Autologous Hematopoietic Stem Cell Research Articles

FGF23 Inhibition Improves Hematopoietic Stem Cell Transplantation in β-Thalassemia

Clinical evidence has established a link between anemias and skeletal abnormalities, although the underlying molecular mechanisms remain elusive. β-thalassemia (βThal) represents a valuable model for studying congenital anemia and associated bone and bone marrow (BM) microenvironment defects. Osteoporosis has a high morbidity in βThal patients, and we demonstrated that impaired hematopoietic stem cell (HSC) function is due to the prolonged persistence in an altered βThal BM niche ( Aprile et al, 2020). The correction of the genetic cause of βThal, mutations in the β-globin gene, is achieved by transplantation of HSCs from healthy donors or autologous HSCs from patients upon gene therapy. In both scenarios, a comprehensive understanding of HSCs and the BM niche is crucial to obtain successful outcomes. Our research focused on the role of fibroblast growth factor 23 (FGF23), a phosphaturic hormone at the crossroads of bone and erythropoiesis. We demonstrated that the elevated erythropoietin characteristic of the disease, leads to increased FGF23 production in both the βThal mouse model ( th3) and βThal patients, negatively affecting bone homeostasis and the interaction between HSCs and the stromal niche. Notably, in vivo FGF23 inhibition by cFGF23 peptide in th3 mice fully rescued bone defects, BM niche and HSC function ( Aprile, Raggi et al, 2023). To mimic the allogenic transplantation, we transplanted wt and th3 cells in a competitive setting into untreated th3 or th3+cFGF23 recipients. We observed partially enhanced engraftment in the cFGF23-treated mice indicating that FGF23 inhibition improves the supportive capacity of the damaged niche. We hypothesized that prolonged cFGF23 administration to recipient mice after transplantation could further restore the BM niche and boost the graft, thus achieving therapeutic outcomes. To establish the proper dose regimen with withdrawal periods for prolonged cFGF23 treatment, we analyzed bone mineral density (BMD) and HSC cell cycle at 1 and 2 weeks after discontinuing cFGF23 administration. Our results showed that rescued BMD was sustained after the discontinuation of treatment for 1 and 2 weeks ( th3 vs. th3+cFGF23 _1wk vs. th3+cFGF23_2wks: 125.9±3.8 vs. 181±19.9 vs. 142±1.6 mg/cm 3, p<0.01). Ongoing histomorphometric analysis will provide a better characterization of bone quality. Additionally, we observed the restoration of defective quiescence in th3 HSCs after 1- and 2 weeks ( th3 vs. th3+cFGF23 _1wk vs. th3+cFGF23_2wks: 77.8±1,4 vs. 92.1±1.8 vs. 87.8±0.9 on Lin neg BM cells, p<0.001). To test autologous transplantation upon gene therapy, we transduced th3 Lin neg BM cells with a lentiviral vector carrying the β-globin gene (GLOBE LV) at MOI 5 resulted in a mean vector copy number of 1 and a transduction efficiency of 50%. We performed competitive transplantation using 1x10 5 (CD45.1) transduced donor th3 cells and 1x10 5 (CD45.2) competitor mock-transduced th3 cells into busulfan-conditioned (CD45.2) untreated th3 or th3+cFGF23 recipient mice. The treated recipient mice received two doses of cFGF23 every 2 weeks as a maintenance regimen. We observed higher engraftment of transduced cells in the peripheral blood of cFGF23-treated mice at 8 weeks post-transplant ( th3 vs. th3+cFGF23: 4.9±1.1 vs. 10.7±1.9 % of CD45.1 engrafted cells, p<0.05). Comparative evaluation of hematological parameters and molecular analysis of transduced cells are ongoing. Targeting FGF23 signaling provides a promising strategy to improve bone defects and HSC-niche alterations in βThal. Here, we show that the use of FGF23 inhibition in the transplantation setting in β-thalassemia results in superior engraftment of donor cells in treated recipients, indicating a potential application to ameliorate the clinical outcome.

Predictive Modeling of Hematopoietic Stem Cell Mobilization and Collection Based on Peripheral Blood Marker

Background: Autologous stem cell transplantation (ASCT) is the major transplantation therapy for patients with lymphoma and MM, and the success of auto-HSCT depends on the mobilization efficiency of peripheral blood HSC. In clinical practice, CD34 + cell count in peripheral blood is often monitored to predict the collection effect and determine the collection time. However, prediction of poor mobilizers is still difficult . Methods: We retrospectively analyzed 108 patients with lymphoma and multiple myeloma(MM) at Chongqing University Cancer Hospital who underwent autologous hematopoietic stem cell (HSC) collection between January 2021 to August 2022. There are two groups: collection success group and collection failure group. Compared the differences of clinical characteristics and impact of peripheral blood related detection indexes before autologous HSC collection. Logistic regression analysis was used to establish a prediction model for the successful collection by multi-marker and further evaluated multi-marker prediction models. Results : There was no significant difference in sex, disease type, disease stage, age, disease status before mobilization, mobilization drugs and chemotherapy courses between the successful collection group and the failed collection group ( P> 0.05). The proportion of patients with mobilization days less than 5 days was higher in the successful collection group ( P< 0.05). The platelet count (PLT), mononuclear cell count (MNC) and absolute CD34 + cell count in the successful collection group were significantly higher than those in the failure group. The sensitivity, specificity and area under the curve (AUC) of combining three indexes were 80.9%, 95.9% and 0.944, respectively. Applied the Logistic regression models to the absolute count of PLT, MNC and CD34 + cells to construct the multi-marker prediction algorithms. The 3-marker model of PLT+MNC+CD34 + cells had the lowest AIC, BIC and high AUC. A prediction model was established based on the absolute count of PLT, MNC and CD34 + cells. Conclusion :Patients with less than 5 days of mobilization have a higher success rate of collection. PLT, MNC and CD34 + cell counts before collection can reflect HSC mobilization in patients with lymphoma and MM, and the combination of the three can improve the accuracy of prediction of collection effect.The predictive model based on the absolute number of PLT, MNC and CD34 + cells have good predictive value. Our study suggests that multi-markers are important diagnostic tools for predicting successful collection.

Gene therapy for neurodegenerative disorders in children: dreams and realities

Gene therapy encompasses the administration of biological medicinal products containing recombinant nucleic acids, mainly DNA, with the aim of treating or curing diseases. This represents a unique therapeutic strategy to reach the brain, in order to prevent or halt a neurodegenerative process. During the past decade, active multidisciplinary research has started to solve many issues for gene therapy in neurodegenerative disorders in terms of vectors, modes of administration, and expression of the therapeutic DNA. The engineering of hematopoietic stem cells (HSC) with lentivirus vectors for ex vivo gene therapy has demonstrated efficiency in reaching the brain through their transformation into microglial/macrophages cells with a long-term gene expression of the therapeutic vector as an alternative to autologous HSC transplants. Two drugs based on this strategy have been approved to date. The first is for metachromatic leukodystrophy (MLD), a severe lysosomal storage disease, and provides high levels of the deficient enzyme; the second one is for cerebral forms of X-linked adrenoleukodystrophy (X-ALD), and works by halting the neuroinflammation process. However, due to the long-lasting effect of the procedure, the therapy is applicable only to pre- or pauci/oligo-symptomatic patients. In vivo gene therapy via direct injection into the brain or the cerebrospinal fluid, but also by intravenous injection, represents a more efficient approach; however, many challenges remain to be solved despite the approval of two drugs: one for the early infantile form of spinal muscular atrophy (SMA), in which the gene product injected intravenously is able to prevent spinal motoneuron neurodegeneration. The second one, for aromatic L-amino acid decarboxylase (AADC) deficiency, provides the defective enzyme to the basal ganglia via intraparenchymal injection. The production of vectors able to reach the brain target cells with a sufficiently high expression remains a major bottleneck. In parallel, efforts must continue in order to better define (i) the natural history and clinical outcomes of many neurodegenerative disorders with childhood onset, and (ii) the mechanisms involved in the neurodegenerative process. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.

Hematopoietic stem-cell gene therapy is associated with restored white matter microvascular function in cerebral adrenoleukodystrophy

Blood-brain barrier disruption marks the onset of cerebral adrenoleukodystrophy (CALD), a devastating cerebral demyelinating disease caused by loss of ABCD1 gene function. The underlying mechanism are not well understood, but evidence suggests that microvascular dysfunction is involved. We analyzed cerebral perfusion imaging in boys with CALD treated with autologous hematopoietic stem-cells transduced with the Lenti-D lentiviral vector that contains ABCD1 cDNA as part of a single group, open-label phase 2-3 safety and efficacy study (NCT01896102) and patients treated with allogeneic hematopoietic stem cell transplantation. We found widespread and sustained normalization of white matter permeability and microvascular flow. We demonstrate that ABCD1 functional bone marrow-derived cells can engraft in the cerebral vascular and perivascular space. Inverse correlation between gene dosage and lesion growth suggests that corrected cells contribute long-term to remodeling of brain microvascular function. Further studies are needed to explore the longevity of these effects.

CD14+/CD31+ monocytes expanded by UM171 correct hemophilia A in zebrafish upon lentiviral gene transfer of factor VIII.

Emerging gene therapy clinical trials test the correction of hemophilia A (HA) by replacing factor VIII (FVIII) in autologous hematopoietic stem cells (HSCs). Although it is known that platelets, monocyte/macrophages, and mesenchymal stromal cells can secrete transgenic FVIII, a systematic examination of blood lineages as extrahepatic sources of FVIII, to our knowledge, has not yet been performed. In this study, we sought to provide a comprehensive map of native and lentivirus-based transgenic FVIII production from HSC stage to mature blood cells, through a flow cytometry analysis. In addition, we generated a model of transient HA in zebrafish based on antisense RNA, to assess the corrective potential of the FVIII-transduced HSCs. We discovered that FVIII production begins at the CD34+ progenitor stage after cytokine stimulation in culture. Among all mature white blood cells, monocytes are the largest producers of native FVIII and can maintain protein overexpression during differentiation from HSCs when transduced by a FVIII lentiviral vector. Moreover, the addition of the HSC self-renewal agonist UM171 to CD34+ cells during transduction expanded a subpopulation of CD14+/CD31+ monocytes with excellent ability to carry the FVIII transgene, allowing the correction of HA phenotype in zebrafish. Finally, the HA zebrafish model showed that f8 RNA is predominantly localized in the hematopoietic system at the larval stage, which indicates a potential contributory role of FVIII in hematopoiesis that warrants further investigation. We believe that this study may be of broad interest to hematologists and researchers striving to advance knowledge and permanent treatments for patients with HA.

Sterility Testing for Hematopoietic Stem Cells.

Over the last two decades, rapid technological advances have led to the wide adoption of cell and gene therapy products for the treatment of a variety of disease states. In this study, we reviewed the literature between 2003 and 2021 to provide a summary of overarching trends associated with microbial contamination in hematopoietic stem cells (HSCs) derived from peripheral blood, bone marrow, and cord blood. We provide a brief background on the regulatory context for human cells, tissues, and cellular and tissue-based products (HCT/Ps) as regulated by the US Food and Drug Administration (FDA), sterility testing expectations for autologous (Section 361) and allogeneic (Section 351) HSC products, and discuss clinical risks associated with the infusion of a contaminated HSC product. Finally, we discuss the expectations for current good tissue practices (cGTP) and current good manufacturing practices (cGMP) for the manufacturing and testing of HSC based on Section 361 and Section 351 categorization, respectively. We provide commentary on what is practiced in the field and discuss the critical need for updates to professional standards that keep pace with advancing technologies with an aim to clarify expectations for manufacturing and testing facilities to improve standardization across institutions.

Complications Associated with Peripherally Inserted Central Catheters (PICC) in People Undergoing Autologous Hematopoietic Stem Cell Transplantation (HSCT) in Home Hospitalization.

The SARS-CoV-2 pandemic generated the need to keep immunosuppressed patients away from hospital institutions for as long as possible. This in turn stimulated the implementation of a home hospitalization model for autologous hematopoietic stem-cell transplantation (HSCT). To analyze whether there are significant differences in post-transplantation complications related to catheters observed in patients treated in the home-transplant care modality compared to patients treated in the hospital. Observational, analytical, longitudinal, and retrospective study of cases and controls. A convenience sample was chosen, in which the cases comprised 20 patients included in the home HSCT care model. For each patient, it was considered suitable to propose two controls among those who received autologous transplantation in the last five years with a baseline demographic and pathological profile similar to the case for whom they were control. The home patients achieved an average of 22.4 ± 2.6 days of evolution with an average of 16.4 ± 2.08 days post-transplant, compared to the hospital process with an average of 21.21 ± 4.18 days of evolution and 15.51 ± 3.96 days post-transplant (evolution days p = 0.022; post-transplant days p = 0.002). A higher percentage of use of parenteral nutrition (p = 0.036) and transfusions (p = 0.003) was observed during the post-transplant phase in the hospital. The rest of the therapeutic measures did not show significant differences. When analyzing the frequency of adverse effects in the post-transplant phase, a significant increase in neutropenic fever (OR = 8.55) and positive blood cultures (OR = 6.65) was observed in hospital patients. Any other significant differences in other variables related to PICC were found (presence and days of neutropenic fever, catheter infection, complications, pathogens, admission to the ICU, or death). Concerning local complications (pain, DVT, Medical adhesive-related Skin Injury, and erythema), there was more erythema in the hospital (p = 0.056). The results obtained indicate that regarding the appearance of complications associated with PICCs in home hospitalization HSCT patients, there are no significant differences compared to hospitalization, so that home care can be a safe context for people with these lines.

Myeloid-derived suppressor cells in multiple myeloma patients at the immune recovery and after high-dose chemotherapy and hematopoietic stem cell transplantation

Introduction. Myeloid-derived suppressor cells (MDSCs) play an important role in restriction of the immune response and are associated with a poor prognosis in cancer. Mobilization of hematopoietic stem cells (HSCs) before high-dose chemotherapy (HCT) with autologous HSC transplantation (auto-HSCT) is accompanied by a signifcant increase in MDSC counts in peripheral blood and apheresis product of multiple myeloma (MM) patients. However, quantitative changes of these cells at the post-transplant and their role at the immune recovery remain unexplored.The study was aimed to analyze the dynamics of circulating MDSC counts and the expression of suppressor molecule arginase-1 in patients with MM in the frst 12 months after HCT and auto-HSCT and evaluate association between MDSCs and transplantation outcomes.Material and Methods. The study included 44 MM patients who underwent HCT and auto-HSCT. The relative number of granulocytic MDSCs (G-MDSCs), monocytic MDSCs (M-MDSCs), and early-stage MDSCs (E-MDSCs), as well as the expression of arginase-1 in each of MDSC subsets was evaluated by fow cytometry in patient peripheral blood samples.Results. At the engraftment (day +12 – +16, leukocytes >1×109 /l), M-MDSC relative count was increased (pU=0.038), as well as the relative (pU=0.003) and absolute (pU˂0.0001) counts of G-MDSCs, decreasing after 6 months down to pre-transplant values (рU=0.007, рU=0.024 and рU=0.02, respectively) and remaining at the same level at the 12-month follow-up period. The absolute count of E-MDSCs by the time of the engraftment decreased transiently (pU=0.004 vs before HCT), gradually recovering by 12-month follow-up (pU=0.032 vs day +12 – +16). The remission within 12 months in the group with G-MDSCs˂0.17 % at the engraftment was observed in 67 ± 11 % of patients, with G-MDSCs >0.17 % – in 94 ± 6 % of patients (p=0.049). During the 12-month post-transplant, the number of M-MDSCs expressing arginase-1 has been increasing, with a tendency to lower values at the engraftment in patients with early MM relapse (pU=0.09).Conclusion. The association of early MM relapse after auto-HSCT with the lower count of G-MDSCs and the lower count of arginase-1+ M-MDSCs at the engraftment suggests that MDSCs is involved in the restriction of homeostatic proliferation as a factor for more effective immune recovery.

New agents-based induction chemotherapy followed by autologous stem cell transplantation and maintenance treatment strategy for multiple myeloma: a single center retrospective study of 300 cases

Objective: To examine the survival and influential factors of an integrated approach of novel agents, autologous hematopoietic stem cell (auto-HSCT) , and maintenance therapy in patients with multiple myeloma (MM) patients from a single center over the past 15 years. Methods: In our center, 300 MM patients who received an integrated strategy of new agents, auto-HSCT, and maintenance therapy over 15 years were retrospectively and prospectively analyzed. Results: The complete remission rates (CR) and ≥very good partial remission rates (VGPR) following induction therapy, transplantation, and maintenance therapy were respectively 35.3% and 55.2% , 72.4% and 80.0% , 89.2% , and 93.4% . When compared to patients receiving double-drug induction, the ≥VGPR and ORR of patients receiving triple-drug induction were improved. No difference existed in CR, ≥VGPR, and ORR between the PAD (bortezomib + liposome doxorubicin+ dexamethasone) and RAD (lenalidomide + liposome doxorubicin + dexamethasone) regimens, but the benefits speed differed. The negative rate of flow minimal residual disease following induction, transplantation, and maintenance was 18.8% (54 cases) , 41.4% (109 cases) , and 58.7% (142 cases) , respectively. The median time to progress (TTP) was 78.7 months and the median overall survival (OS) was 109 months. The median TTP for RISS-Ⅰ-Ⅲ patients were 111.8 months, 77.4 months, and 30.6 months, and the median OS was 118.8 months, 91.4 months, and 48.5 months, respectively. At various points during treatment, the TTP and OS of patients obtaining CR and MRD negative were longer than those of patients who did not obtain CR and MRD negative. TTP was noticeably shorter in high-risk cytogenetic patients compared to standard-risk patients even when CR was acquired during induction. There was no difference in TTP between patients with high-risk cytogenetics and those with standard-risk cytogenetics if MRD negative was acquired during induction. According to a multivariate analysis, the R-ISS stage was a poor predictor of TTP and OS at various treatment intervals. Therapeutic effectiveness was a newly independent prognostic factor following treatment. Conclusion: A median survival of almost 10 years is possible for MM patients who receive an integrated strategy of induction regimens followed by auto-HSCT and maintenance therapy, which significantly improves prognosis. However, this approach did not significantly benefit high-risk cytogenetic MM patients.

Pre-mobilization platelet count predicts stem cell yield during mobilization in patients with multiple myeloma

BackgroundAutologous hematopoietic stem cell (HSC) transplantation remains the recommended treatment for eligible patients with multiple myeloma (MM). Increasing the number of transplanted CD34+ cells shorten the time to hematopoietic reconstitution and increases the overall survival of patients. With the harvest of a sufficient CD34+ cell number being crucial, this study aimed to predict the factors that affect stem cell collection. MethodsWe conducted a retrospective study of 110 patients who were newly diagnosed with MM and underwent autologous HSC collection at Beijing Jishuitan Hospital between March 2016 and July 2022. Multiple factors were analyzed using the Mann–Whitney U tests for between-group comparisons. Differences were considered statistically significant at P ​< ​0.05. ResultsWe found that patient age affected stem cell collection significantly; for patients younger than 55 years, the number of CD34+ cells harvested may be ​≥ ​2 ​× ​106/L, is unlikely to reach 5 ​× ​106/L. Platelet count at initial mobilization was a predictor of the number of CD34+ cells collected. Collection may fail when the platelet count at initial mobilization is below 177 ​× ​109/L and may be excellent when it is higher than 199 ​× ​109/L. ConclusionsThis finding could guide us to predict the approximate number of CD34+ cells collected in advance during autologous transplant mobilization for MM and to decide in advance whether to apply plerixafor to improve the number of HSCs collected.

A Phase I Safety and Feasibility Study to Evaluate Motixafortide (CXCR4/SDF-1 Inhibition) and Natalizumab (VLA-4/VCAM-1 Inhibition) As a Novel Regimen to Mobilize CD34+ Hematopoietic Stem Cells for Gene Therapy in Sickle Cell Disease

Background: Sickle cell disease (SCD) is one of the most common genetic diseases globally. Clinical manifestations of SCD commonly include anemia, pain, vaso-occlusive events and cumulative end organ damage leading to significant morbidity and mortality. Historically, allogeneic hematopoietic cell transplantation (HCT) represented the only curative therapy for SCD, but is associated with significant HCT-related morbidity and mortality which limit its use (PMID: 8663884, PMID: 20007560). Autologous hematopoietic stem cell (HSC) -based gene therapies now offer curative potential with decreased toxicity (PMID: 28249145). However, effective HSC-based gene therapy depends on collection of sufficient HSCs (ideally >10x106 CD34+ cells/kg), typically from peripheral blood (PB) (PMID: 33956057). G-CSF and CXCR4 inhibition (CXCR4i) with plerixafor are the most widely used mobilization strategies (PMID: 19363221, PMID: 19720922). However, G-CSF is associated with risk of fatal vaso-occlusive events in SCD (PMID: 9734950, PMID: 11368061, PMID: 19513902). Meanwhile, short-acting CXCR4i with plerixafor alone does not reliably yield optimal HSC numbers for gene therapy applications (PMID: 30282642, PMID: 29419425, PMID: 29472357). Therefore, developing novel HSC mobilization regimens to rapidly and reliably mobilize optimal CD34+ HSCs for gene therapy in SCD represents an unmet need. Motixafortide (M) is a high-affinity, long-acting CXCR4 inhibitor. The recent Phase III, randomized, controlled GENESIS Trial demonstrated combination M+G-CSF resulted in 88.8% of patients collecting ≥6x106 CD34+ cells/kg (median 10.8x106) within 1 leukapheresis (LP) for HCT. This compares favorably to historical data with plerixafor+G-CSF where 54.2% collected to goal in 1 LP. Motixafortide also mobilized more immunophenotypically primitive HSCs and multi-potent progenitors compared to plerixafor. Meanwhile, transcriptional profiling by single-cell RNA sequencing revealed HSCs mobilized with M have gene expression profiles associated with enhanced regeneration and self-renewal, compared to G-CSF or plerixafor (DOI: 10.1182/blood-2021-144296). Motixafortide alone also mobilized an average of 11.6×106 CD34+ cells/kg in healthy volunteers, while mobilizing 91.6% of allogeneic HSC donors to goal in ≤2 LPs (median 6.07x106) (DOI: 10.1182/blood-2018-99-109701, PMID: 28835380). Natalizumab (N) is a monoclonal antibody to the a4 integrin subunit of a4b1 (VLA-4) capable of VLA4 inhibition (VLA4i). In mice and primates, N led to an ~8-fold increase in PB CD34+ HSCs in 24 hrs (PMID: 7692447). In humans, a single N infusion resulted in a 5- to 6-fold increase PB CD34+ HSCs. Meanwhile, the average PB CD34+ HSC levels after a single dose were similar to levels with repeated doses, indicating rapid mobilization of maximal PB HSCs by 24 hrs after N infusion (PMID: 18195093). Combination CXCR4i and VLA-4i has been well-tolerated and resulted in synergistic mobilization of HSCs in preclinical studies (PMID: 21886173). Therefore, we hypothesize that combination CXCR4i and VLA-4i with M+N represents a safe and effective strategy for robust, rapid and synergistic mobilization of HSCs to PB in patients with SCD. Study Design and Methods: This is a single center, single-arm, dose de-escalation, Phase 1 safety and feasibility study. Key eligibility criteria include patients with SCD (SS or Sβ0) age 18-35 years receiving automated RBC exchanges. Patients with prior HCT or gene therapy will be excluded. We estimate 5 patients in this pilot feasibility study will provide sufficient safety and preliminary efficacy data to guide further development of this novel mobilization strategy. All patients will have baseline labs prior to M (1.25mg/kg, subcutaneous), N (300mg, IV) and M+N dosing. Each patient will then undergo mobilization and LP (1 blood volume), per protocol (see Figure 1). The primary outcome will be to assess the safety and tolerability of M, N and M+N in each SCD patient, defined by dose-limiting toxicities and maximum tolerated dose. Key secondary outcomes include: kinetics of CD34+ HSC mobilization to PB (CD34+ cells/uL), number of CD34+ HSCs collected via LP (CD34+ cells/kg/L), incidence of AEs, pharmacokinetics and the recommended phase 2 dose. Correlative studies include immunophenotypic and single cell transcriptional profiling of CD34+ HSCs from LP product mobilized with M, N and M+N. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Intracellular Iron Overload Induces Metabolic Switching in Active Hematopoietic Stem Cells in Beta-Thalassemia

Beta-thalassemia (BThal) is a complex monogenic disorder, causing severe anemia, ineffective erythropoiesis and multi-organ secondary defects. Iron overload (IO), associated with ineffective erythropoiesis and therapeutic blood transfusions, is one of the main complications of the disease, leading to morbidities in various organs. Despite the improvement in chelation therapies, IO toxicity is still a relevant issue. Correction of BThal is achieved by transplantation of hematopoietic stem cells (HSC) from healthy donors or autologous HSC from patients upon gene therapy. The quality and the engraftment of HSC depend on the bone marrow (BM) microenvironment, thus niche-HSC crosstalk plays a crucial role for transplantation outcome. We provided the first demonstration of impaired function of HSC caused by an altered BM niche in BThal (Aprile et al., Blood 2020). HSC from Hbbth3/+ (th3) BThal mice showed more active cycling profile and response to stress. We reported that IO reduces the hematopoietic supportive capacity of BM mesenchymal stromal cells from patients and recent evidence highlighted that both IO and iron deficiency are sources of cellular stress detrimental to HSC maintenance. Thus, we hypothesized that accumulation of iron might directly affect HSC function in BThal, as a model of chronic IO. Transcriptome analysis of sorted HSC from th3 mice showed a positive enrichment of genes involved in iron homeostasis, such as TfR1, Steap3, Fth1 and Ftl1, suggesting iron uptake and storage. Consistently, BThal HSC displayed higher levels of intracellular free reactive iron, as compared to wild-type (wt) controls (1.7±0.2 calcein MFI fold to wt, p<0.0001). We found that iron specifically accumulates in the mitochondria causing mitochondrial defects, as reduced size and lower membrane potential (0.4±0.05 TMRE/MTG fold to wt, p<0.001). These data, along with the downregulation of mitochondrial biogenesis and mitophagy genes, indicate an accumulation of damaged mitochondria in BThal HSC. In vivo administration of iron dextran to wt mice generated intracellular IO in HSC and was sufficient to decrease the mitochondrial membrane potential at levels comparable to those of th3 HSC, thus suggesting a direct effect of iron on mitochondrial activity. Since mitochondria are the powerhouse of the cell, we wondered if the mitochondrial dysfunction of BThal HSC could affect their production of metabolic energy. Metabolism indeed control HSC function: active HSC are more cycling and, because of their higher energy request, change the metabolism from glycolysis to mitochondrial oxidative phosphorylation (OXPHOS). Interestingly, we found that ATP levels in th3 HSC are lower compared to controls (wt 9.8±2.6 vs. th3 3.7±0.3 ATP nM, p<0.01). In line with mitochondrial dysfunction, in vitro inhibition of OXPHOS did not affect ATP content of BThal HSC since they switch to glycolysis for their energy demand. Consistently, th3 HSC showed positive enrichment of glycolytic genes and higher glucose uptake (wt 1639±163 vs. th3 2401±85 MFI 2NBDG, p<0.05). To unravel the basis of mitochondrial damage caused by IO, we investigated the role of reactive oxygen species (ROS). Iron is one of the sources of ROS and consistently, th3 HSC showed increased activation of antioxidant genes and higher levels of mitochondrial ROS (wt 2507±756 vs. th3 5205±459 MFI MitoSOX, p<0.01). In vivo reduction of mitochondrial ROS by MitoQ rescued mitochondrial activity (th3 0.3±0.07 vs. th3+MitoQ 0.9±0.2 TMRE/MTG fold to wt, p<0.05), thus demonstrating that mitochondrial dysfunction is reversible in BThal. Ongoing experiments will assess the metabolite profile, the restoration of HSC metabolism and in vivo function upon MitoQ and will also test HSC from BThal patients for mitochondrial defects. Overall, our study revealed that the multisystemic complications of IO in BThal also affect HSC. Iron has a direct impact on HSC metabolism by inducing oxidative stress and mitochondrial dysfunction. Despite the active cycling state, BThal HSC switch their metabolism to glycolysis because of the mitochondrial defect. Targeting mitochondrial iron or ROS might provide new tools to preserve HSC function in the setting of autologous transplantation upon gene therapy/editing for BThal. Moreover, this research will add novel insight about the regulation of HSC biology linking iron to mitochondrial metabolism.

Intraosseous injection of SMNP vectors enables CRISPR/Cas9-mediated knock-in of HBB gene into hematopoietic stem and progenitor cells

β-Hemoglobinopathies are hereditary diseases originating from mutations in the hemoglobin beta (HBB) gene. Allogeneic transplantation of hematopoietic stem cells (HSCs) is the only approved treatment to date providing a cure, which is limited due to low histocompatibility from potential donors. Although several clinical trials are introducing the functional HBB gene into autologous HSCs, the ex vivo viral transfection method raises safety concerns for clinical translation. Here, we reported a novel strategy that features direct bone marrow delivery of a CRISPR/Cas9-mediated knock-in system that integrates a copy of the functional HBB gene to the genome by supramolecular nanoparticle (SMNP) nonviral vectors. We demonstrated the feasibility of SMNP vectors for the delivery of the knock-in system. First, the biodistribution of SMNPs was monitored after intraosseous (i.o.) injection in a mouse model. Second, the in vitro CRISPR/Cas9-mediated knock-in of the HBB/GFP gene via SMNP vectors was evaluated in mouse stem cells. Finally, in vivo CRISPR/Cas9-mediated knock-in of mouse hematopoietic stem and progenitor cells (HSPCs) was performed by i.o. injection of SMNP vectors into mouse bone marrow. We believe this strategy presents a unique and innovative approach to treating β-hemoglobinopathies.

Nanoparticles targeting hematopoietic stem and progenitor cells: Multimodal carriers for the treatment of hematological diseases.

Modern-day hematopoietic stem cell (HSC) therapies, such as gene therapy, modify autologous HSCs prior to re-infusion into myelo-conditioned patients and hold great promise for treatment of hematological disorders. While this approach has been successful in numerous clinical trials, it relies on transplantation of ex vivo modified patient HSCs, which presents several limitations. It is a costly and time-consuming procedure, which includes only few patients so far, and ex vivo culturing negatively impacts on the viability and stem cell-properties of HSCs. If viral vectors are used, this carries the additional risk of insertional mutagenesis. A therapy delivered to HSCs in vivo, with minimal disturbance of the HSC niche, could offer great opportunities for novel treatments that aim to reverse disease symptoms for hematopoietic disorders and could bring safe, effective and affordable genetic therapies to all parts of the world. However, substantial unmet needs exist with respect to the in vivo delivery of therapeutics to HSCs. In the last decade, in particular with the development of gene editing technologies such as CRISPR/Cas9, nanoparticles (NPs) have become an emerging platform to facilitate the manipulation of cells and organs. By employing surface modification strategies, different types of NPs can be designed to target specific tissues and cell types in vivo. HSCs are particularly difficult to target due to the lack of unique cell surface markers that can be utilized for cell-specific delivery of therapeutics, and their shielded localization in the bone marrow (BM). Recent advances in NP technology and genetic engineering have resulted in the development of advanced nanocarriers that can deliver therapeutics and imaging agents to hematopoietic stem- and progenitor cells (HSPCs) in the BM niche. In this review we provide a comprehensive overview of NP-based approaches targeting HSPCs to control and monitor HSPC activity in vitro and in vivo, and we discuss the potential of NPs for the treatment of malignant and non-malignant hematological disorders, with a specific focus on the delivery of gene editing tools.

Expression of Inhibitory Molecules (Arginase-1, IDO, and PD-L1) by Myeloid-Derived Suppressor Cells in Multiple Myeloma Patients in Remission.

We studied suppressor potential of myeloid-derived suppressor cells (MDSC) in multiple myeloma patients, including before and after mobilization of hematopoietic stem cells (HSC), by evaluating the expression of arginase-1 (Arg1), indolamine-2,3-dioxygenase (IDO), and PD-L1 in MDSC subsets. The study included 20 multiple myeloma patients in remission, 5 patients with progression, as well as 10 sex-and age-matched healthy donors. The expression of Arg1, IDO, and PD-L1 in circulating granulocytic MDSC (G-MDSC, Lin-HLA-DR-CD33+CD66b+), monocytic MDSC (M-MDSC, CD14+HLA-DRlow/-), and early-stage MDSC (E-MDSC, Lin-HLA-DR-CD33+CD66b-) was evaluated by flow cytometry. Multiple myeloma patients in remission were characterized by reduced expression of Arg1 in M-MDSC in comparison with donors. The expression of Arg1 in M-MDSC depended on the number of induction therapy lines performed and was significantly lower in patients who received ⩾2 lines and responded with remission. Patients with multiple myeloma progression (resistant to therapy) showed significantly increased expression of Arg1 and PD-L1 in M-MDSC, as well as increased expression of Arg1 in E-MDSC. After G-CSF-induced mobilization of HSC, the content of circulating Arg1-expressing M-MDSC increased significantly. Considering the presence of MDSC in apheresis products, MDSC suppressive activity is discussed as a factor affecting the outcomes of autologous HSC transplantation in multiple myeloma patients.

Diverse Approaches to Gene Therapy of Sickle Cell Disease.

Sickle cell disease (SCD) results from a single base pair change in the sixth codon of the β-globin chain of hemoglobin, which promotes aggregation of deoxyhemoglobin, increasing rigidity of red blood cells and causing vaso-occlusive and hemolytic complications. Allogeneic transplant of hematopoietic stem cells (HSCs) can eliminate SCD manifestations but is limited by absence of well-matched donors and immune complications. Gene therapy with transplantation of autologous HSCs that are gene-modified may provide similar benefits without the immune complications. Much progress has been made, and patients are realizing significant clinical improvements in multiple trials using different approaches with lentiviral vector-mediated gene addition to inhibit hemoglobin aggregation. Gene editing approaches are under development to provide additional therapeutic opportunities. Gene therapy for SCD has advanced from an attractive concept to clinical reality.

Correction of Fanconi Anemia Mutations Using Digital Genome Engineering.

Fanconi anemia (FA) is a rare genetic disease in which genes essential for DNA repair are mutated. Both the interstrand crosslink (ICL) and double-strand break (DSB) repair pathways are disrupted in FA, leading to patient bone marrow failure (BMF) and cancer predisposition. The only curative therapy for the hematological manifestations of FA is an allogeneic hematopoietic cell transplant (HCT); however, many (>70%) patients lack a suitable human leukocyte antigen (HLA)-matched donor, often resulting in increased rates of graft-versus-host disease (GvHD) and, potentially, the exacerbation of cancer risk. Successful engraftment of gene-corrected autologous hematopoietic stem cells (HSC) circumvents the need for an allogeneic HCT and has been achieved in other genetic diseases using targeted nucleases to induce site specific DSBs and the correction of mutated genes through homology-directed repair (HDR). However, this process is extremely inefficient in FA cells, as they are inherently deficient in DNA repair. Here, we demonstrate the correction of FANCA mutations in primary patient cells using ‘digital’ genome editing with the cytosine and adenine base editors (BEs). These Cas9-based tools allow for C:G > T:A or A:T > C:G base transitions without the induction of a toxic DSB or the need for a DNA donor molecule. These genetic corrections or conservative codon substitution strategies lead to phenotypic rescue as illustrated by a resistance to the alkylating crosslinking agent Mitomycin C (MMC). Further, FANCA protein expression was restored, and an intact FA pathway was demonstrated by downstream FANCD2 monoubiquitination induction. This BE digital correction strategy will enable the use of gene-corrected FA patient hematopoietic stem and progenitor cells (HSPCs) for autologous HCT, obviating the risks associated with allogeneic HCT and DSB induction during autologous HSC gene therapy.

Hematopoietic Stem Cell Gene-Addition/Editing Therapy in Sickle Cell Disease.

Autologous hematopoietic stem cell (HSC)-targeted gene therapy provides a one-time cure for various genetic diseases including sickle cell disease (SCD) and β-thalassemia. SCD is caused by a point mutation (20A > T) in the β-globin gene. Since SCD is the most common single-gene disorder, curing SCD is a primary goal in HSC gene therapy. β-thalassemia results from either the absence or the reduction of β-globin expression, and it can be cured using similar strategies. In HSC gene-addition therapy, patient CD34+ HSCs are genetically modified by adding a therapeutic β-globin gene with lentiviral transduction, followed by autologous transplantation. Alternatively, novel gene-editing therapies allow for the correction of the mutated β-globin gene, instead of addition. Furthermore, these diseases can be cured by γ-globin induction based on gene addition/editing in HSCs. In this review, we discuss HSC-targeted gene therapy in SCD with gene addition as well as gene editing.

Impact of a shared-care model between community and academic centers for facilitating access to allogeneic and autologous stem cell transplantation.

1510 Background: Despite curative or disease-controlling roles in AML/MDS and MM, access to allogeneic (allo) and autologous (auto) hematopoietic stem cell transplantation (SCT) remains far from universal. Socioeconomic status (SES) and geographic distance from SCT centers have been shown to be barriers to SCT access. In 2016, Hartford HealthCare (HHC) and the Memorial Sloan Kettering Cancer Center (MSK) pioneered a Shared-Care Model (SCM) to streamline access to allo and auto SCT at MSK, featuring a dedicated nurse SCT coordinator, shared hematology tumor boards, MSK-led didactics for HHC providers, and an electronic health record sharing pipeline. We sought to determine if this has improved access to SCT for HHC patients. Methods: A retrospective chart review was conducted of HHC patients aged 18-70 with new diagnoses of AML, MDS, and MM between 2016 and 2020. Socioeconomic status (SES) was estimated by 9-digit zip-code using the Area Deprivation Index (ADI), shown to be a surrogate for healthcare access. Referral or not to a SCT center, referral to MSK through the SCM, and reasons for non-referral were abstracted from the medical record. For patients referred for SCT at MSK, we also captured the number of peri-SCT days in New York City (NYC) and number of subsequent MSK and HHC clinic visits/hospitalizations within 1-year post-SCT. Results: A total of 126 patients was included, with 81 (64%) treated for AML/MDS and 45 (36%) for MM. The median age was 60 years (interquartile range [IQR]: 53-66). The majority were white (n = 101, 80%) followed by 10% (n = 13) Black/African American; 10% (n = 12) were of Hispanic ethnicity. The median ADI percentile was 38 (IQR: 20-51; higher percentiles reflect decreased SES). The median ADI for MSK SCT referrals from New York, New Jersey, and Connecticut 2016-2020 for the same indications was 19 (IQR: 10-30, p &lt; 0.001). A total of 90 patients (71%) were referred to SCT centers. Leading reasons for no referral were favorable-risk disease (n = 10), goals of care (n = 9), and death prior to referral (n = 5); 3 patients were not referred due to comorbidities/performance status. No differences were found between patients referred to MSK vs. other centers. Thirty-four HHC patients were referred to MSK (21 AML/MDS, 13 MM), vs. 3 between 2010 and 2015. Twelve patients underwent allo SCT, with median 97 days in NYC (range: 68-247); 8 underwent auto SCT, with median 21 days in NYC (range: 15-48). Conclusions: Our findings show the feasibility of a shared-care model between a non-SCT-providing large regional hospital system and a major academic transplantation center. Close collaboration between institutions may minimize time patients spend away from home. The SES of HHC referrals was lower than the general MSK population, suggesting that a shared-care model may facilitate access to SCT for patients with previous barriers for this potentially curative therapy.

Hematopoietic Stem Cell Transplantation for Neurological Disorders: A Focus on Inborn Errors of Metabolism.

Hematopoietic stem cells have been investigated and applied for the treatment of certain neurological disorders for a long time. Currently, their therapeutic potential is harnessed in autologous and allogeneic hematopoietic stem cell transplantation (HSCT). Autologous HSCT is helpful in immune-mediated neurological diseases such as Multiple Sclerosis. However, clinical benefits derive more from the immunosuppressive conditioning regimen than the interaction between stem cells and the nervous system. Mainly used for hematologic malignancies, allogeneic HSCT explores the therapeutic potential of donor-derived hematopoietic stem cells. In the neurological setting, it has proven to be most valuable in Inborn Errors of Metabolism, a large spectrum of multisystem disorders characterized by congenital deficiencies in enzymes involved in metabolic pathways. Inborn Errors of Metabolism such as X-linked Adrenoleukodystrophy present with brain accumulation of enzymatic substrates that result in progressive inflammatory demyelination. Allogeneic HSCT can halt ongoing inflammatory neural destruction by replacing hematopoietic-originated microglia with donor-derived myeloid precursors. Microglia, the only neural cells successfully transplanted thus far, are the most valuable source of central nervous system metabolic correction and play a significant role in the crosstalk between the brain and hematopoietic stem cells. After transplantation, engrafted donor-derived myeloid cells modulate the neural microenvironment by recapitulating microglial functions and enhancing repair mechanisms such as remyelination. In some disorders, additional benefits result from the donor hematopoietic stem cell secretome that cross-corrects neighboring neural cells via mannose-6-phosphatase paracrine pathways. The limitations of allogeneic HSCT in this setting relate to the slow turnover of microglia and complications such as graft-vs.-host disease. These restraints have accelerated the development of hematopoietic stem cell gene therapy, where autologous hematopoietic stem cells are collected, manipulated ex vivo to overexpress the missing enzyme, and infused back into the patient. With this cellular drug vehicle strategy, the brain is populated by improved cells and exposed to supraphysiological levels of the flawed protein, resulting in metabolic correction. This review focuses on the mechanisms of brain repair resulting from HSCT and gene therapy in Inborn Errors of Metabolism. A brief mention will also be made on immune-mediated nervous system diseases that are treated with this approach.