Lipolysis of bone marrow adipocytes is required to fuel bone and the marrow niche during energy deficits.
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ABSTRACT:
SUBMITTER: Li Z
PROVIDER: S-EPMC9273217 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Adipocyte infiltration in the bone marrow follows chemotherapy or irradiation. Previous studies indicate that bone marrow fat cells inhibit hematopoietic stem cell function. Recently, Zhou et al. (2017) using state-of-the-art techniques, including sophisticated Cre/loxP technologies, confocal microscopy, in vivo lineage-tracing, flow cytometry, and bone marrow transplantation, reveal that adipocytes promote hematopoietic recovery after irradiation. This study challenges the current view of adipocytes as negative regulators of the hematopoietic stem cells niche, and reopens the discussion about adipocytes' roles in the bone marrow. Strikingly, genetic deletion of stem cell factor specifically from adipocytes leads to deficiency in hematopoietic stem cells, and reduces animal survival after myeloablation, The emerging knowledge from this research will be important for the treatment of multiple hematologic disorders. © 2017 International Society for Advancement of Cytometry.
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Project description:Hematopoiesis advances cardiovascular disease by generating inflammatory leukocytes that attack the arteries, heart and brain. While it is well documented that the bone marrow niche regulates hematopoietic stem cell proliferation and hence the systemic leukocyte pool, it is less clear how cardiovascular disease affects the vasculature forming this niche. Here we show that arterial hypertension, atherosclerosis and myocardial infarction alter the anatomy and function of bone marrow vasculature. Hypertension and atherosclerosis instigated vascular fibrosis, leakage and endothelial dysfunction in the bone marrow. Myocardial infarction induced vascular leakage and bone marrow angiogenesis via Vegf signaling. Endothelial cell-specific deletion of the Vegf receptor 2 limited emergency hematopoiesis after myocardial infarction, indicating that new vasculature supports higher blood cell production. RNA-sequencing of bone marrow endothelial cells revealed inflammatory gene expression in mice with cardiovascular disease. Endothelial cell-specific deletion of interleukin 6 or versican, which were highly expressed in mice with atherosclerosis or myocardial infarction, respectively, reduced hematopoiesis and systemic myeloid cells. Taken together, cardiovascular disease affects the vascular bone marrow niche, thus influencing hematopoietic stem cell behavior and expanding innate immune cell supply to atherosclerotic plaque and ischemic myocardium. Interrupting this feed back loop may constrain cardiovascular inflammation.
2023-11-04 | GSE169267 | GEO
Project description:Bone marrow adipose tissue (BMAT) is preserved or increased in states of caloric restriction. Similarly, we found that BMAT in the tail vertebrae, but not the red marrow in the tibia, resists loss of neutral lipid with acute, 48-hour fasting in rats. The mechanisms underlying this phenomenon and its seemingly distinct regulation from peripheral white adipose tissue (WAT) remain unknown. To test the role of ?-adrenergic stimulation, a major regulator of adipose tissue lipolysis, we examined the responses of BMAT to ?-adrenergic agonists. Relative to inguinal WAT, BMAT had reduced phosphorylation of hormone sensitive lipase (HSL) after treatment with pan-?-adrenergic agonist isoproterenol. Phosphorylation of HSL in response to ?3-adrenergic agonist CL316,243 was decreased by an additional ~90% (distal tibia BMAT) or could not be detected (tail vertebrae). Ex vivo, adrenergic stimulation of lipolysis in purified BMAT adipocytes was also substantially less than iWAT adipocytes and had site-specific properties. Specifically, regulated bone marrow adipocytes (rBMAs) from proximal tibia and femur underwent lipolysis in response to both CL316,243 and forskolin, while constitutive BMAs from the tail responded only to forskolin. This occurred independently of changes in gene expression of ?-adrenergic receptors, which were similar between adipocytes from iWAT and BMAT, and could not be explained by defective coupling of ?-adrenergic receptors to lipolytic machinery through caveolin 1. Specifically, we found that whereas caveolin 1 was necessary to mediate maximal stimulation of lipolysis in iWAT, overexpression of caveolin 1 was insufficient to rescue impaired BMAT signaling. Lastly, we tested the ability of BMAT to respond to 72-hour treatment with CL316,243 in vivo. This was sufficient to cause beiging of iWAT adipocytes and a decrease in iWAT adipocyte cell size. By contrast, adipocyte size in the tail BMAT and distal tibia remained unchanged. However, within the distal femur, we identified a subpopulation of BMAT adipocytes that underwent lipid droplet remodeling. This response was more pronounced in females than in males and resembled lipolysis-induced lipid partitioning rather than traditional beiging. In summary, BMAT has the capacity to respond to ?-adrenergic stimuli, however, its responses are muted and BMAT generally resists lipid hydrolysis and remodeling relative to iWAT. This resistance is more pronounced in distal regions of the skeleton where the BMAT adipocytes are larger with little intervening hematopoiesis, suggesting that there may be a role for both cell-autonomous and microenvironmental determinants. Resistance to ?-adrenergic stimuli further separates BMAT from known regulators of energy partitioning and contributes to our understanding of why BMAT is preserved in states of fasting and caloric restriction.
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Project description:Purpose: To determine mechanisms by which BMAd-Pnpla2 deficiency-causes bone loss in calorie restricted (CR) mice, we profiled global gene expression in bone marrow plugs from distal tibiae, a location highly enriched with bone marrow adipose tissue. Methods: Male control and BMAd-Pnpla2-/- mice at 24 weeks of age were either fed AL or underwent 30% CR for 6 weeks. Distal tibial cBMAT was flushed and cBMAT from two mice was pooled as one sample for RNAseq analyses (n of 3 or 4 per treatment). Results: Using an optimized data analysis workflow, we mapped about 20 million sequence reads per sample to the mouse genome (UCSC mm10) and identified 23,441 transcripts in the bone marrow adipose tissue of WT and Pnpla2 deficiency mice using STAR with default parameters. PCA plots show that RNA profiles from CR groups are distinct from their Ad libitum (AL) controls. Whereas Pnpla2 deficiency in mice fed AL does not cause gene expression to diverge substantially, loss of Pnpla2 interacts with CR resulting in a well-segregated pattern of gene expression Conclusion: Caloric restriction induces dramatic elevations in extracellular matrix organization and skeletal development genes, and energy from BMAd is required for these adaptations.
2022-07-20 | GSE183784 | GEO
Project description:Bone marrow adipocytes fuel emergency hematopoiesis
| PRJNA716047 | ENA
Project description:RATIONALE:Inflammatory stress induced by exposure to bacterial lipopolysaccharide causes hematopoietic stem cell expansion in the bone marrow niche, generating a cellular immune response. As an integral component of the hematopoietic stem cell niche, the bone marrow vasculature regulates the production and release of blood leukocytes, which protect the host against infection but also fuel inflammatory diseases. OBJECTIVE:We aimed to develop imaging tools to explore vascular changes in the bone marrow niche during acute inflammation. METHODS AND RESULTS:Using the TLR (Toll-like receptor) ligand lipopolysaccharide as a prototypical danger signal, we applied multiparametric, multimodality and multiscale imaging to characterize how the bone marrow vasculature adapts when hematopoiesis boosts leukocyte supply. In response to lipopolysaccharide, ex vivo flow cytometry and histology showed vascular changes to the bone marrow niche. Specifically, proliferating endothelial cells gave rise to new vasculature in the bone marrow during hypoxic conditions. We studied these vascular changes with complementary intravital microscopy and positron emission tomography/magnetic resonance imaging. Fluorescence and positron emission tomography integrin ?V?3 imaging signal increased during lipopolysaccharide-induced vascular remodeling. Vascular leakiness, quantified by albumin-based in vivo microscopy and magnetic resonance imaging, rose when neutrophils departed and hematopoietic stem and progenitor cells proliferated more vigorously. CONCLUSIONS:Introducing a tool set to image bone marrow either with cellular resolution or noninvasively within the entire skeleton, this work sheds light on angiogenic responses that accompany emergency hematopoiesis. Understanding and monitoring bone marrow vasculature may provide a key to unlock therapeutic targets regulating systemic inflammation.
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Project description:BM adipocytes (BMAd) are a unique cell population derived from BM mesenchymal progenitors and marrow adipogenic lineage precursors. Although they have long been considered to be a space filler within bone cavities, recent studies have revealed important physiological roles in hematopoiesis and bone metabolism. To date, the approaches used to study BMAd function have been confounded by contributions by nonmarrow adipocytes or by BM stromal cells. To address this gap in the field, we have developed a BMAd-specific Cre mouse model to deplete BMAds by expression of diphtheria toxin A (DTA) or by deletion of peroxisome proliferator-activated receptor gamma (Pparg). We found that DTA-induced loss of BMAds results in decreased hematopoietic stem and progenitor cell numbers and increased bone mass in BMAd-enriched locations, including the distal tibiae and caudal vertebrae. Elevated bone mass appears to be secondary to enhanced endosteal bone formation, suggesting a local effect caused by depletion of BMAd. Augmented bone formation with BMAd depletion protects mice from bone loss induced by caloric restriction or ovariectomy, and it facilitates the bone-healing process after fracture. Finally, ablation of Pparg also reduces BMAd numbers and largely recapitulates high-bone mass phenotypes observed with DTA-induced BMAd depletion.
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Project description:Bone marrow (BM) cells depend on their niche for growth and survival. However, the genes modulated by niche stimuli have not been discriminated yet. For this purpose, we investigated BM aspirations from patients with various hematological malignancies. Each aspirate was fractionated, and the various samples were fixed at different time points and analyzed by microarray. Identification of niche-modulated genes relied on sustained change in expression following loss of niche regulation. Compared with the reference ('authentic') samples, which were fixed immediately following aspiration, the BM samples fixed after longer stay out-of-niche acquired numerous changes in gene-expression profile (GEP). The overall genes modulated included a common subset of functionally diverse genes displaying prompt and sustained 'switch' in expression irrespective of the tumor type. Interestingly, the 'switch' in GEP was reversible and turned 'off-and-on' again in culture conditions, resuming cell-cell-matrix contact versus respread into suspension, respectively. Moreover, the resuming of contact prolonged the survival of tumor cells out-of-niche, and the regression of the 'contactless switch' was followed by induction of a new set of genes, this time mainly encoding extracellular proteins including angiogenic factors and extracellular matrix proteins. Our data set, being unique in authentic expression design, uncovered niche-modulated and niche-modulating genes capable of controlling homing, expansion and angiogenesis.
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Project description:Adipocyte-tumor cell cross-talk is one of the critical mediators of tumor progression and an emerging facilitator of therapy evasion. Tumor cells that metastasize to adipocyte-rich bone marrow take advantage of the interplay between metabolic and inflammatory pathways to activate prosurvival mechanisms that allow them to thrive and escape therapy. Using in vitro and in vivo models of marrow adiposity, we demonstrate that metastatic prostate carcinoma cells engage bone marrow adipocytes in a functional cross-talk that promotes IL1β expression in tumor cells. Tumor-supplied IL1β contributes to adipocyte lipolysis and regulates a proinflammatory phenotype in adipocytes via upregulation of COX-2 and MCP-1. We further show that the enhanced activity of the IL1β/COX-2/MCP-1 axis and a resulting increase in PGE2 production by adipocytes coincide with augmented hypoxia signaling and activation of prosurvival pathways in tumor cells, revealing a potential mechanism of chemoresistance. The major consequence of this interplay is the reduced response of prostate cancer cells to docetaxel, a phenomenon sensitive to the inhibition of lipolysis. IMPLICATIONS: Studies presented herein highlight adipocyte lipolysis as a tumor-regulated metabolic event that engages proinflammatory cross-talk in the microenvironment to promote prostate cancer progression in bone. Understanding the impact of bone marrow adipose tissue on tumor adaptation, survival, and chemotherapy response is fundamentally important, as current treatment options for metastatic prostate cancer are palliative.
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