Niche-derived Semaphorin 4A safeguards functional identity of myeloid-biased hematopoietic stem cells.

Somatic stem cell pools comprise diverse, highly specialized subsets whose individual contribution is critical for the overall regenerative function. In the bone marrow, myeloid-biased hematopoietic stem cells (myHSCs) are indispensable for replenishment of myeloid cells and platelets during inflammatory response but, at the same time, become irreversibly damaged during inflammation and aging. Here we identify an extrinsic factor, semaphorin 4A (Sema4A), which non-cell-autonomously confers myHSC resilience to inflammatory stress.

"Treatment with curative intent": the emergence of genetic therapies for sickle cell anemia.

The root cause of sickle cell anemia has been known for 7 decades, yet no curative therapies have been available other than allogeneic bone marrow transplantation, for which applicability is limited. Two potentially curative therapies based on gene therapy and gene editing strategies have recently received US Food and Drug Administration approval. This review surveys the nature of these therapies and the opportunities and issues raised by the prospect of definitive genetically based therapies being available in clinical practice.

Targeting multiple cell death pathways extends the shelf life and preserves the function of human and mouse neutrophils for transfusion.

Clinical outcomes from granulocyte transfusion (GTX) are disadvantaged by the short shelf life and compromised function of donor neutrophils. Spontaneous neutrophil death is heterogeneous and mediated by multiple pathways. Leveraging mechanistic knowledge and pharmacological screening, we identified a combined treatment, caspases-lysosomal membrane permeabilization-oxidant-necroptosis inhibition plus granulocyte colony-stimulating factor (CLON-G), which altered neutrophil fate by simultaneously targeting multiple cell death pathways.

Zinc Finger Protein SALL4 Functions through an AT-Rich Motif to Regulate Gene Expression.

The zinc finger transcription factor SALL4 is highly expressed in embryonic stem cells, downregulated in most adult tissues, but reactivated in many aggressive cancers. This unique expression pattern makes SALL4 an attractive therapeutic target. However, whether SALL4 binds DNA directly to regulate gene expression is unclear, and many of its targets in cancer cells remain elusive.

VEGF-C protects the integrity of the bone marrow perivascular niche in mice.

Hematopoietic stem cells (HSCs) reside in the bone marrow (BM) stem cell niche, which provides a vital source of HSC regulatory signals. Radiation and chemotherapy disrupt the HSC niche, including its sinusoidal vessels and perivascular cells, contributing to delayed hematopoietic recovery. Thus, identification of factors that can protect the HSC niche during an injury could offer a significant therapeutic opportunity to improve hematopoietic regeneration.

Single-cell transcriptome profiling reveals neutrophil heterogeneity in homeostasis and infection.

The full neutrophil heterogeneity and differentiation landscape remains incompletely characterized. Here, we profiled >25,000 differentiating and mature mouse neutrophils using single-cell RNA sequencing to provide a comprehensive transcriptional landscape of neutrophil maturation, function and fate decision in their steady state and during bacterial infection. Eight neutrophil populations were defined by distinct molecular signatures.

Pathologic angiogenesis in the bone marrow of humanized sickle cell mice is reversed by blood transfusion.

Sickle cell disease (SCD) is a monogenic red blood cell (RBC) disorder with high morbidity and mortality. Here, we report, for the first time, the impact of SCD on the bone marrow (BM) vascular niche, which is critical for hematopoiesis. In SCD mice, we find a disorganized and structurally abnormal BM vascular network of increased numbers of highly tortuous arterioles occupying the majority of the BM cavity, as well as fragmented sinusoidal vessels filled with aggregates of erythroid and myeloid cells.

Cell Cycle Analysis of Hematopoietic Stem and Progenitor Cells by Multicolor Flow Cytometry.

Maintenance of hematopoietic stem cell (HSC) quiescence is critical for self-renewal and differentiation into mature lineages. Therefore, the ability to reliably detect abnormal HSC cycling is essential for experiments that seek to investigate abnormalities of HSC function. The ability to reproducibly evaluate cell cycle status in a rare cell subset requires careful optimization of multiple parameters during cell preparation and sample processing.

Automated typing of red blood cell and platelet antigens: a whole-genome sequencing study.

Background: There are more than 300 known red blood cell (RBC) antigens and 33 platelet antigens that differ between individuals. Sensitisation to antigens is a serious complication that can occur in prenatal medicine and after blood transfusion, particularly for patients who require multiple transfusions. Although pre-transfusion compatibility testing largely relies on serological methods, reagents are not available for many antigens.

Gasdermin D Exerts Anti-inflammatory Effects by Promoting Neutrophil Death.

Gasdermin D (GSDMD) is considered a proinflammatory factor that mediates pyroptosis in macrophages to protect hosts from intracellular bacteria. Here, we reveal that GSDMD deficiency paradoxically augmented host responses to extracellular Escherichia coli, mainly by delaying neutrophil death, which established GSDMD as a negative regulator of innate immunity. In contrast to its activation in macrophages, in which activated inflammatory caspases cleave GSDMD to produce an N-terminal fragment (GSDMD-cNT) to trigger pyroptosis, GSDMD cleavage and activation in neutrophils was caspase independent.

Cell encapsulation utilizing PEG-fibrinogen hydrogel supports viability and enhances productivity under stress conditions.

Recent advances in the bioengineering field have introduced new opportunities enabling cell encapsulation in three-dimensional (3D) structures using either various natural or synthetic materials. However, such hydrogel scaffolds have not been fully biocompatible for cell cultivation due to the lack of physical stability or bioactivity. Here, we utilized a uniquely fabricated semi-synthetic 3D polyethylene glycol-fibrinogen (PEG-Fb) hydrogel scaffold, which exhibits both high stability and high bioactivity, to encapsulate HEK293 cells for the production of human recombinant acetylcholine esterase (AChE).

Positive Regulation of Interleukin-1β Bioactivity by Physiological ROS-Mediated Cysteine S-Glutathionylation.

Reactive oxygen species (ROS)-induced cysteine S-glutathionylation is an important posttranslational modification (PTM) that controls a wide range of intracellular protein activities. However, whether physiological ROS can modulate the function of extracellular components via S-glutathionylation is unknown. Using a screening approach, we identified ROS-mediated cysteine S-glutathionylation on several extracellular cytokines.

Image-guided transplantation of single cells in the bone marrow of live animals.

Transplantation of a single hematopoietic stem cell is an important method for its functional characterization, but the standard transplantation protocol relies on cell homing to the bone marrow after intravenous injection. Here, we present a method to transplant single cells directly into the bone marrow of live mice. We developed an optical platform that integrates a multiphoton microscope with a laser ablation unit for microsurgery and an optical tweezer for cell micromanipulation.

Manufacturing Differences Affect Human Bone Marrow Stromal Cell Characteristics and Function: Comparison of Production Methods and Products from Multiple Centers.

Human bone marrow stromal cells (BMSCs, also known as bone marrow-derived mesenchymal stem cells) are manufactured using many different methods, but little is known about the spectrum of manufacturing methods used and their effects on BMSC characteristics and function. Seven centers using, and one developing, Good Manufacturing Practices (GMP) processes were surveyed as to their production methods. Among the seven centers, all used marrow aspirates as the starting material, but no two centers used the same manufacturing methods.

Reactive Oxygen Species-Producing Myeloid Cells Act as a Bone Marrow Niche for Sterile Inflammation-Induced Reactive Granulopoiesis.

Both microbial infection and sterile inflammation augment bone marrow (BM) neutrophil production, but whether the induced accelerated granulopoiesis is mediated by a common pathway and the nature of such a pathway are poorly defined. We recently established that BM myeloid cell-derived reactive oxygen species (ROS) externally regulate myeloid progenitor proliferation and differentiation in bacteria-elicited emergency granulopoiesis. In this article, we show that BM ROS levels are also elevated during sterile inflammation.

G-CSF maintains controlled neutrophil mobilization during acute inflammation by negatively regulating CXCR2 signaling.

Cytokine-induced neutrophil mobilization from the bone marrow to circulation is a critical event in acute inflammation, but how it is accurately controlled remains poorly understood. In this study, we report that CXCR2 ligands are responsible for rapid neutrophil mobilization during early-stage acute inflammation. Nevertheless, although serum CXCR2 ligand concentrations increased during inflammation, neutrophil mobilization slowed after an initial acute fast phase, suggesting a suppression of neutrophil response to CXCR2 ligands after the acute phase.

Proximity-Based Differential Single-Cell Analysis of the Niche to Identify Stem/Progenitor Cell Regulators.

Physiological stem cell function is regulated by secreted factors produced by niche cells. In this study, we describe an unbiased approach based on the differential single-cell gene expression analysis of mesenchymal osteolineage cells close to, and further removed from, hematopoietic stem/progenitor cells (HSPCs) to identify candidate niche factors. Mesenchymal cells displayed distinct molecular profiles based on their relative location.

Angiogenin Promotes Hematopoietic Regeneration by Dichotomously Regulating Quiescence of Stem and Progenitor Cells.

Regulation of stem and progenitor cell populations is critical in the development, maintenance, and regeneration of tissues. Here, we define a novel mechanism by which a niche-secreted RNase, angiogenin (ANG), distinctively alters the functional characteristics of primitive hematopoietic stem/progenitor cells (HSPCs) compared with lineage-committed myeloid-restricted progenitor (MyePro) cells. Specifically, ANG reduces the proliferative capacity of HSPC while simultaneously increasing proliferation of MyePro cells.

Platelet refractoriness: it's not the B-all and end-all.

In this issue of Blood, Arthur et al uncover that HLA alloantibodies cannot solely account for the immune mechanism in platelet refractoriness.

Comprehensive red blood cell and platelet antigen prediction from whole genome sequencing: proof of principle.

Background: There are 346 serologically defined red blood cell (RBC) antigens and 33 serologically defined platelet (PLT) antigens, most of which have known genetic changes in 45 RBC or six PLT genes that correlate with antigen expression. Polymorphic sites associated with antigen expression in the primary literature and reference databases are annotated according to nucleotide positions in cDNA. This makes antigen prediction from next-generation sequencing data challenging, since it uses genomic coordinates.

DAZL regulates Tet1 translation in murine embryonic stem cells.

Embryonic stem cell (ESC) cultures display a heterogeneous gene expression profile, ranging from a pristine naïve pluripotent state to a primed epiblast state. Addition of inhibitors of GSK3β and MEK (so-called 2i conditions) pushes ESC cultures toward a more homogeneous naïve pluripotent state, but the molecular underpinnings of this naïve transition are not completely understood. Here, we demonstrate that DAZL, an RNA-binding protein known to play a key role in germ-cell development, marks a subpopulation of ESCs that is actively transitioning toward naïve pluripotency.

Myocardial Infarction Activates CCR2(+) Hematopoietic Stem and Progenitor Cells.

Following myocardial infarction (MI), myeloid cells derived from the hematopoietic system drive a sharp increase in systemic leukocyte levels that correlates closely with mortality. The origin of these myeloid cells, and the response of hematopoietic stem and progenitor cells (HSPCs) to MI, however, is unclear. Here, we identify a CCR2(+)CD150(+)CD48(-) LSK hematopoietic subset as the most upstream contributor to emergency myelopoiesis after ischemic organ injury.