RESUMEN
Haematopoietic stem cells (HSCs) home to the bone marrow via, in part, interactions with vascular cell adhesion molecule-1 (VCAM1)1-3. Once in the bone marrow, HSCs are vetted by perivascular phagocytes to ensure their self-integrity. Here we show that VCAM1 is also expressed on healthy HSCs and upregulated on leukaemic stem cells (LSCs), where it serves as a quality-control checkpoint for entry into bone marrow by providing 'don't-eat-me' stamping in the context of major histocompatibility complex class-I (MHC-I) presentation. Although haplotype-mismatched HSCs can engraft, Vcam1 deletion, in the setting of haplotype mismatch, leads to impaired haematopoietic recovery due to HSC clearance by mononuclear phagocytes. Mechanistically, VCAM1 'don't-eat-me' activity is regulated by ß2-microglobulin MHC presentation on HSCs and paired Ig-like receptor-B (PIR-B) on phagocytes. VCAM1 is also used by cancer cells to escape immune detection as its expression is upregulated in multiple cancers, including acute myeloid leukaemia (AML), where high expression associates with poor prognosis. In AML, VCAM1 promotes disease progression, whereas VCAM1 inhibition or deletion reduces leukaemia burden and extends survival. These results suggest that VCAM1 engagement regulates a critical immune-checkpoint gate in the bone marrow, and offers an alternative strategy to eliminate cancer cells via modulation of the innate immune tolerance.
Asunto(s)
Leucemia Mieloide Aguda , Molécula 1 de Adhesión Celular Vascular , Médula Ósea , Células Madre Hematopoyéticas/metabolismo , Humanos , Tolerancia Inmunológica , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Células Madre Neoplásicas , Molécula 1 de Adhesión Celular Vascular/genética , Molécula 1 de Adhesión Celular Vascular/metabolismoRESUMEN
Haematopoietic stem cells (HSCs) tightly regulate their quiescence, proliferation, and differentiation to generate blood cells during the entire lifetime. The mechanisms by which these critical activities are balanced are still unclear. Here, we report that Macrophage-Erythroblast Attacher (MAEA, also known as EMP), a receptor thus far only identified in erythroblastic island, is a membrane-associated E3 ubiquitin ligase subunit essential for HSC maintenance and lymphoid potential. Maea is highly expressed in HSCs and its deletion in mice severely impairs HSC quiescence and leads to a lethal myeloproliferative syndrome. Mechanistically, we have found that the surface expression of several haematopoietic cytokine receptors (e.g. MPL, FLT3) is stabilised in the absence of Maea, thereby prolonging their intracellular signalling. This is associated with impaired autophagy flux in HSCs but not in mature haematopoietic cells. Administration of receptor kinase inhibitor or autophagy-inducing compounds rescues the functional defects of Maea-deficient HSCs. Our results suggest that MAEA provides E3 ubiquitin ligase activity, guarding HSC function by restricting cytokine receptor signalling via autophagy.
Asunto(s)
Autofagosomas/genética , Autofagia/genética , Moléculas de Adhesión Celular/metabolismo , Proteínas del Citoesqueleto/metabolismo , Células Madre Hematopoyéticas/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Animales , Autofagosomas/efectos de los fármacos , Autofagosomas/metabolismo , Autofagosomas/ultraestructura , Autofagia/efectos de los fármacos , Moléculas de Adhesión Celular/genética , Proteínas del Citoesqueleto/genética , Perfilación de la Expresión Génica , Hematopoyesis/efectos de los fármacos , Hematopoyesis/genética , Células Madre Hematopoyéticas/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía Electrónica de Transmisión , Estabilidad Proteica , Receptores de Trombopoyetina/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Serina-Treonina Quinasas TOR/metabolismo , Ubiquitina-Proteína Ligasas/genética , Ubiquitinación , Tirosina Quinasa 3 Similar a fms/metabolismoRESUMEN
In the version of this article originally published, the key for Fig. 4c was incorrect. The symbols for 'Sham' and 'Den' were reversed. The error has been corrected in the PDF and HTML versions of the manuscript.
RESUMEN
Aging of hematopoietic stem cells (HSCs) is associated with a decline in their regenerative capacity and multilineage differentiation potential, contributing to the development of blood disorders. The bone marrow microenvironment has recently been suggested to influence HSC aging, but the underlying mechanisms remain largely unknown. Here we show that HSC aging critically depends on bone marrow innervation by the sympathetic nervous system (SNS), as loss of SNS nerves or adrenoreceptor ß3 signaling in the bone marrow microenvironment of young mice led to premature HSC aging, as evidenced by appearance of HSC phenotypes reminiscent of physiological aging. Strikingly, supplementation of a sympathomimetic acting selectively on adrenoreceptor ß3 to old mice significantly rejuvenated the in vivo function of aged HSCs, suggesting that the preservation or restitution of bone marrow SNS innervation during aging may hold the potential for new HSC rejuvenation strategies.
Asunto(s)
Médula Ósea/inervación , Senescencia Celular , Células Madre Hematopoyéticas/patología , Degeneración Nerviosa/patología , Receptores Adrenérgicos beta 3/metabolismo , Nicho de Células Madre , Animales , Eliminación de Gen , Células Madre Hematopoyéticas/metabolismo , Células Madre Mesenquimatosas/metabolismo , Células Madre Mesenquimatosas/patología , Ratones Endogámicos C57BL , Transducción de SeñalRESUMEN
Hematopoietic stem cells (HSCs) are mobilized from niches in the bone marrow (BM) to the blood circulation by the cytokine granulocyte colony-stimulating factor (G-CSF) through complex mechanisms. Among these, signals from the sympathetic nervous system regulate HSC egress via its niche, but how the brain communicates with the BM remains largely unknown. Here we show that muscarinic receptor type-1 (Chrm1) signaling in the hypothalamus promotes G-CSF-elicited HSC mobilization via hormonal priming of the hypothalamic-pituitary-adrenal (HPA) axis. Blockade of Chrm1 in the CNS, but not the periphery, reduces HSC mobilization. Mobilization is impaired in Chrm1-∕- mice and rescued by parabiosis with wild-type mice, suggesting a relay by a blood-borne factor. We have identified the glucocorticoid (GC) hormones as critical for optimal mobilization. Physiological levels of corticosterone promote HSC migration via the GC receptor Nr3c1-dependent signaling and upregulation of actin-organizing molecules. These results uncover long-range regulation of HSC migration emerging from the brain.
Asunto(s)
Sistema Nervioso Central/efectos de los fármacos , Sistema Nervioso Central/metabolismo , Glucocorticoides/farmacología , Factor Estimulante de Colonias de Granulocitos/farmacología , Animales , Células de la Médula Ósea/citología , Células de la Médula Ósea/efectos de los fármacos , Línea Celular Tumoral , Citometría de Flujo , Técnica del Anticuerpo Fluorescente , Movilización de Célula Madre Hematopoyética , Humanos , Hibridación in Situ , Ratones , Ratones Mutantes , Receptor Muscarínico M1/genética , Receptor Muscarínico M1/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/efectos de los fármacosRESUMEN
Arterioles and sinusoids of the bone marrow (BM) are accompanied by stromal cells that express nerve/glial antigen 2 (NG2) and leptin receptor (LepR), and constitute specialized niches that regulate quiescence and proliferation of haematopoietic stem cells (HSCs). However, how niche cells differentially regulate HSC functions remains unknown. Here, we show that the effects of cytokines regulating HSC functions are dependent on the producing cell sources. Deletion of chemokine C-X-C motif ligand 12 (Cxcl12) or stem cell factor (Scf) from all perivascular cells marked by nestin-GFP dramatically depleted BM HSCs. Selective Cxcl12 deletion from arteriolar NG2+ cells, but not from sinusoidal LepR+ cells, caused HSC reductions and altered HSC localization in BM. By contrast, deletion of Scf in LepR+ cells, but not NG2+ cells, led to reductions in BM HSC numbers. These results uncover distinct contributions of cytokines derived from perivascular cells in separate vascular niches to HSC maintenance.
Asunto(s)
Citocinas/metabolismo , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Nicho de Células Madre , Animales , Antígenos , Arteriolas/citología , Médula Ósea/metabolismo , Recuento de Células , Quimiocina CXCL12/metabolismo , Eliminación de Gen , Proteínas Fluorescentes Verdes/metabolismo , Imagenología Tridimensional , Integrasas/metabolismo , Ratones Transgénicos , Nestina/metabolismo , Proteoglicanos , Receptores de Leptina/metabolismo , Análisis de Secuencia de ARN , Factor de Células Madre/metabolismoRESUMEN
Perivascular mesenchymal stem and progenitor cells (MSPCs) are critical for forming a healthy hematopoietic stem cell (HSC) niche. However, the interactions and influence of acute myelogenous leukemia (AML) stem cells with the microenvironment remain largely unexplored. We have unexpectedly found that neuropathy of the sympathetic nervous system (SNS) promotes leukemic bone marrow infiltration in an MLL-AF9 AML model. Development of AML disrupts SNS nerves and the quiescence of Nestin(+) niche cells, leading to an expansion of phenotypic MSPCs primed for osteoblastic differentiation at the expense of HSC-maintaining NG2(+) periarteriolar niche cells. Adrenergic signaling promoting leukemogenesis is transduced by the ß2, but not ß3, adrenergic receptor expressed on stromal cells of leukemic bone marrow. These results indicate that sympathetic neuropathy may represent a mechanism for the malignancy in order to co-opt the microenvironment and suggest separate mesenchymal niche activities for malignant and healthy hematopoietic stem cells in the bone marrow.