α globin deficit. The presence of two α0 alleles, resulting in a complete four-gene defect (α--/--), constitutes a lethal in utero condition known as Hemoglobin (Hb) Barts hydrops fetalis syndrome. This arises from the inability of hemoglobin, deficient in α chains, to adequately transport oxygen. Consequently, this severe variant typically onsets during fetal development, often culminating in intrauterine death towards the end of gestation or dying shortly postpartum due to the compounded effects of severe anemia and resultant hypoxia. This study endeavors to establish an α-thalassemia mouse model via transplantation of embryonic liver cells harboring a dual α allele knockout, with a subsequent focus on comprehensively characterizing its hematological parameters and associated phenotypic indicators. To generate an α-globin chain-deficient mouse model, we transplanted fetal liver cells (harvested at embryonic day 13.5 from homozygous C57BL/6J-CD45.2-HBA-DKO mice) into C57BL/6 wild-type recipients preconditioned with 800 cGy irradiation. Multiple blood routine indicators, blood smear assessments, and spleen weight measurements, were subsequently conducted to characterize the model. Initially, model mice exhibited elevated white blood cell and lymphocyte counts relative to controls, potentially indicative of a possible immune reaction, though this response waned over time. Characteristic of the disease, these mice displayed significantly diminished mean corpuscular hemoglobin content and concentration, alongside heightened numbers of HbH inclusions and spleen weights. Furthermore, red blood cellindices, such as red blood cell count, hematocrit, red cell distribution width-coefficient of variation, and red cell distribution width-standard deviation, were all markedly increased in the model mice. Notably, model mice demonstrated significantly elevated values for mean platelet volume, platelet distribution width, and platelet large cell ratio percentage, reflective of aberrant platelet characteristics. Concurrently, a time-dependent increase in basophil percentages accompanied decreases in platelet count, platelet crit, and platelet larger cell count, collectively implying a progressively severe anemic state. Moreover, the progression from low to high levels of reticulocyte percentage and absolute reticulocyte count further corroborated an escalating tendency towards hemolysis. The model mice also experienced a substantial decline in body weight, underscoring the profound impact of disease progression on their health.

Haploidentical Hematopoietic Stem Cell Transplantation in Pediatric Transfusion-Dependent Thalassemia: A Systematic Review and Meta-Analysis

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) presents a promising therapeutic option for pediatric transfusion-dependent thalassemia, particularly in the scarcity of matched donors. Despite its potential, the comprehensive evaluation of this method through large-scale prospective studies remains lacking. This study aims to systematically summarize the efficacy and safety of haplo-HSCT in thalassemia, thereby providing further evidence-based insights for clinical practice. A comprehensive literature search was conducted across PubMed, Embase, and Web of Science databases through June 2024 to ensure a robust analysis of the available evidence. Data extraction was independently performed by 2 reviewers. The analysis utilized the inverse variance method with a 95% confidence interval (95% CI) to calculate the pooled proportion. To assess the heterogeneity among the studies, Cochran's Q test and Higgins' I-squared statistical methods were utilized. A random-effects model was employed to accommodate the variability between study results. Furthermore, subgroup analyses were explored differences in outcomes based on conditioning regimens and graft versus host disease (GVHD) prophylaxis. Conditioning regimens were categorized into reduced-intensity conditioning and myeloablative conditioning regimens. GVHD prophylaxis was classified into post-transplantation cyclophosphamide and non-post-transplantation cyclophosphamide. In this meta-analysis, we reviewed data from 10 studies encompassing 356 patients with thalassemia who underwent haplo-HSCT. Out of these, 328 patients survived until the follow-up date, resulting in a pooled overall survival rate of 92.4% (95% CI, 86.9-96.7; I² = 54.32%). The thalassemia-free survival was 84.5% (95% CI, 75.3-91.9; I² = 77.64%), and the graft failure rate was 8.1% (95% CI, 2.5-16.4; I² = 81.78%). The transplantation-related mortality stood at 7.4% (95% CI, 3.6-12.5; I² = 55.74%), with infections noted as the primary cause of death. The pooled proportion of acute graft versus host disease (aGVHD), grade 2-4 aGVHD, and grade 3-4 aGVHD were 29.6% (95% CI, 16.7-42.5, I² = 92.48%), 22.3% (95% CI, 10.1-42.1, I² = 80.06%), and 9.1% (95% CI, 2.8-17.7, I² = 67.92%), respectively. Subgroup analyses revealed no significant differences in these outcomes when comparing myeloablative conditioning to reduced-intensity conditioning, or post-transplantation cyclophosphamide to non-post-transplantation cyclophosphamide prophylaxis. However, variations in sample size, patient's age and geographic region among the studies suggest these factors as potential sources of heterogeneity. Haploidentical hematopoietic stem cell transplantation utilizes donors who are partially HLA-matched, typically family members, making it a viable option for transfusion-dependent thalassemia when fully matched donors are not available.

A novel conditioning regimen with pre-transplantation immunosuppression reduces the complication rates in hematopoietic stem cell transplantation in transfusion-dependent β-thalassemia

BACKGROUND

Allo-HSCT is a curative therapy for patients with transfusion-dependent thalassemia (TDT). The high incidence of transplant-related complications is becoming an obstacle to safe and effective unrelated donor (URD) transplantation.

METHODS

In this retrospective study, we reported the survival outcomes and complications of transplantation in thalassemia patients using a novel regimen consisting of pre-transplantation immunosuppression (PTIS) and modified myeloablative conditioning based on intravenous busulfan, cyclophosphamide, fludarabine, and rabbit anti-human thymocyte immunoglobulin.

RESULTS

A total of 88 thalassemia patients received the novel conditioning regimen (NCR group), while 118 patients received the conventional conditioning regimen (CCR group). The median age at HSCT in the NCR group was older (7 years vs. 4 years, p < 0.05). No patient in the NCR group experienced primary graft failure, while the 3-year probabilities of OS and TFS were 96.6% and 93.2%, respectively. Even when the intensity of conditioning was reduced, OS (94.8% vs. 94.3%, p = 0.848) and TFS (89.8% vs. 92.5%, p = 0.663) in URD transplants in the NCR group were comparable to those in the CCR group, while the risk of autoimmune hemolytic anemia (AIHA) (0% vs. 15.1%) was lower. In addition, the NCR group had lower rates of mixed chimerism (7.1%).

CONCLUSIONS

URD transplantation can achieve a comparable prognosis to matched sibling donor (MSD) transplantation with a lower incidence of AIHA due to PTIS and modified myeloablative conditioning regimen.

Stem cell graft dose and composition could impact on the expansion of donor-derived clones after allogeneic hematopoietic stem cell transplantation - a virtual clinical trial

Introduction

Hematopoietic stem cell transplantation is a potentially curative intervention for a broad range of diseases. However, there is evidence that malignant or pre-malignant clones contained in the transplant can expand in the recipient and trigger donor-derived malignancies. This observation has gained much attention in the context of clonal hematopoiesis, a medical condition where significant amounts of healthy blood cells are derived from a small number of hematopoietic stem cell clones. In many cases the dominating clones carry mutations conferring a growth advantage and thus could undergo malignant transformation in the recipient. Since clonal hematopoiesis exists in a significant proportion of potential stem cell donors, a more detailed understanding of its role for stem cell transplantation is required.

Methods

We propose mechanistic computational models and perform virtual clinical trials to investigate clonal dynamics during and after allogenic hematopoietic stem cell transplantation. Different mechanisms of clonal expansion are considered, including mutation-related changes of stem cell proliferation and self-renewal, aberrant response of mutated cells to systemic signals, and self-sustaining chronic inflammation triggered by the mutated cells.

Results

Model simulations suggest that an aberrant response of mutated cells to systemic signals is sufficient to explain the frequently observed quick expansion of the mutated clone shortly after transplantation which is followed by a stabilization of the mutated cell number at a constant value. In contrary, a mutation-related increase of self-renewal or self-sustaining chronic inflammation lead to ongoing clonal expansion. Our virtual clinical trials suggest that a low number of transplanted stem cells per kg of body weight increases the transplantation-related expansion of donor-derived clones, whereas the transplanted progenitor dose or growth factor support after transplantation have no impact on clonal dynamics. Furthermore, in our simulations the change of the donors' variant allele frequencies in the year before stem cell donation is associated with the expansion of donor-derived clones in the recipient.

Discussion

This in silico study provides insights in the mechanisms leading to clonal expansion and identifies questions that could be addressed in future clinical trials.

Advancements and challenges in stem cell transplantation for regenerative medicine

Stem cell transplantation has emerged as a promising avenue in regenerative medicine, potentially facilitating tissue repair in degenerative diseases and injuries. This review comprehensively examines recent developments and challenges in stem cell transplantation. It explores the identification and isolation of various stem cell types, including embryonic, induced pluripotent, and adult stem cells derived from multiple sources. Additionally, the review highlights the tissue-specific applications of these stem cells, focusing on bone and cartilage regeneration, treatment of neurological disorders, and management of hematological conditions. Future advancements and effective resolution of current challenges will be crucial in fully realizing the potential of stem cell transplantation in regenerative medicine. With responsible and ethical practices, the field can potentially transform disease and injury treatment, ultimately improving the quality of life for countless individuals.

Comprehensive analysis of thalassemia alleles (CATSA) based on third-generation sequencing is a comprehensive and accurate approach for neonatal thalassemia screening

Thalassemia is one of the most common and damaging monogenic diseases in the world. It is caused by pathogenic variants of α- and/or β-globin genes, which disrupt the balance of these two protein chains and leads to α-thalassemia or β-thalassemia, respectively. Patients with α-thalassemia or β-thalassemia could exhibit a severe phenotype, with no simple and effective treatment. A three-tiered strategy of carrier screening, prenatal diagnosis and newborn screening has been established in China for the prevention and control of thalassemia, of which the first two parts have been studied thoroughly. The implementation of neonatal thalassemia screening is lagging, and the effectiveness of various screening programs has not yet been demonstrated. In this study, hemoglobin capillary electrophoresis (CE), hotspot testing method, and third-generation sequencing (TGS) were used in the variant detection of 2000 newborn samples, to assess the efficacy of these methods in neonatal thalassemia screening. Compared with CE (249, 12.45 %) and hotspot analysis (424, 21.2 %), CATSA detected the largest number of thalassemia variants (535, 26.75 %), which included 24 hotspot variants, increased copy number of α-globin gene, rare pathogenic variants, and three unreported potentially disease-causing variants. More importantly, CATSA directly determined the cis-trans relationship of variants in three newborns, which greatly shortens the clinical diagnosis time of thalassemia. CATSA showed a great advantage over other genetic tests and could become the most powerful technical support for the three-tiered prevention and control strategy of thalassemia.

Αlpha-thalassemia: A practical overview

α-Thalassemia is an inherited blood disorder characterized by decreased synthesis of α-globin chains that results in an imbalance of α and β globin and thus varying degrees of ineffective erythropoiesis, decreased red blood cell (RBC) survival, chronic hemolytic anemia, and subsequent comorbidities. Clinical presentation varies depending on the genotype, ranging from a silent or mild carrier state to severe, transfusion-dependent or lethal disease. Management of patients with α-thalassemia is primarily supportive, addressing either symptoms (eg, RBC transfusions for anemia), complications of the disease, or its transfusion-dependence (eg, chelation therapy for iron overload). Several novel therapies are also in development, including curative gene manipulation techniques and disease modifying agents that target ineffective erythropoiesis and chronic hemolytic anemia. This review of α-thalassemia and its various manifestations provides practical information for clinicians who practice beyond those regions where it is found with high frequency.

Treosulfan Exposure Predicts Thalassemia-Free Survival in Patients with Beta Thalassemia Major Undergoing Allogeneic Hematopoietic Cell Transplantation

A toxicity-reduced conditioning regimen with treosulfan, fludarabine, and thiotepa in patients with high-risk β-thalassemia major has significantly improved hematopoietic stem cell transplantation (HCT) outcomes. However, complications resulting from regimen-related toxicities (RRTs), mixed chimerism, and graft rejection remain a challenge. We evaluated the dose-exposure-response relationship of treosulfan and its active metabolite S, S-EBDM, in a uniform cohort of patients with β-thalassemia major to identify whether therapeutic drug monitoring (TDM) and dose adjustment of treosulfan is feasible. Plasma treosulfan/S, S-EBDM levels were measured in 77 patients using a validated liquid chromatography with tandem mass spectrometry method, and the pharmacokinetic parameters were estimated using nlmixr2. The influence of treosulfan and S, S-EBDM exposure, and GSTA1/NQO1 polymorphisms on graft rejection, RRTs, chimerism status, and 1-year overall survival (OS), and thalassemia-free survival (TFS) were assessed. We observed that treosulfan exposure was lower in patients with graft rejection than those without (1,655 vs. 2,037 mg•h/L, P = 0.07). Pharmacodynamic modeling analysis to identify therapeutic cutoff revealed that treosulfan exposure ≥1,660 mg•hour/L was significantly associated with better 1-year TFS (97% vs. 81%, P = 0.02) and a trend to better 1-year OS (90% vs. 69%, P = 0.07). Further, multivariate analysis adjusting for known pre-HCT risk factors also revealed treosulfan exposure <1,660 mg•h/L (hazard ratio (HR) = 3.23; 95% confidence interval (CI) = 1.12-9.34; P = 0.03) and GSTA1*B variant genotype (HR = 3.75; 95% CI = 1.04-13.47; P = 0.04) to be independent predictors for inferior 1-year TFS. We conclude that lower treosulfan exposure increases the risk of graft rejection and early transplant-related mortality affecting TFS. As no RRTs were observed with increasing treosulfan exposure, TDM-based dose adjustment could be feasible and beneficial.