History of hematopoietic cell transplantation: challenges and progress

Tissue Engineering and Regenerative Medicine: Perspectives and Challenges

From the pioneering days of cell therapy to the achievement of bioprinting organs, tissue engineering, and regenerative medicine have seen tremendous technological advancements, offering solutions for restoring damaged tissues and organs. However, only a few products and technologies have received United States Food and Drug Administration approval. This review highlights significant progress in cell therapy, extracellular vesicle-based therapy, and tissue engineering. Hematopoietic stem cell transplantation is a powerful tool for treating many diseases, especially hematological malignancies. Mesenchymal stem cells have been extensively studied. The discovery of induced pluripotent stem cells has revolutionized disease modeling and regenerative applications, paving the way for personalized medicine. Gene therapy represents an innovative approach to the treatment of genetic disorders. Additionally, extracellular vesicle-based therapies have emerged as rising stars, offering promising solutions in diagnostics, cell-free therapeutics, drug delivery, and targeted therapy. Advances in tissue engineering enable complex tissue constructs, further transforming the field. Despite these advancements, many technical, ethical, and regulatory challenges remain. This review addresses the current bottlenecks, emphasizing novel technologies and interdisciplinary research to overcome these hurdles. Standardizing practices and conducting clinical trials will balance innovation and regulation, improving patient outcomes and quality of life.

Update in GVHD Prophylaxis: Novel Pharmacologic and Graft Manipulation Strategies

Prevention of graft-versus-host disease (GVHD) is critical to successful allogeneic hematopoietic cell transplantation (HCT), but for many years was difficult to achieve. Advances in the understanding of allogeneic HCT biology and immunology have paved the way for novel clinical approaches to GVHD prophylaxis, highlighted by the broad adoption of posttransplant cyclophosphamide and the approval of abatacept by the US Food and Drug Administration to prevent acute GVHD. Patients undergoing allogeneic HCT are now experiencing severe acute GVHD at historically low rates, and significant improvements in preventing chronic GVHD are also being achieved. This review highlights key pharmacological approaches and graft manipulation strategies being used or investigated for GVHD prophylaxis. Furthermore, we discuss the ongoing unmet needs in GVHD prevention and the challenges in addressing these areas in future clinical trials.

The impact of ABO compatibility on allogeneic hematopoietic cell transplantation outcomes: a contemporary and comprehensive study from the transplant complications working party of the EBMT

The role of ABO blood group system mismatch on allogeneic hematopoietic cell transplantation (allo-HCT) outcomes is controversial since current publications of large datasets are lacking. We retrospectively analyzed 30,487 patients transplanted between 2010 and 2021 using the EBMT registry to assess ABO incompatibility's effect on non-relapse mortality (NRM), overall survival (OS), progression-free survival (PFS), relapse incidence (RI), acute GvHD (aGvHD), chronic GvHD (cGvHD), and neutrophil engraftment. Transplantations were classified as ABO-compatible (56.3%), major (18.1%), minor (20.1%), and bidirectional (5.5%) incompatibilities. Mainly peripheral blood stem cells (PBSC) were used as the cell source in 85.6% of cases. Multivariate analysis found no significant association between compatibility status, with the compatible group serving as the reference, and NRM, OS, PFS, RI or cGvHD. The incidence of non-engraftment was significantly higher in the major (HR 1.04, 95% CI 1.01-1.07, p = 0.021) and bidirectional (HR 1.09, 95% CI 1.03-1.15, p = 0.003) incompatibilities. At the same time, the risk of severe aGvHD grades III-IV was lower in the major incompatibility group (HR 0.85, 95% CI 0.77-0.94, p = 0.001). Our large contemporary study, showing no major impact on outcomes, suggests that the ABO blood group system should not be a primary consideration in donor selection for PBSC-based allo-HCT.

Hematopoietic stem cell transplantation in Crohn's disease: a comprehensive review

PURPOSE OF REVIEW

Despite advances in medical therapies for the treatment of Crohn's disease (CD), 20-30% of patients fail to respond to these therapies (i.e. refractory CD). Medically refractory CD leads to significant disability increasing morbidity and mortality. To prevent the disability of refractory CD, hematopoietic stem cell transplantation (SCT) has emerged as a therapeutic strategy.

RECENT FINDINGS

Autologous (auto-SCT) and allogeneic SCT (allo-SCT) have been explored in clinical trials for refractory CD patients. We will review the stem cell transplant process, how each part of stem cell transplantation affects clinical efficacy and safety, and how specific clinical trials advanced our understanding of the role of stem cell transplant in the treatment of refractory CD.

SUMMARY

As multiple clinical trials using the same auto-SCT protocol demonstrated auto-SCT as clinically efficacious for refractory CD it supports that this treatment may be adopted as standard of care for select patients with refractory CD. To establish auto-SCT as a standard therapy will require the creation of international registries to track long-term SCT outcomes and translational studies to refine SCT protocols for CD patients as a cellular therapy that truly restores healthy intestinal immune cell populations from hematopoietic stem cells.

Second pregnancy in China 5 years after ovarian tissue transplantation to prevent iatrogenic POI

OBJECTIVE

This article reports the second live birth in China after frozen-thawed ovarian tissue transplantation to prevent iatrogenic premature ovarian insufficiency (POI).

METHOD

A patient with aplastic anemia received ovarian tissue cryopreservation before hematopoietic stem cell transplantation, and four ovarian cortex strips were thawed and transplanted into her peritoneal pocket 18 months later.

RESULTS

Pregnancy occurred spontaneously 5 years after grafting, and a healthy girl was born at 39 weeks of gestation. Until now, the child has developed normally without any major diseases.

CONCLUSION

Ovarian tissue cryopreservation and transplantation (OTCT) can be assessed as a successful method especially to prevent iatrogenic POI. In our cryobank for OTCT, which is the first official one in China, intensive research to improve this method has been performed, and we propose after our success for the second pregnancy in China to include this method in the official guidelines for prevention and treatment of (especially iatrogenic) POI.

Diverse potential of chimeric antigen receptor-engineered cell therapy: Beyond cancer

BACKGROUND

Chimeric antigen receptor (CAR)-engineered cell therapies have made significant progress in haematological cancer treatment. This success has motivated researchers to investigate its potential applications in non-cancerous diseases, with substantial strides already made in this field.

MAIN BODY

This review summarises the latest research on CAR-engineered cell therapies, with a particular focus on CAR-T cell therapy for non-cancerous diseases, including but not limited to infectious diseases, autoimmune diseases, cardiac diseases and immune-mediated disorders in transplantation. Additionally, the review discusses the current obstacles that need to be addressed for broader clinical applications.

CONCLUSION

With ongoing research and continuous improvements, CAR-engineered cell therapy holds promise as a potent tool for treating various diseases in the future.

KEY POINTS

CAR-engineered cell therapy has expanded beyond cancer to treat autoimmune diseases, infections, cardiac diseases, and transplant-related rejection. The CAR platform is diverse, with various cell types such as CAR-T, CAR-NK, and CAR-M potentially suited for different disease contexts. The safety, efficacy, and practicality of CAR cell therapy in non-cancer diseases remain challenging, requiring further technological optimization and clinical translation.

An interpretive phenomenological study on the lived experiences of allogeneic hematopoietic cell transplantation patients 'in an Islamic context'

PURPOSE

Allogeneic hematopoietic cell transplantation (allo-HCT) has serious complications despite its potential curative effects. Some of these complications can impede ongoing treatment and healing. Transplantation is a long journey that requires close follow-up and monitoring. In-depth knowledge of patient perspectives is essential to provide quality care at all levels. This study aimed to explore the lived experiences of allo-HCT patients.

METHODS

An interpretive phenomenological design was employed in this study. One-to-one virtual semistructured in-depth interviews were conducted with nine adult allo-HCT patients. Interviews were transcribed verbatim, and data were analyzed by Diekelmann's seven-stage analysis technique. The study was carried out at Princess Noorah Oncology Center (PNOC) at Jeddah city.

RESULTS

The participants were found to experience a range of physical and psychological changes as they progressed through the transplantation stages. These changes were interconnected and portrayed challenges dealing with transplantation. Overall, the findings revealed the complex and multifaceted nature of the recovery process, illustrating the delicate balance survivors are trying to reach through deep reasoning and mental adaptations. The experiences of the participants were captured in several themes: Transplantation knowledge aligned with patient preferences, transplantation course, perspective shift and transformation, family role transition, mental wellness, surrender, support system, and patience.

CONCLUSION

This study demonstrated the experiences of allo-HCT patients, how these patients transitioned from one stage to another, and the intellectual skills they embraced through this transition process. The findings reflected the coping strategies and mechanisms used by patients to overcome hardship and revealed aspects of illness and wellness concepts.

Assessing the visibility and public engagement of bone marrow and stem cell transplantation research: An altmetric analysis

Background

Bone marrow and stem cell transplantation have led to significant advancements in modern medicine, offering potential cures for various hematological disorders and specific cancers. This study aims to investigate and analyze research in this field using altmetrics in a world outside the academic scholarly and publishing environment.

Methods

This study examines articles in the field of bone marrow and stem cell transplantation in a ten-year period (2013-2022) extracted from the Web of Science database. The Altmetric Explorer database and tool were used to extract data. After an initial review of the data for their completeness and accuracy, the study considered descriptive reports, statistical analyses, bibliometric network analysis, and overlaps between articles, journals, and research centers in terms of the Altmetric Attention Score (AAS) and citations using Excel, SPSS, Python, R, and VOSviewer.

Result

This study evaluated 12924 articles published in 293 journals. Findings show that 85.67% of the articles were mentioned at least once on various social media and their tools. The AAS varied between 0 and 1125, and the median of this score was 2. The highest score was assigned to an article that provides critical insights into the outcomes of patients with refractory diffuse large B-cell lymphoma (DLBCL). Mendeley, X (formerly Twitter), and News were the most important and active social tools, respectively, where these articles were mentioned. The highest number of tweets, news stories, Facebook posts, and policy documents were from the USA, USA, USA, and UK, respectively. The @PaperbirdsM and @MayoClinic accounts on X had the highest tweet and follower statistics, respectively. The University of Texas MD Anderson Cancer Center also had the highest number of mentions on social networks. Network analysis maps of the top AAS articles showed "Stem Cell Transplantation" as the most popular author keyword, with Blood having the most influence at the journal level, the USA at the country level, Memorial Sloan Kettering Cancer Center at the research center level, and Kenneth C. Anderson at the author level. Finally, the results of the tests showed a significant correlation between citation and Altmetric indicators/AAS. However, nor were there differences in AAS based on the open access status of articles or the journal quartile.

Conclusion

A high percentage of articles in this field are present on social networks and platforms. Furthermore, highly cited articles on social media have attracted more attention. Both traditional and web-based metrics offer different perspectives on scholarly impact. While each provides valuable insights, further research is needed to explore how these metrics can be effectively combined for a more comprehensive evaluation of scientific outputs.

A case report of donor cell-derived hematologic neoplasms 9 years after allogeneic hematopoietic cell transplantation

BACKGROUND

The treatment of blood cancers has been revolutionized by hematopoietic stem cell transplantation. Owing to this method, we are able to effectively treat most blood cancers. However, in some cases, one of the greatest problems is the risk of relapse. Most often, relapse of the disease manifests itself as cancer cells with the same characteristics as the primary cancer. Nevertheless, a very small percentage of patients develop other blood cancers from donor cells. Donor cell-derived hematologic neoplasms are extremely rare complications that arise after hematopoietic stem cell transplantation.

CASE PRESENTATION

In this study we described a patient who underwent hematopoietic stem cell transplantation due to acute myeloid leukemia and subsequently developed triple-negative myeloproliferative neoplasms with mutations in the ASXL1, SETBP1 and EZH2 genes 9 years later. Over the next two years, the disease progressed and MDS/AML developed. Unfortunately, the patient died during induction therapy.

CONCLUSIONS

Donor cell-derived hematologic neoplasms are rare but significant complications after HSCT. Early diagnosis and intervention are crucial to improving patient prognosis. Further studies are needed to better understand the pathogenesis of this condition and develop more effective therapeutic strategies.

Deciphering the Complexities of Adult Human Steady State and Stress-Induced Hematopoiesis: Progress and Challenges

Human hematopoietic stem cells (HSCs) have traditionally been viewed as self-renewing, multipotent cells with enormous potential in sustaining essential steady state blood and immune cell production throughout life. Indeed, around 86% (1011-1012) of new cells generated daily in a healthy young human adult are of hematopoietic origin. Therapeutically, human HSCs have contributed to over 1.5 million hematopoietic cell transplants (HCTs) globally, making this the most successful regenerative therapy to date. We will commence this review by briefly highlighting selected key achievements (from 1868 to the end of the 20th century) that have contributed to this accomplishment. Much of our knowledge of hematopoiesis is based on small animal models that, despite their enormous importance, do not always recapitulate human hematopoiesis. Given this, we will critically review the progress and challenges faced in identifying adult human HSCs and tracing their lineage differentiation trajectories, referring to murine studies as needed. Moving forward and given that human hematopoiesis is dynamic and can readily adjust to a variety of stressors, we will then discuss recent research advances contributing to understanding (i) which HSPCs maintain daily steady state human hematopoiesis, (ii) where these are located, and (iii) which mechanisms come into play when homeostatic hematopoiesis switches to stress-induced or emergency hematopoiesis.

Next-generation sequencing protocol of hematopoietic stem cells (HSCs). Step-by-step overview and troubleshooting guide

Populations of very small embryonic-like stem cells (VSELs) (CD34+lin-CD45- and CD133+lin-CD45-), circulating in the peripheral blood of adults in small numbers, have been identified in several human tissues and together with the populations of hematopoietic stem cells (HSCs) (CD34+lin-CD45+) and CD133+lin-CD45+constitute a pool of cells with self-renewal and pluripotent stem cell characteristics. Using advanced cell staining and sorting strategies, we isolated populations of VSELs and HSCs for bulk RNA-Seq analysis to compare the transcriptomic profiles of both cell populations. Libraries were prepared from an extremely small number of cells; however, their good quality was preserved, and they met the criteria for sequencing. We present here a step-by-step NGS protocol for sequencing VSELs and HSC with a description of troubleshooting during library preparation and sequencing.

Role of Neurotransmitters in Steady State Hematopoiesis, Aging, and Leukemia

Haematopoiesis within the bone marrow (BM) represents a complex and dynamic process intricately regulated by neural signaling pathways. This delicate orchestration is susceptible to disruption by factors such as aging, diabetes, and obesity, which can impair the BM niche and consequently affect haematopoiesis. Genetic mutations in Tet2, Dnmt3a, Asxl1, and Jak2 are known to give rise to clonal haematopoiesis of intermediate potential (CHIP), a condition linked to age-related haematological malignancies. Despite these insights, the exact roles of circadian rhythms, sphingosine-1-phosphate (S1P), stromal cell-derived factor-1 (SDF-1), sterile inflammation, and the complement cascade on various BM niche cells remain inadequately understood. Further research is needed to elucidate how BM niche cells contribute to these malignancies through neural regulation and their potential in the development of gene-corrected stem cells. This literature review describes the updated functional aspects of BM niche cells in haematopoiesis within the context of haematological malignancies, with a particular focus on neural signaling and the potential of radiomitigators in acute radiation syndrome. Additionally, it underscores the pressing need for technological advancements in stem cell-based therapies to alleviate the impacts of immunological stressors. Recent studies have illuminated the microheterogeneity and temporal stochasticity of niche cells within the BM during haematopoiesis, emphasizing the updated roles of neural signaling and immunosurveillance. The development of gene-corrected stem cells capable of producing blood, immune cells, and tissue-resident progeny is essential for combating age-related haematological malignancies and overcoming immunological challenges. This review aims to provide a comprehensive overview of these evolving insights and their implications for future therapeutic strategies.

Cell Therapy as a Way to Increase the Effectiveness of Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is a standard method for treating a number of pathologies, primarily blood diseases. Timely restoration of the immune system after HSCT is a critical factor associated with the development of complications such as relapses or secondary tumors and various infections, as well as the graft-versus-host reaction in allogeneic transplantation, which ultimately affects the survival of patients. Introduction into the recipient's body of immune system cells that are incapable of sensitization by recipient antigens during the period of immune reconstitution can increase the rate of restoration of the immune system, as well as reduce the risk of complications. This review presents the results of studies on cell therapy with various cell subpopulations of both bone marrow and mesenchymal origin during HSCT.

Stem cell therapy approaches for non-malignant diseases & non-haematological diseases in India: A systematic review

Background & objectives Our study aims to provide the diversity of stem cell use for non-malignant, non-haematological diseases in India through the lens of clinical trials. Methods A PRISMA approach was used to evaluate the safety and efficacy of stem cell use for the period 2001-2021 in India. The outcomes were measured using each disease category, types of stem cells, the origin of stem cells, safety, and efficacy. Results Of the 9206 studies screened, 61 studies that were relevant to stem cell use for non-malignant diseases were included for analysis. Autologous stem cells (75%) were used predominantly compared to allogenic stem cells (18.33%), followed by mixed type (6.67%). Use of bone marrow-derived stem cells (51%) was dominant, followed by melanocytes (19%), adipose (7%), haematopoietic (12%), and (11%) other types of stem cells. The study revealed 37 randomized clinical trial studies conducted in the government research hospital compared to the non-government. Interpretation & conclusions Maintaining the gold standard for stem cell therapy requires randomized clinical trials with large sample sizes, control groups, failures, adverse effects, etc. It is important to have a monitoring and regulation system in stem cell clinical research activities with enough preclinical data and repeated exchanges between the bench and the bedside.

Interventional antibiotic treatment replacing antibiotic prophylaxis during allogeneic hematopoietic stem cell transplantation is safe and leads to a reduction of antibiotic administration

Patients undergoing allogeneic hematopoietic stem cell transplantation (alloHSCT) face an elevated risk of infection-related mortality, particularly during the pre-engraftment period. Although systemic antibiotic prophylaxis (SAP) is commonly employed during neutropenia, it is linked to disruptions in the intestinal microbiome, increasing the risk of graft-versus-host disease (GVHD), Clostridium difficile infection (CDI), and colonization with multi-drug resistant (MDR) bacteria. In our retrospective analysis, we evaluated the safety and efficacy of an exclusively interventional antibiotic treatment (IAT) compared to SAP in adult alloHSCT patients. In comparison to SAP, IAT resulted in a significantly reduced duration of antibiotic therapy (24 vs. 18 days, p < 0.001), although the cumulative incidence (CI) of bloodstream infections (BSI) by day + 100 post-HSCT was significantly higher in the IAT group compared to SAP (40% vs. 13%, p < 0.001). However, this did not lead to a significant increase in ICU transfers (13% vs. 6%, p = ns) or a higher CI of non-relapse mortality (NRM) at 3 years (11% vs. 10%, p = ns). With a median follow-up of 1052 days, the 3-year overall survival (OS) rates were 69% and 66% for the SAP and IAT cohorts, respectively (p = ns). The CI of acute GVHD grade II-IV (30% vs. 39%) at 100 days or chronic GVHD of any grade (50% vs. 45%) at 3 years did not differ significantly between the SAP and IAT groups. There was a tendency towards a higher CI of severe chronic GVHD in the SAP cohort (28% vs. 13%, p = 0.08). Our single center experience in conducting alloHSCT without antibiotic prophylaxis but with stringent guidelines for prompt antibiotic intervention demonstrated no disadvantages in terms of OS and NRM. IAT led to significantly reduced consumption of cefotaxime, carbapenem, and glycopeptide antibiotics. In conclusion, our findings suggest that replacing SAP with the proposed IAT procedure is both safe and feasible.

Soluble MICA concentrations and genetic variability of MICA and its NKG2D receptor as factors affecting Graft-versus-Host Disease development after allogeneic haematopoietic stem cell transplantation

Despite new treatment strategies, graft-versus-host disease (GvHD) remains a formidable complication after allogeneic hematopoietic stem cell transplantation (HSCT). This study aimed to investigate the impact of polymorphisms and expression of MICA and NKG2D receptor on the development of GvHD in allogeneic HSCT recipients. Soluble MICA (sMICA) concentration was measured in serum collected 30 days after transplantation and the genetic variability of MICA and NKG2D genes was evaluated. The frequency of NKG2D+NK cells was determined by flow cytometry before and (21, 30, 60 and 90 days) after transplantation. Recipients with acute GvHD grades II-IV carried the NKG2D rs1049174 C allele more frequently than controls or patients with no or mild disease. Patients with chronic GvHD had higher frequency of NKG2D expressing NK cells posttransplant, reflecting increased activity of their NK cells. Although no direct relationship between MICA SNPs and GvHD were observed, the presence of MICA rs1051792 GG genotype correlated with elevated sMICA levels and increased serum level of sMICA was associated with higher risk of chronic GvHD. Our findings suggest that sMICA concentration may serve as a potential biomarker for chronic GvHD and emphasize the impact of genetic variability of NKG2D and its surface expression on the HSCT outcome.

Allostimulation leads to emergence of a human B cell population with increased expression of HLA class I antigen presentation-associated molecules and the immunoglobulin receptor FcRL5

In the extensive literature characterizing lymphocyte contributions to transplant-related pathologies including allograft rejection and graft-versus-host disease, T cell-focused investigation has outpaced investigation of B cells. Most B cell-related reports describe regulatory and antibody-producing functions, with less focus on the potential role of antigen-presenting capacity. Using in vitro human mixed lymphocyte reactions (MLRs) to model allostimulation, we analyzed responder B cells using transcriptional analysis, flow cytometry, and microscopy. We observed emergence of an activated responder B cell subpopulation phenotypically similar to that described in individuals with graft-versus-host disease or allograft rejection. This population had markedly increased expression of FcRL5 (Fc receptor like 5) and molecules associated with human leukocyte antigen class I antigen presentation. Consistent with this phenotype, these cells demonstrated increased internalization of irradiated cell debris and dextran macromolecules. The proportion of this subpopulation within MLR responders also correlated with emergence of activated, cytotoxic CD8+ T cells. B cells of similar profile were quite infrequent in unstimulated blood from healthy individuals but readily identifiable in disaggregated human splenocytes and increased in both cases upon allostimulation. Further characterization of the emergence and function of this subpopulation could potentially contribute to identification of novel biomarkers and targeted therapeutics relevant to curbing transplant-related pathology.

Optimization of pre-enrichment strategies for mouse hematopoietic stem cell isolation and metabolomic analysis

Blood cell production arises from the activity of hematopoietic stem cells (HSCs), defined by their self-renewal capacity and ability to give rise to all mature blood cell types. The mouse remains one of the most studied species in hematological research, and markers to define and isolate mouse HSCs are well-established. Given the very low frequency of HSCs in the bone marrow, stem cell pre-enrichment by red blood cell lysis and magnetic cell separation is often performed as part of the isolation process to reduce sorting times. Several pre-enrichment strategies are available, differing in their speed, degree of enrichment, final cell yield, and cost. In the current study, we performed a side-by-side comparison and provide a decision tree to help researchers select a pre-enrichment strategy for mouse HSC isolation depending on their downstream application. We then compared different pre-enrichment techniques in combination with metabolomics analysis of HSCs, where speed, yield and temperature during pre-enrichment are crucial factors, and found that the choice of pre-enrichment strategy significantly impacts the number of metabolites detected and levels of individual metabolites in HSCs.

Characterization of clonal dynamics using duplex sequencing in donor-recipient pairs decades after hematopoietic cell transplantation

After allogeneic hematopoietic cell transplantation (HCT), a very small number of donor stem cells reconstitute the recipient hematopoietic system, whereas the donor is left with a near-normal pool of stem cells. We hypothesized that the increased replicative stress on transplanted donor cells in the recipient could lead to the disproportionate proliferation of clonal hematopoiesis (CH) variants. We obtained blood samples from 16 related donor-recipient pairs at a median of 33.8 years (range: 6.6 to 45.7) after HCT, including the longest surviving HCT recipients in the world. For 11 of 16 pairs, a donor sample from the time of HCT was available for comparison. We performed ultrasensitive duplex sequencing of genes recurrently mutated in myeloid malignancies and CH, as well as a set of functionally neutral genomic regions representative of human genomic content at large. CH variants were observed in all donors, even those as young as 12 years old. Where donor pre-HCT sample was available, the average mutation rate in donors compared to recipients post-HCT was similar (2.0% versus 2.6% per year, respectively) within genes recurrently mutated in myeloid malignancies. Twenty-two (5.6%) of the 393 variants shared between paired donors and recipients post-HCT showed ≥10-fold higher variant allele frequency (VAF) in the recipient. A longer time since HCT was positively associated with the expansion of shared variant VAFs in the recipient. In conclusion, even decades after HCT, there does not appear to be widespread accelerated clonal expansion in the transplanted cells, highlighting the immense regenerative capacity of the human hematopoietic system.

Development of a quantitative prediction algorithm for human cord blood-derived CD34+ hematopoietic stem-progenitor cells using parametric and non-parametric machine learning models

The transplantation of CD34+ hematopoietic stem-progenitor cells (HSPCs) derived from cord blood serves as the standard treatment for selected hematological, oncological, metabolic, and immunodeficiency disorders, of which the dose is pivotal to the clinical outcome. Based on numerous maternal and neonatal parameters, we evaluated the predictive power of mathematical pipelines to the proportion of CD34+ cells in the final cryopreserved cord blood product adopting both parametric and non-parametric algorithms. Twenty-four predictor variables associated with the cord blood processing of 802 processed cord blood units randomly sampled in 2020-2022 were retrieved and analyzed. Prediction models were developed by adopting the parametric (multivariate linear regression) and non-parametric (random forest and back propagation neural network) statistical models to investigate the data patterns for determining the single outcome (i.e., the proportion of CD34+ cells). The multivariate linear regression model produced the lowest root-mean-square deviation (0.0982). However, the model created by the back propagation neural network produced the highest median absolute deviation (0.0689) and predictive power (56.99%) in comparison to the random forest and multivariate linear regression. The predictive model depending on a combination of continuous and discrete maternal with neonatal parameters associated with cord blood processing can predict the CD34+ dose in the final product for clinical utilization. The back propagation neural network algorithm produces a model with the highest predictive power which can be widely applied to assisting cell banks for optimal cord blood unit selection to ensure the highest chance of transplantation success.

Long-Term Human Immune Reconstitution, T-Cell Development, and Immune Reactivity in Mice Lacking the Murine Major Histocompatibility Complex: Validation with Cellular and Gene Expression Profiles

BACKGROUND

Humanized mice transplanted with CD34+ hematopoietic cells (HPCs) are broadly used to study human immune responses and infections in vivo and for testing therapies pre-clinically. However, until now, it was not clear whether interactions between the mouse major histocompatibility complexes (MHCs) and/or the human leukocyte antigens (HLAs) were necessary for human T-cell development and immune reactivity.

METHODS

We evaluated the long-term (20-week) human hematopoiesis and human T-cell development in NOD Scid Gamma (NSG) mice lacking the expression of MHC class I and II (NSG-DKO). Triplicate experiments were performed with HPCs obtained from three donors, and humanization was confirmed in the reference strain NOD Rag Gamma (NRG). Further, we tested whether humanized NSG-DKO mice would respond to a lentiviral vector (LV) systemic delivery of HLA-A*02:01, HLA-DRB1*04:01, human GM-CSF/IFN-α, and the human cytomegalovirus gB antigen.

RESULTS

Human immune reconstitution was detectable in peripheral blood from 8 to 20 weeks after the transplantation of NSG-DKO. Human single positive CD4+ and CD8+ T-cells were detectable in lymphatic tissues (thymus, bone marrow, and spleen). LV delivery harnessed the detection of lymphocyte subsets in bone marrow (αβ and γδ T-cells and NK cells) and the expression of HLA-DR. Furthermore, RNA sequencing showed that LV delivery increased the expression of different human reactome pathways, such as defense responses to other organisms and viruses.

CONCLUSIONS

Human T-cell development and reactivity are independent of the expression of murine MHCs in humanized mice. Therefore, humanized NSG-DKO is a promising new model for studying human immune responses, as it abrogates the xenograft mouse MHC interference.

Allogeneic Stem Cell Transplant in Hematological Disorders: A Decade of Experience

Background: Allogeneic hematopoietic cell transplantation (allo-HCT) is a complex procedure with the potential to provide curative treatment for various hematological disorders. This study aims to evaluate the outcomes of allo-HCT in hematological diseases and identify significant complications in a single-center setting. Materials and Methods: We conducted a retrospective analysis of 180 patients with hematological diseases who underwent allo-HCT between January 2011 and December 2021. Key outcomes, including indications for transplantation, overall survival, engraftment time, relapse rates, graft-versus-host disease (GVHD), and transplant-related mortality (TRM) were assessed. Results: The most common indications for allo-HCT were benign hematological diseases, particularly aplastic anemia, and thalassemia major. Despite the majority of patients receiving fully matched transplants, acute GVHD was observed in 30% of the cohort. Graft failure occurred in 13 patients, with primary and secondary graft failure rates of 1.6% and 5.5%, respectively. Sepsis emerged as the primary cause of non-relapsed mortality at day 100 and beyond. The overall survival rate in this study was 62%, with 79% of patients disease-free on their last visit. Conclusion: This study provides valuable insights into the treatment strategies and patient care of allo-HCT for hematological disorders by offering a comprehensive overview of multiple relevant outcomes. The findings underscore the significance of addressing complications and risk factors associated with allogeneic transplantation, including GVHD and infections. Future research should focus on further optimizing transplantation techniques to minimize complications and enhance patient survival.

Salivary flow rate, subjective oral dryness and dental caries 5 years after haematopoietic cell transplantation

BACKGROUND

The aim of this study was to describe salivary flow rate, subjective oral dryness and dental caries 5 years post haematopoietic cell transplantation (HCT).

METHODS

HCT survivors of a previous longitudinal observational cohort study in the Netherlands (the H-OME study) were invited to participate in this additional follow-up after 5 years (the HOME2 study). During the additional follow-up appointment, stimulated (SWS) and unstimulated whole saliva (UWS) was collected, participants rated subjective oral dryness on a 0 - 10 scale, and caries lesions were assessed. Furthermore, dental records, including treatments and radiographs, were requested for the 5 years preceding and the 5 years following transplantation. Paired t-tests were performed to determine changes in UWS and SWS flow rates and subjective oral dryness from pre-HCT, and to compare the number of caries-related dental treatments (restorations, endodontic treatments or extractions) before and after HCT. Hyposalivation of UWS (< 0.2 mL/min) and SWS (< 0.7 mL/min) at 3 and 12 months, was used to explore the predictive potential of hyposalivation on a high dental treatment need (> 3 treatments) over the 5 years post-HCT.

RESULTS

Five years post-HCT, 39 HCT survivors were included. The mean UWS flow rate was 0.36 mL/min (SD 0.26) and the mean SWS flow rate 1.02 (SD 0.57); survivors were diagnosed with a median of 0 dentine lesions (range 0 - 12) and 73% reported a subjective oral dryness score ≥ 1. Survivors underwent a median of 3 (range 0 - 20) dental treatments during the 5 years following transplantation. The mean difference in UWS 5 years post-HCT compared to pre-HCT was 0.03 (95% CI: -0.07 - 10.12), the mean difference for SWS was -0.18 (95% CI: -0.45 - 0.08) and for subjective oral dryness 1.2 (95% CI: 0.2 - 2.1). In the 5 years post-HCT, non-significantly more treatments were performed compared to the 5 years pre-HCT (mean difference: 0.5, 95%CI: -1.2 - 2.2). Seventy eight percent of patients with hyposalivation of SWS at 12 months had a high dental treatment need, compared with 38% with no hyposalivation.

CONCLUSIONS

Five years post-HCT, mean UWS and SWS flow rates were not significantly different from pre-HCT levels but subjective oral dryness scores were elevated.

Postmortem pathologic findings in dogs that underwent total body irradiation and hematopoietic cell transplant: A case series of five dogs with B-cell multicentric lymphoma

Alternative therapies that can help achieve complete remission in dogs with lymphoma include total body irradiation and hematopoietic cell transplant, though there are few reports describing successes and pathologic sequelae of these procedures. During a 10-year period, 94 dogs with multicentric lymphoma received a hematopoietic cell transplant following total body irradiation at North Carolina State University College of Veterinary Medicine. Seven of these 94 dogs (7%) died prior to discharge, five (5%) of which presented for postmortem examination. Of these dogs, four received an autologous hematopoietic cell transplant, while one received a haploidentical allogeneic hematopoietic cell transplant. All five dogs had bone marrow depletion with all hematopoietic lines affected. Three had systemic candidiasis, while two had bacterial infections. To the authors' knowledge, this is the first report to document pathologic findings and development of systemic mycoses in dogs post total-body irradiation therapy and hematopoietic cell transplant.

Antiviral Agents for Preventing Cytomegalovirus Disease in Recipients of Hematopoietic Cell Transplantation

This systematic review discusses the use of prophylaxis to prevent cytomegalovirus (CMV) infection in recipients who have undergone hematopoietic cell transplantation. It highlights the need for new approaches to control and prevent CMV infection. The approval of the anti-CMV drug letermovir has made antiviral prophylaxis more popular. CMV-specific T cell-mediated immunity tests are effective in identifying patients who have undergone immune reconstitution and predicting disease progression. Maribavir (MBV) has been approved for the treatment of post-transplant CMV infection/disease in adolescents. Adoptive T-cell therapy and the PepVax CMV vaccine show promise in tackling refractory and resistant CMV. However, the effectiveness of PepVax in reducing CMV viremia/disease was not demonstrated in a phase II trial. Cell-mediated immunity assays are valuable for personalized management plans, but more interventional studies are needed. MBV and adoptive T-cell therapy are promising treatments, and trials for CMV vaccines are ongoing.

Bioengineered niches that recreate physiological extracellular matrix organisation to support long-term haematopoietic stem cells

Long-term reconstituting haematopoietic stem cells (LT-HSCs) are used to treat blood disorders via stem cell transplantation. The very low abundance of LT-HSCs and their rapid differentiation during in vitro culture hinders their clinical utility. Previous developments using stromal feeder layers, defined media cocktails, and bioengineering have enabled HSC expansion in culture, but of mostly short-term HSCs and progenitor populations at the expense of naive LT-HSCs. Here, we report the creation of a bioengineered LT-HSC maintenance niche that recreates physiological extracellular matrix organisation, using soft collagen type-I hydrogels to drive nestin expression in perivascular stromal cells (PerSCs). We demonstrate that nestin, which is expressed by HSC-supportive bone marrow stromal cells, is cytoprotective and, via regulation of metabolism, is important for HIF-1α expression in PerSCs. When CD34+ve HSCs were added to the bioengineered niches comprising nestin/HIF-1α expressing PerSCs, LT-HSC numbers were maintained with normal clonal and in vivo reconstitution potential, without media supplementation. We provide proof-of-concept that our bioengineered niches can support the survival of CRISPR edited HSCs. Successful editing of LT-HSCs ex vivo can have potential impact on the treatment of blood disorders.

Special Report: Summary of the eighth workshop of the worldwide network for blood and marrow transplantation on the status and issues related to hematopoietic stem cell transplantation in near-east countries, held in Pakistan from September 22 to 23, 2022

The eighth workshop of the Worldwide Network for Blood and Marrow Transplantation (WBMT) was held in Islamabad, Pakistan, from September 22 to 23, 2022, aiming to foster hematopoietic stem cell transplant (HSCT) activity in the World Health Organization (WHO) Eastern Mediterranean Region (EMRO). Participating countries, including Pakistan, Oman, Iran, and Saudi Arabia, reported increased HSCT in the last few years, whereas others from the EMRO and beyond, including Qatar, United Arab Emirates, Nepal, and Bangladesh, started HSCT recently and have developed HSCT programs with excellent results. During educational sessions and open dialog, participating teams and international experts from the WBMT shared their experience and discussed minimum essential requirements for establishing and expanding HSCT in emerging countries, indications for HSCT training and dissemination of knowledge, stem cell donor selection and safety, quality assurance in transplant centers, and the value and importance of transplant outcome databases. International support, collaboration, and local engagement, including government participation and WHO assistance, are valuable in increasing HSCT access worldwide.

Bone marrow Tfr2 deletion improves the therapeutic efficacy of the activin-receptor ligand trap RAP-536 in β-thalassemic mice

β-thalassemia is a disorder characterized by anemia, ineffective erythropoiesis (IE), and iron overload, whose treatment still requires improvement. The activin receptor-ligand trap Luspatercept, a novel therapeutic option for β-thalassemia, stimulates erythroid differentiation inhibiting the transforming growth factor β pathway. However, its exact mechanism of action and the possible connection with erythropoietin (Epo), the erythropoiesis governing cytokine, remain to be clarified. Moreover, Luspatercept does not correct all the features of the disease, calling for the identification of strategies that enhance its efficacy. Transferrin receptor 2 (TFR2) regulates systemic iron homeostasis in the liver and modulates the response to Epo of erythroid cells, thus balancing red blood cells production with iron availability. Stimulating Epo signaling, hematopoietic Tfr2 deletion ameliorates anemia and IE in Hbbth3/+ thalassemic mice. To investigate whether hematopoietic Tfr2 inactivation improves the efficacy of Luspatercept, we treated Hbbth3/+ mice with or without hematopoietic Tfr2 (Tfr2BMKO/Hbbth3/+) with RAP-536, the murine analog of Luspatercept. As expected, both hematopoietic Tfr2 deletion and RAP-536 significantly ameliorate IE and anemia, and the combined approach has an additive effect. Since RAP-536 has comparable efficacy in both Hbbth3/+ and Tfr2BMKO/Hbbth3/+ animals, we propose that the drug promotes erythroid differentiation independently of TFR2 and EPO stimulation. Notably, the lack of Tfr2, but not RAP-536, can also attenuate iron-overload and related complications. Overall, our results shed further light on the mechanism of action of Luspatercept and suggest that strategies aimed at inhibiting hematopoietic TFR2 might improve the therapeutic efficacy of activin receptor-ligand traps.

Clostridium butyricum MIYAIRI 588 contributes to the maintenance of intestinal microbiota diversity early after haematopoietic cell transplantation

In patients undergoing haematopoietic stem-cell transplantation (HSCT), the intestinal microbiota plays an important role in prognosis, transplant outcome, and complications such as graft-versus-host disease (GVHD). Our prior research revealed that patients undergoing HSCT substantially differed from healthy controls. In this retrospective study, we showed that administering Clostridium butyricum MIYAIRI 588 (CBM588) as a live biotherapeutic agent is associated with maintaining intestinal microbiota in the early post-HSCT period. Alpha diversity, which reflects species richness, declined considerably in patients who did not receive CBM588, whereas it remained consistent in those who received CBM588. In addition, β-diversity analysis revealed that CBM588 did not alter the gut microbiota structure at 7-21 days post-HSCT. Patients who developed GVHD showed structural changes in their microbiota from the pre-transplant period, which was noticeable on day 14 before developing GVHD. Enterococcus was significantly prevalent in patients with GVHD after HSCT, and the population of Bacteroides was maintained from the pre-HSCT period through to the post-HSCT period. Patients who received CBM588 exhibited a contrasting trend, with lower relative abundances of both genera Enterococcus and Bacteroides. These results suggest that preoperative treatment with CBM588 could potentially be beneficial in maintaining intestinal microbiota balance.

Rebuilding and rebooting immunity with stem cells

Advances in modern medicine have enabled a rapid increase in lifespan and, consequently, have highlighted the immune system as a key driver of age-related disease. Immune regeneration therapies present exciting strategies to address age-related diseases by rebooting the host's primary lymphoid tissues or rebuilding the immune system directly via biomaterials or artificial tissue. Here, we identify important, unanswered questions regarding the safety and feasibility of these therapies. Further, we identify key design parameters that should be primary considerations guiding technology design, including timing of application, interaction with the host immune system, and functional characterization of the target patient population.

Low dose post-transplant cyclophosphamide and sirolimus induce mixed chimerism with CTLA4-Ig or lymphocyte depletion in an MHC-mismatched murine allotransplantation model

Allogeneic hematopoietic cell transplantation (allo-HCT) offers a curative option for patients with certain non-malignant hematological diseases. High-dose post-transplant cyclophosphamide (PT-Cy) (200 mg/kg) and sirolimus (3 mg/kg), (HiC) synergistically induce stable mixed chimerism. Further, sirolimus and cytotoxic T lymphocyte-associated antigen-4 immunoglobulin (CTLA4-Ig), also known as Abatacept (Aba), promote immune tolerance and allograft survival. Here, in a major histocompatibility complex (MHC)-mismatched allo-HCT murine model, we combined Aba and/or T-cell depleting anti-Thy1.2 (Thy) with a lower dose of PT-Cy (50 mg/kg) and Sirolimus (3 mg/kg), (LoC). While mice in the LoC group showed graft rejection, the addition of Thy to LoC induced similar donor chimerism levels when compared to the HiC group. However, the addition of Aba to LoC led to graft acceptance only in younger mice. When Thy was added to the LoC+Aba setting, graft acceptance was restored in both age groups. Engrafted groups displayed significantly reduced frequencies of recipient-specific interferon-γ-producing T cells as well as an increased frequency in regulatory T cells (Tregs) except in the LoC+Aba group. Splenocytes from engrafted mice showed no proliferation upon restimulation with Balb/c stimulators. Collectively, in combination with Aba or Thy, LoC may be considered to reduce graft rejection in patients who undergo allo-HCT.

Transplantation and Cellular Therapy for Older Adults-The MSK Approach

PURPOSE OF REVIEW

Hematologic malignances more commonly affect older individuals and often present with advanced, higher risk disease than younger patients. Allogeneic and autologous hematopoietic cell transplantation is well-established treatment modalities with curative potential following either frontline treatments for these diseases or salvage therapy in the relapsed or refractory setting. More recently, novel cellular immunotherapy such as chimeric antigen receptor T-cell therapy has been shown to lead to high response rate and durable remission in many patients with advanced blood cancers.

RECENT FINDINGS

Given unique characteristics of older patients, how best to deliver these higher-intensity and time sensitive treatment modalities for them remains challenging. Moreover, their short-term and potential long-term impact on their functional status, cognitive status, and quality of life may be significant considerations for many older patients. All these issues contributed to the lack of access and significant underutilization of these potential curative treatment strategies. In this review, we present up to date evidence to support potential benefits of transplantation and cellular therapy for older adults, their steady improving outcomes, and most importantly, highlight the use of geriatric assessment to help select appropriate older patients and optimize them prior to and following transplantation and cellular therapy. We specifically describe our approach at Memorial Sloan Kettering Cancer Center and encouraging early results from its implementation.

Respiratory Syncytial Virus Infections in Recipients of Bone Marrow Transplants: A Systematic Review and Meta-Analysis

Human Respiratory Syncytial Virus (RSV) is a common cause of respiratory tract infections. Usually associated with infants and children, an increasing amount of evidence suggests that RSV can cause substantial morbidity and mortality in immunocompromised individuals, including recipients of bone marrow transplantation (BMT). The present systematic review was therefore designed in accordance with the PRISMA guidelines to collect available evidence about RSV infections in BMT recipients. Three medical databases (PubMed, Embase, and MedRxiv) were therefore searched for eligible observational studies published up to 30 September 2023 and collected cases were pooled in a random-effects model. Heterogeneity was assessed using I2 statistics. Reporting bias was assessed by means of funnel plots and regression analysis. Overall, 30 studies were retrieved, including 20,067 BMT cases and 821 RSV infection episodes. Of them, 351 were lower respiratory tract infections, and a total of 78 RSV-related deaths were collected. A pooled attack rate of 5.40% (95% confidence interval [95%CI] 3.81 to 7.60) was identified, with a corresponding incidence rate of 14.77 cases per 1000 person-years (95%CI 9.43 to 20.11), and a case fatality ratio (CFR) of 7.28% (95%CI 4.94 to 10.60). Attack rates were higher in adults (8.49%, 95%CI 5.16 to 13.67) than in children (4.79%, 95%CI 3.05 to 7.45), with similar CFR (5.99%, 95%CI 2.31 to 14.63 vs. 5.85%, 95%CI 3.35 to 10.02). By assuming RSV attack rates as a reference group, influenza (RR 0.518; 95%CI 0.446 to 0.601), adenovirus (RR 0.679, 95%CI 0.553 to 0.830), and human metapneumovirus (RR 0.536, 95%CI 0.438 to 0.655) were associated with a substantially reduced risk for developing corresponding respiratory infection. Despite the heterogeneous settings and the uneven proportion of adult and pediatric cases, our study has identified high attack rates and a substantial CFR of RSV in recipients of BMT, stressing the importance of specifically tailored preventive strategies and the need for effective treatment options.

ERS/EBMT clinical practice guidelines on treatment of pulmonary chronic graft-versus-host disease in adults

Chronic graft-versus-host disease (cGvHD) is a common complication after allogeneic haematopoietic stem cell transplantation, characterised by a broad disease spectrum that can affect virtually any organ. Although pulmonary cGvHD is a less common manifestation, it is of great concern due to its severity and poor prognosis. Optimal management of patients with pulmonary cGvHD is complicated and no standardised approach is available. The purpose of this joint European Respiratory Society (ERS) and European Society for Blood and Marrow Transplantation task force was to develop evidence-based recommendations regarding the treatment of pulmonary cGvHD phenotype bronchiolitis obliterans syndrome in adults. A multidisciplinary group representing specialists in haematology, respiratory medicine and methodology, as well as patient advocates, formulated eight PICO (patient, intervention, comparison, outcome) and two narrative questions. Following the ERS standardised methodology, we conducted systematic reviews to address these questions and used the Grading of Recommendations Assessment, Development and Evaluation approach to develop recommendations. The resulting guideline addresses common therapeutic options (inhalation therapy, fluticasone-azithromycin-montelukast, imatinib, ibrutinib, ruxolitinib, belumosudil, extracorporeal photopheresis and lung transplantation), as well as other aspects of general management, such as lung functional and radiological follow-up and pulmonary rehabilitation, for adults with pulmonary cGvHD phenotype bronchiolitis obliterans syndrome. These recommendations include important advancements that could be incorporated in the management of adults with pulmonary cGvHD, primarily aimed at improving and standardising treatment and improving outcomes.

Comparison of fludarabine/melphalan (FluMel) with fludarabine/melphalan/BCNU or thiotepa (FBM/FTM) in patients with AML in first complete remission undergoing allogeneic hematopoietic stem cell transplantation - a registry study on behalf of the EBMT Acute Leukemia Working Party

Conditioning protocols for patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) are being developed continuously to improve their anti-leukemic efficacy and reduce their toxicity. In this study, we compared the conditioning protocol of fludarabine with melphalan 140 mg/m2 (FluMel) with conditioning protocols based on this same backbone but with an additional alkylating agent i.e., either fludarabine/BCNU (also known as carmustine)/melphalan (FBM), or fludarabine/thiotepa/melphalan (FTM) 110 mg/m2. We included 1272 adult patients (FluMel, n = 1002; FBM/FTM, n = 270) with acute myeloid leukemia (AML) with intermediate/poor cytogenetic risk in first complete remission (CR) from the registry of the EBMT Acute Leukemia Working Party. Despite patients in the FBM/FTM group were older (64.1 years vs. 59.8 years, p < 0.001) and had a worse Karnofsky performance score (KPS < 90, 33% vs. 24%, p = 0.003), they showed a better overall survival (OS) (2 y OS: 68.3% vs. 58.1%, p = 0.02) and less non-relapse mortality (NRM) (2 y NRM: 15.8% vs. 22.2%, p = 0.009) compared to patients treated with FluMel. No significant differences were observed in relapse incidence (RI) (2 y RI: 24.9% vs. 23.7%, p = 0.62). In conclusion, the addition of a second alkylating agent (BCNU/carmustine or thiotepa) to FluMel as FBM/FTM conditioning, improves OS in AML patients in first CR with intermediate/poor risk cytogenetics after allo-HCT.

Development and Validation of a Concise Objectifiable Risk Evaluation Score for Non-Relapse Mortality after Allogeneic Hematopoietic Stem Cell Transplantation

We aimed to develop a concise objectifiable risk evaluation (CORE) tool for predicting non-relapse mortality (NRM) and overall survival (OS) after allogeneic hematopoietic stem cell transplantation (allo-HCT). A total of 1120 adult patients who had undergone allo-HCT at our center between 2013 and 2020 were divided into training, first, and second validation cohorts. Objectifiable, patient-related factors impacting NRM in univariate and multivariate analyses were: serum albumin, serum creatinine, serum C-reactive protein (CRP), heart function (LVEF), lung function (VC, FEV1), and patient age. Hazard ratios were assigned points (0-3) based on their impact on NRM and summed to the individual CORE HCT score. The CORE HCT score stratified patients into three distinct low-, intermediate-, and high-risk groups with two-year NRM rates of 9%, 22%, and 46%, respectively, and OS rates of 73%, 55%, and 35%, respectively (p < 0.001). These findings were confirmed in a first and a second recently treated validation cohort. Importantly, the CORE HCT score remained informative across various conditioning intensities, disease-specific subgroups, and donor types, but did not impact relapse incidence. A comparison of CORE HCT vs. HCT Comorbidity Index (HCT-CI) in the second validation cohort revealed better performance of the CORE HCT score with c-statistics for NRM and OS of 0.666 (SE 0.05, p = 0.001) and 0.675 (SE 0.039, p < 0.001) vs. 0.431 (SE 0.057, p = 0.223) and 0.535 (SE 0.042, p = 0.411), respectively. The CORE HCT score is a concise and objectifiable risk evaluation tool for adult patients undergoing allo-HCT for malignant disease. External multicenter validation is underway.

Cellular and animal models for the investigation of β-thalassemia

β-Thalassemia is a genetic form of anemia due to mutations in the β-globin gene, that leads to ineffective and extramedullary erythropoiesis, abnormal red blood cells and secondary iron-overload. The severity of the disease ranges from mild to lethal anemia based on the residual levels of globins production. Despite being a monogenic disorder, the pathophysiology of β-thalassemia is multifactorial, with different players contributing to the severity of anemia and secondary complications. As a result, the identification of effective therapeutic strategies is complex, and the treatment of patients is still suboptimal. For these reasons, several models have been developed in the last decades to provide experimental tools for the study of the disease, including erythroid cell lines, cultures of primary erythroid cells and transgenic animals. Years of research enabled the optimization of these models and led to decipher the mechanisms responsible for globins deregulation and ineffective erythropoiesis in thalassemia, to unravel the role of iron homeostasis in the disease and to identify and validate novel therapeutic targets and agents. Examples of successful outcomes of these analyses include iron restricting agents, currently tested in the clinics, several gene therapy vectors, one of which was recently approved for the treatment of most severe patients, and a promising gene editing strategy, that has been shown to be effective in a clinical trial. This review provides an overview of the available models, discusses pros and cons, and the key findings obtained from their study.

Use of subgroup-specific hematopoietic stem cell collection efficiencies to improve truncation calculations for large-volume leukapheresis procedures

PURPOSE

A critical component of optimizing peripheral blood (PB) hematopoietic stem cell (HSC) collections is accurately determining the processed blood volume required to collect the targeted number of HSCs. Fundamental to most truncation equations employed to determine this volume is the procedure's estimated collection efficiency (CE), which is typically applied uniformly across all HSC collections. Few studies have explored the utility of using different CEs in subpopulations of donors that have substantially different CEs than the institutional average.

METHODS

Initial procedures from 343 autologous and 179 allogeneic HSC collections performed from 2018 to 2021 were retrospectively analyzed. Predictive equations were developed to determine theoretical truncation rates in various donor subgroups.

RESULTS

Quantitative variables (pre-procedure cell counts) and qualitative variables (relatedness to recipient, gender, method of venous access, and mobilization strategy) were found to significantly impact CE. However, much of the variability in CE between donors could not be explained by the variables assessed. Analyses of procedures with high pre-collection PB cell counts identified lower CE values for these donors' truncation equations which still allow truncation but minimize risk of collecting less CD34+ cells than requested.

CONCLUSIONS

Individualized CE does not substantially improve truncation volume calculations over use of a fixed CE and adds complexity to these calculations. The optimal fixed CE varies between autologous and allogeneic donors, and donors with high pre-collection PB cell counts in either of these groups. This model will be clinically validated and continuously refined through analysis of future HSC collections.

The effect of conditioning regimen and prescribed medications on hyposalivation in haematopoietic cell transplantation (HCT) patients: an 18-month prospective longitudinal study

OBJECTIVES

Haematopoietic cell transplantation (HCT) preceded by a conditioning regimen is an established treatment option for (non)malignant haematologic disorders. We aim to describe the development of hyposalivation over time in HCT recipients, and determine risk indicators.

MATERIALS AND METHODS

A multi-centre prospective longitudinal observational study was conducted. Unstimulated (UWS) and stimulated (SWS) whole saliva was collected before HCT, early post-HCT, and after 3, 6, 12, and 18 months. The effect of type of transplantation (allogeneic vs autologous) and intensity (full vs reduced) of the conditioning regimen on hyposalivation (UWS < 0.2 mL/min; SWS < 0.7 mL/min) was explored.

RESULTS

A total of 125 HCT recipients were included. More than half of the patients had hyposalivation early post-HCT; a quarter still had hyposalivation after 12 months. The conditioning intensity was a risk indicator in the development of hyposalivation of both UWS (OR: 3.9, 95% CI: 1.6-10.6) and SWS (OR: 8.2, 95% CI: 2.9-24.6). After 3 and 12 months, this effect was not statistically significant anymore.

CONCLUSIONS

Hyposalivation affects the majority of patients early post-HCT. The conditioning intensity and the type of transplantation were significant risk indicators in the development of hyposalivation. The number of prescribed medications, total body irradiation as part of the conditioning regimen and oral mucosal graft-versus-host disease did not influence hyposalivation significantly.

CLINICAL RELEVANCE

Because of the high prevalence of hyposalivation, HCT recipients will have an increased risk of oral complications. It might be reasonable to plan additional check-ups in the dental practice and consider additional preventive strategies.

Neutral sphingomyelinase blockade enhances hematopoietic stem cell fitness through an integrated stress response

Hematopoietic stem and progenitor cell (HSPC) transplantation serves as a curative therapy for many benign and malignant hematopoietic disorders and as a platform for gene therapy. However, growing needs for ex vivo manipulation of HSPC-graft products are limited by barriers in maintaining critical self-renewal and quiescence properties. The role of sphingolipid metabolism in safeguarding these essential cellular properties has been recently recognized, but not yet widely explored. Here, we demonstrate that pharmacologic and genetic inhibition of neutral sphingomyelinase 2 (nSMase-2) leads to sustained improvements in long-term competitive transplantation efficiency after ex vivo culture. Mechanistically, nSMase-2 blockade activates a canonical integrated stress response (ISR) and promotes metabolic quiescence in human and murine HSPCs. These adaptations result in part from disruption in sphingolipid metabolism that impairs the release of nSMase-2-dependent extracellular vesicles (EVs). The aggregate findings link EV trafficking and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, transient nSMase-2 inhibition enables ex vivo graft manipulation with enhanced HSPC potency.

A research on the influence of G-CSF mobilization on donor's peripheral blood MDSCs and its relationship with patient prognosis

OBJECTIVE

To discuss the effects of mobilization of healthy donors with granulocyte colony-stimulating factor (G-CSF) on the absolute values and functions of myeloid-derived suppressor cells (MDSCs) and subpopulations of M-MDSCs and P-MDSCs in their peripheral blood. In addition, this study also aims to investigate the impacts of the adoptively transferred MDSCs from the grafts to the patients on their prognosis and immune reconstitution.

METHODS

The selection of 72 donors and 72 patients were conducted for allogeneic hematopoietic stem cell transplantation (allo-HSCT) from August 2022 to December 2022 at Lu Daopei Hospital in Beijing, China. Statistical calculations were performed by Wilcoxon signed-rank test, Kruskal Wallis test, χ2 test, Kaplan Meier test, and log-rank test to analyze the data.

RESULTS & CONCLUSION

G-CSF induced significant amplification of MDSCs in the peripheral blood of donors in percentage and absolute values. Whether the level of P-MDSCs in patients conducted for the adoptive transfer of P - MDSCs is higher than 3.7× 107/kg or lower than 1.4× 107/kg leads to a poor prognosis of the patients. Ensuring a balanced state of MDSCs is crucial for effective immunotherapy. Transferring a high level of MDSCs from the graft to the patient's body is advantageous for the development of MDSCs while simultaneously inhibiting the proliferation of lymphocyte subgroups.

Novel therapies for graft versus host disease with a focus on cell therapies

Graft versus host disease (GVHD) can occur at any period post allogeneic hematopoietic stem cell transplantation as a common clinical complication contributing to significant morbidity and mortality. Acute GVHD develops in approximately 30-50% of patients receiving transplants from matched related donors. High doses of steroids are used as first-line treatment, but are unsuccessful in around 40% of patients, resulting in the diagnosis of steroid-refractory acute GVHD. Consensus has yet to develop for the management of steroid-refractory acute GVHD, and prognosis at six months has been estimated at around 50%. Thus, it is critical to find effective treatments that increase survival of steroid-refractory acute GVHD. This article describes the currently known characteristics, pathophysiology, and treatments for GVHD, with a special focus on recent advances in cell therapies. In particular, a novel cell therapy using decidua stromal cells (DSCs) was recently shown to have promising results for acute GVHD, with improved effectiveness over previous treatments including mesenchymal stromal cells. At the Karolinska Institute, severe acute GVHD patients treated with placenta-derived DSCs supplemented with either 5% albumin or 10% AB plasma displayed a one-year survival rate of 76% and 47% respectively. Furthermore, patients with steroid-refractory acute GVHD, displayed survival rates of 73% with albumin and 31% with AB plasma-supplemented DSCs, compared to the 20% survival rate in the mesenchymal stromal cell control group. Adverse events and deaths were found to be attributed only to complications of hematopoietic stem cell transplant and GVHD, not to the study intervention. ASC Therapeutics, Inc, in collaboration with the Karolinska Institute, will soon initiate a phase 2 multicenter, open-label study to further assess the efficacy and safety of intravenous DSC treatment in sixty patients with Grade II-IV steroid-refractory acute GVHD. This novel cell therapy represents a promising treatment to combat the poor prognosis that steroid-refractory acute GVHD patients currently face.

Caries, periodontitis and tooth loss after haematopoietic stem cell transplantation: A systematic review

OBJECTIVE

A systematic review was conducted to assess scientific knowledge concerning the effect of haematopoietic stem cell transplantation (HSCT) on the occurrence of caries, periodontal conditions and tooth loss, and to evaluate the prevalence of these diseases in adult HSCT survivors (PROSPERO 152906).

METHODS

PubMed and Embase were searched for papers, published from January 2000 until November 2020 without language restriction, assessing prevalence, incidence or parameters of caries, periodontal conditions and tooth loss in HSCT recipients (≥80% transplanted in adulthood). Bias risk was assessed with checklists from Joanna Briggs Institute, and data synthesis was performed by narrative summary.

RESULTS

Eighteen papers were included (1618 subjects). Half were considered at high risk of bias. Longitudinal studies did not show caries progression, decline in periodontal health or tooth loss after HSCT. The prevalence in HSCT survivors ranged from 19% to 43% for caries, 11% to 67% for periodontitis, and 2% to 5% for edentulism. Certainty in the body of evidence was very low.

CONCLUSIONS

Haematopoietic stem cell transplantation, on the short term, may have little to no effect on caries, periodontal conditions and tooth loss. Caries and periodontitis may be more common in HSCT survivors compared with the general population, whereas edentulism may be comparable. However, the evidence for all conclusions is very uncertain.

Mobilization-based engraftment of haematopoietic stem cells: a new perspective for chemotherapy-free gene therapy and transplantation

INTRODUCTION

In haematopoietic stem cell transplantation (HSCT), haematopoietic stem cells (HSCs) from a healthy donor replace the patient's ones. Ex vivo HSC gene therapy (HSC-GT) is a form of HSCT in which HSCs, usually from an autologous source, are genetically modified before infusion, to generate a progeny of gene-modified cells. In HSCT and HSC-GT, chemotherapy is administered before infusion to free space in the bone marrow (BM) niche, which is required for the engraftment of infused cells. Here, we review alternative chemotherapy-free approaches to niche voidance that could replace conventional regimens and alleviate the morbidity of the procedure.

SOURCES OF DATA

Literature was reviewed from PubMed-listed peer-reviewed articles. No new data are presented in this article.

AREAS OF AGREEMENT

Chemotherapy exerts short and long-term toxicity to haematopoietic and non-haematopoietic organs. Whenever chemotherapy is solely used to allow engraftment of donor HSCs, rather than eliminating malignant cells, as in the case of HSC-GT for inborn genetic diseases, non-genotoxic approaches sparing off-target tissues are highly desirable.

AREAS OF CONTROVERSY

In principle, HSCs can be temporarily moved from the BM niches using mobilizing drugs or selectively cleared with targeted antibodies or immunotoxins to make space for the infused cells. However, translation of these principles into clinically relevant settings is only at the beginning, and whether therapeutically meaningful levels of chimerism can be safely established with these approaches remains to be determined.

GROWING POINTS

In pre-clinical models, mobilization of HSCs from the niche can be tailored to accommodate the exchange and engraftment of infused cells. Infused cells can be further endowed with a transient engraftment advantage.

AREAS TIMELY FOR DEVELOPING RESEARCH

Inter-individual efficiency and kinetics of HSC mobilization need to be carefully assessed. Investigations in large animal models of emerging non-genotoxic approaches will further strengthen the rationale and encourage application to the treatment of selected diseases.

Prophylactic Mitigation of Acute Graft versus Host Disease by Novel 2-(Pyrrolidin-1-ylmethyl)pyrrole-Based Stimulation-2 (ST2) Inhibitors

Hematopoietic cell transplantation (HCT) is a proven and potentially curable therapy for hematological malignancies and inherited hematological disease. The main risk of HCT is the development of graft versus host disease (GVHD) acquired in up to 50% of patients. Upregulation of soluble ST2 (sST2) is a key clinical biomarker for GVHD prognosis and was shown to be a potential therapeutic target for GVHD. Agents targeting sST2 to reduce the sST2 level after HCT have the potential to mitigate GVHD progression. Here, we report 32 (or XY52) as the lead ST2 inhibitor from our optimization campaign. XY52 had improved inhibitory activity and metabolic stability in vitro and in vivo. XY52 suppressed proinflammatory T-cell proliferation while increasing regulatory T cells in vitro. In a clinically relevant GVHD model, a 21-day prophylactic regimen of XY52 reduced plasma sST2 and IFN-γ levels and GVHD score and extended survival in mice. XY52 represented a significant improvement over our previous compound, iST2-1, and further optimization of XY52 is warranted. The small-molecule ST2 inhibitors can potentially be used as a biomarker-guided therapy for mitigating GVHD in future clinical applications.

Immunotherapy in Acute Leukemias: Past Success Paves the Way for Future Progress

Immunotherapy as a cancer treatment modality has undergone recent widespread proliferation across all cancer types, especially amongst patients with solid tumors. However, the longest tenured immunotherapy approach to cancer is allogeneic stem cell transplantation (allo-SCT) for two hematologic malignancies: acute myeloid and acute lymphoid leukemia (AML and ALL, respectively). While allo-SCT remains a standard of care for eligible patients, recent advances/applications of monoclonal antibodies, immune checkpoint inhibitors, bispecific T-cell engagers (BiTEs), and CAR T-cell therapy are changing the treatment landscape for these acute leukemias by either direct to tumor immune targeting or through decreased toxicities that expand patient eligibility. Pre-clinical data and clinical trials have shown promising results for novel immunotherapies in acute leukemia, and multiple ongoing trials are investigating these novel approaches. While there have been promising results with these approaches, particularly in the relapsed/refractory setting, there remain challenges in optimizing the use of these therapies, such as managing cytokine release syndrome and other immune-related toxicities. Immunotherapy is a rapidly evolving field in the treatment of acute leukemia and has the potential to significantly impact the management of both AML and ALL. This review highlights the history of immunotherapy in the treatment of acute leukemias, the evolution of immunotherapy into more targeted approaches, the potential benefits and limitations of different immune targeting approaches, and ongoing research and development in the field.

Beyond αβ T cells: NK, iNKT, and γδT cell biology in leukemic patients and potential for off-the-shelf adoptive cell therapies for AML

Acute myeloid leukemia (AML) remains an elusive disease to treat, let alone cure, even after highly intensive therapies such as stem cell transplants. Adoptive cell therapeutic strategies based on conventional alpha beta (αβ)T cells are an active area of research in myeloid neoplasms given their remarkable success in other hematologic malignancies, particularly B-cell-derived acute lymphoid leukemia, myeloma, and lymphomas. Several limitations have hindered clinical application of adoptive cell therapies in AML including lack of leukemia-specific antigens, on-target-off-leukemic toxicity, immunosuppressive microenvironments, and leukemic stem cell populations elusive to immune recognition and destruction. While there are promising T cell-based therapies including chimeric antigen receptor (CAR)-T designs under development, other cytotoxic lymphocyte cell subsets have unique phenotypes and capabilities that might be of additional benefit in AML treatment. Of particular interest are the natural killer (NK) and unconventional T cells known as invariant natural killer T (iNKT) and gamma delta (γδ) T cells. NK, iNKT, and γδT cells exhibit intrinsic anti-malignant properties, potential for alloreactivity, and human leukocyte-antigen (HLA)-independent function. Here we review the biology of each of these unconventional cytotoxic lymphocyte cell types and compare and contrast their strengths and limitations as the basis for adoptive cell therapies for AML.

A novel mesenchymal stem cell-based regimen for acute myeloid leukemia differentiation therapy

Currently the main treatment of acute myeloid leukemia (AML) is chemotherapy combining hematopoietic stem cell transplantation. However, the unbearable side effect of chemotherapy and the high risk of life-threatening infections and disease relapse following hematopoietic stem cell transplantation restrict its application in clinical practice. Thus, there is an urgent need to develop alternative therapeutic tactics with significant efficacy and attenuated adverse effects. Here, we revealed that umbilical cord-derived mesenchymal stem cells (UC-MSC) efficiently induced AML cell differentiation by shuttling the neutrophil elastase (NE)-packaged extracellular vesicles (EVs) into AML cells. Interestingly, the generation and release of NE-packaged EVs could be dramatically increased by vitamin D receptor (VDR) activation in UC-MSC. Chemical activation of VDR by using its agonist 1α,25-dihydroxyvitamin D3 efficiently enhanced the pro-differentiation capacity of UC-MSC and then alleviated malignant burden in AML mouse model. Based on these discoveries, to evade the risk of hypercalcemia, we synthetized and identified sw-22, a novel non-steroidal VDR agonist, which exerted a synergistic pro-differentiation function with UC-MSC on mitigating the progress of AML. Collectively, our findings provided a non-gene editing MSC-based therapeutic regimen to overcome the differentiation blockade in AML.

Pretransplant systemic metabolic profiles in allogeneic hematopoietic stem cell transplant recipients - identification of patient subsets with increased transplant-related mortality

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is used in the treatment of high-risk acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS); however, the treatment has high risk of severe transplantation-related mortality (TRM). In this study, we examined pretransplantation serum samples derived from 92 consecutive allotransplant recipients with AML or MDS. Using nontargeted metabolomics, we identified 1274 metabolites including 968 of known identity (named biochemicals). We further investigated metabolites that differed significantly when comparing patients with and without early extensive fluid retention, pretransplantation inflammation (both being associated with increased risk of acute graft-versus-host disease [GVHD]/nonrelapse mortality) and development of systemic steroid-requiring acute GVHD (aGVHD). All three factors are associated with TRM and were also associated with significantly altered amino acid metabolism, although there was only a minor overlap between these three factors with regard to significantly altered individual metabolites. Furthermore, steroid-requiring aGVHD was especially associated with altered taurine/hypotaurine, tryptophan, biotin, and phenylacetate metabolism together with altered malate-aspartate shuttle and urea cycle regulation. In contrast, pretransplantation inflammation was associated with a weaker modulation of many different metabolic pathways, whereas extensive fluid retention was associated with a weaker modulation of taurine/hypotaurine metabolism. An unsupervised hierarchical cluster analysis based on the 13 most significantly identified metabolites associated with aGVHD identified a patient subset with high metabolite levels and increased frequencies of MDS/MDS-AML, steroid-requiring aGVHD and early TRM. On the other hand, a clustering analysis based on metabolites that were significantly altered for aGVHD, inflammation, and fluid retention comparison groups identified a patient subset with a highly significant association with TRM. Our study suggests that the systemic pretransplantation metabolic profiles can be used to identify patient subsets with an increased frequency of TRM.