RESUMEN
Atrial fibrillation (AFib) and the risk of its lethal complications are propelled by fibrosis, which induces electrical heterogeneity and gives rise to reentry circuits. Atrial TREM2+ macrophages secrete osteopontin (encoded by Spp1), a matricellular signaling protein that engenders fibrosis and AFib. Here we show that silencing Spp1 in TREM2+ cardiac macrophages with an antibody-siRNA conjugate reduces atrial fibrosis and suppresses AFib in mice, thus offering a new immunotherapy for the most common arrhythmia.
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Atrial fibrillation disrupts contraction of the atria, leading to stroke and heart failure. We deciphered how immune and stromal cells contribute to atrial fibrillation. Single-cell transcriptomes from human atria documented inflammatory monocyte and SPP1+ macrophage expansion in atrial fibrillation. Combining hypertension, obesity, and mitral valve regurgitation (HOMER) in mice elicited enlarged, fibrosed, and fibrillation-prone atria. Single-cell transcriptomes from HOMER mouse atria recapitulated cell composition and transcriptome changes observed in patients. Inhibiting monocyte migration reduced arrhythmia in Ccr2-∕- HOMER mice. Cell-cell interaction analysis identified SPP1 as a pleiotropic signal that promotes atrial fibrillation through cross-talk with local immune and stromal cells. Deleting Spp1 reduced atrial fibrillation in HOMER mice. These results identify SPP1+ macrophages as targets for immunotherapy in atrial fibrillation.
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Fibrilación Atrial , Macrófagos , Osteopontina , Animales , Humanos , Ratones , Fibrilación Atrial/genética , Fibrilación Atrial/inmunología , Atrios Cardíacos , Macrófagos/inmunología , Insuficiencia de la Válvula Mitral/genética , Osteopontina/genética , Eliminación de Gen , Movimiento Celular , Análisis de Expresión Génica de una Sola CélulaRESUMEN
After myocardial infarction (MI), emergency hematopoiesis produces inflammatory myeloid cells that accelerate atherosclerosis and promote heart failure. Since the balance between glycolysis and mitochondrial metabolism regulates hematopoietic stem cell homeostasis, metabolic cues may influence emergency myelopoiesis. Here, we show in humans and female mice that hematopoietic progenitor cells increase fatty acid metabolism after MI. Blockade of fatty acid oxidation by deleting carnitine palmitoyltransferase (Cpt1A) in hematopoietic cells of Vav1Cre/+Cpt1Afl/fl mice limited hematopoietic progenitor proliferation and myeloid cell expansion after MI. We also observed reduced bone marrow adiposity in humans, pigs and mice following MI. Inhibiting lipolysis in adipocytes using AdipoqCreERT2Atglfl/fl mice or local depletion of bone marrow adipocytes in AdipoqCreERT2iDTR mice also curbed emergency hematopoiesis. Furthermore, systemic and regional sympathectomy prevented bone marrow adipocyte shrinkage after MI. These data establish a critical role for fatty acid metabolism in post-MI emergency hematopoiesis.
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Sudden cardiac death, arising from abnormal electrical conduction, occurs frequently in patients with coronary heart disease. Myocardial ischemia simultaneously induces arrhythmia and massive myocardial leukocyte changes. In this study, we optimized a mouse model in which hypokalemia combined with myocardial infarction triggered spontaneous ventricular tachycardia in ambulatory mice, and we showed that major leukocyte subsets have opposing effects on cardiac conduction. Neutrophils increased ventricular tachycardia via lipocalin-2 in mice, whereas neutrophilia associated with ventricular tachycardia in patients. In contrast, macrophages protected against arrhythmia. Depleting recruited macrophages in Ccr2 -/- mice or all macrophage subsets with Csf1 receptor inhibition increased both ventricular tachycardia and fibrillation. Higher arrhythmia burden and mortality in Cd36 -/- and Mertk -/- mice, viewed together with reduced mitochondrial integrity and accelerated cardiomyocyte death in the absence of macrophages, indicated that receptor-mediated phagocytosis protects against lethal electrical storm. Thus, modulation of leukocyte function provides a potential therapeutic pathway for reducing the risk of sudden cardiac death.
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Obesity is an important risk factor for atrial fibrillation (AF), but a better mechanistic understanding of obesity-related atrial fibrillation is required. Serum glucocorticoid kinase 1 (SGK1) is a kinase positioned within multiple obesity-related pathways, and prior work has shown a pathologic role of SGK1 signaling in ventricular arrhythmias. We validated a mouse model of obesity-related AF using wild-type mice fed a high-fat diet. RNA sequencing of atrial tissue demonstrated substantial differences in gene expression, with enrichment of multiple SGK1-related pathways, and we showed upregulated of SGK1 transcription, activation, and signaling in obese atria. Mice expressing a cardiac specific dominant-negative SGK1 were protected from obesity-related AF, through effects on atrial electrophysiology, action potential characteristics, structural remodeling, inflammation, and sodium current. Overall, this study demonstrates the promise of targeting SGK1 in a mouse model of obesity-related AF.
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Fibrilación Atrial , Proteínas Serina-Treonina Quinasas , Animales , Ratones , Fibrilación Atrial/genética , Fibrilación Atrial/prevención & control , Modelos Animales de Enfermedad , Glucocorticoides/metabolismo , Atrios Cardíacos/patología , Obesidad/complicaciones , Obesidad/genética , Obesidad/metabolismo , Sodio/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismoRESUMEN
Abnormal hematopoiesis advances cardiovascular disease by generating excess inflammatory leukocytes that attack the arteries and the heart. The bone marrow niche regulates hematopoietic stem cell proliferation and hence the systemic leukocyte pool, but whether cardiovascular disease affects the hematopoietic organ's microvasculature is unknown. Here we show that hypertension, atherosclerosis and myocardial infarction (MI) instigate endothelial dysfunction, leakage, vascular fibrosis and angiogenesis in the bone marrow, altogether leading to overproduction of inflammatory myeloid cells and systemic leukocytosis. Limiting angiogenesis with endothelial deletion of Vegfr2 (encoding vascular endothelial growth factor (VEGF) receptor 2) curbed emergency hematopoiesis after MI. We noted that bone marrow endothelial cells assumed inflammatory transcriptional phenotypes in all examined stages of cardiovascular disease. Endothelial deletion of Il6 or Vcan (encoding versican), genes shown to be highly expressed in mice with atherosclerosis or MI, reduced hematopoiesis and systemic myeloid cell numbers in these conditions. Our findings establish that cardiovascular disease remodels the vascular bone marrow niche, stimulating hematopoiesis and production of inflammatory leukocytes.
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Interactions between the immune and central nervous systems strongly influence brain health. Although the blood-brain barrier restricts this crosstalk, we now know that meningeal gateways through brain border tissues facilitate intersystem communication. Cerebrospinal fluid (CSF), which interfaces with the glymphatic system and thereby drains the brain's interstitial and perivascular spaces, facilitates outward signaling beyond the blood-brain barrier. In the present study, we report that CSF can exit into the skull bone marrow. Fluorescent tracers injected into the cisterna magna of mice migrate along perivascular spaces of dural blood vessels and then travel through hundreds of sub-millimeter skull channels into the calvarial marrow. During meningitis, bacteria hijack this route to invade the skull's hematopoietic niches and initiate cranial hematopoiesis ahead of remote tibial sites. As skull channels also directly provide leukocytes to meninges, the privileged sampling of brain-derived danger signals in CSF by regional marrow may have broad implications for inflammatory neurological disorders.
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Sistema Glinfático , Meningitis Bacterianas , Animales , Médula Ósea , Encéfalo/irrigación sanguínea , Líquido Cefalorraquídeo , Sistema Glinfático/fisiología , Hematopoyesis , Ratones , CráneoRESUMEN
Autonomic nerves control organ function through the sympathetic and parasympathetic branches, which have opposite effects. In the bone marrow, sympathetic (adrenergic) nerves promote hematopoiesis; however, how parasympathetic (cholinergic) signals modulate hematopoiesis is unclear. Here, we show that B lymphocytes are an important source of acetylcholine, a neurotransmitter of the parasympathetic nervous system, which reduced hematopoiesis. Single-cell RNA sequencing identified nine clusters of cells that expressed the cholinergic α7 nicotinic receptor (Chrna7) in the bone marrow stem cell niche, including endothelial and mesenchymal stromal cells (MSCs). Deletion of B cell-derived acetylcholine resulted in the differential expression of various genes, including Cxcl12 in leptin receptor+ (LepR+) stromal cells. Pharmacologic inhibition of acetylcholine signaling increased the systemic supply of inflammatory myeloid cells in mice and humans with cardiovascular disease.
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Acetilcolina , Hematopoyesis , Animales , Linfocitos B , Colinérgicos , Hematopoyesis/genética , Ratones , Nicho de Células MadreRESUMEN
Clonal hematopoiesis, a condition in which individual hematopoietic stem cell clones generate a disproportionate fraction of blood leukocytes, correlates with higher risk for cardiovascular disease. The mechanisms behind this association are incompletely understood. Here, we show that hematopoietic stem cell division rates are increased in mice and humans with atherosclerosis. Mathematical analysis demonstrates that increased stem cell proliferation expedites somatic evolution and expansion of clones with driver mutations. The experimentally determined division rate elevation in atherosclerosis patients is sufficient to produce a 3.5-fold increased risk of clonal hematopoiesis by age 70. We confirm the accuracy of our theoretical framework in mouse models of atherosclerosis and sleep fragmentation by showing that expansion of competitively transplanted Tet2-/- cells is accelerated under conditions of chronically elevated hematopoietic activity. Hence, increased hematopoietic stem cell proliferation is an important factor contributing to the association between cardiovascular disease and clonal hematopoiesis.
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Aterosclerosis/patología , Hematopoyesis Clonal , Células Madre Hematopoyéticas/patología , Envejecimiento/patología , Animales , Apolipoproteínas E/genética , Aterosclerosis/genética , Médula Ósea/metabolismo , Proliferación Celular , Evolución Clonal , Modelos Animales de Enfermedad , Femenino , Humanos , Ratones , Ratones Endogámicos C57BL , Modelos Biológicos , Privación de Sueño/patologíaRESUMEN
BACKGROUND: Ibrutinib is a Bruton tyrosine kinase inhibitor with remarkable efficacy against B-cell cancers. Ibrutinib also increases the risk of atrial fibrillation (AF), which remains poorly understood. METHODS: We performed electrophysiology studies on mice treated with ibrutinib to assess inducibility of AF. Chemoproteomic analysis of cardiac lysates identified candidate ibrutinib targets, which were further evaluated in genetic mouse models and additional pharmacological experiments. The pharmacovigilance database, VigiBase, was queried to determine whether drug inhibition of an identified candidate kinase was associated with increased reporting of AF. RESULTS: We demonstrate that treatment of mice with ibrutinib for 4 weeks results in inducible AF, left atrial enlargement, myocardial fibrosis, and inflammation. This effect was reproduced in mice lacking Bruton tyrosine kinase, but not in mice treated with 4 weeks of acalabrutinib, a more specific Bruton tyrosine kinase inhibitor, demonstrating that AF is an off-target side effect. Chemoproteomic profiling identified a short list of candidate kinases that was narrowed by additional experimentation leaving CSK (C-terminal Src kinase) as the strongest candidate for ibrutinib-induced AF. Cardiac-specific Csk knockout in mice led to increased AF, left atrial enlargement, fibrosis, and inflammation, phenocopying ibrutinib treatment. Disproportionality analyses in VigiBase confirmed increased reporting of AF associated with kinase inhibitors blocking Csk versus non-Csk inhibitors, with a reporting odds ratio of 8.0 (95% CI, 7.3-8.7; P<0.0001). CONCLUSIONS: These data identify Csk inhibition as the mechanism through which ibrutinib leads to AF. Registration: URL: https://ww.clinicaltrials.gov; Unique identifier: NCT03530215.
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Adenina/análogos & derivados , Antineoplásicos/toxicidad , Fibrilación Atrial/inducido químicamente , Función del Atrio Izquierdo/efectos de los fármacos , Proteína Tirosina Quinasa CSK/antagonistas & inhibidores , Atrios Cardíacos/efectos de los fármacos , Frecuencia Cardíaca/efectos de los fármacos , Piperidinas/toxicidad , Inhibidores de Proteínas Quinasas/toxicidad , Potenciales de Acción/efectos de los fármacos , Adenina/toxicidad , Agammaglobulinemia Tirosina Quinasa/deficiencia , Agammaglobulinemia Tirosina Quinasa/genética , Animales , Fibrilación Atrial/enzimología , Fibrilación Atrial/fisiopatología , Proteína Tirosina Quinasa CSK/genética , Proteína Tirosina Quinasa CSK/metabolismo , Bases de Datos Genéticas , Atrios Cardíacos/enzimología , Atrios Cardíacos/fisiopatología , Humanos , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Ratones Noqueados , Medición de Riesgo , Factores de RiesgoRESUMEN
Bone-marrow endothelial cells in the haematopoietic stem-cell niche form a network of blood vessels that regulates blood-cell traffic as well as the maintenance and function of haematopoietic stem and progenitor cells. Here, we report the design and in vivo performance of systemically injected lipid-polymer nanoparticles encapsulating small interfering RNA (siRNA), for the silencing of genes in bone-marrow endothelial cells. In mice, nanoparticles encapsulating siRNA sequences targeting the proteins stromal-derived factor 1 (Sdf1) or monocyte chemotactic protein 1 (Mcp1) enhanced (when silencing Sdf1) or inhibited (when silencing Mcp1) the release of stem and progenitor cells and of leukocytes from the bone marrow. In a mouse model of myocardial infarction, nanoparticle-mediated inhibition of cell release from the haematopoietic niche via Mcp1 silencing reduced leukocytes in the diseased heart, improved healing after infarction and attenuated heart failure. Nanoparticle-mediated RNA interference in the haematopoietic niche could be used to investigate haematopoietic processes for therapeutic applications in cancer, infection and cardiovascular disease.
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Sistemas de Liberación de Medicamentos/métodos , Silenciador del Gen/efectos de los fármacos , Células Madre Hematopoyéticas/efectos de los fármacos , Nanopartículas/administración & dosificación , Nanopartículas/química , ARN Interferente Pequeño/administración & dosificación , ARN Interferente Pequeño/química , Nicho de Células Madre/genética , Animales , Células de la Médula Ósea/efectos de los fármacos , Células de la Médula Ósea/metabolismo , Células Cultivadas , Modelos Animales de Enfermedad , Células Endoteliales/efectos de los fármacos , Células Endoteliales/metabolismo , Células Madre Hematopoyéticas/metabolismo , Ratones Endogámicos C57BL , Infarto del Miocardio/prevención & controlRESUMEN
BACKGROUND: Diabetes mellitus is a prevalent public health problem that affects about one-third of the US population and leads to serious vascular complications with increased risk for coronary artery disease. How bone marrow hematopoiesis contributes to diabetes mellitus complications is incompletely understood. We investigated the role of bone marrow endothelial cells in diabetic regulation of inflammatory myeloid cell production. METHODS: In 3 types of mouse diabetes mellitus, including streptozotocin, high-fat diet, and genetic induction using leptin-receptor-deficient db/db mice, we assayed leukocytes, hematopoietic stem and progenitor cells (HSPC). In addition, we investigated bone marrow endothelial cells with flow cytometry and expression profiling. RESULTS: In diabetes mellitus, we observed enhanced proliferation of HSPC leading to augmented circulating myeloid cell numbers. Analysis of bone marrow niche cells revealed that endothelial cells in diabetic mice expressed less Cxcl12, a retention factor promoting HSPC quiescence. Transcriptome-wide analysis of bone marrow endothelial cells demonstrated enrichment of genes involved in epithelial growth factor receptor (Egfr) signaling in mice with diet-induced diabetes mellitus. To explore whether endothelial Egfr plays a functional role in myelopoiesis, we generated mice with endothelial-specific deletion of Egfr (Cdh5CreEgfrfl/fl). We found enhanced HSPC proliferation and increased myeloid cell production in Cdh5CreEgfrfl/fl mice compared with wild-type mice with diabetes mellitus. Disrupted Egfr signaling in endothelial cells decreased their expression of the HSPC retention factor angiopoietin-1. We tested the functional relevance of these findings for wound healing and atherosclerosis, both implicated in complications of diabetes mellitus. Inflammatory myeloid cells accumulated more in skin wounds of diabetic Cdh5CreEgfrfl/fl mice, significantly delaying wound closure. Atherosclerosis was accelerated in Cdh5CreEgfrfl/fl mice, leading to larger and more inflamed atherosclerotic lesions in the aorta. CONCLUSIONS: In diabetes mellitus, bone marrow endothelial cells participate in the dysregulation of bone marrow hematopoiesis. Diabetes mellitus reduces endothelial production of Cxcl12, a quiescence-promoting niche factor that reduces stem cell proliferation. We describe a previously unknown counterregulatory pathway, in which protective endothelial Egfr signaling curbs HSPC proliferation and myeloid cell production.
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Células de la Médula Ósea/metabolismo , Células Endoteliales/metabolismo , Mielopoyesis , Animales , Diabetes Mellitus Experimental , Modelos Animales de Enfermedad , Factor de Crecimiento Epidérmico/metabolismo , Receptores ErbB/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Masculino , Ratones , Modelos Biológicos , Células Mieloides/metabolismo , Mielopoyesis/genética , Transducción de Señal , TranscriptomaRESUMEN
Unhealthy diet, lack of exercise, psychosocial stress, and insufficient sleep are increasingly prevalent modifiable risk factors for cardiovascular disease. Accumulating evidence indicates that these risk factors may fuel chronic inflammatory processes that are active in atherosclerosis and lead to myocardial infarction and stroke. In concert with hyperlipidemia, maladaptive immune system activities can contribute to disease progression and increase the probability of adverse events. In this review, we discuss recent insight into how the above modifiable risk factors influence innate immunity. Specifically, we focus on pathways that raise systemic myeloid cell numbers and modulate immune cell phenotypes, reviewing hematopoiesis, leukocyte trafficking, and innate immune cell accumulation in cardiovascular organs. Often, relevant mechanisms that begin with lifestyle choices and lead to cardiovascular events span multiple organ systems, including the central nervous, endocrine, metabolic, hematopoietic, immune and, finally, the cardiovascular system. We argue that deciphering such pathways provides not only support for preventive interventions but also opportunities to develop biomimetic immunomodulatory therapeutics that mitigate cardiovascular inflammation.
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Enfermedades Cardiovasculares/prevención & control , Estilo de Vida Saludable , Factores de Riesgo de Enfermedad Cardiaca , Hematopoyesis , Inmunidad Innata , Células Mieloides/inmunología , Conducta de Reducción del Riesgo , Animales , Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/inmunología , Enfermedades Cardiovasculares/metabolismo , Dieta Saludable , Ejercicio Físico , Humanos , Células Mieloides/metabolismo , Factores Protectores , Medición de Riesgo , Transducción de Señal , SueñoRESUMEN
BACKGROUND: Recurrent myocardial infarction (MI) is common in patients with coronary artery disease and is associated with high mortality. Long-term reprogramming of myeloid progenitors occurs in response to inflammatory stimuli and alters the organism's response to secondary inflammatory challenges. OBJECTIVES: This study examined the effect of recurrent MI on bone marrow response and cardiac inflammation. METHODS: The investigators developed a surgical mouse model in which 2 subsequent MIs affected different left ventricular regions in the same mouse. Recurrent MI was induced by ligating the left circumflex artery followed by the left anterior descending coronary artery branch. The study characterized the resulting ischemia by whole-heart fluorescent coronary angiography after optical organ clearing and by cardiac magnetic resonance imaging. RESULTS: A first MI-induced bone marrow "memory" via a circulating signal, reducing hematopoietic maintenance factor expression in bone marrow macrophages. This dampened the organism's reaction to subsequent events. Despite a similar extent of injury according to troponin levels, recurrent MI caused reduced emergency hematopoiesis and less leukocytosis than a first MI. Consequently, fewer leukocytes migrated to the ischemic myocardium. The hematopoietic response to lipopolysaccharide was also mitigated after a previous MI. The increase of white blood count in 28 patients was lower after recurrent MI compared with their first MI. CONCLUSIONS: The data suggested that hematopoietic and innate immune responses are shaped by a preceding MI.
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Infarto de la Pared Anterior del Miocardio/inmunología , Modelos Animales de Enfermedad , Hematopoyesis , Anciano , Anciano de 80 o más Años , Animales , Infarto de la Pared Anterior del Miocardio/sangre , Femenino , Humanos , Leucocitosis , Macrófagos/fisiología , Masculino , Ratones , Persona de Mediana Edad , Parabiosis , Recurrencia , Estudios RetrospectivosRESUMEN
A sedentary lifestyle, chronic inflammation and leukocytosis increase atherosclerosis; however, it remains unclear whether regular physical activity influences leukocyte production. Here we show that voluntary running decreases hematopoietic activity in mice. Exercise protects mice and humans with atherosclerosis from chronic leukocytosis but does not compromise emergency hematopoiesis in mice. Mechanistically, exercise diminishes leptin production in adipose tissue, augmenting quiescence-promoting hematopoietic niche factors in leptin-receptor-positive stromal bone marrow cells. Induced deletion of the leptin receptor in Prrx1-creERT2; Leprfl/fl mice reveals that leptin's effect on bone marrow niche cells regulates hematopoietic stem and progenitor cell (HSPC) proliferation and leukocyte production, as well as cardiovascular inflammation and outcomes. Whereas running wheel withdrawal quickly reverses leptin levels, the impact of exercise on leukocyte production and on the HSPC epigenome and transcriptome persists for several weeks. Together, these data show that physical activity alters HSPCs via modulation of their niche, reducing hematopoietic output of inflammatory leukocytes.
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Aterosclerosis/terapia , Enfermedades Cardiovasculares/terapia , Células Madre Hematopoyéticas/metabolismo , Inflamación/terapia , Condicionamiento Físico Animal , Tejido Adiposo/metabolismo , Animales , Aterosclerosis/prevención & control , Enfermedades Cardiovasculares/genética , Enfermedades Cardiovasculares/fisiopatología , Enfermedades Cardiovasculares/prevención & control , Epigenoma/genética , Ejercicio Físico/fisiología , Hematopoyesis/genética , Hematopoyesis/fisiología , Proteínas de Homeodominio/genética , Humanos , Inflamación/fisiopatología , Leucocitos/metabolismo , Leucocitosis/fisiopatología , Leucocitosis/terapia , Ratones , Receptores de Leptina/genética , Conducta Sedentaria , Transcriptoma/genéticaRESUMEN
Myocardial infarction, stroke, and sepsis trigger systemic inflammation and organism-wide complications that are difficult to manage. Here, we examined the contribution of macrophages residing in vital organs to the systemic response after these injuries. We generated a comprehensive catalog of changes in macrophage number, origin, and gene expression in the heart, brain, liver, kidney, and lung of mice with myocardial infarction, stroke, or sepsis. Predominantly fueled by heightened local proliferation, tissue macrophage numbers increased systemically. Macrophages in the same organ responded similarly to different injuries by altering expression of tissue-specific gene sets. Preceding myocardial infarction improved survival of subsequent pneumonia due to enhanced bacterial clearance, which was caused by IFNÉ£ priming of alveolar macrophages. Conversely, EGF receptor signaling in macrophages exacerbated inflammatory lung injury. Our data suggest that local injury activates macrophages in remote organs and that targeting macrophages could improve resilience against systemic complications following myocardial infarction, stroke, and sepsis.
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Susceptibilidad a Enfermedades , Macrófagos/inmunología , Macrófagos/metabolismo , Animales , Biomarcadores , Recuento de Células , Susceptibilidad a Enfermedades/inmunología , Receptores ErbB/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Redes Reguladoras de Genes , Isquemia/etiología , Isquemia/metabolismo , Macrófagos Alveolares/inmunología , Macrófagos Alveolares/metabolismo , Ratones , Células Musculares/inmunología , Células Musculares/metabolismo , Infarto del Miocardio/etiología , Infarto del Miocardio/metabolismo , Especificidad de Órganos/genética , Especificidad de Órganos/inmunología , Neumonía/etiología , Neumonía/metabolismo , Neumonía/patologíaRESUMEN
The role of nonclassical monocytes (NCMs) in health and disease is emerging, but their location and function within tissues remain poorly explored. Imaging of NCMs has been limited by the lack of an established single NCM marker. Here, we characterize the immune checkpoint molecule PD-L1 (CD274) as an unequivocal marker for tracking NCMs in circulation and pinpoint their compartmentalized distribution in tissues by two-photon microscopy. Visualization of PD-L1+ NCMs in relation to bone marrow vasculature reveals that conversion of classical monocytes into NCMs requires contact with endosteal vessels. Furthermore, PD-L1+ NCMs are present in tertiary lymphoid organs (TLOs) under inflammatory conditions in both mice and humans, and NCMs exhibit a PD-L1-dependent immunomodulatory function that promotes T cell apoptosis within TLOs. Our findings establish an unambiguous tool for the investigation of NCMs and shed light on their origin and function.
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Antígeno B7-H1/inmunología , Monocitos/inmunología , Músculos Abdominales/inmunología , Animales , Anticuerpos/farmacología , Médula Ósea/inmunología , Femenino , Fémur , Inmunoglobulina G/inmunología , Masculino , Ratones Endogámicos C57BL , Ratones Transgénicos , Linfocitos T/inmunologíaRESUMEN
RATIONALE: After a stroke, patients frequently experience altered systemic immunity resulting in peripheral immunosuppression and higher susceptibility to infections, which is at least partly attributed to lymphopenia. The mechanisms that profoundly change the systemic leukocyte repertoire after stroke are incompletely understood. Emerging evidence indicates that stroke alters hematopoietic output of the bone marrow. OBJECTIVE: To explore the mechanisms that lead to defects of B lymphopoiesis after ischemic stroke. METHODS AND RESULTS: We here report that ischemic stroke triggers brain-bone marrow communication via hormonal long-range signals that regulate hematopoietic B lineage decisions. Bone marrow fluorescence-activated cell sorter analyses and serial intravital microscopy indicate that transient middle cerebral artery occlusion in mice arrests B-cell development beginning at the pro-B-cell stage. This phenotype was not rescued in Myd88-/- and TLR4-/- mice with disrupted TLR (Toll-like receptor) signaling or after blockage of peripheral sympathetic nerves. Mechanistically, we identified stroke-induced glucocorticoid release as the main instigator of B lymphopoiesis defects. B-cell lineage-specific deletion of the GR (glucocorticoid receptor) in CD19-Cre loxP Nr3c1 mice attenuated lymphocytopenia after transient middle cerebral artery. In 20 patients with acute stroke, increased cortisol levels inversely correlated with blood lymphocyte numbers. CONCLUSIONS: Our data demonstrate that the hypothalamic-pituitary-adrenal axis mediates B lymphopoiesis defects after ischemic stroke.