LABORATORY RESEARCH Ezh1 Is Required for Hematopoietic Stem Cell Maintenance and Prevents Senescence-Like Cell Cycle Arrest Researchers showed that Ezh1 maintains repopulating hematopoietic stem cells (HSCs) in a slow-cycling, undifferentiated state, protecting them from senescence. Ezh1 ablation induces significant loss of adult HSCs, with concomitant impairment of their self-renewal capacity due to a potent senescence response. [Cell Stem Cell] Abstract | Graphical Abstract LRF-Mediated Dll4 Repression in Erythroblasts Is Necessary for Hematopoietic Stem Cell Maintenance Scientists report a novel mechanism that prevents hematopoietic stem cells (HSCs) from undergoing premature lymphoid differentiation in bone marrow. Using a series of in vivo mouse models and functional HSC assays, they showed that leukemia/lymphoma related factor (LRF) is necessary for HSC maintenance by functioning as an erythroid-specific repressor of Delta-like 4 (Dll4) expression. [Blood] Abstract Inhibition of T Cell Protein Tyrosine Phosphatase Enhances IL-18-Dependent Hematopoietic Stem Cell Expansion Researchers report that inhibition of T cell protein tyrosine phosphatase, an enzyme involved in the regulation of cytokine signaling, through gene knockout results in a nine-fold increase in the number of hematopoietic progenitors in murine bone marrow. [Stem Cells] Abstract Tie2+ Bone Marrow Endothelial Cells Regulate Hematopoietic Stem Cell Regeneration following Radiation Injury Investigators utilized genetic models to determine if radioprotection of bone marrow endothelial cells could facilitate hematopoietic regeneration following radiation-induced myelosuppression. [Stem Cells] Abstract SUMO1-Activating Enzyme Subunit 1 Is Essential for the Survival of Hematopoietic Stem/Progenitor Cells in Zebrafish Researchers report the isolation and characterization of a zebrafish mutant, tangohkz5, which shows defects of definitive hematopoiesis. In tangohkz5 mutants, hematopoietic stem/progenitor cells initiate normally in the aorta-gonad-mesonephros and subsequently colonize the caudal hematopoietic tissue. [Development] Abstract Resveratrol Ameliorates Ionizing Irradiation-Induced Long-Term Hematopoietic Stem Cell Injury in Mice Previous studies showed that total body irradiation (TBI) induces long-term bone marrow (BM) suppression in part by induction of hematopoietic stem cell (HSC) senescence through NADPH oxidase 4-derived reactive oxygen species. In the present study, scientists examined if resveratrol, a potent antioxidant and a putative activator of Sirtuin 1, can ameliorate TBI-induced long-term BM injury by inhibiting radiation-induced chronic oxidative stress and senescence in HSCs. [Free Radic Biol Med] Abstract Nitric Oxide Depletion Alters Hematopoietic Stem Cell Commitment toward Immunogenic Dendritic Cells Investigators depleted autocrine NO• production, using NG-Monomethyl-L-arginine monoacetate and paracrine NO•, using oxy-hemoglobin as a NO• scavenger during in vitro differentiation of human peripheral blood hemopoietic stem cells to immunogenic dendritic cells. They monitored the NO• level, cell proliferation, phenotype and differentiation potential. [Biochim Biophys Acta] Abstract SOD2 Deficiency in Hematopoietic Cells in Mice Results in Reduced Red Blood Cell Deformability and Increased Heme Degradation To investigate the potential damage to mature red blood cells (RBCs) resulting from super oxide dismutase-2 (SOD2) deficiency in precursor cells, researchers studied RBCs from mice in which fetal liver stem cells deficient in SOD2 were capable of efficiently rescuing lethally irradiated host animals. [Exp Hematol] Abstract CLINICAL RESEARCH Randomized Trial of Myeloablative Conditioning Regimens: Busulfan Plus Cyclophosphamide versus Busulfan Plus Fludarabine Researchers conducted a phase III randomized clinical trial to compare two myeloablative conditioning regimens for allogeneic hematopoietic cell transplantation in patients with leukemia and myelodysplastic syndrome. [J Clin Oncol] Abstract Allogeneic Hematopoietic Cell Transplantation for XIAP Deficiency: An International Survey Reveals Poor Outcomes In order to estimate the success of hematopoietic cell transplantation for patients with XIAP deficiency, investigators conducted an international survey of transplant outcomes. Data was reported for 19 patients. [Blood] Abstract Prediction of Area under the Cyclosporine Concentration vs Time Curve in Children undergoing Hematopoietic Stem Cell Transplant This prospective study aimed to validate a previously developed first dose limited sampling strategy (LSS) to predict cyclosporine area under the concentration-versus-time curve (AUC) and to develop and then validate an LSS to predict cyclosporine AUC at steady-state. [Biol Blood Marrow Transplant] Abstract |