Yoshiko Iwamoto

Massachusetts General Hospital, Boston, Massachusetts, United States

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Publications (50)742.95 Total impact

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    ABSTRACT: Therapeutic nanoparticles (TNPs) aim to deliver drugs more safely and effectively to cancers, yet clinical results have been unpredictable owing to limited in vivo understanding. Here we use single-cell imaging of intratumoral TNP pharmacokinetics and pharmacodynamics to better comprehend their heterogeneous behaviour. Model TNPs comprising a fluorescent platinum(IV) pro-drug and a clinically tested polymer platform (PLGA-b-PEG) promote long drug circulation and alter accumulation by directing cellular uptake toward tumour-associated macrophages (TAMs). Simultaneous imaging of TNP vehicle, its drug payload and single-cell DNA damage response reveals that TAMs serve as a local drug depot that accumulates significant vehicle from which DNA-damaging Pt payload gradually releases to neighbouring tumour cells. Correspondingly, TAM depletion reduces intratumoral TNP accumulation and efficacy. Thus, nanotherapeutics co-opt TAMs for drug delivery, which has implications for TNP design and for selecting patients into trials.
    Full-text · Article · Oct 2015 · Nature Communications
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    ABSTRACT: Purpose To determine if myeloperoxidase (MPO) is involved in epileptogenesis and if molecular nuclear imaging can be used to noninvasively map inflammatory changes in epileptogenesis. Materials and Methods The animal and human studies were approved by the institutional review boards. Pilocarpine-induced epileptic mice were treated with 4-aminobenzoic acid hydrazide (n = 46), a specific irreversible MPO inhibitor, or saline (n = 42). Indium-111-bis-5-hydroxytryptamide-diethylenetriaminepentaacetate was used to image brain MPO activity (n = 6 in the 4-aminobenzoic acid hydrazide and saline groups; n = 5 in the sham group) by using single photon emission computed tomography/computed tomography. The role of MPO in the development of spontaneous recurrent seizures was assessed by means of clinical symptoms and biochemical and histopathologic data. Human brain specimens from a patient with epilepsy and a patient without epilepsy were stained for MPO. The Student t test, one-way analysis of variance, and Mann-Whitney and Kruskal-Wallis tests were used. Differences were regarded as significant if P was less than .05. Results MPO and leukocytes increased in the brain during epileptogenesis (P < .05). Blocking MPO delayed spontaneous recurrent seizures (99.6 vs 142 hours, P = .016), ameliorated the severity of spontaneous recurrent seizures (P < .05), and inhibited mossy fiber sprouting (Timm index, 0.31 vs 0.03; P = .003). Matrix metalloproteinase activity was upregulated during epileptogenesis in an MPO-dependent manner (1.44 vs 0.94 U/mg, P = .049), suggesting that MPO acts upstream of matrix metalloproteinases. MPO activity was mapped during epileptogenesis in vivo in the hippocampal regions. Resected temporal lobe tissue from a human patient with refractory epilepsy but not the temporal lobe tissue from a patient without seizures demonstrated positive MPO immunostaining, suggesting high translational potential for this imaging technology. Conclusion The findings of this study highlight an important role for MPO in epileptogenesis and show MPO to be a potential therapeutic target and imaging biomarker for epilepsy. (©) RSNA, 2015 Online supplemental material is available for this article.
    No preview · Article · Sep 2015 · Radiology
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    ABSTRACT: Rationale: Local plaque macrophage proliferation and monocyte production in hematopoietic organs promote progression of atherosclerosis. Therefore, non-invasive imaging of proliferation could serve as a biomarker and monitor therapeutic intervention. Objective: To explore (18)F-fluorothymidine ((18)F-FLT) PET-CT imaging of cell proliferation in atherosclerosis. Methods and results: (18)F-FLT PET-CT was performed in mice, rabbits and humans with atherosclerosis. In ApoE(-/-) mice, increased (18)F-FLT signal was observed in atherosclerotic lesions, spleen and bone marrow (SUV wild-type versus ApoE(-/-) mice, 0.05±0.01 versus 0.17±0.01, P<0.05 in aorta; 0.13±0.01 versus 0.28±0.02, P<0.05 in bone marrow; 0.06±0.01 versus 0.22±0.01, P<0.05 in spleen), corroborated by ex vivo scintillation counting and autoradiography. Flow cytometry confirmed significantly higher proliferation of macrophages in aortic lesions and hematopoietic stem and progenitor cells in the spleen and bone marrow in these mice. In addition, (18)F-FLT plaque signal correlated with the duration of high cholesterol diet (r2=0.33, p<0.05). Aortic 18F-FLT uptake was reduced when cell proliferation was suppressed with 5-FU in ApoE(-/-) mice (p<0.05). In rabbits, inflamed atherosclerotic vasculature with the highest (18)F-fluorodeoxyglucose uptake enriched (18)F-FLT. In patients with atherosclerosis, (18)F-FLT signal significantly increased in the inflamed carotid artery and in the aorta. Conclusions: (18)F-FLT PET imaging may serve as an imaging biomarker for cell proliferation in plaque and hematopoietic activity in individuals with atherosclerosis.
    Full-text · Article · Sep 2015 · Circulation Research
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    ABSTRACT: Background: -Myocardial infarction (MI) is an ischemic wound that recruits millions of leukocytes. MI-associated blood leukocytosis correlates inversely with patient survival, yet the signals driving heightened leukocyte production after MI remain incompletely understood. Methods and results: -Using parabiosis surgery, this study shows that soluble danger signals, among them interleukin-1 beta (IL-1β), increase bone marrow hematopoietic stem cell (HSC) proliferation after MI. Data obtained in bone marrow reconstitution experiments reveal that IL-1β enhances HSC proliferation by both direct actions on hematopoietic cells and through modulating the bone marrow's hematopoietic microenvironment. An antibody that neutralizes IL-1β suppresses these effects. Anti-IL-1β treatment dampens the post-MI increase in HSC proliferation. Consequently decreased leukocyte numbers in the blood and infarct reduce inflammation and diminish post-MI heart failure in ApoE(-/-) mice with atherosclerosis. Conclusions: -The presented insight into post-MI bone marrow activation identifies a mechanistic target for muting inflammation in the ischemically damaged heart.
    No preview · Article · Sep 2015 · Circulation
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    ABSTRACT: The ability to isolate pure pancreatic ß-cells would greatly aid multiple areas of diabetes research. We developed a fluorescent exendin-4-like neopeptide conjugate for the rapid purification and isolation of functional mouse pancreatic β-cells. By targeting the glucagon-like peptide-1 receptor with the fluorescent conjugate, β-cells could be quickly isolated by flow cytometry and were >99% insulin positive. These studies were confirmed by immunostaining, microscopy and gene expression profiling on isolated cells. Gene expression profiling studies of cytofluorometrically sorted β-cells from 4 and 12 week old NOD mice provided new insights into the genetic programs at play of different stages of type-1 diabetes development. The described isolation method should have broad applicability to the β-cell field.
    Full-text · Article · Sep 2015 · Scientific Reports
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    ABSTRACT: -Healing after myocardial infarction (MI) involves the biphasic accumulation of inflammatory Ly-6C(high) and reparative Ly-6C(low) monocytes/macrophages. Excessive inflammation disrupts the balance between the two phases, impairs infarct healing, and contributes to left ventricle remodeling and heart failure. Lipoprotein-associated phospholipase A2 (Lp-PLA2), a member of the phospholipase A2 family of enzymes, produced predominantly by leukocytes, participates in host defenses and disease. Elevated Lp-PLA2 levels associate with increased risk of cardiovascular events across diverse patient populations, but the mechanisms by which the enzyme elicits its effects remain unclear. This study tested the role of Lp-PLA2 in healing after MI. -In response to MI, Lp-PLA2 levels markedly increased in the circulation. To test the functional importance of Lp-PLA2, we generated chimeric mice whose bone marrow-derived leukocytes were Lp-PLA2-deficient (bmLp-PLA2 (-/-)). Compared to WT controls, bmLp-PLA2 (-/-) mice subjected to MI had lower serum levels of inflammatory cytokines TNFα, IL-1β and IL-6, and decreased number of circulating inflammatory myeloid cells. Accordingly, bmLp-PLA2 (-/-) mice developed smaller and less inflamed infarcts with reduced numbers of infiltrating neutrophils and inflammatory Ly-6C(high) monocytes. During the later, reparative phase, infarcts of bmLp-PLA2 (-/-) mice contained Ly-6C(low) macrophages with a skewed M2-prone gene expression signature, increased collagen deposition, fewer inflammatory cells, and improved indices of angiogenesis. Consequently, the hearts of bmLp-PLA2 (-/-) mice healed more efficiently, as determined by improved left ventricle (LV) remodeling and ejection fraction. -Lp-PLA2 augments the inflammatory response after myocardial infarction and antagonizes healing by disrupting the balance between inflammation and repair, providing a rationale for focused study of ventricular function and heart failure after targeting this enzyme acutely in MI.
    Full-text · Article · Jul 2015 · Circulation Heart Failure
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    ABSTRACT: Myeloperoxidase (MPO), a highly oxidative enzyme secreted by leukocytes has been implicated in human and experimental non-alcoholic steatohepatitis (NASH), but the underlying mechanisms remain unknown. Here, we investigated how MPO contributes to progression from steatosis to NASH. In C57Bl/6J mice fed a diet deficient in methionine and choline to induce NASH, neutrophils and to a lesser extent inflammatory monocytes are markedly increased compared to sham mice, and secrete abundant amounts of MPO. Through generation of HOCl, MPO directly causes hepatocyte death in vivo. In vitro experiments demonstrate mitochondrial permeability transition pore induction via activation of SAPK/JNK and PARP. MPO also contributes to activation of HSCs, the most important source of collagen in the liver. In vitro MPO-activated HSCs have an activation signature (MAPK and PI3K-AKT phosphorylation), and upregulate COL1A1, α-SMA, and CXCL1. MPO-derived oxidative stress also activates TGF-β in vitro, and TGF-β signaling inhibition with SB-431542 decreased steatosis and fibrosis in vivo. Conversely, congenital absence of MPO results in reduced hepatocyte injury, decreased levels of TGF-β, fewer activated HSCs, and less severe fibrosis in vivo. Innovation and Conclusion: Cumulatively, these findings demonstrate important cross talk between inflammatory myeloid cells, hepatocytes, and HSCs via MPO, and establish MPO as part of a pro-apoptotic and pro-fibrotic pathway of progression in NASH, as well as a potential therapeutic target to ameliorate this disease.
    No preview · Article · May 2015 · Antioxidants & Redox Signaling
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    ABSTRACT: Following myocardial infarction (MI), myeloid cells derived from the hematopoietic system drive a sharp increase in systemic leukocyte levels that correlates closely with mortality. The origin of these myeloid cells, and the response of hematopoietic stem and progenitor cells (HSPCs) to MI, however, is unclear. Here, we identify a CCR2(+)CD150(+)CD48(-) LSK hematopoietic subset as the most upstream contributor to emergency myelopoiesis after ischemic organ injury. This subset has 4-fold higher proliferation rates than CCR2(-)CD150(+)CD48(-) LSK cells, displays a myeloid differentiation bias, and dominates the migratory HSPC population. We further demonstrate that the myeloid translocation gene 16 (Mtg16) regulates CCR2(+) HSPC emergence. Mtg16(-/-) mice have decreased levels of systemic monocytes and infarct-associated macrophages and display compromised tissue healing and post-MI heart failure. Together, these data provide insights into regulation of emergency hematopoiesis after ischemic injury and identify potential therapeutic targets to modulate leukocyte output after MI. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · May 2015 · Cell stem cell
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    ABSTRACT: Quantification of cell-cycle state at a single-cell level is essential to understand fundamental three-dimensional (3D) biological processes such as tissue development and cancer. Analysis of 3D in vivo images, however, is very challenging. Today's best practice, manual annotation of select image events, generates arbitrarily sampled data distributions, which are unsuitable for reliable mechanistic inferences. Here, we present an integrated workflow for quantitative in vivo cell-cycle profiling. It combines image analysis and machine learning methods for automated 3D segmentation and cell-cycle state identification of individual cell-nuclei with widely varying morphologies embedded in complex tumor environments. We applied our workflow to quantify cell-cycle effects of three antimitotic cancer drugs over 8 d in HT-1080 fibrosarcoma xenografts in living mice using a data set of 38,000 cells and compared the induced phenotypes. In contrast to results with 2D culture, observed mitotic arrest was relatively low, suggesting involvement of additional mechanisms in their antitumor effect in vivo.
    Preview · Article · Apr 2015 · Nature Methods
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    ABSTRACT: Splenic myelopoiesis provides a steady flow of leukocytes to inflamed tissues, and leukocytosis correlates with cardiovascular mortality. Yet regulation of hematopoietic stem cell (HSC) activity in the spleen is incompletely understood. Here, we show that red pulp vascular cell adhesion molecule 1 (VCAM-1)+ macrophages are essential to extramedullary myelopoiesis because these macrophages use the adhesion molecule VCAM-1 to retain HSCs in the spleen. Nanoparticle-enabled in vivo RNAi silencing of the receptor for macrophage colony stimulation factor (M-CSFR) blocked splenic macrophage maturation, reduced splenic VCAM-1 expression and compromised splenic HSC retention. Both, depleting macrophages in CD169 iDTR mice or silencing VCAM-1 in macrophages released HSCs from the spleen. When we silenced either VCAM-1 or M-CSFR in mice with myocardial infarction or in ApoE-/- mice with atherosclerosis, nanoparticle-enabled in vivo RNAi mitigated blood leukocytosis, limited inflammation in the ischemic heart, and reduced myeloid cell numbers in atherosclerotic plaques.
    No preview · Article · Apr 2015 · Journal of Experimental Medicine
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    ABSTRACT: Sepsis is a frequently fatal condition characterized by an uncontrolled and harmful host reaction to microbial infection. Despite the prevalence and severity of sepsis, we lack a fundamental grasp of its pathophysiology. Here we report that the cytokine interleukin-3 (IL-3) potentiates inflammation in sepsis. Using a mouse model of abdominal sepsis, we showed that innate response activator B cells produce IL-3, which induces myelopoiesis of Ly-6C(high) monocytes and neutrophils and fuels a cytokine storm. IL-3 deficiency protects mice against sepsis. In humans with sepsis, high plasma IL-3 levels are associated with high mortality even after adjusting for prognostic indicators. This study deepens our understanding of immune activation, identifies IL-3 as an orchestrator of emergency myelopoiesis, and reveals a new therapeutic target for treating sepsis. Copyright © 2015, American Association for the Advancement of Science.
    Full-text · Article · Mar 2015 · Science
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    ABSTRACT: Purpose: To test if MPO-Gd, a gadolinium-based magnetic resonance (MR) imaging probe that is sensitive and specific for the proinflammatory and oxidative enzyme myeloperoxidase (MPO), which is secreted by certain inflammatory cells, is more sensitive than diethylenetriaminepentaacetic acid (DTPA)-Gd in revealing early subclinical and chronic disease activity in the brain in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Materials and methods: The protocol for animal experiments was approved by the institutional animal care committee. A total of 61 female SJL mice were induced with EAE. Mice underwent MPO-Gd- or DTPA-Gd-enhanced MR imaging on days 6, 8, and 10 after induction, before clinical disease develops, and during chronic disease at remission and the first relapse. Brains were harvested at these time points for flow cytometric evaluation of immune cell subtypes and immunohistochemistry. Statistical analysis was performed, and P < .05 was considered to indicate a significant difference. Results: MPO-Gd helps detect earlier (5.2 vs 2.3 days before symptom onset, P = .004) and more (3.1 vs 0.3, P = .008) subclinical inflammatory lesions compared with DTPA-Gd, including in cases in which there was no evidence of overt blood-brain barrier (BBB) breakdown detected with DTPA-Gd enhancement. The number of MPO-Gd-enhancing lesions correlated with early infiltration of MPO-secreting monocytes and neutrophils into the brain (r = 0.91). MPO-Gd also helped detect more lesions during subclinical disease at remission (5.5 vs 1.3, P = .006) and at the first relapse (9.0 vs 2.7, P = .03) than DTPA-Gd, which also correlated well with the presence and accumulation of MPO-secreting inflammatory cells in the brain (r = 0.93). Conclusion: MPO-Gd specifically reveals lesions with inflammatory monocytes and neutrophils, which actively secrete MPO. These results demonstrate the feasibility of detection of subclinical inflammatory disease activity in vivo, which is different from overt BBB breakdown.
    No preview · Article · Dec 2014 · Radiology
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    ABSTRACT: Tumor-stromal interactions are a determining factor in cancer progression. In vivo, the interaction interface is associated with spatially-resolved distributions of cancer and stromal phenotypes. Here, we establish a micropatterned tumor-stromal assay (μTSA) with laser capture microdissection to control the location of co-cultured cells and analyze bulk and interfacial tumor-stromal signaling in driving cancer progression. μTSA reveals a spatial distribution of phenotypes in concordance with human estrogen receptor-positive (ER+) breast cancer samples, and heterogeneous drug activity relative to the tumor-stroma interface. Specifically, an unknown mechanism of reversine is shown in targeting tumor-stromal interfacial interactions using ER+ MCF-7 breast cancer and bone marrow-derived stromal cells. Reversine suppresses MCF-7 tumor growth and bone metastasis in vivo by reducing tumor stromalization including collagen deposition and recruitment of activated stromal cells. This study advocates μTSA as a platform for studying tumor microenvironmental interactions and cancer field effects with applications in drug discovery and development.
    Full-text · Article · Dec 2014 · Nature Communications
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    ABSTRACT: Exposure to psychosocial stress is a risk factor for many diseases, including atherosclerosis. Although incompletely understood, interaction between the psyche and the immune system provides one potential mechanism linking stress and disease inception and progression. Known cross-talk between the brain and immune system includes the hypothalamic-pituitary-adrenal axis, which centrally drives glucocorticoid production in the adrenal cortex, and the sympathetic-adrenal-medullary axis, which controls stress-induced catecholamine release in support of the fight-or-flight reflex. It remains unknown, however, whether chronic stress changes hematopoietic stem cell activity. Here we show that stress increases proliferation of these most primitive hematopoietic progenitors, giving rise to higher levels of disease-promoting inflammatory leukocytes. We found that chronic stress induced monocytosis and neutrophilia in humans. While investigating the source of leukocytosis in mice, we discovered that stress activates upstream hematopoietic stem cells. Under conditions of chronic variable stress in mice, sympathetic nerve fibers released surplus noradrenaline, which signaled bone marrow niche cells to decrease CXCL12 levels through the β3-adrenergic receptor. Consequently, hematopoietic stem cell proliferation was elevated, leading to an increased output of neutrophils and inflammatory monocytes. When atherosclerosis-prone Apoe(-/-) mice were subjected to chronic stress, accelerated hematopoiesis promoted plaque features associated with vulnerable lesions that cause myocardial infarction and stroke in humans.
    Full-text · Article · Jun 2014 · Nature Medicine
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    ABSTRACT: Background: Myocarditis is characterized by inflammatory cell infiltration of the heart and subsequent deterioration of cardiac function. Monocytes are the most prominent population of accumulating leucocytes. We investigated whether in vivo administration of nanoparticle-encapsulated siRNA targeting chemokine (C-C motif) receptor 2 (CCR2)-a chemokine receptor crucial for leucocyte migration in humans and mice--reduces inflammation in autoimmune myocarditis. Methods and results: In myocardium of patients with myocarditis, CCL2 mRNA levels and CCR2(+) cells increased (P < 0.05), motivating us to pursue CCR2 silencing. Flow cytometric analysis showed that siRNA silencing of CCR2 (siCCR2) reduced the number of Ly6C(high) monocytes in hearts of mice with acute autoimmune myocarditis by 69% (P < 0.05), corroborated by histological assessment. The nanoparticle-delivered siRNA was not only active in monocytes but also in bone marrow haematopoietic progenitor cells. Treatment with siCCR2 reduced the migration of bone marrow granulocyte macrophage progenitors into the blood. Cellular magnetic resonance imaging (MRI) after injection of macrophage-avid magnetic nanoparticles detected myocarditis and therapeutic effects of RNAi non-invasively. Mice with acute myocarditis showed enhanced macrophage MRI contrast, which was prevented by siCCR2 (P < 0.05). Follow-up MRI volumetry revealed that siCCR2 treatment improved ejection fraction (P < 0.05 vs. control siRNA-treated mice). Conclusion: This study highlights the importance of CCR2 in the pathogenesis of myocarditis. In addition, we show that siCCR2 affects leucocyte progenitor trafficking. The data also point to a novel therapeutic strategy for the treatment of myocarditis.
    Full-text · Article · Jun 2014 · European Heart Journal
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    ABSTRACT: Pneumonia is a major cause of mortality worldwide and a serious problem in critical care medicine, but the immunophysiological processes that confer either protection or morbidity are not completely understood. We show that in response to lung infection, B1a B cells migrate from the pleural space to the lung parenchyma to secrete polyreactive emergency immunoglobulin M (IgM). The process requires innate response activator (IRA) B cells, a transitional B1a-derived inflammatory subset which controls IgM production via autocrine granulocyte/macrophage colony-stimulating factor (GM-CSF) signaling. The strategic location of these cells, coupled with the capacity to produce GM-CSF-dependent IgM, ensures effective early frontline defense against bacteria invading the lungs. The study describes a previously unrecognized GM-CSF-IgM axis and positions IRA B cells as orchestrators of protective IgM immunity.
    Full-text · Article · May 2014 · Journal of Experimental Medicine
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    ABSTRACT: Macrophages populate the steady-state myocardium. Previously, all macrophages were thought to arise from monocytes; however, it emerged that in several organs tissue-resident macrophages may self-maintain through local proliferation. To study the contribution of monocytes to cardiac resident macrophages in steady-state, after macrophage depletion in CD11b(DTR/+) mice and in myocardial infarction. Using in vivo fate mapping and flow cytometry, we estimated that during steady-state the heart macrophage population turns over in about one month. To explore the source of cardiac resident macrophages, we joined the circulation of mice using parabiosis. After 6 weeks, we observed blood monocyte chimerism of 35.3±3.4% while heart macrophages showed a much lower chimerism of 2.7±0.5% (p<0.01). Macrophages self renewed locally through proliferation: 2.1±0.3% incorporated BrdU 2 hours after a single injection and 13.7±1.4% heart macrophages stained positive for the cell cycle marker Ki67. The cells likely participate in defense against infection, as we found them to ingest fluorescently labeled bacteria. In ischemic myocardium, we observed that tissue resident macrophages died locally while some also migrated to hematopoietic organs. If the steady-state was perturbed by coronary ligation or diphtheria toxin-induced macrophage depletion in CD11b(DTR/+) mice, blood monocytes replenished heart macrophages. However, in the chronic phase after myocardial infarction, macrophages residing in the infarct were again independent from the blood monocyte pool, returning to the steady-state situation. In this study we show differential contribution of monocytes to heart macrophages during steady-state, after macrophage depletion or in the acute and chronic phase after myocardial infarction. We found that macrophages participate in the immunosurveillance of myocardial tissue. These data correspond with previous studies on tissue-resident macrophages and raise important questions on the fate and function of macrophages during the development of heart failure.
    Full-text · Article · May 2014 · Circulation Research
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    ABSTRACT: Healing after myocardial infarction (MI) involves the biphasic accumulation of inflammatory Ly-6C(high) and reparative Ly-6C(low) monocytes/macrophages (Mo/MΦ). According to one model, Mo/MΦ heterogeneity in the heart originates in the blood and involves the sequential recruitment of distinct monocyte subsets that differentiate to distinct macrophages. Alternatively, heterogeneity may arise in tissue from one circulating subset via local macrophage differentiation and polarization. The orphan nuclear hormone receptor, Nr4a1, is essential to Ly-6C(low) monocyte production but dispensable to Ly-6C(low) macrophage differentiation; dependence on Nr4a1 can thus discriminate between systemic and local origins of macrophage heterogeneity. This study tested the role of Nr4a1 in MI in the context of the two Mo/MΦ accumulation scenarios. We show that Ly-6C(high) monocytes infiltrate the infarcted myocardium and, unlike Ly-6C(low) monocytes, differentiate to cardiac macrophages. In the early, inflammatory phase of acute myocardial ischemic injury, Ly-6C(hig)h monocytes accrue in response to a brief Ccl2 burst. In the second, reparative phase, accumulated Ly-6C(high) monocytes give rise to reparative Ly-6C(low) F4/80high macrophages that proliferate locally. In the absence of Nr4a1, Ly-6C(high) monocytes express heightened levels of Ccr2 on their surface, avidly infiltrate the myocardium, and differentiate to abnormally inflammatory macrophages, which results in defective healing and compromised heart function. Ly-6C(high) monocytes orchestrate both inflammatory and reparative phases during MI and depend on Nr4a1 to limit their influx and inflammatory cytokine expression.
    Full-text · Article · Mar 2014 · Circulation Research
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    ABSTRACT: Atherosclerotic lesions grow via the accumulation of leukocytes and oxidized lipoproteins in the vessel wall. Leukocytes can attenuate or augment atherosclerosis through the release of cytokines, chemokines, and other mediators. Deciphering how leukocytes develop, oppose and complement each other's function, and shape the course of disease, can illuminate understanding of atherosclerosis. Innate response activator (IRA) B cells are a recently described population of GM-CSF-secreting cells of hitherto unknown function in atherosclerosis. Here we show that IRA B cells arise during atherosclerosis in mice and humans. In response to high cholesterol diet, IRA B cell numbers increase preferentially in secondary lymphoid organs via Myd88-dependent signaling. Mixed chimeric mice lacking B cell-derived GM-CSF develop smaller lesions with fewer macrophages and effector T cells. Mechanistically, IRA B cells promote the expansion of classical dendritic cells, which then generate IFNγ-producing TH1 cells. This IRA B cell-dependent TH1 skewing manifests in an IgG1 to IgG2c isotype switch in the immunoglobulin response against oxidized lipoproteins. GM-CSF-producing IRA B cells alter adaptive immune processes and shift the leukocyte response toward a TH1-associated mileu that aggravates atherosclerosis.
    Full-text · Article · Jan 2014 · Circulation
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    ABSTRACT: The aim of the study was to test wether silencing of the transcription factor Interferon Regulatory Factor 5 (IRF5) in cardiac macrophages improves infarct healing and attenuates post-MI remodeling. In healing wounds, M1➛M2 macrophage phenotype transition supports resolution of inflammation and tissue repair. Persistence of inflammatory M1 macrophages may derail healing and compromise organ functions. The transcription factor IRF5 promotes genes associated with M1 macrophages. Here we used nanoparticle-delivered siRNA to silence the transcription factor IRF5 in macrophages residing in myocardial infarcts (MI) and in surgically induced skin wounds in mice. Infarct macrophages expressed high levels of IRF5 during the early inflammatory wound healing stages (day 4 after coronary ligation) whereas expression of the transcription factor decreased during the resolution of inflammation (day 8). Following in vitro screening, we identified an siRNA sequence that, when delivered by nanoparticles to wound macrophages, efficiently suppressed expression of IRF5 in vivo. Reduction of IRF5 expression, a factor that regulates macrophage polarization, reduced inflammatory M1 macrophage markers, supported resolution of inflammation, accelerated cutaneous and infarct healing and attenuated development of post-MI heart failure after coronary ligation as measured by protease targeted FMT-CT imaging and cardiac MRI (p<0.05 respectively). This work identifies a new therapeutic avenue to augment resolution of inflammation in healing infarcts by macrophage phenotype manipulation. This therapeutic concept may be used to attenuate post-MI remodeling and heart failure.
    Full-text · Article · Dec 2013 · Journal of the American College of Cardiology

Publication Stats

2k Citations
742.95 Total Impact Points

Institutions

  • 2010-2015
    • Massachusetts General Hospital
      • • Center for Systems Biology
      • • Center for Molecular Imaging Research
      Boston, Massachusetts, United States
  • 2009-2015
    • Harvard University
      Cambridge, Massachusetts, United States
  • 2012
    • CSL Behring
      KPD, Pennsylvania, United States
  • 2010-2012
    • Harvard Medical School
      • Department of Medicine
      Boston, Massachusetts, United States