Germline assessment for alloHSCT candidates over 50 years: A 'Fast-Track' screening in myeloid neoplasms

Patients aged 50 or above diagnosed with myeloid neoplasms (MNs) are typically not candidates for germline testing. However, approximately 8% carry pathogenic germline variants. Allogeneic haematopoietic stem cell transplantation (alloHSCT) remains an option for those aged over 50; neglecting germline testing could mask the risk for relative donor cell-derived MN. We propose a germline-augmented somatic panel (GASP), combining MN predisposition genes with a myeloid somatic panel for timely germline variant identification when initial testing is not indicated. Out of our 133 whole-exome-sequenced MN cases aged over 50 years, 9% had pathogenic/likely variants. GASP detected 92%, compared to 50% with somatic-only panel. Our study highlights the relevance of germline screening in MN, particularly for alloHSCT candidates without established germline-testing recommendations.

Evaluating the performance of large language models in haematopoietic stem cell transplantation decision-making

In a first-of-its-kind study, we assessed the capabilities of large language models (LLMs) in making complex decisions in haematopoietic stem cell transplantation. The evaluation was conducted not only for Generative Pre-trained Transformer 4 (GPT-4) but also conducted on other artificial intelligence models: PaLm 2 and Llama-2. Using detailed haematological histories that include both clinical, molecular and donor data, we conducted a triple-blind survey to compare LLMs to haematology residents. We found that residents significantly outperformed LLMs (p = 0.02), particularly in transplant eligibility assessment (p = 0.01). Our triple-blind methodology aimed to mitigate potential biases in evaluating LLMs and revealed both their promise and limitations in deciphering complex haematological clinical scenarios.

Mesenchymal stem/stromal cells from human pluripotent stem cell-derived brain organoid enhance the ex vivo expansion and maintenance of hematopoietic stem/progenitor cells

BACKGROUND

Mesenchymal stem/stromal cells (MSCs) are of great therapeutic value due to their role in maintaining the function of hematopoietic stem/progenitor cells (HSPCs). MSCs derived from human pluripotent stem cells represent an ideal alternative because of their unlimited supply. However, the role of MSCs with neural crest origin derived from HPSCs on the maintenance of HSPCs has not been reported.

METHODS

Flow cytometric analysis, RNA sequencing and differentiation ability were applied to detect the characteristics of stromal cells from 3D human brain organoids. Human umbilical cord blood CD34+ (UCB-CD34+) cells were cultured in different coculture conditions composed of stromal cells and umbilical cord MSCs (UC-MSCs) with or without a cytokine cocktail. The hematopoietic stroma capacity of stromal cells was tested in vitro with the LTC-IC assay and in vivo by cotransplantation of cord blood nucleated cells and stroma cells into immunodeficient mice. RNA and proteomic sequencing were used to detect the role of MSCs on HSPCs.

RESULTS

The stromal cells, derived from both H1-hESCs and human induced pluripotent stem cells forebrain organoids, were capable of differentiating into the classical mesenchymal-derived cells (osteoblasts, chondrocytes, and adipocytes). These cells expressed MSC markers, thus named pluripotent stem cell-derived MSCs (pMSCs). The pMSCs showed neural crest origin with CD271 expression in the early stage. When human UCB-CD34+ HSPCs were cocultured on UC-MSCs or pMSCs, the latter resulted in robust expansion of UCB-CD34+ HSPCs in long-term culture and efficient maintenance of their transplantability. Comparison by RNA sequencing indicated that coculture of human UCB-CD34+ HSPCs with pMSCs provided an improved microenvironment for HSC maintenance. The pMSCs highly expressed the Wnt signaling inhibitors SFRP1 and SFRP2, indicating that they may help to modulate the cell cycle to promote the maintenance of UCB-CD34+ HSPCs by antagonizing Wnt activation.

CONCLUSIONS

A novel method for harvesting MSCs with neural crest origin from 3D human brain organoids under serum-free culture conditions was reported. We demonstrate that the pMSCs support human UCB-HSPC expansion in vitro in a long-term culture and the maintenance of their transplantable ability. RNA and proteomic sequencing indicated that pMSCs provided an improved microenvironment for HSC maintenance via mechanisms involving cell-cell contact and secreted factors and suppression of Wnt signaling. This represents a novel method for large-scale production of MSCs of neural crest origin and provides a potential approach for development of human hematopoietic stromal cell therapy for treatment of dyshematopoiesis.

Spotlight on the impact of viral infections on Hematopoietic Stem Cells (HSCs) with a focus on COVID-19 effects

Hematopoietic stem cells (HSCs) are known for their significant capability to reconstitute and preserve a functional hematopoietic system in long-term periods after transplantation into conditioned hosts. HSCs are thus crucial cellular targets for the continual repair of inherited hematologic, metabolic, and immunologic disorders. In addition, HSCs can undergo various fates, such as apoptosis, quiescence, migration, differentiation, and self-renewal. Viruses continuously pose a remarkable health risk and request an appropriate, balanced reaction from our immune system, which as well as affects the bone marrow (BM). Therefore, disruption of the hematopoietic system due to viral infection is essential. In addition, patients for whom the risk-to-benefit ratio of HSC transplantation (HSCT) is acceptable have seen an increase in the use of HSCT in recent years. Hematopoietic suppression, BM failure, and HSC exhaustion are all linked to chronic viral infections. Virus infections continue to be a leading cause of morbidity and mortality in HSCT recipients, despite recent advancements in the field. Furthermore, whereas COVID-19 manifests initially as an infection of the respiratory tract, it is now understood to be a systemic illness that significantly impacts the hematological system. Patients with advanced COVID-19 often have thrombocytopenia and blood hypercoagulability. In the era of COVID-19, Hematological manifestations of COVID-19 (i.e., thrombocytopenia and lymphopenia), the immune response, and HSCT may all be affected by the SARS-CoV-2 virus in various ways. Therefore, it is important to determine whether exposure to viral infections may affect HSCs used for HSCT, as this, in turn, may affect engraftment efficiency. In this article, we reviewed the features of HSCs, and the effects of viral infections on HSCs and HSCT, such as SARS-CoV-2, HIV, cytomegalovirus, Epstein-Barr virus, HIV, etc. Video Abstract.

Pathophysiology of gastrointestinal acute graft-versus-host disease and the potential role of glucagon-like peptide 2

Acute graft-versus-host disease (aGVHD) is a life-threatening complication after allogeneic haematopoietic cell transplantation, with gastrointestinal (GI) tract involvement (GI aGVHD) being one of the leading causes of morbidity and mortality. Whilst systemic steroids are the standard first-line treatment for aGVHD, approximately 50% of patients become steroid refractory (SR), which is associated with poor outcomes. Existing options for SR-GVHD are limited, and there is a significant unmet need for new non-immunosuppressive treatment approaches in patients with GI aGVHD. Here, we review newer concepts in the pathogenesis of GI aGVHD and present the evidence for the role of glucagon-like peptide 2 (GLP-2) in maintaining and protecting GI epithelial cells, including the enterocytes, intestinal stem cells and Paneth cells, which are direct targets of aGVHD. Finally, we discuss the therapeutic rationale for GLP-2 treatment as a tissue regeneration approach and the potential use of the novel GLP-2 analogue apraglutide as an adjunctive treatment for GI aGVHD.

Dlk1 maintains adult mice long-term HSCs by activating Notch signaling to restrict mitochondrial metabolism

BACKGROUND

Adult hematopoietic stem cells (HSCs) homeostasis is critically important in maintaining lifelong hematopoiesis. However, how adult HSCs orchestrate its homeostasis remains not fully understood. Imprinted gene Dlk1 has been shown to play critical role in mouse embryonic hematopoiesis and in regulation of stem cells, but its physiological roles in adult HSCs are unknown.

METHODS

We performed gene expression analysis of Dlk1, and constructed conditional Dlk1 knockout (KO) mice by crossing Mx1 cre mice with Dlk^flox/flox mice. Western blot and quantitative PCR were used to detect Dlk1 KO efficiency. Flow cytometry was performed to investigate the effects of Dlk1 KO on HSCs, progenitors and linage cells in primary mice. Competitive HSCs transplantation and secondary transplantation was used to examine the effects of Dlk1 KO on long-term hematopoietic repopulation potential of HSCs. RNA-Seq and cell metabolism assays was used to determine the underlying mechanisms.

RESULTS

Dlk1 was highly expressed in adult mice long-term HSCs (LT-HSCs) relative to progenitors and mature lineage cells. Dlk1 KO in adult mice HSCs drove HSCs enter active cell cycle, and expanded phenotypical LT-HSCs, but undermined its long-term hematopoietic repopulation potential. Dlk1 KO resulted in an increase in HSCs' metabolic activity, including glucose uptake, ribosomal translation, mitochondrial metabolism and ROS production, which impaired HSCs function. Further, Dlk1 KO in adult mice HSCs attenuated Notch signaling, and re-activation of Notch signaling under Dlk1 KO decreased the mitochondrial activity and ROS production, and rescued the changes in frequency and absolute number of HSCs. Scavenging ROS by antioxidant N-acetylcysteine could inhibit mitochondrial metabolic activity, and rescue the changes in HSCs caused by Dlk1 KO.

CONCLUSION

Our study showed that Dlk1 played an essential role in maintaining HSC homeostasis, which is realized by governing cell cycle and restricting mitochondrial metabolic activity.

Full chimaeric CAR.CIK from patients engrafted after allogeneic haematopoietic cell transplant: Feasibility, anti-leukaemic potential and alloreactivity across major human leukocyte antigen barriers

Cytokine-induced killer lymphocytes (CIK) are a promising alternative to conventional donor lymphocyte infusion (DLI), following allogeneic haematopoietic cell transplantation (HCT), due to their intrinsic anti-tumour activity and reduced risk of graft-versus-host disease (GVHD). We explored the feasibility, anti-leukaemic activity and alloreactive risk of CIK generated from full-donor chimaeric (fc) patients and genetically redirected by a chimeric antigen receptor (CAR) (fcCAR.CIK) against the leukaemic target CD44v6. fcCAR.CIK were successfully ex-vivo expanded from leukaemic patients in complete remission after HCT confirming their intense preclinical anti-leukaemic activity without enhancing the alloreactivity across human leukocyte antigen (HLA) barriers. Our study provides translational bases to support clinical studies with fcCAR.CIK, a sort of biological bridge between the autologous and allogeneic sources, as alternative DLI following HCT.

CRISPR/Cas9 genome editing to create nonhuman primate models for studying stem cell therapies for HIV infection

Nonhuman primates (NHPs) are well-established basic and translational research models for human immunodeficiency virus (HIV) infections and pathophysiology, hematopoietic stem cell (HSC) transplantation, and assisted reproductive technologies. Recent advances in CRISPR/Cas9 gene editing technologies present opportunities to refine NHP HIV models for investigating genetic factors that affect HIV replication and designing cellular therapies that exploit genetic barriers to HIV infections, including engineering mutations into CCR5 and conferring resistance to HIV/simian immunodeficiency virus (SIV) infections. In this report, we provide an overview of recent advances and challenges in gene editing NHP embryos and discuss the value of genetically engineered animal models for developing novel stem cell-based therapies for curing HIV.

Microbiota Signals Suppress B Lymphopoiesis With Aging in Mice

Aging is associated with significant changes in hematopoiesis that include a shift from lymphopoiesis to myelopoiesis and an expansion of phenotypic hematopoietic stem cells (HSCs) with impaired self-renewal capacity and myeloid-skewed lineage differentiation. Signals from commensal flora support basal myelopoiesis in young mice; however, their contribution to hematopoietic aging is largely unknown. Here, we characterize hematopoiesis in young and middle-aged mice housed under specific pathogen free (SPF) and germ-free (GF) conditions. The marked shift from lymphopoiesis to myelopoiesis that develops during aging of SPF mice is mostly abrogated in GF mice. Compared with aged SPF mice, there is a marked expansion of B lymphopoiesis in aged GF mice, which is evident at the earliest stages of B cell development. The expansion of phenotypic and functional HSCs that occurs with aging is similar in SPF and GF mice. However, HSCs from young GF mice have increased lymphoid lineage output, and the aging-associated expansion of myeloid-biased HSCs is significantly attenuated in GF mice. Consistent with these data, RNA expression profiling of phenotypic HSCs from aged GF mice show enrichment for non-myeloid biased HSCs. Surprisingly, the RNA expression profiling data also suggest that inflammatory signaling is increased in aged GF HSCs compared with aged SPF HSCs. Collectively, these data suggest that microbiota-related signals suppress B lymphopoiesis at multiple stages of development and contribute to the expansion of myeloid-biased HSCs that occurs with aging.

Combining Mobilizing Agents with Busulfan to Reduce Chemotherapy-Based Conditioning for Hematopoietic Stem Cell Transplantation

In the context of hematopoietic stem cell (HSC) transplantation, conditioning with myelo- and immune-ablative agents is used to eradicate the patient’s diseased cells, generate space in the marrow and suppress immune reactions prior to the infusion of donor HSCs. While conditioning is required for effective and long-lasting HSC engraftment, currently used regimens are also associated with short and long-term side effects on extramedullary tissues and even mortality. Particularly in patients with severe combined immunodeficiency (SCID), who are generally less than 1-year old at the time of transplantation and often suffer from existing comorbidities. There is a pressing need for development of alternative, less toxic conditioning regimens. Hence, we here aimed to improve efficacy of currently used myeloablative protocols by combining busulfan with stem-cell niche-directed therapeutic agents (G-CSF or plerixafor) that are approved for clinical use in stem cell mobilization. T, B and myeloid cell recovery was analyzed in humanized NSG mice after different conditioning regimens. Increasing levels of human leukocyte chimerism were observed in a busulfan dose-dependent manner, showing comparable immune recovery as with total body irradiation in CD34-transplanted NSG mice. Notably, a better T cell reconstitution compared to TBI was observed after busulfan conditioning not only in NSG mice but also in SCID mouse models. Direct effects of reducing the stem cell compartment in the bone marrow were observed after G-CSF and plerixafor administration, as well as in combination with low doses of busulfan. Unfortunately, these direct effects on the stem population in the bone marrow were not reflected in increased human chimerism or immune recovery after CD34 transplantation in NSG mice. These results indicate moderate potential of reduced conditioning regimens for clinical use relevant for all allogeneic transplants.

Treatment for pure red cell aplasia after major ABO-incompatible allogeneic stem cell transplantation: a multicentre study

Pure red cell aplasia (PRCA) following allogeneic haematopoietic stem cell transplantation (aHSCT) with major ABO incompatibility is responsible for transfusion dependent anaemia, impaired quality of life and iron overload. We conducted a retrospective study, over a 10-year period, which included all consecutive patients who received a major ABO mismatched aHSCT, to assess the impact of specific treatment on PRCA. We did not observe any PRCA in the 57 aHSCT issued from cord blood. Among the remaining 631 patients, cumulative incidence of PRCA was 10·5% [range 8·2-13.0]. The median duration of resolved PRCA was 171 days [IQR 116; 261]. Pre-transplant high isohaemagglutinins titre was associated with an increased risk of PRCA (P < 10^-4 ). PRCA did not affect overall survival (P = 0·95). Twenty-two patients (33·3%) received at least one specific treatment. The most commonly used treatments were rituximab (17 patients) and donor lymphocyte infusion (DLI; seven patients). Regarding PRCA resolution, we did not observe a significant difference between treated or untreated subjects (HR = 0·93, 95% confidence interval (CI) 0·48- 1·80; P = 0·82). Similar results were observed with erythropoietin treatment (22 patients, HR = 0·86 95% CI: [0·47-1·57] P = 0·62). Our data do not support the use of erythropoietin, rituximab or DLI for the treatment of PRCA.

BRCC36 functions noncatalytically to promote antiviral response by maintaining STAT1 protein stability

Viral infection is a serious threat to both normal population and clinical patients. STAT1 plays central roles in host defense against viral infection. How STAT1 protein maintains stable in different conditions remains largely unknown. Here, we identified BRCC36 as a potent regulator of STAT1 protein stability. Mechanistically, BRCC36 maintains STAT1 levels by utilizing USP13 to form a balanced complex for antagonizing Smurf1-mediated degradation. Importantly, cellular BRCC36 deficiency results in rapid downregulation of STAT1 during viral infection, whereas a supplement of BRCC36 maintains STAT1 protein levels and host antiviral immunity in vivo. Moreover, we revealed that BRCC36 expression was downregulated in allogeneic HSC transplantation (allo-HSCT) mice that showed increased susceptibility to viral infection. Supplementing BRCC36 enhanced antiviral response of allo-HSCT mice by maintaining STAT1 stability. This study uncovers a critical role of BRCC36 in STAT1 protein stability and could provide potential strategies for enhancing clinical antiviral therapy.

Prognostic plasma biomarkers of early complications and graft-versus-host disease in patients undergoing allogeneic hematopoietic stem cell transplantation

Early complications post hematopoietic stem cell transplantation (HSCT) such as sinusoidal obstruction syndrome (SOS) and graft versus host disease (GVHD) can be life threatening. Although several biomarkers have been identified to correlate with these complications and their response to treatment, these are yet to be used in clinical practice. Here, we evaluated circulating endothelial cells (CECs) (n = 26) and plasma biomarkers (ST2, REG3α, VCAM1, ICAM1, TIM3) (N = 210) at early time points, to determine their association with early complications post-HSCT. Elevated CEC counts at the end of conditioning was associated with GVHD, indicating endothelial damage during HSCT. Plasma levels of REG3α, VCAM1, ICAM1, and TIM3 on day 14 (D14) and D14 ICAM1 and D28 ST2 were significantly higher in patients with SOS and aGVHD, respectively. Upon sub-group analysis, D28 ST2, D14/D28 REG3α, and D14ICAM1 levels were significantly higher in patients with gastrointestinal GVHD, while D28ST2 was higher in those with skin/liver GVHD. High ST2 levels on D28 was significantly associated with non-relapse mortality (NRM) and overall survival. Our results suggest that elevated ST2 levels on D28 could predict the likelihood of developing aGVHD and could influence NRM and OS.

Evolution of Peripheral Blood Stem Cell Transplantation

Blood-derived progenitors have become the predominant source of hematopoietic stem cells for clinical transplantation. The main advantages compared to the bone marrow are as follows: harvesting blood stem cells is less painful for the donor, utilizes much less resources such as operating theater time and general anesthesia, and, above all, is associated with significantly accelerated reconstitution. The latter has ultimately improved patient safety as a consequence of significantly shortened aplastic phase and hence reduced morbidity and mortality after transplantation. Basic and translational research efforts in the 1960s to the mid-1980s have made the first blood stem cell transplantation in Heidelberg in 1985 possible. Diverse groups around the world have contributed to incremental knowledge that culminated in the first successful attempts in blood stem cell transplantation. These efforts have spawned modern research into stem cell biology and the immune modulatory effects of allogeneic transplantations.

CD56-Positive Acute Myeloid Leukemia Following Treatment of Hairy Cell Leukemia with Cladribine - Report of 2 Cases and Review of the Literature

Treatment of hairy cell leukemia (HCL) with alfa-interferon and purine analogs significantly prolongs survival in these patients. However, with life prolongation, an increased risk of secondary malignancies has been reported. Acute myeloid leukemia (AML), as a second malignancy after HCL treatment is extremely rare and has been reported in only 12 cases so far. We here report additional 2 cases of CD56+ AML developed after sustained clinical remission of HCL achieved with cladribine (2 and 6 years after, respectively). The first patient refused chemotherapy and shortly thereafter died. The second patient responded to chemotherapy and was successfully allo-transplanted. Three years later, the patient is in stable clinical remission, which is a unique case in the literature. In conclusion, it is not clear whether development of AML in HCL patients is caused by mutagenic potential of the applied chemotherapy or by immune suppression/ perturbations as a characteristic of the underlying disease.

How I manage patients with relapsed/refractory diffuse large B cell lymphoma

Despite progress in the upfront treatment of diffuse large B cell lymphoma (DLBCL), patients still experience relapses. Salvage chemotherapy followed by autologous stem cell transplantation (ASCT) is the standard second‐line treatment for relapsed and refractory (R/R) DLBCL. However, half of the patients will not be eligible for transplantation due to ineffective salvage treatment, and the other half will relapse after ASCT. In randomized studies, no salvage chemotherapy regimen is superior to another. The outcomes are affected by the secondary International Prognostic Index at relapse and various biological factors. The strategy is less clear in patients who require third‐line treatment. A multicohort retrospective non‐Hodgkin lymphoma research (SCHOLAR‐1) study conducted in 636 patients with refractory DLBCL showed an objective response rate of 26% (complete response 7%) to the next line of therapy with a median overall survival of 6·3 months. In the case of a response followed by transplantation, long‐term survival can be achieved in DLBCL patients. There is clearly a need for new drugs that improve salvage efficacy. Encouraging results have been reported with chimeric antigen receptor ‐T cell engineering, warranting further studies in a well‐defined control group of refractory patients. The Collaborative Trial in Relapsed Aggressive Lymphoma (CORAL) was used as a handy framework to build the discussion.

Systematic patient involvement for homebased outpatient administration of complex chemotherapy in acute leukemia and lymphoma

Based on experience with comprehensive patient involvement, we present data from implementation of portable, programmable infusion pumps (PPP) for home-based chemotherapy administration in patients with acute leukaemia and in lymphoma patients receiving (carmustine, etoposide, cytarabine, melphalan) BEAM regimen. Data from 84 patients, receiving 177 cycles of PPP administered chemotherapy, showed convincing safety with minor equipment errors encountered and with high patient satisfaction. In-hospital days could be reduced with 52% out of a total of 1197 treatment days. Homebased PPP has several advantages from a patient perspective and furthermore frees up in-hospital beds for patients in need of them.

Regulated apoptosis of genetically modified hematopoietic stem and progenitor cells via an inducible caspase-9 suicide gene in rhesus macaques

The high risk of insertional oncogenesis reported in clinical trials using integrating retroviral vectors to genetically modify hematopoietic stem and progenitor cells (HSPCs) requires the development of safety strategies to minimize risks associated with novel cell and gene therapies. The ability to ablate genetically modified cells in vivo is desirable, should an abnormal clone emerge. Inclusion of "suicide genes" in vectors to facilitate targeted ablation of vector-containing abnormal clones in vivo is one potential safety approach. We tested whether the inclusion of the "inducible Caspase-9" (iCasp9) suicide gene in a gamma-retroviral vector facilitated efficient elimination of vector-containing HSPCs and their hematopoietic progeny in vivo long-term, in an autologous non-human primate transplantation model. Following stable engraftment of iCasp9 expressing hematopoietic cells in rhesus macaques, administration of AP1903, a chemical inducer of dimerization able to activate iCasp9, specifically eliminated vector-containing cells in all hematopoietic lineages long-term, suggesting activity at the HSPC level. Between 75% and 94% of vector-containing cells were eliminated by well-tolerated AP1903 dosing, but lack of complete ablation was linked to lower iCasp9 expression in residual cells. Further investigation of resistance mechanisms demonstrated upregulation of Bcl-2 in hematopoietic cell lines transduced with the vector and resistant to AP1903 ablation. These results demonstrate both the potential and the limitations of safety approaches using iCasp9 to HSPC-targeted gene therapy settings, in a model with great relevance to clinical development.