Leukemia inhibitory factor (LIF) receptor amplifies pathogenic activation of fibroblasts in lung fibrosis.

Fibrosis drives end-organ damage in many diseases. However, clinical trials targeting individual upstream activators of fibroblasts, such as TGFß, have largely failed. Here, we target the leukemia inhibitory factor receptor (LIFR) as a "master amplifier" of multiple upstream activators of lung fibroblasts. In idiopathic pulmonary fibrosis (IPF), the most common fibrotic lung disease, we found that lung myofibroblasts had high LIF expression. Further, TGFß1, one of the key drivers of fibrosis, upregulated LIF expression in IPF fibroblasts. In vitro anti-LIFR antibody blocking on human IPF lung fibroblasts reduced induction of profibrotic genes downstream of TGFß1, IL-4 and IL-13. Further, siRNA silencing of LIFR in IPF precision cut lung slices reduced expression of fibrotic proteins. Together, we find that LIFR drives an autocrine positive feedback loop that amplifies and sustains pathogenic activation of IPF fibroblasts downstream of multiple external stimuli, implicating LIFR as a therapeutic target in fibrosis. Significance Statement: Fibroblasts have a central role in the pathogenesis of fibrotic diseases. However, due to in part to multiple profibrotic stimuli, targeting a single activator of fibroblasts, like TGFß, has not yielded successful clinical treatments. We hypothesized that a more effective therapeutic strategy is identifying a downstream "master amplifier" of a range of upstream profibrotic stimuli. This study identifies the leukemia inhibitory factor receptor (LIFR) on fibrotic lung fibroblasts amplifies multiple profibrotic stimuli, such as IL-13 and TGFß. Blocking LIFR reduced fibrosis in ex vivo lung tissue from patients with idiopathic pulmonary fibrosis (IPF). LIFR, acting as a master amplifier downstream of fibroblast activation, offers an alternative therapeutic strategy for fibrotic diseases.

Integrated Immunopeptidomic and Proteomic Analysis of COVID-19 lung biopsies.

Introduction: Severe respiratory illness is the most prominent manifestation of patients infected with SARS-CoV-2, and yet the molecular mechanisms underlying severe lung disease in COVID-19 affected patients still require elucidation. Human leukocyte antigen class I (HLA-I) expression is crucial for antigen presentation and the host's response to SARS-CoV-2. Methods: To gain insights into the immune response and molecular pathways involved in severe lung disease, we performed immunopeptidomic and proteomic analyses of lung tissues recovered at four COVID-19 autopsy and six non-COVID-19 transplants. Results: We found signals of tissue injury and regeneration in lung fibroblast and alveolar type I/II cells, resulting in the production of highly immunogenic self-antigens within the lungs of COVID-19 patients. We also identified immune activation of the M2c macrophage as the primary source of HLA-I presentation and immunogenicity in this context. Additionally, we identified 28 lung signatures that can serve as early plasma markers for predicting infection and severe COVID-19 disease. These protein signatures were predominantly expressed in macrophages and epithelial cells and were associated with complement and coagulation cascades. Discussion: Our findings emphasize the significant role of macrophage-mediated immunity in the development of severe lung disease in COVID-19 patients.

Consensus statement on the processing, interpretation and reporting of temporal artery biopsy for arteritis.

Giant cell arteritis (GCA) is the most common systemic vasculitis in adults in Europe and North America, typically involving the extra-cranial branches of the carotid arteries and the thoracic aorta. Despite advances in noninvasive imaging, temporal artery biopsy (TAB) remains the gold standard for establishing a GCA diagnosis. The processing of TAB depends largely on individual institutional protocol, and the interpretation and reporting practices vary among pathologists. To address this lack of uniformity, the Society for Cardiovascular Pathology formed a committee tasked with establishing consensus guidelines for the processing, interpretation, and reporting of TAB specimens, based on the existing literature. This consensus statement includes a discussion of the differential diagnoses including other forms of arteritis and noninflammatory changes of the temporal artery.

Extrafollicular IgD-CD27-CXCR5-CD11c- DN3 B cells infiltrate inflamed tissues in autoimmune fibrosis and in severe COVID-19.

Although therapeutic B cell depletion dramatically resolves inflammation in many diseases in which antibodies appear not to play a central role, distinct extrafollicular pathogenic B cell subsets that accumulate in disease lesions have hitherto not been identified. The circulating immunoglobulin D (IgD)-CD27-CXCR5-CD11c+ DN2 B cell subset has been previously studied in some autoimmune diseases. A distinct IgD-CD27-CXCR5-CD11c- DN3 B cell subset accumulates in the blood both in IgG4-related disease, an autoimmune disease in which inflammation and fibrosis can be reversed by B cell depletion, and in severe COVID-19. These DN3 B cells prominently accumulate in the end organs of IgG4-related disease and in lung lesions in COVID-19, and double-negative B cells prominently cluster with CD4+ T cells in these lesions. Extrafollicular DN3 B cells may participate in tissue inflammation and fibrosis in autoimmune fibrotic diseases, as well as in COVID-19.

Recurrent Tumor Suppressor Alterations in Primary Pericardial Mesothelioma.

Primary pericardial mesotheliomas are extremely rare, accounting for <1% of all mesotheliomas, and their molecular genetic features and predisposing factors remain to be determined. Here, we report the clinicopathologic, immunohistochemical, and molecular genetic findings of 3 pericardial mesotheliomas without pleural involvement. Three cases diagnosed between 2004 and 2022 were included in the study and analyzed by immunohistochemistry and targeted next-generation sequencing (NGS); corresponding nonneoplastic tissue was sequenced in all cases. Two patients were female and 1 was male, aged between 66 and 75 years. Two patients each had prior asbestos exposure and were smokers. Histologic subtypes were epithelioid in 2 cases and biphasic in 1 case. Immunohistochemical staining identified expression of cytokeratin AE1/AE3 and calretinin in all cases, D2-40 in 2 cases, and WT1 in 1 case. Staining for tumor suppressors revealed loss of p16, MTAP, and Merlin (NF2) expression in 2 cases and loss of BAP1 and p53 in 1 case. Abnormal cytoplasmic BAP1 expression was observed in an additional case. Protein expression abnormalities correlated with NGS results, which showed concurrent complete genomic inactivation of CDKN2A/p16, CDKN2B, MTAP, and NF2 in 2 mesotheliomas and of BAP1 and TP53 in 1 mesothelioma each, respectively. In addition, 1 patient harbored a pathogenic BRCA1 germline mutation, which resulted in biallelic inactivation in the mesothelioma. All mesotheliomas were mismatch repair proficient and showed several chromosomal gains and losses. All patients died from disease. Our study demonstrates that pericardial mesotheliomas share common morphologic, immunohistochemical, and molecular genetic features with pleural mesothelioma, including recurrent genomic inactivation of canonical tumor suppressors. Our study adds new insights into the genetic landscape of primary pericardial mesothelioma and highlights BRCA1 loss as a potential contributing factor in a subset of cases, thereby contributing to refined precision diagnostics for this rare cancer.

The flutemetamol analogue cyano-flutemetamol detects myocardial AL and ATTR amyloid deposits: a post-mortem histofluorescence analysis.

BACKGROUND: [18F]flutemetamol is a PET radioligand used to image brain amyloid, but its detection of myocardial amyloid is not well-characterized. This histological study characterized binding of fluorescently labeled flutemetamol (cyano-flutemetamol) to amyloid deposits in myocardium. METHODS: Myocardial tissue was obtained post-mortem from 29 subjects with cardiac amyloidosis including transthyretin wild-type (ATTRwt), hereditary/variant transthyretin (ATTRv) and immunoglobulin light-chain (AL) types, and from 10 cardiac amyloid-free controls. Most subjects had antemortem electrocardiography, echocardiography, SPECT and cardiac MRI. Cyano-flutemetamol labeling patterns and integrated density values were evaluated relative to fluorescent derivatives of Congo red (X-34) and Pittsburgh compound-B (cyano-PiB). RESULTS: Cyano-flutemetamol labeling was not detectable in control subjects. In subjects with cardiac amyloidosis, cyano-flutemetamol labeling matched X-34- and cyano-PiB-labeled, and transthyretin- or lambda light chain-immunoreactive, amyloid deposits and was prevented by formic acid pre-treatment of myocardial sections. Cyano-flutemetamol mean fluorescence intensity, when adjusted for X-34 signal, was higher in the ATTRwt than the AL group. Cyano-flutemetamol integrated density correlated strongly with echocardiography measures of ventricular septal thickness and posterior wall thickness, and with heart mass. CONCLUSION: The high selectivity of cyano-flutemetamol binding to myocardial amyloid supports the diagnostic utility of [18F]flutemetamol PET imaging in patients with ATTR and AL types of cardiac amyloidosis.

Systematic dissection, preservation, and multiomics in whole human and bovine hearts.

OBJECTIVES: We sought to develop a rigorous, systematic protocol for the dissection and preservation of human hearts for biobanking that expands previous success in postmortem transcriptomics to multiomics from paired tissue. BACKGROUND: Existing cardiac biobanks consist largely of biopsy tissue or explanted hearts in select diseases and are insufficient for correlating whole organ phenotype with clinical data. METHODS: We demonstrate optimal conditions for multiomics interrogation (ribonucleic acid (RNA) sequencing, untargeted metabolomics) in hearts by evaluating the effect of technical variables (storage solution, temperature) and simulated postmortem interval (PMI) on RNA and metabolite stability. We used bovine (n=3) and human (n=2) hearts fixed in PAXgene or snap-frozen with liquid nitrogen. RESULTS: Using a paired Wald test, only two of the genes assessed were differentially expressed between left ventricular samples from bovine hearts stored in PAXgene at 0 and 12 hours PMI (FDR q<0.05). We obtained similar findings in human left ventricular samples, suggesting stability of RNA transcripts at PMIs up to 12 hours. Different library preparation methods (mRNA poly-A capture vs. rRNA depletion) resulted in similar quality metrics with both library preparations achieving >95% of reads properly aligning to the reference genomes across all PMIs for bovine and human hearts. PMI had no effect on RNA Integrity Number or quantity of RNA recovered at the time points evaluated. Of the metabolites identified (855 total) using untargeted metabolomics of human left ventricular tissue, 503 metabolites remained stable across PMIs (0, 4, 8, 12 hours). Most metabolic pathways retained several stable metabolites. CONCLUSIONS: Our data demonstrate a technically rigorous, reproducible protocol that will enhance cardiac biobanking practices and facilitate novel insights into human CVD. CONDENSED ABSTRACT: Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Current biobanking practices insufficiently capture both the diverse array of phenotypes present in CVDs and the spatial heterogeneity across cardiac tissue sites. We have developed a rigorous and systematic protocol for the dissection and preservation of human cardiac biospecimens to enhance the availability of whole organ tissue for multiple applications. When combined with longitudinal clinical phenotyping, our protocol will enable multiomics in hearts to deepen our understanding of CVDs.

Multimodality imaging to distinguish between benign and malignant cardiac masses.

BACKGROUND: To compare the diagnostic accuracy of CMR and FDG-PET/CT and their complementary role to distinguish benign vs malignant cardiac masses. METHODS: Retrospectively assessed patients with cardiac mass who underwent CMR and FDG-PET/CT within a month between 2003 and 2018. RESULTS: 72 patients who had CMR and FDG-PET/CT were included. 25 patients (35%) were diagnosed with benign and 47 (65%) were diagnosed with malignant masses. 56 patients had histological correlation: 9 benign and 47 malignant masses. CMR and FDG-PET/CT had a high accuracy in differentiating benign vs malignant masses, with the presence of CMR features demonstrating a higher sensitivity (98%), while FDG uptake with SUVmax/blood pool ≥ 3.0 demonstrating a high specificity (88%). Combining multiple (> 4) CMR features and FDG uptake (SUVmax/blood pool ratio ≥ 3.0) yielded a sensitivity of 85% and specificity of 88% to diagnose malignant masses. Over a mean follow-up of 2.6 years (IQR 0.3-3.8 years), risk-adjusted mortality were highest among patients with an infiltrative border on CMR (adjusted HR 3.1; 95% CI 1.5-6.5; P = .002) or focal extracardiac FDG uptake (adjusted HR 3.8; 95% CI 1.9-7.7; P < .001). CONCLUSION: Although CMR and FDG-PET/CT can independently diagnose benign and malignant masses, the combination of these modalities provides complementary value in select cases.

Bronchoscopic Thermal Vapour Ablation for Localized Cancer Lesions of the Lung: A Clinical Feasibility Treat-and-Resect Study.

BACKGROUND: Bronchoscopic thermal vapour ablation (BTVA) is an established and approved modality for minimally invasive lung volume reduction in severe emphysema. Preclinical data suggest potential for BTVA in minimally invasive ablation of lung cancer lesions. OBJECTIVES: The objective of this study is to establish the safety, feasibility, and ablative efficacy of BTVA for minimally invasive ablation of lung cancers. METHODS: Single arm treat-and-resect clinical feasibility study of patients with biopsy-confirmed lung cancer. A novel BTVA for lung cancer (BTVA-C) system for minimally invasive treatment of peripheral pulmonary tumours was used to deliver 330 Cal thermal vapour energy via bronchoscopy to target lesion. Patients underwent planned lobectomy to complete oncologic care. Pre-surgical CT chest and post-resection histologic analysis were performed to evaluate ablative efficacy. RESULTS: Six patients underwent BTVA-C, and 5 progressed to planned lobectomy. Median procedure duration was 12 min. No major procedure-related complications occurred. All 5 resected lesions were part-solid lung adenocarcinomas with median solid component size 1.32±0.36 cm. Large uniform ablation zones were seen in 4 patients where thermal dose exceeded 3 Cal/mL, with complete/near-complete necrosis of target lesions seen in 2 patients. Tumour positioned within ablation zones demonstrated necrosis in >99% of cross-sectional area examined. CONCLUSION: BTVA of lung tumours is feasible and well tolerated, with preliminary evidence suggesting high potential for effective ablation of tumours. Thermal injury is well demarcated, and uniform tissue necrosis is observed within ablation zones receiving sufficient thermal dose per volume of lung. Treatment of smaller volumes and ensuring adequate thermal dose may be important for ablative efficacy.

Feasibility of somatostatin receptor-targeted imaging for detection of myocardial inflammation: A pilot study.

BACKGROUND: Gallium-68 Dotatate binds preferentially to somatostatin receptor (sstr) subtype-2 (sstr-2) on inflammatory cells. We aimed at investigating the potential clinical use of sstr-targeted imaging for the detection of myocardial inflammation. METHODS: Thirteen patients, with suspected cardiac sarcoidosis (CS) based on clinical history and myocardial uptake on recent fluorine-18 fluorodeoxyglucose (FDG) PET, were enrolled to undergo Dotatate PET after FDG-PET (median time 37 days [IQR 25-55]). Additionally, we investigated ex-vivo the immunohistochemistry expression of sstr-2 in 3 explanted sarcoid hearts. RESULTS: All FDG scans showed cardiac uptake (focal/multifocal = 6, focal on diffuse/heterogeneous = 7), and 46% (n = 6) extra-cardiac uptake (mediastinal/hilar). In comparison, Dotatate scans showed definite abnormal cardiac uptake (focal/multifocal) in 4 patients, probably abnormal (heterogenous/patchy) in 3, and negative uptake in 6 cases. Similarly, 6 patients had increased mediastinal/hilar Dotatate uptake. Overall concordance of FDG and Dotatate uptake was 54% in the heart and 100% for thoracic nodal activity. Quantitatively, FDG maximum standardized uptake value was 5.0 times [3.8-7.1] higher in the heart, but only 2.25 times [1.7-3.0; P = .019] higher in thoracic nodes relative to Dotatate. Ex-vivo, sstr-2 immunostaining was weakly seen within well-formed granulomas in all 3 examined sarcoid heart specimens with no significant staining of background myocardium or normal myocardium. CONCLUSION: Our preliminary data suggest that, compared to FDG imaging, somatostatin receptor-targeted imaging may be less sensitive for the detection of myocardial inflammation, but comparable for detecting extra-cardiac inflammation.

Loss of Bcl-6-Expressing T Follicular Helper Cells and Germinal Centers in COVID-19.

Humoral responses in coronavirus disease 2019 (COVID-19) are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined post mortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers and a striking reduction in Bcl-6+ germinal center B cells but preservation of AID+ B cells. Absence of germinal centers correlated with an early specific block in Bcl-6+ TFH cell differentiation together with an increase in T-bet+ TH1 cells and aberrant extra-follicular TNF-α accumulation. Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific "disease-related" B cell populations. These data identify defective Bcl-6+ TFH cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections, and suggest that achieving herd immunity through natural infection may be difficult.

Paclitaxel-loaded expansile nanoparticles improve survival following cytoreductive surgery in pleural mesothelioma xenografts.

OBJECTIVE: Malignant pleural mesothelioma is a lethal malignancy with poor survival and high local recurrence rates despite multimodal therapy with cytoreduction and chemoradiation. We evaluated the antitumor efficacy of a paclitaxel-loaded pH-responsive expansile nanoparticle (PTX-eNP) in 2 clinically relevant murine xenograft models of malignant pleural mesothelioma. METHODS: Luciferase-transfected MSTO-211H human mesothelioma cells were injected into the thoracic cavity of immunodeficient Nu/J mice. Tumor burden was monitored by bioluminescent imaging. Animals were randomized into 2 models of disease treatment chemotherapy with PTX-eNPs alone delivered locally for early limited disease or cytoreductive surgery plus local PTX-eNP chemotherapy for advanced disease. Within each disease model, anti-tumor efficacy of PTX-eNP was compared against standard formulation paclitaxel and drug-empty nanoparticles. Influence on survival was calculated. Fluorescently labeled PTX-eNPs and immunohistochemistry evaluated in vivo drug localization to tumor. RESULTS: Intrathoracic injection of MSTO-211H resulted in large tumor deposits distributed within the pleural space of the murine thoracic cavity. Local multidose treatment with PTX-eNPs alone in limited stage disease more than doubled survival compared with drug-empty nanoparticles (P ≤ .0001) and standard formulation paclitaxel (P = .0004). In the model of advanced disease, local multidose treatment with PTX-eNPs following cytoreductive surgery also prolonged survival by 126% and 69.4% compared with drug-empty nanoparticles (P = .0018) and standard formulation paclitaxel (P = .03457), respectively. Immunohistology demonstrated PTX-eNP accumulation within tumor cells in vitro and in vivo. CONCLUSIONS: Local delivery of paclitaxel via eNPs confers prolonged survival in a murine model of malignant pleural mesothelioma as single modality treatment for limited disease and in combination with cytoreductive surgery for advanced disease.

The axis of local cardiac endogenous Klotho-TGF-ß1-Wnt signaling mediates cardiac fibrosis in human.

BACKGROUND: Cardiovascular fibrosis is a major contributor to cardiovascular disease, the primary cause of death in patients with chronic kidney disease (CKD). We previously reported expression of endogenous Klotho in human arteries, and that CKD is a state of Klotho deficiency, resulting in vascular calcification, but myocardial expression of Klotho is poorly understood. This study aimed to further clarify endogenous Klotho's functional roles in cardiac fibrosis in patients with underlying CKD. METHODS AND RESULTS: Human atrial appendage specimens were collected during cardiac surgery from individuals with or without CKD. Cardiac fibrosis was quantified using trichrome staining. For endogenous Klotho functional studies, primary human cardiomyocytes (HCMs) were treated with uremic serum from CKD patients or recombinant human TGF-ß1. The effects of endogenous Klotho in HCMs were studied using Klotho-siRNA and Klotho-plasmid transfection. Both gene and protein expression of endogenous Klotho are found in human heart, but decreased Klotho expression is clearly associated with the degree of cardiac fibrosis in CKD patients. Moreover, we show that endogenous Klotho is expressed by HCMs and cardiac fibroblasts (HCFs) but that HCM expression is suppressed by uremic serum or TGF-ß1. Klotho knockdown or overexpression aggravates or mitigates TGF-ß1-induced fibrosis and canonical Wnt signaling in HCMs, respectively. Furthermore, co-culture of HCMs with HCFs increases TGF-ß1-induced fibrogenic proteins in HCFs, but overexpression of endogenous Klotho in HCMs mitigates this effect, suggesting functional crosstalk between HCMs and HCFs. CONCLUSIONS: Our data from analysis of human hearts as well as functional in vitro studies strongly suggests that the loss of cardiac endogenous Klotho in CKD patients, specifically in cardiomyocytes, facilitates intensified TGF-ß1 signaling which enables more vigorous cardiac fibrosis through upregulated Wnt signaling. Upregulation of endogenous Klotho inhibits pathogenic Wnt/ß-catenin signaling and may offer a novel strategy for prevention and treatment of cardiac fibrosis in CKD patients.

Safety of inhaled hydrogen gas in healthy mice.

The purpose of this work was to determine the safety of inhaled hydrogen gas in healthy animals. Female mice were exposed to medical air with or without hydrogen gas (concentration 2.4%) for 72 hours (n = 25 mice/group). Mice underwent a standardized and validated neurobehavioral examination, SmithKline Beecham, Harwell, Imperial College, Royal London Hospital, Phenotype Assessment (SHIRPA) protocol, prior to and following the exposure period. Blood was withdrawn for serologic evaluation and all major organ tissues were evaluated histologically. The average hydrogen concentration within the chamber was 2.27%. Following exposure, there was no significant change in body weight in either group. Similarly, there was no significant change in the total SHIRPA score, although hydrogen-treated mice exhibited significantly lower spontaneous locomotor activity (P < 0.0001) in a subset of the test; all other aspects of the mouse neurologic exam were normal in hydrogen-treated animals. Brain histopathology was also normal in all mice, as was the histology of all other major organs. There were no significant differences in complete blood count, serum chemistry, or arterial blood gases between control and hydrogen-treated mice (P > 0.05 for all). Hydrogen gas did not appear to cause significant adverse effects when administered to healthy mice for 72 hours, with the possible exception of decreased spontaneous locomotor activity. The study was approved by the Institutional Animal Care and Use Committee at Boston Children's Hospital, USA (approved number 18-01-3536) on January 25, 2018.

Myocarditis in the Setting of Cancer Therapeutics: Proposed Case Definitions for Emerging Clinical Syndromes in Cardio-Oncology

Recent developments in cancer therapeutics have improved outcomes but have also been associated with cardiovascular complications. Therapies harnessing the immune system have been associated with an immune-mediated myocardial injury described as myocarditis. Immune checkpoint inhibitors are one such therapy with an increasing number of case and cohort reports describing a clinical syndrome of immune checkpoint inhibitor­associated myocarditis. Although the full spectrum of immune checkpoint inhibitor­associated cardiovascular disease still needs to be fully defined, described cases of myocarditis range from syndromes with mild signs and symptoms to fatal events. These observations in the clinical setting stand in contrast to outcomes from randomized clinical trials in which myocarditis is a rare event that is investigator reported and lacking in a specific case definition. The complexities associated with diagnosis, as well as the heterogeneous clinical presentation of immune checkpoint inhibitor­associated myocarditis, have made ascertainment and identification of myocarditis with high specificity challenging in clinical trials and other data sets, limiting the ability to better understand the incidence, outcomes, and predictors of these rare events. Therefore, establishing a uniform definition of myocarditis for application in clinical trials of cancer immunotherapies will enable greater understanding of these events. We propose an operational definition of cancer therapy-associated myocarditis that may facilitate case ascertainment and report and therefore may enhance the understanding of the incidence, outcomes, and risk factors of this novel clinical syndrome.

Diagnostic Accuracy of Advanced Imaging in Cardiac Sarcoidosis.

Background The diagnostic yield of cardiac sarcoidosis (CS) by endomyocardial biopsy is limited. Fluorodeoxyglucose (FDG) positron emission tomography (PET) and cardiac magnetic resonance imaging (MRI) may facilitate noninvasive diagnosis, but the accuracy of this approach is not well defined. We aimed to correlate findings from FDG PET and cardiac MRI with histological findings from explanted hearts of patients who underwent cardiac transplantation. Methods We analyzed the explanted heart histology for all patients who underwent cardiac transplant at our center from April 2008 to July 2018 and had pretransplant FDG PET (n=18) or cardiac MRI (n=31). The likelihood of CS based on FDG PET or cardiac MRI was categorized in a blinded fashion using a previously published method. RESULTS: Using a CS probable cutoff for FDG PET resulted in a sensitivity of 100.0% (95% CI, 54.1%-100.0%) and a specificity of 33.3% (95% CI, 9.9%-65.1%). Three of the 9 CS probable by FDG PET cases were found to be arrhythmogenic cardiomyopathy. The test characteristics of cardiac MRI are more challenging to comment on using our data as there was only one confirmed case of CS on post-transplant histological assessment. Of the 8 CS highly probable or probable cases by cardiac MRI, 3 were found to be dilated cardiomyopathy, and 2 were found to be end-stage hypertrophic cardiomyopathy. Conclusions FDG PET and cardiac MRI can help facilitate the diagnosis of CS in patients with advanced heart failure with a high degree of sensitivity but lower specificity.

T cell checkpoint regulators in the heart.

T lymphocyte-mediated immune responses in the heart are potentially dangerous because they can interfere with the electromechanical function. Furthermore, the myocardium has limited regenerative capacity to repair damage caused by effector T cells. Myocardial T cell responses are normally suppressed by multiple mechanisms of central and peripheral tolerance. T cell inhibitory molecules, so called immune checkpoints, limit the activation and effector function of heart antigen-reactive T cells that escape deletion during development in the thymus. Programmed cell protein death-1 (PD-1) and cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) are checkpoint molecules homologous to the costimulatory receptor CD28, and they work to block activating signals from the T cell antigen receptor and CD28. Nonetheless, PD-1 and CTLA-4 function in different ways and at different steps in a T cell response to antigen. Studies in mice have established that genetic deficiencies of checkpoint molecules, including PD-1, PD-L1, CTLA-4, and lymphocyte activation gene-3, result in enhanced risk of autoimmune T cell-mediated myocarditis and increased pathogenicity of heart antigen-specific effector T cells. The PD-1/PD-L1 pathway appears to be particularly important in cardiac protection from T cells. PD-L1 is markedly up-regulated on myocardial cells by interferon-gamma secreted by T cells and PD-1 or PD-L1 deficiency synergizes with other defects in immune regulation in promoting myocarditis. Consistent with these studies, myocarditis has emerged as a serious adverse reaction of cancer therapies that target checkpoint molecules to enhance anti-tumour T cell responses. Histopathology and immunohistochemical analyses of myocardial tissue from immune checkpoint blockade (ICB)-treated patients echoes findings in checkpoint-deficient mice. Many questions about myocarditis in the setting of cancer immunotherapy still need to be answered, including the nature of the target antigens, genetic risk factors, and variations in the disease with combined therapies. Addressing these questions will require further immunological analyses of blood and heart tissue from patients treated with ICB.

Cardiovascular toxicities associated with immune checkpoint inhibitors.

Cardiovascular toxicities associated with immune checkpoint inhibitors (ICIs) have been reported in case series but have been underappreciated due to their recent emergence, difficulties in diagnosis and non-specific clinical manifestations. ICIs are antibodies that block negative regulators of the T cell immune response, including cytotoxic T lymphocyte-associated protein-4 (CTLA-4), programmed cell death protein-1 (PD-1), and PD-1 ligand (PD-L1). While ICIs have introduced a significant mortality benefit in several cancer types, the augmented immune response has led to a range of immune-related toxicities, including cardiovascular toxicity. ICI-associated myocarditis often presents with arrhythmias, may co-exist with myositis and myasthenia gravis, can be severe, and portends a poor prognosis. In addition, pericardial disease, vasculitis, including temporal arteritis, and non-inflammatory heart failure, have been recently described as immune-related toxicities from ICI. This narrative review describes the epidemiology, diagnosis, pathophysiology, and treatment of cardiovascular toxicities of ICI therapy, highlighting recent developments in the field in the past year.