Publications by authors named "Kory J Lavine"

63 Publications

SVEP1 is a human coronary artery disease locus that promotes atherosclerosis.

Sci Transl Med 2021 Mar;13(586)

Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, Saint Louis, MO 63110, USA.

A low-frequency variant of sushi, von Willebrand factor type A, EGF, and pentraxin domain-containing protein 1 (SVEP1), an extracellular matrix protein, is associated with risk of coronary disease in humans independent of plasma lipids. Despite a robust statistical association, if and how SVEP1 might contribute to atherosclerosis remained unclear. Here, using Mendelian randomization and complementary mouse models, we provide evidence that SVEP1 promotes atherosclerosis in humans and mice and is expressed by vascular smooth muscle cells (VSMCs) within the atherosclerotic plaque. VSMCs also interact with SVEP1, causing proliferation and dysregulation of key differentiation pathways, including integrin and Notch signaling. Fibroblast growth factor receptor transcription increases in VSMCs interacting with SVEP1 and is further increased by the coronary disease-associated variant p.D2702G. These effects ultimately drive inflammation and promote atherosclerosis. Together, our results suggest that VSMC-derived SVEP1 is a proatherogenic factor and support the concept that pharmacological inhibition of SVEP1 should protect against atherosclerosis in humans.
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http://dx.doi.org/10.1126/scitranslmed.abe0357DOI Listing
March 2021

SARS-CoV-2 Infects Human Engineered Heart Tissues and Models COVID-19 Myocarditis.

JACC Basic Transl Sci 2021 Feb 26. Epub 2021 Feb 26.

Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.

There is ongoing debate as to whether cardiac complications of coronavirus disease 2019 (COVID-19) result from myocardial viral infection or are secondary to systemic inflammation and/or thrombosis. We provide evidence that cardiomyocytes are infected in patients with COVID-19 myocarditis and are susceptible to severe acute respiratory syndrome coronavirus 2. We establish an engineered heart tissue model of COVID-19 myocardial pathology, define mechanisms of viral pathogenesis, and demonstrate that cardiomyocyte severe acute respiratory syndrome coronavirus 2 infection results in contractile deficits, cytokine production, sarcomere disassembly, and cell death. These findings implicate direct infection of cardiomyocytes in the pathogenesis of COVID-19 myocardial pathology and provides a model system to study this emerging disease.
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http://dx.doi.org/10.1016/j.jacbts.2021.01.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7909907PMC
February 2021

Lymphatic drainage from bronchus-associated lymphoid tissue in tolerant lung allografts promotes peripheral tolerance.

J Clin Invest 2020 12;130(12):6718-6727

Departments of Surgery.

Tertiary lymphoid organs are aggregates of immune and stromal cells including high endothelial venules and lymphatic vessels that resemble secondary lymphoid organs and can be induced at nonlymphoid sites during inflammation. The function of lymphatic vessels within tertiary lymphoid organs remains poorly understood. During lung transplant tolerance, Foxp3+ cells accumulate in tertiary lymphoid organs that are induced within the pulmonary grafts and are critical for the local downregulation of alloimmune responses. Here, we showed that tolerant lung allografts could induce and maintain tolerance of heterotopic donor-matched hearts through pathways that were dependent on the continued presence of the transplanted lung. Using lung retransplantation, we showed that Foxp3+ cells egressed from tolerant lung allografts via lymphatics and were recruited into donor-matched heart allografts. Indeed, survival of the heart allografts was dependent on lymphatic drainage from the tolerant lung allograft to the periphery. Thus, our work indicates that cellular trafficking from tertiary lymphoid organs regulates immune responses in the periphery. We propose that these findings have important implications for a variety of disease processes that are associated with the induction of tertiary lymphoid organs.
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http://dx.doi.org/10.1172/JCI136057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7685742PMC
December 2020

SARS-CoV-2 Infects Human Engineered Heart Tissues and Models COVID-19 Myocarditis.

bioRxiv 2020 Nov 5. Epub 2020 Nov 5.

Epidemiological studies of the COVID-19 pandemic have revealed evidence of cardiac involvement and documented that myocardial injury and myocarditis are predictors of poor outcomes. Nonetheless, little is understood regarding SARS-CoV-2 tropism within the heart and whether cardiac complications result directly from myocardial infection. Here, we develop a human engineered heart tissue model and demonstrate that SARS-CoV-2 selectively infects cardiomyocytes. Viral infection is dependent on expression of angiotensin-I converting enzyme 2 (ACE2) and endosomal cysteine proteases, suggesting an endosomal mechanism of cell entry. After infection with SARS-CoV-2, engineered tissues display typical features of myocarditis, including cardiomyocyte cell death, impaired cardiac contractility, and innate immune cell activation. Consistent with these findings, autopsy tissue obtained from individuals with COVID-19 myocarditis demonstrated cardiomyocyte infection, cell death, and macrophage-predominate immune cell infiltrate. These findings establish human cardiomyocyte tropism for SARS-CoV-2 and provide an experimental platform for interrogating and mitigating cardiac complications of COVID-19.
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http://dx.doi.org/10.1101/2020.11.04.364315DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7654892PMC
November 2020

Limited proliferation capacity of aortic intima resident macrophages requires monocyte recruitment for atherosclerotic plaque progression.

Nat Immunol 2020 10 7;21(10):1194-1204. Epub 2020 Sep 7.

Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO, USA.

Early atherosclerosis depends upon responses by immune cells resident in the intimal aortic wall. Specifically, the healthy intima is thought to be populated by vascular dendritic cells (DCs) that, during hypercholesterolemia, initiate atherosclerosis by being the first to accumulate cholesterol. Whether these cells remain key players in later stages of disease is unknown. Using murine lineage-tracing models and gene expression profiling, we reveal that myeloid cells present in the intima of the aortic arch are not DCs but instead specialized aortic intima resident macrophages (Mac) that depend upon colony-stimulating factor 1 and are sustained by local proliferation. Although Mac comprise the earliest foam cells in plaques, their proliferation during plaque progression is limited. After months of hypercholesterolemia, their presence in plaques is overtaken by recruited monocytes, which induce Mac-defining genes. These data redefine the lineage of intimal phagocytes and suggest that proliferation is insufficient to sustain generations of macrophages during plaque progression.
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http://dx.doi.org/10.1038/s41590-020-0768-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7502558PMC
October 2020

Beyond genomics-technological advances improving the molecular characterization and precision treatment of heart failure.

Heart Fail Rev 2021 Mar 3;26(2):405-415. Epub 2020 Sep 3.

Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8231, St. Louis, MO, 63110, USA.

Dilated cardiomyopathy (DCM) is a major cause of heart failure and cardiovascular mortality. In the past 20 years, there has been an overwhelming focus on developing therapeutics that target common downstream disease pathways thought to be involved in all forms of heart failure independent of the initial etiology. While this strategy is effective at the population level, individual responses vary tremendously and only approximately one third of patients receive benefit from modern heart failure treatments. In this perspective, we propose that DCM should be considered as a collection of diseases with a common phenotype of left ventricular dilation and systolic dysfunction rather than a single disease entity, and that mechanism-based classification of disease subtypes will revolutionize our understanding and clinical approach towards DCM. We discuss how these efforts are central to realizing the potential of precision medicine and how they are empowered by the development of new tools that allow investigators to strategically employ genomic and transcriptomic information. Finally, we outline an investigational strategy to (1) define DCM at the patient level, (2) develop new tools to model and mechanistically dissect subtypes of human heart failure, and (3) harness these insights for the development of precision therapeutics.
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http://dx.doi.org/10.1007/s10741-020-10021-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7897225PMC
March 2021

A Minimal-Invasive Approach for Standardized Induction of Myocardial Infarction in Mice.

Circ Res 2020 Oct 28;127(9):1214-1216. Epub 2020 Aug 28.

Department of Internal Medicine III, University of Heidelberg, Germany (F.S., Y.Z., L.L., M.H.K., H.A.K., F.L.).

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http://dx.doi.org/10.1161/CIRCRESAHA.120.317794DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7739440PMC
October 2020

Heterogeneous origins and functions of mouse skeletal muscle-resident macrophages.

Proc Natl Acad Sci U S A 2020 08 13;117(34):20729-20740. Epub 2020 Aug 13.

Department of Neurology, Boston University School of Medicine, Boston, MA 02118;

Tissue-resident macrophages can originate from embryonic or adult hematopoiesis. They play important roles in a wide range of biological processes including tissue remodeling during organogenesis, organ homeostasis, repair following injury, and immune response to pathogens. Although the origins and tissue-specific functions of resident macrophages have been extensively studied in many other tissues, they are not well characterized in skeletal muscle. In the present study, we have characterized the ontogeny of skeletal muscle-resident macrophages by lineage tracing and bone marrow transplant experiments. We demonstrate that skeletal muscle-resident macrophages originate from both embryonic hematopoietic progenitors located within the yolk sac and fetal liver as well as definitive hematopoietic stem cells located within the bone marrow of adult mice. Single-cell-based transcriptome analyses revealed that skeletal muscle-resident macrophages are distinctive from resident macrophages in other tissues as they express a distinct complement of transcription factors and are composed of functionally diverse subsets correlating to their origins. Functionally, skeletal muscle-resident macrophages appear to maintain tissue homeostasis and promote muscle growth and regeneration.
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http://dx.doi.org/10.1073/pnas.1915950117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456122PMC
August 2020

Eosinophils Confer Protection Following Myocardial Infarction.

Authors:
Kory J Lavine

JACC Basic Transl Sci 2020 Jul 27;5(7):682-684. Epub 2020 Jul 27.

Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri.

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http://dx.doi.org/10.1016/j.jacbts.2020.06.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393425PMC
July 2020

Chemokine Receptor 2-targeted Molecular Imaging in Pulmonary Fibrosis. A Clinical Trial.

Am J Respir Crit Care Med 2021 01;203(1):78-89

Department of Radiology.

Idiopathic pulmonary fibrosis (IPF) is a progressive inflammatory lung disease without effective molecular markers of disease activity or treatment responses. Monocyte and interstitial macrophages that express the C-C motif CCR2 (chemokine receptor 2) are active in IPF and central to fibrosis. To phenotype patients with IPF for potential targeted therapy, we developed Cu-DOTA-ECL1i, a radiotracer to noninvasively track CCR2 monocytes and macrophages using positron emission tomography (PET). CCR2 cells were investigated in mice with bleomycin- or radiation-induced fibrosis and in human subjects with IPF. The CCR2 cell populations were localized relative to fibrotic regions in lung tissue and characterized using immunolocalization, single-cell mass cytometry, and RNA hybridization and then correlated with parallel quantitation of lung uptake by Cu-DOTA-ECL1i PET. Mouse models established that increased Cu-DOTA-ECL1i PET uptake in the lung correlates with CCR2 cell infiltration associated with fibrosis ( = 72). As therapeutic models, the inhibition of fibrosis by IL-1β blockade ( = 19) or antifibrotic pirfenidone ( = 18) reduced CCR2 macrophage accumulation and uptake of the radiotracer in mouse lungs. In lung tissues from patients with IPF, CCR2 cells concentrated in perifibrotic regions and correlated with radiotracer localization ( = 21). Human imaging revealed little lung uptake in healthy volunteers ( = 7), whereas subjects with IPF ( = 4) exhibited intensive signals in fibrotic zones. These findings support a role for imaging CCR2 cells within the fibrogenic niche in IPF to provide a molecular target for personalized therapy and monitoring.Clinical trial registered with www.clinicaltrials.gov (NCT03492762).
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http://dx.doi.org/10.1164/rccm.202004-1132OCDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7781144PMC
January 2021

Targeted PET Imaging of Chemokine Receptor 2-Positive Monocytes and Macrophages in the Injured Heart.

J Nucl Med 2021 01 22;62(1):111-114. Epub 2020 May 22.

Department of Radiology, Washington University School of Medicine, St. Louis, Missouri

Proinflammatory macrophages are important mediators of inflammation after myocardial infarction and of allograft injury after heart transplantation. The aim of this study was to image the recruitment of proinflammatory chemokine receptor 2-positive (CCR2+) cells in multiple heart injury models. Cu-DOTA-extracellular loop 1 inverso (ECL1i) PET was used to image CCR2+ monocytes and macrophages in a heart transplantation mouse model. Flow cytometry was performed to characterize CCR2+ cells. Autoradiography on a human heart specimen was conducted to confirm binding specificity. Cu- and Ga-DOTA-ECL1i were compared in an ischemia-reperfusion injury mouse model. Cu-DOTA-ECL1i showed sensitive and specific detection of CCR2+ cells in all tested mouse models, with efficacy comparable to that of Ga-DOTA-ECL1i. Flow cytometry demonstrated specific expression of CCR2 on monocytes and macrophages. The tracer binds to human CCR2. This work establishes the utility of Cu-DOTA-ECL1i to image CCR2+ monocytes and macrophages in mouse models and provides the requisite preclinical information to translate the targeted clinical-grade CCR2 imaging probe for clinical investigation of heart diseases.
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http://dx.doi.org/10.2967/jnumed.120.244673DOI Listing
January 2021

Isolation of Macrophage Subsets and Stromal Cells from Human and Mouse Myocardial Specimens.

J Vis Exp 2019 12 17(154). Epub 2019 Dec 17.

Department of Medicine, Washington University School of Medicine; Department of Immunology and Pathology, Washington University School of Medicine; Department of Developmental Biology, Washington University School of Medicine;

Macrophages represent the most heterogeneous and abundant immune cell populations in the heart and are central in driving inflammation and reparative responses after cardiac injury. How various subsets of macrophages orchestrate the immune responses after cardiac injury is an active area of research. Presented here is a simple protocol that our lab performs routinely, for the extraction of macrophages from mouse and human myocardium specimens obtained from healthy and diseased individuals. Briefly, this protocol involves enzymatic digestion of cardiac tissue to generate a single cell suspension, followed by antibody staining, and flow cytometry. This technique is suitable for functional assays performed on sorted cells as well as bulk and single cell RNA sequencing. A major advantage of this protocol is its simplicity, minimal day to day variation and wide applicability allowing investigation of macrophage heterogeneity across various mouse models and human disease entities.
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http://dx.doi.org/10.3791/60015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7222227PMC
December 2019

Role of donor macrophages after heart and lung transplantation.

Am J Transplant 2020 05 29;20(5):1225-1235. Epub 2020 Jan 29.

Department of Medicine, Washington University, Saint Louis, Missouri, USA.

Since the 1960s, heart and lung transplantation has remained the optimal therapy for patients with end-stage disease, extending and improving quality of life for thousands of individuals annually. Expanding donor organ availability and immunologic compatibility is a priority to help meet the clinical demand for organ transplant. While effective, current immunosuppression is imperfect as it lacks specificity and imposes unintended adverse effects such as opportunistic infections and malignancy that limit the health and longevity of transplant recipients. In this review, we focus on donor macrophages as a new target to achieve allograft tolerance. Donor organ-directed therapies have the potential to improve allograft survival while minimizing patient harm related to global suppression of recipient immune responses. Topics highlighted include the role of ontogenically distinct donor macrophage populations in ischemia-reperfusion injury and rejection, including their interaction with allograft-infiltrating recipient immune cells and potential therapeutic approaches. Ultimately, a better understanding of how donor intrinsic immunity influences allograft acceptance and survival will provide new opportunities to improve the outcomes of transplant recipients.
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http://dx.doi.org/10.1111/ajt.15751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7202685PMC
May 2020

TFEB activation in macrophages attenuates postmyocardial infarction ventricular dysfunction independently of ATG5-mediated autophagy.

JCI Insight 2019 11 1;4(21). Epub 2019 Nov 1.

Cardiovascular Division and Center for Cardiovascular Research, Department of Medicine.

Lysosomes are at the epicenter of cellular processes critical for inflammasome activation in macrophages. Inflammasome activation and IL-1β secretion are implicated in myocardial infarction (MI) and resultant heart failure; however, little is known about how macrophage lysosomes regulate these processes. In mice subjected to cardiac ischemia/reperfusion (IR) injury and humans with ischemic cardiomyopathy, we observed evidence of lysosomal impairment in macrophages. Inducible macrophage-specific overexpression of transcription factor EB (TFEB), a master regulator of lysosome biogenesis (Mϕ-TFEB), attenuated postinfarction remodeling, decreased abundance of proinflammatory macrophages, and reduced levels of myocardial IL-1β compared with controls. Surprisingly, neither inflammasome suppression nor Mϕ-TFEB-mediated attenuation of postinfarction myocardial dysfunction required intact ATG5-dependent macroautophagy (hereafter termed "autophagy"). RNA-seq of flow-sorted macrophages postinfarction revealed that Mϕ-TFEB upregulated key targets involved in lysosomal lipid metabolism. Specifically, inhibition of the TFEB target, lysosomal acid lipase, in vivo abrogated the beneficial effect of Mϕ-TFEB on postinfarction ventricular function. Thus, TFEB reprograms macrophage lysosomal lipid metabolism to attenuate remodeling after IR, suggesting an alternative paradigm whereby lysosome function affects inflammation.
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http://dx.doi.org/10.1172/jci.insight.127312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6948771PMC
November 2019

New Approaches to Target Inflammation in Heart Failure: Harnessing Insights from Studies of Immune Cell Diversity.

Annu Rev Physiol 2020 02 28;82:1-20. Epub 2019 Oct 28.

Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA; email:

Despite mounting evidence implicating inflammation in cardiovascular diseases, attempts at clinical translation have shown mixed results. Recent preclinical studies have reenergized this field and provided new insights into how to favorably modulate cardiac macrophage function in the context of acute myocardial injury and chronic disease. In this review, we discuss the origins and roles of cardiac macrophage populations in the steady-state and diseased heart, focusing on the human heart and mouse models of ischemia, hypertensive heart disease, and aortic stenosis. Specific attention is given to delineating the roles of tissue-resident and recruited monocyte-derived macrophage subsets. We also highlight emerging concepts of monocyte plasticity and heterogeneity among monocyte-derived macrophages, describe possible mechanisms by which infiltrating monocytes acquire unique macrophage fates, and discuss the putative impact of these populations on cardiac remodeling. Finally, we discuss strategies to target inflammatory macrophage populations.
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http://dx.doi.org/10.1146/annurev-physiol-021119-034412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7202684PMC
February 2020

Macrophage Plasticity and Function in the Eye and Heart.

Trends Immunol 2019 09 15;40(9):825-841. Epub 2019 Aug 15.

Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA; Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA. Electronic address:

Macrophages are important mediators of inflammation and tissue remodeling. Recent insights into the heterogeneity of macrophage subpopulations have renewed interest in their functional diversity in homeostasis and disease. In addition, their plasticity enables them to perform a variety of functions in response to changing tissue contexts, such as those imposed by aging. These qualities make macrophages particularly intriguing cells given their dichotomous role in protecting against, or accelerating, diseases of the cardiovascular system and the eye, two tissues that are particularly susceptible to the effects of aging. We review novel perspectives on macrophage biology, as informed by recent studies detailing the diversity of macrophage identity and function, as well as mechanisms influencing macrophage behavior that might offer opportunities for new therapeutic strategies.
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http://dx.doi.org/10.1016/j.it.2019.07.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6719788PMC
September 2019

Immunomodulatory role of non-neuronal cholinergic signaling in myocardial injury.

JCI Insight 2019 06 4;5. Epub 2019 Jun 4.

Whereas prior studies have demonstrated an important immunomodulatory role for the neuronal cholinergic system in the heart, the role of the non-neuronal cholinergic system is not well understood. To address the immunomodulatory role of the non-neuronal cholinergic system in the heart we used a previously validated diphtheria toxin (DT)-induced cardiomyocyte ablation model (Rosa26-DTMlc2v-Cre mice). DT-injected Rosa26-DTMlc2v-Cre mice were treated with diluent or Pyridostigmine Bromide (PYR), a reversible cholinesterase inhibitor. PYR treatment resulted in increased survival and decreased numbers of MHC-IIlowCCR2+ macrophages in DT-injected Rosa26-DTMlc2v-Cre mice compared to diluent treated Rosa26-DTMlc2v-Cre mice. Importantly, the expression of CCL2/7 mRNA and protein was reduced in the hearts of PYR-treated mice. Backcrossing Rosa26-DTMlc2v-Cre mice with a transgenic mouse line (Chat-ChR2) that constitutively overexpresses the vesicular acetylcholine transporter (VAChT) resulted in decreased expression of Ccl2/7 mRNA and decreased numbers of CD68+ cells in DT-injured Rosa26-DTMlc2v-Cre/Chat-ChR2 mouse hearts, consistent with the pharmacologic studies with PYR. In vitro studies with cultures of LPS-stimulated peritoneal macrophages revealed a concentration-dependent reduction in CCL2 secretion following stimulation with ACh, nicotine and muscarine. Viewed together, these findings reveal a previously unappreciated immunomodulatory role for the non-neuronal cholinergic system in regulating homeostatic responses in the heart following tissue injury.
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http://dx.doi.org/10.1172/jci.insight.128961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6675555PMC
June 2019

Publisher Correction: Self-renewing resident cardiac macrophages limit adverse remodeling following myocardial infarction.

Nat Immunol 2019 May;20(5):664

Toronto General Hospital Research Institute, University Health Network (UHN), Toronto, Canada.

In the version of this article initially published, the equal contribution of the third author was omitted. The footnote links for that author should be "Sara Nejat" and the correct statement is as follows: "These authors contributed equally: Sarah A. Dick, Jillian A. Macklin, Sara Nejat." The error has been corrected in the HTML and PDF versions of the article.
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http://dx.doi.org/10.1038/s41590-019-0363-8DOI Listing
May 2019

Ferroptotic cell death and TLR4/Trif signaling initiate neutrophil recruitment after heart transplantation.

J Clin Invest 2019 02 26;129(6):2293-2304. Epub 2019 Feb 26.

Department of Surgery and.

Non-apoptotic forms of cell death can trigger sterile inflammation through the release of danger-associated molecular patterns, which are recognized by innate immune receptors. However, despite years of investigation the mechanisms which initiate inflammatory responses after heart transplantation remain elusive. Here, we demonstrate that ferrostatin-1 (Fer-1), a specific inhibitor of ferroptosis, decreases the level of pro-ferroptotic hydroperoxy-arachidonoyl-phosphatidylethanolamine, reduces cardiomyocyte cell death and blocks neutrophil recruitment following heart transplantation. Inhibition of necroptosis had no effect on neutrophil trafficking in cardiac grafts. We extend these observations to a model of coronary artery ligation-induced myocardial ischemia reperfusion injury where inhibition of ferroptosis resulted in reduced infarct size, improved left ventricular systolic function, and reduced left ventricular remodeling. Using intravital imaging of cardiac transplants, we uncover that ferroptosis orchestrates neutrophil recruitment to injured myocardium by promoting adhesion of neutrophils to coronary vascular endothelial cells through a TLR4/TRIF/type I IFN signaling pathway. Thus, we have discovered that inflammatory responses after cardiac transplantation are initiated through ferroptotic cell death and TLR4/Trif-dependent signaling in graft endothelial cells. These findings provide a platform for the development of therapeutic strategies for heart transplant recipients and patients, who are vulnerable to ischemia reperfusion injury following restoration of coronary blood flow.
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http://dx.doi.org/10.1172/JCI126428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6546457PMC
February 2019

Molecular Imaging Visualizes Recruitment of Inflammatory Monocytes and Macrophages to the Injured Heart.

Circ Res 2019 03;124(6):881-890

Department of Medicine (B.K., G.F., G.B., S.L.B., K.J.L.), Washington University School of Medicine, St. Louis, MO.

Rationale: Paradigm shifting studies have revealed that the heart contains functionally diverse populations of macrophages derived from distinct embryonic and adult hematopoietic progenitors. Under steady-state conditions, the heart is largely populated by CCR2- (C-C chemokine receptor type 2) macrophages of embryonic descent. After tissue injury, a dramatic shift in macrophage composition occurs whereby CCR2+ monocytes are recruited to the heart and differentiate into inflammatory CCR2+ macrophages that contribute to heart failure progression. Currently, there are no techniques to noninvasively detect CCR2+ monocyte recruitment into the heart and thus identify patients who may be candidates for immunomodulatory therapy.

Objective: To develop a noninvasive molecular imaging strategy with high sensitivity and specificity to visualize inflammatory monocyte and macrophage accumulation in the heart.

Methods And Results: We synthesized and tested the performance of a positron emission tomography radiotracer (Ga-DOTA [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-ECL1i [extracellular loop 1 inverso]) that allosterically binds to CCR2. In naive mice, the radiotracer was quickly cleared from the blood and displayed minimal retention in major organs. In contrast, biodistribution and positron emission tomography demonstrated strong myocardial tracer uptake in 2 models of cardiac injury (diphtheria toxin induced cardiomyocyte ablation and reperfused myocardial infarction). Ga-DOTA-ECL1i signal localized to sites of tissue injury and was independent of blood pool activity as assessed by quantitative positron emission tomography and ex vivo autoradiography. Ga-DOTA-ECL1i uptake was associated with CCR2+ monocyte and CCR2+ macrophage infiltration into the heart and was abrogated in CCR2 mice, demonstrating target specificity. Autoradiography demonstrated that Ga-DOTA-ECL1i specifically binds human heart failure specimens and with signal intensity associated with CCR2+ macrophage abundance.

Conclusions: These findings demonstrate the sensitivity and specificity of Ga-DOTA-ECL1i in the mouse heart and highlight the translational potential of this agent to noninvasively visualize CCR2+ monocyte recruitment and inflammatory macrophage accumulation in patients.
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http://dx.doi.org/10.1161/CIRCRESAHA.118.314030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435034PMC
March 2019

Tissue Resident CCR2- and CCR2+ Cardiac Macrophages Differentially Orchestrate Monocyte Recruitment and Fate Specification Following Myocardial Injury.

Circ Res 2019 01;124(2):263-278

From the Department of Medicine (G.B., A.B., A.L. Koenig, I.L., J.M., B.I., C.W., A. Kovacs, K.J.L.), Washington University School of Medicine, St. Louis, MO.

Rationale: Recent advancements have brought to light the origins, complexity, and functions of tissue-resident macrophages. However, in the context of tissue injury or disease, large numbers of monocytes infiltrate the heart and are thought to contribute to adverse remodeling and heart failure pathogenesis. Little is understood about the diversity of monocytes and monocyte-derived macrophages recruited to the heart after myocardial injury, including the mechanisms that regulate monocyte recruitment and fate specification.

Objective: We sought to test the hypothesis that distinct subsets of tissue-resident CCR2- (C-C chemokine receptor 2) and CCR2+ macrophages orchestrate monocyte recruitment and fate specification after myocardial injury.

Methods And Results: We reveal that in numerous mouse models of cardiomyocyte cell death (permanent myocardial infarction, reperfused myocardial infarction, and diphtheria toxin cardiomyocyte ablation), there is a shift in macrophage ontogeny whereby tissue-resident macrophages are predominately replaced by infiltrating monocytes and monocyte-derived macrophages. Using syngeneic cardiac transplantation to model ischemia-reperfusion injury and distinguish tissue-resident from recruited cell populations in combination with intravital 2-photon microscopy, we demonstrate that monocyte recruitment is differentially orchestrated by distinct subsets of tissue-resident cardiac macrophages. Tissue-resident CCR2+ macrophages promote monocyte recruitment through an MYD88 (myeloid differentiation primary response 88)-dependent mechanism that results in release of MCPs (monocyte chemoattractant proteins) and monocyte mobilization. In contrast, tissue-resident CCR2- macrophages inhibit monocyte recruitment. Using CD (cluster of differentiation) 169-DTR (diphtheria toxin receptor) and CCR2-DTR mice, we further show that selective depletion of either tissue-resident CCR2- or CCR2+ macrophages before myocardial infarction results in divergent effects on left ventricular function, myocardial remodeling, and monocyte recruitment. Finally, using single-cell RNA sequencing, we show that tissue-resident cardiac macrophages differentially instruct monocyte fate specification.

Conclusions: Collectively, these observations establish the mechanistic basis by which monocytes are initially recruited to the injured heart and provide new insights into the heterogeneity of monocyte-derived macrophages.
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http://dx.doi.org/10.1161/CIRCRESAHA.118.314028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6626616PMC
January 2019

Self-renewing resident cardiac macrophages limit adverse remodeling following myocardial infarction.

Nat Immunol 2019 01 11;20(1):29-39. Epub 2018 Dec 11.

Toronto General Hospital Research Institute, University Health Network (UHN), Toronto, Canada.

Macrophages promote both injury and repair after myocardial infarction, but discriminating functions within mixed populations remains challenging. Here we used fate mapping, parabiosis and single-cell transcriptomics to demonstrate that at steady state, TIMD4LYVE1MHC-IICCR2 resident cardiac macrophages self-renew with negligible blood monocyte input. Monocytes partially replaced resident TIMD4LYVE1MHC-IICCR2 macrophages and fully replaced TIMD4LYVE1MHC-IICCR2 macrophages, revealing a hierarchy of monocyte contribution to functionally distinct macrophage subsets. Ischemic injury reduced TIMD4 and TIMD4 resident macrophage abundance, whereas CCR2 monocyte-derived macrophages adopted multiple cell fates within infarcted tissue, including those nearly indistinguishable from resident macrophages. Recruited macrophages did not express TIMD4, highlighting the ability of TIMD4 to track a subset of resident macrophages in the absence of fate mapping. Despite this similarity, inducible depletion of resident macrophages using a Cx3cr1-based system led to impaired cardiac function and promoted adverse remodeling primarily within the peri-infarct zone, revealing a nonredundant, cardioprotective role of resident cardiac macrophages.
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http://dx.doi.org/10.1038/s41590-018-0272-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6565365PMC
January 2019

The Macrophage in Cardiac Homeostasis and Disease: JACC Macrophage in CVD Series (Part 4).

J Am Coll Cardiol 2018 10;72(18):2213-2230

Zena and Michael A. Wiener Cardiovascular Institute, Icahn School of Medicine at Mount Sinai, New York, New York. Electronic address:

Macrophages are integral components of cardiac tissue and exert profound effects on the healthy and diseased heart. Paradigm shifting studies using advanced molecular techniques have revealed significant complexity within these macrophage populations that reside in the heart. In this final of a 4-part review series covering the macrophage in cardiovascular disease, the authors review the origins, dynamics, cell surface markers, and respective functions of each cardiac macrophage subset identified to date, including in the specific scenarios of myocarditis and after myocardial infarction. Looking ahead, a deeper understanding of the diverse and often dichotomous functions of cardiac macrophages will be essential for the development of targeted therapies to mitigate injury and orchestrate recovery of the diseased heart. Moreover, as macrophages are critical for cardiac healing, they are an emerging focus for therapeutic strategies aimed at minimizing cardiomyocyte death, ameliorating pathological cardiac remodeling, and for treating heart failure and after myocardial infarction.
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http://dx.doi.org/10.1016/j.jacc.2018.08.2149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6209119PMC
October 2018

The human heart contains distinct macrophage subsets with divergent origins and functions.

Nat Med 2018 08 11;24(8):1234-1245. Epub 2018 Jun 11.

Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, Saint Louis, MO, USA.

Paradigm-shifting studies in the mouse have identified tissue macrophage heterogeneity as a critical determinant of immune responses. In contrast, surprisingly little is known regarding macrophage heterogeneity in humans. Macrophages within the mouse heart are partitioned into CCR2- and CCR2+ subsets with divergent origins, repopulation mechanisms, and functions. Here, we demonstrate that the human myocardium also contains distinct subsets of CCR2- and CCR2+ macrophages. Analysis of sex-mismatched heart transplant recipients revealed that CCR2- macrophages are a tissue-resident population exclusively replenished through local proliferation, whereas CCR2+ macrophages are maintained through monocyte recruitment and proliferation. Moreover, CCR2- and CCR2+ macrophages have distinct functional properties, analogous to reparative CCR2- and inflammatory CCR2+ macrophages in the mouse heart. Clinically, CCR2+ macrophage abundance is associated with left ventricular remodeling and systolic function in heart failure patients. Collectively, these observations provide initial evidence for the functional importance of macrophage heterogeneity in the human heart.
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http://dx.doi.org/10.1038/s41591-018-0059-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082687PMC
August 2018

Spleen-derived classical monocytes mediate lung ischemia-reperfusion injury through IL-1β.

J Clin Invest 2018 07 21;128(7):2833-2847. Epub 2018 May 21.

Department of Surgery, Washington University in St. Louis, St. Louis, Missouri, USA.

Ischemia-reperfusion injury, a form of sterile inflammation, is the leading risk factor for both short-term mortality following pulmonary transplantation and chronic lung allograft dysfunction. While it is well recognized that neutrophils are critical mediators of acute lung injury, processes that guide their entry into pulmonary tissue are not well understood. Here, we found that CCR2+ classical monocytes are necessary and sufficient for mediating extravasation of neutrophils into pulmonary tissue during ischemia-reperfusion injury following hilar clamping or lung transplantation. The classical monocytes were mobilized from the host spleen, and splenectomy attenuated the recruitment of classical monocytes as well as the entry of neutrophils into injured lung tissue, which was associated with improved graft function. Neutrophil extravasation was mediated by MyD88-dependent IL-1β production by graft-infiltrating classical monocytes, which downregulated the expression of the tight junction-associated protein ZO-2 in pulmonary vascular endothelial cells. Thus, we have uncovered a crucial role for classical monocytes, mobilized from the spleen, in mediating neutrophil extravasation, with potential implications for targeting of recipient classical monocytes to ameliorate pulmonary ischemia-reperfusion injury in the clinic.
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http://dx.doi.org/10.1172/JCI98436DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6025976PMC
July 2018

Visualization of Monocytic Cells in Regressing Atherosclerotic Plaques by Intravital 2-Photon and Positron Emission Tomography-Based Imaging-Brief Report.

Arterioscler Thromb Vasc Biol 2018 05 22;38(5):1030-1036. Epub 2018 Mar 22.

From the Department of Surgery (W.L., H.-M.H., S.T., R.H., J.M.G., A.E.G., D.K.)

Objective: Aortic arch transplants have advanced our understanding of processes that contribute to progression and regression of atherosclerotic plaques. To characterize the dynamic behavior of monocytes and macrophages in atherosclerotic plaques over time, we developed a new model of cervical aortic arch transplantation in mice that is amenable to intravital imaging.

Approach And Results: Vascularized aortic arch grafts were transplanted heterotropically to the right carotid arteries of recipient mice using microsurgical suture techniques. To image immune cells in atherosclerotic lesions during regression, plaque-bearing aortic arch grafts from B6 ApoE-deficient donors were transplanted into syngeneic CXCR1 GFP reporter mice. Grafts were evaluated histologically, and monocytic cells in atherosclerotic plaques in ApoE-deficient grafts were imaged intravitally by 2-photon microscopy in serial fashion. In complementary experiments, CCR2 cells in plaques were serially imaged by positron emission tomography using specific molecular probes. Plaques in ApoE-deficient grafts underwent regression after transplantation into normolipidemic hosts. Intravital imaging revealed clusters of largely immotile CXCR1 monocytes/macrophages in regressing plaques that had been recruited from the periphery. We observed a progressive decrease in CXCR1 monocytic cells in regressing plaques and a decrease in CCR2 positron emission tomography signal during 4 months.

Conclusions: Cervical transplantation of atherosclerotic mouse aortic arches represents a novel experimental tool to investigate cellular mechanisms that contribute to the remodeling of atherosclerotic plaques.
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http://dx.doi.org/10.1161/ATVBAHA.117.310517DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5920767PMC
May 2018

Recognition of self-DNA drives cardiac inflammation: why broken hearts fail.

Nat Med 2017 12;23(12):1400-1401

Center for Cardiovascular Research, Division of Cardiology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.

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http://dx.doi.org/10.1038/nm.4455DOI Listing
December 2017

A CD103 Conventional Dendritic Cell Surveillance System Prevents Development of Overt Heart Failure during Subclinical Viral Myocarditis.

Immunity 2017 11;47(5):974-989.e8

Toronto General Hospital Research Institute, University Health Network (UHN), Toronto ON, M5G 1L7, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto ON, M5S 1A1, Canada; Department of Immunology, University of Toronto, Toronto ON, M5S 1A1, Canada; Peter Munk Cardiac Centre, Toronto ON, M5G 1L7, Canada; Ted Rogers Centre for Heart Research, Toronto ON, M5G 1L7, Canada. Electronic address:

Innate and adaptive immune cells modulate heart failure pathogenesis during viral myocarditis, yet their identities and functions remain poorly defined. We utilized a combination of genetic fate mapping, parabiotic, transcriptional, and functional analyses and demonstrated that the heart contained two major conventional dendritic cell (cDC) subsets, CD103 and CD11b, which differentially relied on local proliferation and precursor recruitment to maintain their tissue residency. Following viral infection of the myocardium, cDCs accumulated in the heart coincident with monocyte infiltration and loss of resident reparative embryonic-derived cardiac macrophages. cDC depletion abrogated antigen-specific CD8 T cell proliferative expansion, transforming subclinical cardiac injury to overt heart failure. These effects were mediated by CD103 cDCs, which are dependent on the transcription factor BATF3 for their development. Collectively, our findings identified resident cardiac cDC subsets, defined their origins, and revealed an essential role for CD103 cDCs in antigen-specific T cell responses during subclinical viral myocarditis.
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http://dx.doi.org/10.1016/j.immuni.2017.10.011DOI Listing
November 2017

Cardiac Lymphatic Vessels, Transport, and Healing of the Infarcted Heart.

JACC Basic Transl Sci 2017 08 28;2(4):477-483. Epub 2017 Aug 28.

Department of Pathology & Immunology, Washington University School of Medicine, St Louis, MO, 63110 USA.

The lymphatic vasculature plays a key role throughout the body in regulating tissue fluid homeostasis, lipid transport, and immune surveillance. Whereas it has been appreciated that the heart relies on lymphatic vessels to maintain fluid balance and that such balance must be tightly maintained to allow for normal cardiac output, it has only recently come to light that the lymphatic vasculature might serve as a therapeutic target to promote optimal healing following myocardial ischemia and infarction. We review the subject of cardiac lymphatic vessels herein and highlight studies that imply targeting of lymphatic vessel development or transport may serve as a promising avenue for future clinical application in the context of ischemic injury.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628514PMC
http://dx.doi.org/10.1016/j.jacbts.2017.02.005DOI Listing
August 2017