Targeting hematologic malignancies by inhibiting E-selectin: A sweet spot for AML therapy?

E-selectin, a cytoadhesive glycoprotein, is expressed on venular endothelial cells and mediates leukocyte localization to inflamed endothelium, the first step in inflammatory cell extravasation into tissue. Constitutive marrow endothelial E-selectin expression also supports bone marrow hematopoiesis via NF-κB-mediated signaling. Correspondingly, E-selectin interaction with E-selectin ligand (sialyl Lewisx) on acute myeloid leukemia (AML) cells leads to chemotherapy resistance in vivo. Uproleselan (GMI-1271) is a carbohydrate analog of sialyl Lewisx that blocks E-selectin binding. A Phase 2 trial of MEC chemotherapy combined with uproleselan for relapsed/refractory AML showed a median overall survival of 8.8 months and low (2%) rates of severe oral mucositis. Clinical trials seek to confirm activity in AML and mitigation of neutrophil-mediated adverse events (mucositis and diarrhea) after intensive chemotherapy. In this review we summarize E-selectin biology and the rationale for uproleselan in combination with other therapies for hematologic malignancies. We also describe uproleselan pharmacology and ongoing clinical trials.

Characterization of Human Engraftment and Hemophagocytic Lymphohistiocytosis in NSG-SGM3 Neonate Mice Engrafted with Purified CD34+ Hematopoietic Stem Cells.

Immunodeficient mice bearing human immune systems, or "humanized" chimeric mice, are widely used in basic research, along with the preclinical stages of drug development. Nonobese diabetic-severe combined immunodeficiency (NOD-SCID) IL2Rγnull (NSG) mice expressing human stem cell factor, granulocyte-macrophage colony stimulating factor, and interleukin-3 (NSG-SGM3) support robust development of human myeloid cells and T cells but have reduced longevity due to the development of fatal hemophagocytic lymphohistiocytosis (HLH). Here, we describe an optimized protocol for development of human immune chimerism in NSG-SGM3 mice. We demonstrate that efficient human CD45+ reconstitution can be achieved and HLH delayed by engraftment of neonatal NSG-SGM3 with low numbers of human umbilical cord-derived CD34+ hematopoietic stem cells in the absence of preconditioning irradiation.

[Application of scientific knowledge: knowledge translation in an institute of science and technology in public health]. / Aplicação do saber científico: a translação do conhecimento em um instituto de ciência e tecnologia em saúde pública.

Knowledge translation (KT) aims at the practical use of scientific research results and at the monitoring of the benefits caused to the population's health. In health, the government and especially society expect that investments in research will produce results that go beyond the production and publication of knowledge, provoking outcomes such as public policies, systems, products, and technologies to benefit the health of the population. However, closing the gaps between research and application requires overcoming a number of challenges. This study aimed to propose strategies to foster the process of transforming the scientific knowledge generated in research into actions and products that contribute to improving the population's health based on the identification of barriers and facilitating factors of a health science and technology institute. The reports of interviews conducted with 16 researchers showed 10 categories of barriers, especially: "limited funding to the science and technology institute" and "insufficient technical support for knowledge translation". "Infrastructure and institutional support" was the facilitating factor category participants mentioned the most. Finally, we developed the artifact "strategies and approaches for overcoming barriers to implement research results". Among the strategies, we suggest the inclusion of a knowledge translation discipline in stricto sensu graduate programs and the creation of an instance in the organizational structure of the science and technology institute to technically and managerially support the application of research results.

A translação do conhecimento (TC) tem como propósito a utilização prática dos resultados de pesquisas científicas e o monitoramento dos benefícios causados à saúde da população. Na área de saúde, o governo e, principalmente, a sociedade esperam que os investimentos em pesquisas obtenham resultados que vão além da produção e da publicação do conhecimento, e provoquem soluções como políticas públicas, sistemas, produtos e tecnologias para beneficiar a saúde da população. Contudo, verifica-se ainda a necessidade de superar diversos desafios para eliminar as lacunas existentes entre a investigação e a aplicação. O objetivo deste estudo é propor estratégias, com base na identificação de barreiras e fatores facilitadores de um instituto de ciência e tecnologia (ICT) em saúde, para fomentar o processo de transformação do conhecimento científico, gerado nas pesquisas, em ações e produtos que contribuam para a melhoria da saúde da população. Os relatos das entrevistas, realizadas com 16 pesquisadores, permitiram a identificação de 10 categorias de barreiras, tendo destaque: "financiamento em ciência, tecnologia e informação (CT&I) limitado" e "apoio técnico insuficiente para a translação do conhecimento". "Infraestrutura e apoio institucional" foi a categoria de fatores facilitadores mais citada pelos participantes. Por fim, foi desenvolvido o artefato "estratégias e abordagens para superação de barreiras à implementação de resultados de pesquisa". Entre as estratégias, sugere-se a inclusão de uma disciplina de TC nos programas de pós-graduação stricto sensu e a criação de uma instância na estrutura organizacional do ICT voltada à prestação de suporte técnico e gerencial à aplicação de resultados de pesquisa.

La traslación del conocimiento (TC) tiene como propósito el uso práctico de los resultados de investigaciones científicas y el seguimiento de los beneficios causados a la salud de la población. En el área de la salud, el gobierno y, sobre todo, la sociedad esperan que las inversiones en investigaciones obtengan resultados que vayan más allá de la producción y publicación de conocimiento, y provoquen resultados, como políticas públicas, sistemas, productos y tecnologías en beneficio de la salud de la población. Sin embargo, se observa aun la necesidad de superar diversos desafíos para eliminar las brechas entre la investigación y la aplicación. El objetivo de este estudio es proponer estrategias con base en la identificación de barreras y factores facilitadores de un instituto de ciencia y tecnología (ICT) en salud, para fomentar el proceso de transformación del conocimiento científico generado en las investigaciones en acciones y productos que contribuyan a mejorar la salud de la población. Los relatos de las entrevistas a 16 investigadores permitieron identificar 10 categorías de barreras, con énfasis en: "financiación en CT&I limitado" y "apoyo técnico insuficiente para la traslación del conocimiento". "Infraestructura y apoyo institucional" fue la categoría de factores facilitadores más citada por los participantes. Finalmente, se desarrolló el artefacto "estrategias y enfoques para la superación de barreras a la implementación de resultados de investigación". Entre las estrategias, se sugiere la inclusión de una asignatura de TC en los programas de posgrado stricto sensu y la creación de una instancia en la estructura organizacional del ICT orientada a brindar apoyo técnico y gerencial a la aplicación de los resultados de la investigación.

Decision Support Frameworks in Public Health Emergencies: A Systematic Review of Dynamic Models in Complex Contexts.

Public health emergencies are extraordinary events of disease spread, with health, economic, and social consequences, which require coordinated actions by governments and society. This work aims to analyze scopes, application possibilities, challenges, and gaps of decision support frameworks in PHE management, using the components of the Health Emergency and Disaster Risk Management Framework (H-EDRM) and the Preparedness, Prevention, Response and Recovery Model (PPRR Model), providing guidelines for the development of new models. A systematic literature review was carried out using the Web of Science, Scopus, and Pubmed knowledge databases on studies published between 2016 and 2023, and thirty-six articles were selected. The outcomes show a concentration of frameworks on short-term emergency response operations, with a limited emphasis on the political and strategic components that drive actors and responsibilities. Management prioritizes monitoring, evaluation, and information management frameworks. However, the models need to overcome the challenges of multisectoral and interdisciplinary action, different levels of decisions and actors, data sharing, and development of common platforms of evidence for decisions fitted to the various emergencies.

Plataforma tecnológica como suporte para translação do conhecimento em saúde / Technological platform as a support for health knowledge translation / La plataforma tecnológica como soporte para la transferencia de conocimientos en salud

A translação do conhecimento (TC) visa à utilização prática dos resultados de pesquisas científicas e o monitoramento dos benefícios causados à saúde da população. O objetivo deste estudo foi instrumentalizar a instância de suporte à TC por meio da identificação dos requisitos funcionais de uma proposta de plataforma tecnológica. Fundamentando-se no Design Science Research, o estudo se enquadra como uma pesquisa qualitativa procurando resolver um problema prático num contexto específico. Por meio de um grupo focal confirmatório com profissionais e pesquisadores de um instituto de ciência e tecnologia em saúde, foram identificadas 11 categorias de requisitos funcionais: Órgãos Regulatórios, Infraestrutura de Implementação, Banco de Dados, Capacitações em TC, Eventos de TC, Perfil de Consultas, Portal TC, Avaliação de Iniciativas, Apoio Institucional, Ferramenta de Busca Parametrizada e Prospecção de Projetos de Pesquisa. A modelagem da proposta contemplou as sugestões de funcionalidades para instrumentalizar o processo de aplicação prática dos conhecimentos decorrentes das pesquisas

Knowledge translation (KT) aims at the practical use of scientific research results and the monitoring of the benefits caused to the population's health. The objective of this study was to instrumentalize the TC support instance by identifying the functional requirements of a proposed technological platform. Based on Design Science Research, the study is framed as qualitative research seeking to solve a practical problem in a specific context. Through a confirmatory focus group with professionals and researchers from a health science and technology institute, 11 categories of functional requirements were identified: Regulatory Bodies, Implementation Infrastructure, Database, Capacity Building, KT Events, Query Profile, KT Portal, Initiative Evaluation, Institutional Support, Parameterized Search Tool, and Research Project Prospecting. The modeling of the proposal contemplated the suggestions of functionalities to instrumentalize the process of the practical application of the knowledge resulting from the research

La traslación del conocimiento (TC) tiene como objetivo el uso práctico de los resultados de la investigación científica y el seguimiento de los beneficios causados a la salud de la población. El objetivo de este estudio fue instrumentalizar la instancia de apoyo a la TC a través de la identificación de requisitos funcionales de una plataforma tecnológica propuesta. Basado en Design Science Research, el estudio se enmarca como una investigación cualitativa que busca resolver un problema práctico en un contexto específico. A través de un grupo focal confirmatorio con profesionales e investigadores de un instituto de ciencia y tecnología de la salud, se identificaron 11 categorías de requisitos funcionales: Órganos Reguladores, Infraestructura de Implementación, Base de Datos, Capacitación, Eventos de TC, Perfil de Consulta, Portal de TC, Evaluación de Iniciativas, Apoyo Institucional, Herramienta de Búsqueda Parametrizada y Prospección de Proyectos de Investigación. El modelado de la propuesta incluyó las sugerencias de funcionalidades para instrumentalizar el proceso de aplicación práctica del conocimiento surgido de la investigación

Bacterial Lipopolysaccharides Exacerbate Neurogenic Heterotopic Ossification Development.

Neurogenic heterotopic ossifications (NHO) are heterotopic bones that develop in periarticular muscles after severe central nervous system (CNS) injuries. Several retrospective studies have shown that NHO prevalence is higher in patients who suffer concomitant infections. However, it is unclear whether these infections directly contribute to NHO development or reflect the immunodepression observed in patients with CNS injury. Using our mouse model of NHO induced by spinal cord injury (SCI) between vertebrae T11 to T13 , we demonstrate that lipopolysaccharides (LPS) from gram-negative bacteria exacerbate NHO development in a toll-like receptor-4 (TLR4)-dependent manner, signaling through the TIR-domain-containing adapter-inducing interferon-ß (TRIF/TICAM1) adaptor rather than the myeloid differentiation primary response-88 (MYD88) adaptor. We find that T11 to T13 SCI did not significantly alter intestinal integrity nor cause intestinal bacteria translocation or endotoxemia, suggesting that NHO development is not driven by endotoxins from the gut in this model of SCI-induced NHO. Relevant to the human pathology, LPS increased expression of osteoblast markers in cultures of human fibro-adipogenic progenitors isolated from muscles surrounding NHO biopsies. In a case-control retrospective study in patients with traumatic brain injuries, infections with gram-negative Pseudomonas species were significantly associated with NHO development. Together these data suggest a functional association between gram-negative bacterial infections and NHO development and highlights infection management as a key consideration to avoid NHO development in patients. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Analysis of brain activation and wave frequencies during a sentence completion task: a paradigm used with EEG in aphasic participants.

Aphasia is a language disorder that occurs after brain injury and directly affects an individual's communication. The incidence of stroke increases with age, and one-third of people who have had a stroke develop aphasia. The severity of aphasia changes over time and some aspects of language may improve, while others remain compromised. Battery task training strategies are used in the rehabilitation of aphasics. The idea of this research is to use electroencephalography (EEG) as a non-invasive method, of electrophysiological monitoring, with a group of aphasic patients in rehabilitation process in a prevention and rehabilitation unit of the person with disabilities of the Unified Health System (SUS), of reference in the state of Bahia-Brazil. In this study, the goal is to analyze brain activation and wave frequencies of aphasic individuals during a sentence completion task, to possibly assist health professionals with the analysis of the aphasic subject's rehabilitation and task redefinition. We adopted the functional magnetic resonance imaging (fMRI) paradigm, proposed by the American Society for Functional Neuroradiology as a reference paradigm. We applied the paradigm in the group of aphasics with preserved comprehension, right hemiparesis, and left hemisphere injured or affected by stroke. We analyzed four electrodes (F3/F4 and F7/F8) corresponding to the left/right frontal cortex. Preliminary results of this study indicate a more robust activation in the right hemisphere (average of aphasics), with a difference of approximately 14% higher in Theta and Alpha frequencies, with 8% higher in low Beta (BetaL) and with approximately 1% higher in high Beta frequency (BetaH), Gamma frequency was higher by approximately 3% in the left hemisphere of the brain. The difference in electrical activation may be revealing to us a migration of language to the non-language dominant hemisphere. We point to possible evidence suggesting that EEG may be a promising tool for monitoring the rehabilitation of the aphasic subject.

Imaging Flow Cytometric Analysis of Primary Bone Marrow Erythroblastic Islands.

The erythroblastic island (EBI) is a multicellular functional erythropoietic unit comprising a central macrophage nurturing a rosette of maturing erythroblasts. Since the discovery of EBIs more than half a century ago, EBIs are still studied by traditional microscopy methods after enrichment by sedimentation. These isolation methods are not quantitative and do not enable precise quantification of EBI numbers or frequency in the bone marrow or spleen tissues. Conventional flow cytometric methods have enabled quantification of cell aggregates co-expressing macrophage and erythroblast markers; however, it is unknown whether these aggregates contain EBIs as these aggregates cannot be visually assessed for EBI content. Combining the strengths of both microscopy and flow cytometry methods, in this chapter we describe an imaging flow cytometry method to analyze and quantitatively measure EBIs from the mouse bone marrow. This method is adaptable to other tissues such as the spleen or to other species provided that fluorescent antibodies specific to macrophages and erythroblasts are available.

Aplicação do saber científico: a translação do conhecimento em um instituto de ciência e tecnologia em saúde pública / Application of scientific knowledge: knowledge translation in an institute of science and technology in public health / Aplicación del saber científico: la traslación de conocimiento en un instituto de ciencia y tecnología en salud pública

Resumo: A translação do conhecimento (TC) tem como propósito a utilização prática dos resultados de pesquisas científicas e o monitoramento dos benefícios causados à saúde da população. Na área de saúde, o governo e, principalmente, a sociedade esperam que os investimentos em pesquisas obtenham resultados que vão além da produção e da publicação do conhecimento, e provoquem soluções como políticas públicas, sistemas, produtos e tecnologias para beneficiar a saúde da população. Contudo, verifica-se ainda a necessidade de superar diversos desafios para eliminar as lacunas existentes entre a investigação e a aplicação. O objetivo deste estudo é propor estratégias, com base na identificação de barreiras e fatores facilitadores de um instituto de ciência e tecnologia (ICT) em saúde, para fomentar o processo de transformação do conhecimento científico, gerado nas pesquisas, em ações e produtos que contribuam para a melhoria da saúde da população. Os relatos das entrevistas, realizadas com 16 pesquisadores, permitiram a identificação de 10 categorias de barreiras, tendo destaque: "financiamento em ciência, tecnologia e informação (CT&I) limitado" e "apoio técnico insuficiente para a translação do conhecimento". "Infraestrutura e apoio institucional" foi a categoria de fatores facilitadores mais citada pelos participantes. Por fim, foi desenvolvido o artefato "estratégias e abordagens para superação de barreiras à implementação de resultados de pesquisa". Entre as estratégias, sugere-se a inclusão de uma disciplina de TC nos programas de pós-graduação stricto sensu e a criação de uma instância na estrutura organizacional do ICT voltada à prestação de suporte técnico e gerencial à aplicação de resultados de pesquisa.

Abstract: Knowledge translation (KT) aims at the practical use of scientific research results and at the monitoring of the benefits caused to the population's health. In health, the government and especially society expect that investments in research will produce results that go beyond the production and publication of knowledge, provoking outcomes such as public policies, systems, products, and technologies to benefit the health of the population. However, closing the gaps between research and application requires overcoming a number of challenges. This study aimed to propose strategies to foster the process of transforming the scientific knowledge generated in research into actions and products that contribute to improving the population's health based on the identification of barriers and facilitating factors of a health science and technology institute. The reports of interviews conducted with 16 researchers showed 10 categories of barriers, especially: "limited funding to the science and technology institute" and "insufficient technical support for knowledge translation". "Infrastructure and institutional support" was the facilitating factor category participants mentioned the most. Finally, we developed the artifact "strategies and approaches for overcoming barriers to implement research results". Among the strategies, we suggest the inclusion of a knowledge translation discipline in stricto sensu graduate programs and the creation of an instance in the organizational structure of the science and technology institute to technically and managerially support the application of research results.

Resumen: La traslación del conocimiento (TC) tiene como propósito el uso práctico de los resultados de investigaciones científicas y el seguimiento de los beneficios causados a la salud de la población. En el área de la salud, el gobierno y, sobre todo, la sociedad esperan que las inversiones en investigaciones obtengan resultados que vayan más allá de la producción y publicación de conocimiento, y provoquen resultados, como políticas públicas, sistemas, productos y tecnologías en beneficio de la salud de la población. Sin embargo, se observa aun la necesidad de superar diversos desafíos para eliminar las brechas entre la investigación y la aplicación. El objetivo de este estudio es proponer estrategias con base en la identificación de barreras y factores facilitadores de un instituto de ciencia y tecnología (ICT) en salud, para fomentar el proceso de transformación del conocimiento científico generado en las investigaciones en acciones y productos que contribuyan a mejorar la salud de la población. Los relatos de las entrevistas a 16 investigadores permitieron identificar 10 categorías de barreras, con énfasis en: "financiación en CT&I limitado" y "apoyo técnico insuficiente para la traslación del conocimiento". "Infraestructura y apoyo institucional" fue la categoría de factores facilitadores más citada por los participantes. Finalmente, se desarrolló el artefacto "estrategias y enfoques para la superación de barreras a la implementación de resultados de investigación". Entre las estrategias, se sugiere la inclusión de una asignatura de TC en los programas de posgrado stricto sensu y la creación de una instancia en la estructura organizacional del ICT orientada a brindar apoyo técnico y gerencial a la aplicación de los resultados de la investigación.

Remote Heart Rate Prediction in Virtual Reality Head-Mounted Displays Using Machine Learning Techniques.

Head-mounted displays are virtual reality devices that may be equipped with sensors and cameras to measure a patient's heart rate through facial regions. Heart rate is an essential body signal that can be used to remotely monitor users in a variety of situations. There is currently no study that predicts heart rate using only highlighted facial regions; thus, an adaptation is required for beats per minute predictions. Likewise, there are no datasets containing only the eye and lower face regions, necessitating the development of a simulation mechanism. This work aims to remotely estimate heart rate from facial regions that can be captured by the cameras of a head-mounted display using state-of-the-art EVM-CNN and Meta-rPPG techniques. We developed a region of interest extractor to simulate a dataset from a head-mounted display device using stabilizer and video magnification techniques. Then, we combined support vector machine and FaceMash to determine the regions of interest and adapted photoplethysmography and beats per minute signal predictions to work with the other techniques. We observed an improvement of 188.88% for the EVM and 55.93% for the Meta-rPPG. In addition, both models were able to predict heart rate using only facial regions as input. Moreover, the adapted technique Meta-rPPG outperformed the original work, whereas the EVM adaptation produced comparable results for the photoplethysmography signal.

The role of the neuronal microenvironment in sensory function and pain pathophysiology.

The high prevalence of pain and the at times low efficacy of current treatments represent a significant challenge to healthcare systems worldwide. Effective treatment strategies require consideration of the diverse pathophysiologies that underlie various pain conditions. Indeed, our understanding of the mechanisms contributing to aberrant sensory neuron function has advanced considerably. However, sensory neurons operate in a complex dynamic microenvironment that is controlled by multidirectional interactions of neurons with non-neuronal cells, including immune cells, neuronal accessory cells, fibroblasts, adipocytes, and keratinocytes. Each of these cells constitute and control the microenvironment in which neurons operate, inevitably influencing sensory function and the pathology of pain. This review highlights the importance of the neuronal microenvironment for sensory function and pain, focusing on cellular interactions in the skin, nerves, dorsal root ganglia, and spinal cord. We discuss the current understanding of the mechanisms by which neurons and non-neuronal cells communicate to promote or resolve pain, and how this knowledge could be used for the development of mechanism-based treatments.

Oncostatin M regulates hematopoietic stem cell (HSC) niches in the bone marrow to restrict HSC mobilization.

We show that pro-inflammatory oncostatin M (OSM) is an important regulator of hematopoietic stem cell (HSC) niches in the bone marrow (BM). Treatment of healthy humans and mice with granulocyte colony-stimulating factor (G-CSF) dramatically increases OSM release in blood and BM. Using mice null for the OSM receptor (OSMR) gene, we demonstrate that OSM provides a negative feed-back acting as a brake on HSPC mobilization in response to clinically relevant mobilizing molecules G-CSF and CXCR4 antagonist. Likewise, injection of a recombinant OSM molecular trap made of OSMR complex extracellular domains enhances HSC mobilization in poor mobilizing C57BL/6 and NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ mice. Mechanistically, OSM attenuates HSC chemotactic response to CXCL12 and increases HSC homing to the BM signaling indirectly via BM endothelial and mesenchymal cells which are the only cells expressing OSMR in the BM. OSM up-regulates E-selectin expression on BM endothelial cells indirectly increasing HSC proliferation. RNA sequencing of HSCs from Osmr-/- and wild-type mice suggest that HSCs have altered cytoskeleton reorganization, energy usage and cycling in the absence of OSM signaling in niches. Therefore OSM is an important regulator of HSC niche function restraining HSC mobilization and anti-OSM therapy combined with current mobilizing regimens may improve HSPC mobilization for transplantation.

Macrophages form erythropoietic niches and regulate iron homeostasis to adapt erythropoiesis in response to infections and inflammation.

It has recently emerged that tissue-resident macrophages are key regulators of several stem cell niches orchestrating tissue formation during development, as well as postnatally, when they also organize the repair and regeneration of many tissues including the hemopoietic tissue. The fact that macrophages are also master regulators and effectors of innate immunity and inflammation allows them to coordinate hematopoietic response to infections, injuries, and inflammation. After recently reviewing the roles of phagocytes and macrophages in regulating normal and pathologic hematopoietic stem cell niches, we now focus on the key roles of macrophages in regulating erythropoiesis and iron homeostasis. We review herein the recent advances in understanding how macrophages at the center of erythroblastic islands form an erythropoietic niche that controls the terminal differentiation and maturation of erythroblasts into reticulocytes; how red pulp macrophages in the spleen control iron recycling and homeostasis; how these macrophages coordinate emergency erythropoiesis in response to blood loss, infections, and inflammation; and how persistent infections or inflammation can lead to anemia of inflammation via macrophages. Finally, we discuss the technical challenges associated with the molecular characterization of erythroid island macrophages and red pulp macrophages.

Prostacyclin is an endosteal bone marrow niche component and its clinical analog iloprost protects hematopoietic stem cell potential during stress.

Hematopoietic stem cells (HSCs) with superior reconstitution potential are reported to be enriched in the endosteal compared to central bone marrow (BM) region. To investigate whether specific factors at the endosteum may contribute to HSC potency, we screened for candidate HSC niche factors enriched in the endosteal compared to central BM regions. Together with key known HSC supporting factors Kitl and Cxcl12, we report that prostacyclin/prostaglandin I2 (PGI2 ) synthase (Ptgis) was one of the most highly enriched mRNAs (>10-fold) in endosteal compared to central BM. As PGI2 signals through receptors distinct from prostaglandin E2 (PGE2 ), we investigated functional roles for PGI2 at the endosteal niche using therapeutic PGI2 analogs, iloprost, and cicaprost. We found PGI2 analogs strongly reduced HSC differentiation in vitro. Ex vivo iloprost pulse treatment also significantly boosted long-term competitive repopulation (LT-CR) potential of HSCs upon transplantation. This was associated with increased tyrosine-phosphorylation of transducer and activator of transcription-3 (STAT3) signaling in HSCs but not altered cell cycling. In vivo, iloprost administration protected BM HSC potential from radiation or granulocyte colony-stimulating factor-induced exhaustion, and restored HSC homing potential with increased Kitl and Cxcl12 transcription in the BM. In conclusion, we propose that PGI2 is a novel HSC regulator enriched in the endosteum that promotes HSC regenerative potential following stress.

Role of macrophages and phagocytes in orchestrating normal and pathologic hematopoietic niches.

The bone marrow (BM) contains a mosaic of niches specialized in supporting different maturity stages of hematopoietic stem and progenitor cells such as hematopoietic stem cells and myeloid, lymphoid, and erythroid progenitors. Recent advances in BM imaging and conditional gene knockout mice have revealed that niches are a complex network of cells of mesenchymal, endothelial, neuronal, and hematopoietic origins, together with local physicochemical parameters. Within these complex structures, phagocytes, such as neutrophils, macrophages, and dendritic cells, all of which are of hematopoietic origin, have been found to be important in regulating several niches in the BM, including hematopoietic stem cell niches, erythropoietic niches, and niches involved in endosteal bone formation. There is also increasing evidence that these macrophages have an important role in adapting hematopoiesis, erythropoiesis, and bone formation in response to inflammatory stressors and play a key part in maintaining the integrity and function of these. Likewise, there is also accumulating evidence that subsets of monocytes, macrophages, and other phagocytes contribute to the progression and response to treatment of several lymphoid malignancies such as multiple myeloma, Hodgkin lymphoma, and non-Hodgkin lymphoma, as well as lymphoblastic leukemia, and may also play a role in myelodysplastic syndrome and myeloproliferative neoplasms associated with Noonan syndrome and aplastic anemia. In this review, the potential functions of macrophages and other phagocytes in normal and pathologic niches are discussed, as are the challenges in studying BM and other tissue-resident macrophages at the molecular level.

Adhesion to E-selectin primes macrophages for activation through AKT and mTOR.

The endothelial adhesion protein E-selectin/CD62E is not required for leukocyte homing, unlike closely related family member P-selectin/CD62P. As transmigration through the endothelium is one of the first steps in generating a local immune response, we hypothesized that E-selectin may play additional roles in the early stages of immune activation. We found contact with E-selectin, but not P-selectin or vascular cell adhesion molecule 1 (CD106), induced phosphorylation of protein kinase B (AKT) and nuclear factor-κB in mouse bone marrow-derived macrophages (BMDMs) in vitro. This occurred within 15 min of E-selectin contact and was dependent on phosphatidylinositol-3 kinase activity. Binding to E-selectin activated downstream proteins including mammalian target of rapamycin, p70 ribosomal protein S6 kinase and eukaryotic translation initiation factor 4E-binding protein 1. Functionally, adhesion to E-selectin induced upregulation of CD86 expression and CCL2 secretion. We next asked whether contact with E-selectin impacts further BMDM stimulation. We found enhanced secretion of both interleukin (IL)-10 and CCL2, but not tumor necrosis factor or IL-6 in response to lipopolysaccharide (LPS) stimulation after adhesion to E-selectin. Importantly, adhesion to E-selectin did not polarize BMDMs to one type of response but enhanced both arginase activity and nitric oxide production following IL-4 or LPS stimulation, respectively. In cultured human monocytes, adhesion to E-selectin similarly induced phosphorylation of AKT. Finally, when E-selectin was blocked in vivo in mice, thioglycollate-elicited macrophages showed reduced CD86 expression, validating our in vitro studies. Our results imply functions for E-selectin beyond homing and suggest that E-selectin plays an early role in priming and amplifying innate immune responses.

Bacterial Lipopolysaccharides Suppress Erythroblastic Islands and Erythropoiesis in the Bone Marrow in an Extrinsic and G- CSF-, IL-1-, and TNF-Independent Manner.

Anemia of inflammation (AI) is the second most prevalent anemia after iron deficiency anemia and results in persistent low blood erythrocytes and hemoglobin, fatigue, weakness, and early death. Anemia of inflammation is common in people with chronic inflammation, chronic infections, or sepsis. Although several studies have reported the effect of inflammation on stress erythropoiesis and iron homeostasis, the mechanisms by which inflammation suppresses erythropoiesis in the bone marrow (BM), where differentiation and maturation of erythroid cells from hematopoietic stem cells (HSCs) occurs, have not been extensively studied. Here we show that in a mouse model of acute sepsis, bacterial lipopolysaccharides (LPS) suppress medullary erythroblastic islands (EBIs) and erythropoiesis in a TLR-4- and MyD88-dependent manner with concomitant mobilization of HSCs. LPS suppressive effect on erythropoiesis is indirect as erythroid progenitors and erythroblasts do not express TLR-4 whereas EBI macrophages do. Using cytokine receptor gene knock-out mice LPS-induced mobilization of HSCs is G-CSF-dependent whereas LPS-induced suppression of medullary erythropoiesis does not require G- CSF-, IL- 1-, or TNF-mediated signaling. Therefore suppression of medullary erythropoiesis and mobilization of HSCs in response to LPS are mechanistically distinct. Our findings also suggest that EBI macrophages in the BM may sense innate immune stimuli in response to acute inflammation or infections to rapidly convert to a pro-inflammatory function at the expense of their erythropoietic function.

Acute Myeloid Leukemia Chemo-Resistance Is Mediated by E-selectin Receptor CD162 in Bone Marrow Niches.

The interactions of leukemia cells with the bone marrow (BM) microenvironment is critical for disease progression and resistance to treatment. We have recently found that the vascular adhesion molecule E-(endothelial)-selectin is a key niche component that directly mediates acute myeloid leukemia (AML) chemo-resistance, revealing E-selectin as a promising therapeutic target. To understand how E-selectin promotes AML survival, we investigated the potential receptors on AML cells involved in E-selectin-mediated chemo-resistance. Using CRISPR-Cas9 gene editing to selectively suppress canonical E-selectin receptors CD44 or P-selectin glycoprotein ligand-1 (PSGL-1/CD162) from human AML cell line KG1a, we show that CD162, but not CD44, is necessary for E-selectin-mediated chemo-resistance in vitro. Using preclinical models of murine AML, we then demonstrate that absence of CD162 on AML cell surface leads to a significant delay in the onset of leukemia and a significant increase in sensitivity to chemotherapy in vivo associated with a more rapid in vivo proliferation compared to wild-type AML and a lower BM retention. Together, these data reveal for the first time that CD162 is a key AML cell surface receptor involved in AML progression, BM retention and chemo-resistance. These findings highlight specific blockade of AML cell surface CD162 as a potential novel niche-based strategy to improve the efficacy of AML therapy.

Endothelial E-selectin inhibition improves acute myeloid leukaemia therapy by disrupting vascular niche-mediated chemoresistance.

The endothelial cell adhesion molecule E-selectin is a key component of the bone marrow hematopoietic stem cell (HSC) vascular niche regulating balance between HSC self-renewal and commitment. We now report in contrast, E-selectin directly triggers signaling pathways that promote malignant cell survival and regeneration. Using acute myeloid leukemia (AML) mouse models, we show AML blasts release inflammatory mediators that upregulate endothelial niche E-selectin expression. Alterations in cell-surface glycosylation associated with oncogenesis enhances AML blast binding to E-selectin and enable promotion of pro-survival signaling through AKT/NF-κB pathways. In vivo AML blasts with highest E-selectin binding potential are 12-fold more likely to survive chemotherapy and main contributors to disease relapse. Absence (in Sele-/- hosts) or therapeutic blockade of E-selectin using small molecule mimetic GMI-1271/Uproleselan effectively inhibits this niche-mediated pro-survival signaling, dampens AML blast regeneration, and strongly synergizes with chemotherapy, doubling the duration of mouse survival over chemotherapy alone, whilst protecting endogenous HSC.

Imaging flow cytometry reveals that granulocyte colony-stimulating factor treatment causes loss of erythroblastic islands in the mouse bone marrow.

The erythroblastic island (EBI) is a multicellular structure forming an erythropoietic niche consisting of a central macrophage surrounded by a rosette of maturing erythroblasts. Since their discovery more than 60 years ago, simultaneous quantification and visualization of EBIs remain difficult. Although flow cytometry enables high-throughput quantification of cell aggregates co-expressing macrophage and erythroblast markers, it cannot visually confirm whether the aggregates are genuine EBIs. While immunofluorescence microscopy allows visualization of EBIs, its low throughput limits its use for quantification. In the current study we employed nine-channel imaging flow cytometry (IFC) to develop a method to directly visualize and quantify EBIs in the mouse bone marrow. We found that EBI central macrophages do express F4/80, VCAM-1, and CD169, but not CD11b or Ly6G, and that CD11b+Ly6G+F4/80- granulocytes are found associated at the periphery of 40%-60% EBIs. Furthermore, we show for the first time using IFC that in vivo treatment with the hematopoietic stem cell-mobilizing cytokine granulocyte colony-stimulating factor (G-CSF) reduced EBI frequency in the bone marrow by more than 100-fold. These results indicate that mobilizing doses of G-CSF cause a collapse of EBIs in the bone marrow.