Canonical Wnt; a safeguard and threat for Erythropoiesis

Myeloid dysplastic syndrome (MDS) reflects a preleukemic BM disorder with limited treatment options and poor disease survival1. As only a minority of MDS patients is eligible to curative hematopoietic stem cell (HSC) transplantation, there is an urgent need to develop alternative treatment options. Chronic activation of Wnt/β-catenin has been implicated to underlie MDS formation and recently assigned to drive MDS transformation to acute myeloid leukemia (AML). Wnt/β-catenin signaling therefore may harbor a pharmaceutical target to treat MDS and/or prevent leukemia formation. However, targeting the Wnt/β-catenin pathway will also affect healthy hematopoiesis in MDS patients.The control of Wnt/β-catenin on healthy hematopoiesis is poorly understood. Whereas Wnt/β-catenin is dispensable for steady-state erythropoiesis, its activity is essential for stress erythropoiesis in response to BM injury and anemia. Manipulation of Wnt/β-catenin signaling in MDS may therefore deregulate stress erythropoiesis and even increase anemia severity. Here we provide a comprehensive overview of the most recent and established insights in the field to acquire more insight into the control of Wnt/β-catenin signaling on healthy and inefficient erythropoiesis as seen in MDS.

Relapse risk factors during allogeneic stem cell transplantation in children, adolescents and young adults with acute lymphoblastic leukemia

More than 20–25 % of patients with acute leukemia underwent transplantation of HSC from HLA-identical sibling or unrelated donor had relapse.Therefore, the purpose of this study was to evaluate the influence of different factors on the risk of post-transplantation relapse in children and teenagers with acute lymphoblastic leukemia (ALL).The gender, the age of a donor at the time of transplantation; the gender, the age of a recipient at the time of transplantation; the type, the number of relapses of previous HSCTs; the type of conditioning; the type of transplantation; the source of stem cells; transplant parameters; the acute (aGVHD) and chronic (cGVHD) graft-versus-host disease or its absence; the KIRalloreactivity of donor NK cells were estimated as risk factors for the disease relapse in our study.We established that the recipient’s age of less than 4 years at the time of transplantation (p = 0.0042); the time of relapse (very early and early) (p = 0.0047); the absence of aGVHD (p = 0.0183) or cGVHD (p = 0.0384) have been the important factors for the disease relapse of patients with ALL after allogeneic HSC transplantation.

Nature or Nurture? Role of the Bone Marrow Microenvironment in the Genesis and Maintenance of Myelodysplastic Syndromes

Myelodysplastic syndrome (MDS) are clonal haematopoietic stem cell (HSC) disorders driven by a complex combination(s) of changes within the genome that result in heterogeneity in both clinical phenotype and disease outcomes. MDS is among the most common of the haematological cancers and its incidence markedly increases with age. Currently available treatments have limited success, with <5% of patients undergoing allogeneic HSC transplantation, a procedure that offers the only possible cure. Critical contributions of the bone marrow microenvironment to the MDS have recently been investigated. Although the better understanding of the underlying biology, particularly genetics of haematopoietic stem cells, has led to better disease and risk classification; however, the role that the bone marrow microenvironment plays in the development of MDS remains largely unclear. This review provides a comprehensive overview of the latest developments in understanding the aetiology of MDS, particularly focussing on understanding how HSCs and the surrounding immune/non-immune bone marrow niche interacts together.

Human Schwann Cell Transplantation for Spinal Cord Injury: Prospects and Challenges in Translational Medicine

The benefits of transplanting cultured Schwann cells (SCs) for the treatment of spinal cord injury (SCI) have been systematically investigated in experimental animals since the early 1990s. Importantly, human SC (hSC) transplantation for SCI has advanced to clinical testing and safety has been established via clinical trials conducted in the USA and abroad. However, multiple barriers must be overcome to enable accessible and effective treatments for SCI patients. This review presents available information on hSC transplantation for SCI with the intention to uncover gaps in our knowledge and discuss areas for future development. To this end, we introduce the historical progression of the work that supports existing and prospective clinical initiatives and explain the reasons for the choice of hSCs while also addressing their limitations as cell therapy products. A search of the relevant literature revealed that rat SCs have served as a preclinical model of reference since the onset of investigations, and that hSC transplants are relatively understudied, possibly due to the sophisticated resources and expertise needed for the traditional processing of hSC cultures from human nerves. In turn, we reason that additional experimentation and a reexamination of the available data are needed to understand the therapeutic value of hSC transplants taking into consideration that the manufacturing of the hSCs themselves may require further development for extended uses in basic research and clinical settings.

Osteopontin and Transplantation: Where Are We Now?

Organ transplantation represents the optimal therapeutic tool for patients with end-stage organ failure. Hematopoietic stem cell transplantation (HSCT) is likewise an effective therapy for a wide range of malignant and non-malignant diseases. Better understanding of transplantation immunology and the use of multi-modal immunosuppression protocols, can decrease the risk of graft failure and graft-versus-host disease (GVHD) after HSCT. Nevertheless, a major challenge of modern transplantology still seems to be finding non-invasive biomarkers for recipients selection, monitoring of allograft function, and diagnosis of rejection. Since proinflammatory cytokine osteopontin (OPN) is closely involved in regulating both adaptive and innate immune responses, as well as the pathogenesis of inflammatory and autoimmune diseases, it is likely to play an important role in organ and HSC transplantation. This review is to summarize recent advances in our knowledge about OPN function in the kidney, heart, liver, lung, and HSC transplantation. Most studies found that elevated OPN is associated with poorer graft function in kidney, heart, liver and lung recipients. Moreover, some reports suggested that this protein can play role in GVHD pathogenesis. However, due to relatively small number of similar studies, as well as some inconclusive results, future investigation in this field is needed to verify if OPN can serve as a biomarker of organ and HSC transplantation. The knowledge about such markers will promote our understanding of the mechanisms underlying graft dysfunction and posttransplant mortality. In addition, such knowledge may be helpful in the development of new treatment strategies and identification of recipients with increased risk of allograft failure.

Hematopoietic stem cell requirement for macrophage regeneration is tissue-specific

Tissue-resident macrophages (TRMΦ) are important immune sentinels responsible for maintaining tissue and immune homeostasis within their specific niche. Recently, the origins of TRMΦ have undergone intense scrutiny where now most TRMΦ are thought to originate early during embryonic development independent of hematopoietic stem cells (HSCs). We previously characterized two distinct subsets of mouse peritoneal cavity macrophages (Large and Small Peritoneal Macrophages; LPM and SPM, respectively) whose origins and relationship to both fetal and adult long-term (LT)-HSCs have not been fully investigated. Here we employ highly purified LT-HSC transplantation and in vivo lineage tracing to show a dual ontogeny for LPM and SPM, where the initial wave of peritoneal macrophages is seeded from yolk sac-derived precursors, which later require LT-HSCs for regeneration. In contrast, transplanted fetal and adult LT-HSCs are not able to regenerate brain-resident microglia. Thus, we demonstrate that LT-HSCs retain the potential to develop into TRMΦ, but their requirement is tissue-specific.

Screening of Hematopoietic Small Molecules Facilitates the Establishment of a Chemically Defined Hsc Expansion Medium With Enhanced Performance

Hematopoietic stem cells (HSC), known for their ability to multipotent and self-renew, are often used in HSC transplantation for the treatment of hematological diseases and malignancies. Umbilical cord blood (UCB) and mobilized peripheral blood (mPB), which are alternatives to bone marrow (BM) for HSC transplantation, have reduced HSC. To address this restriction, the ex vivo expansion of HSCs is a highly promising therapeutic approach rather than the use of a double-cord blood unit that induces delays in hematopoietic recovery. We have previously shown that knockout of HSC quiescence genes could increase the HSC pool in vivo. Thus, we thought that targeting HSC quiescence regulators using small molecules could be used for ex vivo expansion of both mPB and UCB-HSC. The goal was to identify novel hematopoietic small molecules (HSMs) and their combinations, and to enhance performance of human HSC expansion medium. We identified and analyzed 35 possible HSMs targeting HSC quiescence factors. We assessed their impact on human HSPC activity, including expansion, quiescence, multilineage capacity, cycling capability and metabolism. We have also investigated their cytotoxic and genotoxic effects on human HSPCs. On the other hand, a transplantation study was performed on immunocompromised mice for the evaluation of the repopulation and engraftment capacities of the expanded cells. We observed that BML-260 and TAME molecules robustly increased both the mPB and UCB-HSPC content and activated the re-entry of HSCs into the cell cycle. Colony Forming Unit (CFU) assay confirmed their improved multilineage capacity. BML-260 proved safer for the viability of expanded cells based on cytotoxicity and genotoxicity assays. In addition, gene expression analysis showed that BML-260 and TAME molecules contributed to HSC expansion by modulating cell cycle kinetics, including p27, Skp2 and Cdh1. In conjunction with these in vitro results, we have observed that BML-260-expanded HSCs had a strong hematopoietic reconstitution capacity. After the determination of the most effective molecule as BML-260, a comparative study of chemically defined media, including various supplements, was analyzed in addition to the BML-260 molecule. These results from in vitro and xenotransplantation experiments have shown that BML-260 molecules can be used therapeutically for human HSC expansion and regulation of HSC activity. In addition, the medium composition found may be a novel platform for human HSC expansion to used in clinical trials.

Radiation-induced bystander effects impair transplanted human hematopoietic stem cells via oxidative DNA damage

Total body irradiation (TBI) is commonly used in host conditioning regimens for human hematopoietic stem cell (HSC) transplantation to treat various hematological disorders. Exposure to TBI not only induces acute myelosuppression and immunosuppression but also impairs the various components of the HSC niche in recipients. Our previous study demonstrated that radiation-induced bystander effects (RIBE) of irradiated recipients decreased the long-term repopulating ability of transplanted mouse HSCs. However, RIBE on human HSCs have not been studied. Here, we report that RIBE on transplanted human hematopoietic cells impaired the long-term hematopoietic reconstitution of human HSCs as well as the colony-forming ability of human hematopoietic progenitor cells (HPCs). Our further studies found that the RIBE-affected human hematopoietic cells showed enhanced DNA damage responses, cell cycle arrest and p53-dependent apoptosis, mainly due to oxidative stress. Moreover, multiple antioxidants could mitigate these bystander effects, though at different efficacies both in vitro and in vivo. Taken together, these findings suggest that RIBE impairs human HSCs by oxidative DNA damage. This study provides definitive evidence for RIBE in transplanted human HSCs and further justifies the necessity for conducting clinical trials to assess the ability of multiple antioxidants to improve the efficacy of HSC transplantation for patients with hematological or non-hematological disorders.

Prostaglandin E2 Enhances Aged Hematopoietic Stem Cell Function

Aging of hematopoiesis is associated with increased frequency and clonality of hematopoietic stem cells (HSCs), along with functional compromise and myeloid bias, with donor age being a significant variable in survival after HSC transplantation. No clinical methods currently exist to enhance aged HSC function, and little is known regarding how aging affects molecular responses of HSCs to biological stimuli. Exposure of HSCs from young fish, mice, nonhuman primates, and humans to 16,16-dimethyl prostaglandin E2 (dmPGE2) enhances transplantation, but the effect of dmPGE2 on aged HSCs is unknown. Here we show that ex vivo pulse of bone marrow cells from young adult (3 mo) and aged (25 mo) mice with dmPGE2 prior to serial competitive transplantation significantly enhanced long-term repopulation from aged grafts in primary and secondary transplantation (27% increase in chimerism) to a similar degree as young grafts (21% increase in chimerism; both p<0.05). RNA sequencing of phenotypically-isolated HSCs indicated that the molecular responses to dmPGE2 are similar in young and old, including CREB1 activation and increased cell survival and homeostasis. Common genes within these pathways identified likely key mediators of HSC enhancement by dmPGE2 and age-related signaling differences. HSC expression of the PGE2 receptor EP4, implicated in HSC function, increased with age in both mRNA and surface protein. This work suggests that aging does not alter the major dmPGE2 response pathways in HSCs which mediate enhancement of both young and old HSC function, with significant implications for expanding the therapeutic potential of elderly HSC transplantation.

Umbilical cord blood CD34+ cells administration improved neurobehavioral status and alleviated brain injury in a mouse model of cerebral palsy

Purpose Cerebral palsy (CP) is the most common neuromuscular disease in children, and currently, there is no cure. Several studies have reported the benefits of umbilical cord blood (UCB) cell treatment for CP. However, these studies either examined the effects of UCB cell fraction with a short experimental period or used neonatal rat models for a long-term study which displayed an insufficient immunological reaction and clearance of human stem cells. Here, we developed a CP model by hypoxia-ischemic injury (HI) using immunodeficient mice and examined the effects of human UCB CD34+ hematopoietic stem cells (HSCs) on CP therapy over a period of 8 weeks. Methods Sixty postnatal day-9 (P9) mouse pups were randomly divided into 4 groups (n = 15/group) as follows: (1) sham operation (control group), (2) HI-induced CP model, (3) CP model with CD34+ HSC transplantation, and (4) CP model with CD34- cell transplantation. Eight weeks after insult, the sensorimotor performance was analyzed by rotarod treadmill, gait dynamic, and open field assays. The pathological changes in brain tissue of mice were determined by HE staining, Nissl staining, and MBP immunohistochemistry of the hippocampus in the mice. Results HI brain injury in mice pups resulted in significant behavioral deficits and loss of neurons. Both CD34+ HSCs and CD34- cells improved the neurobehavioral statuses and alleviated the pathological brain injury. In comparison with CD34- cells, the CD34+ HSC compartments were more effective. Conclusion These findings indicate that CD34+ HSC transplantation was neuroprotective in neonatal mice and could be an effective therapy for CP.