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Cardiac Allograft Vasculopathy (CAV) is a significant determinant of long-term allograft survival. While CAV and classic atherosclerosis are unique, the cellular landscape and functional relevance of the diverse cell types leading to disease pathogenesis is incompletely understood. To date, no targeted therapies are available. Here, we interrogate the diverse cellular heterogeneity in human and murine CAV and propose novel mechanisms of disease pathogenesis. From explanted human hearts, we performed next generation sequencing and immunohistochemistry to define the unique cellular landscape and diversity in CAV lesions. To enable further understanding of the cellular diversity in CAV we used a murine model of CAV (B6 into BM12) and performed immunohistochemistry. To interrogate the potential functional relevance of these cell populations, we have ongoing experiments using targeted genetic depletion murine lines. Single nuclear RNA-sequencing of human CAV demonstrated a diverse cellular landscape with prominent populations of myeloid cells, T-cells, fibroblasts, and smooth muscle cells. Immunohistochemistry staining with fibroblast activating protein, periostin, and CD4 confirmed the presence of these populations as well as the presence of a tertiary lymphoid organ. Our murine model recapitulated the CAV phenotype by both histology and immunohistochemistry. In this study, we explored the temporal and spatial landscape of immune and stromal cells in both human and murine CAV. We show a robust myeloid and T-cell compartment as well as the presence of smooth muscle cells and activated fibroblasts. Based on these characterizations, we have begun to dissect the functional relevance of these cell populations to the development and progression of vasculopathy with targeted genetic depletion models. This study lays the foundation for future investigation of putative cell-cell crosstalk that could be targeted to reduce the burden of CAV in heart transplant recipients. [ABSTRACT FROM AUTHOR]

Percutaneous coronary intervention (PCI) of bifurcation lesions remains challenging with a higher risk of adverse outcomes. Whether adjunctive intravascular ultrasound (IVUS) imaging improves outcomes of PCI of bifurcation lesions remains unclear. This study sought to determine the long-term clinical outcomes associated with using IVUS for percutaneous treatment of coronary bifurcation lesions. From April 2003 through August 2010, 449 patients with 471 bifurcation lesions underwent PCI with (n = 247) and without (n = 202) the use of IVUS. Clinical outcomes (death, myocardial infarction [MI], periprocedural MI, stent thrombosis, target vessel revascularization [TVR], and target lesion revascularization [TLR]) were compared between patients undergoing PCI with and without IVUS using univariate and propensity score-adjusted analyses. Most patients (61%) presented with acute coronary syndrome and 89% of bifurcations lesions were Medina class 1,1,1. After propensity score adjustment, use of IVUS was associated with significantly lower rates of death or MI (odds ratio 0.38, 95% confidence interval 0.20 to 0.74, p = 0.005), death (odds ratio 0.40, 95% confidence interval 0.18 to 0.88, p = 0.02), MI (odds ratio 0.37, 95% confidence interval 0.14 to 0.98, p = 0.04), periprocedural MI (odds ratio 0.45, 95% confidence interval 0.20 to 0.97, p = 0.04), TVR (odds ratio 0.28, 95% confidence interval 0.14 to 0.53, p <0.0001), and TLR (odds ratio 0.27, 95% confidence interval 0.14 to 0.53, p = 0.0003) compared to no IVUS. In conclusion, IVUS-guided treatment of complex bifurcation lesions was associated with significantly lower rates of adverse cardiac events at late follow-up. Further study is warranted to evaluate the role of IVUS guidance in improving long-term outcomes after PCI of bifurcation lesions. [ABSTRACT FROM AUTHOR]

Background: Immune checkpoint inhibitor (ICI) usage has resulted in immune-related adverse events in patients with cancer, such as accelerated atherosclerosis. Of immune cells involved in atherosclerosis, the role of CCR2+ (CC motif chemokine receptor 2-positive) proinflammatory macrophages is well documented. However, there is no noninvasive approach to determine the changes of these cells in vivo following ICI treatment and explore the underlying mechanisms of immune-related adverse events. Herein, we aim to use a CCR2 (CC motif chemokine receptor 2)-targeted radiotracer and positron emission tomography (PET) to assess the aggravated inflammatory response caused by ICI treatment in mouse atherosclerosis models and explore the mechanism of immune-related adverse events., Methods: Apoe -/- mice and Ldlr -/- mice were treated with an ICI, anti-PD1 (programmed cell death protein 1) antibody, and compared with those injected with either isotype control IgG or saline. The radiotracer 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-ECL1i (extracellular loop 1 inverso) was used for PET imaging of CCR2+ macrophages. Atherosclerotic arteries were collected for molecular characterization., Results: CCR2 PET revealed significantly higher radiotracer uptake in both Apoe -/- and Ldlr -/- mice treated with anti-PD1 compared with the control groups. The increased expression of CCR2+ cells in Apoe -/- and Ldlr -/- mice was confirmed by immunostaining and flow cytometry. Single-cell RNA sequencing revealed elevated expression of CCR2 in myeloid cells. Mechanistically, IFNγ (interferon gamma) was essential for aggravated inflammation and atherosclerotic plaque progression following anti-PD1 treatment., Conclusions: Accelerated atherosclerotic plaque inflammation triggered by anti-PD1 treatment can be noninvasively detected by 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-ECL1i PET. Aggravated plaque inflammation is time- and dose-dependent and predominately mediated by IFNγ signaling. This study warrants further investigation of CCR2 PET as a noninvasive approach to visualize atherosclerotic plaque inflammation and explore the underlying mechanism following ICI treatment.

Introduction: Subarachnoid hemorrhage (SAH) is characterized by intense central inflammation, leading to substantial post-hemorrhagic complications such as vasospasm and delayed cerebral ischemia. Given the anti-inflammatory effect of transcutaneous auricular vagus nerve stimulation (taVNS) and its ability to promote brain plasticity, taVNS has emerged as a promising therapeutic option for SAH patients. However, the effects of taVNS on cardiovascular dynamics in critically ill patients, like those with SAH, have not yet been investigated. Given the association between cardiac complications and elevated risk of poor clinical outcomes after SAH, it is essential to characterize the cardiovascular effects of taVNS to ensure this approach is safe in this fragile population. Therefore, we assessed the impact of both acute taVNS and repetitive taVNS on cardiovascular function in this study., Methods: In this randomized clinical trial, 24 SAH patients were assigned to either a taVNS treatment or a Sham treatment group. During their stay in the intensive care unit, we monitored patient electrocardiogram (ECG) readings and vital signs. We compared long-term changes in heart rate, heart rate variability, QT interval, and blood pressure between the two groups. Additionally, we assessed the effects of acute taVNS by comparing cardiovascular metrics before, during, and after the intervention. We also explored acute cardiovascular biomarkers in patients exhibiting clinical improvement., Results: We found that repetitive taVNS did not significantly alter heart rate, QT interval, blood pressure, or intracranial pressure. However, taVNS increased overall heart rate variability and parasympathetic activity compared to the sham treatment. The increase in parasympathetic activity was most pronounced from 2-4 days after initial treatment (Cohen's d = 0.50). Acutely, taVNS increased heart rate, blood pressure, and peripheral perfusion index without affecting the corrected QT interval, intracranial pressure, or heart rate variability. The acute post-treatment elevation in heart rate was more pronounced in patients who experienced a decrease of more than one point in their Modified Rankin Score at the time of discharge., Conclusions: Our study found that taVNS treatment did not induce adverse cardiovascular effects, such as bradycardia or QT prolongation, supporting its development as a safe immunomodulatory treatment approach for SAH patients. The observed acute increase in heart rate after taVNS treatment may serve as a biomarker for SAH patients who could derive greater benefit from this treatment., Trial Registration: NCT04557618., Competing Interests: Declaration of competing interest Eric Leuthardt has stock ownership in Neurolutions, Face to Face Biometrics, Caeli Vascular, Acera, Sora Neuroscience, Inner Cosmos, Kinetrix, NeuroDev, Inflexion Vascular, Aurenar, Cordance Medical, Silent Surgical, and Petal Surgical. He is a consultant for E15, Neurolutions, Inc., Petal Surgical. Washington University owns equity in Neurolutions. Anna Huguenard has stock ownership in Aurenar.

Competing Interests: Disclosures None.

Tissue-resident macrophages are complementary to proinflammatory macrophages to promote the progression of atherosclerosis. The noninvasive detection of their presence and dynamic variation will be important to the understanding of their role in the pathogenesis of atherosclerosis. The goal of this study was to develop a targeted PET radiotracer for imaging CD163-positive (CD163+) macrophages in multiple mouse atherosclerosis models and assess the potential of CD163 as a biomarker for atherosclerosis in humans. Methods: CD163-binding peptide was identified using phage display and conjugated with a NODAGA chelator for 64 Cu radiolabeling ([ 64 Cu]Cu-ICT-01). CD163-overexpressing U87 cells were used to measure the binding affinity of [ 64 Cu]Cu-ICT-01. Biodistribution studies were performed on wild-type C57BL/6 mice at multiple time points after tail vein injection. The sensitivity and specificity of [ 64 Cu]Cu-ICT-01 in imaging CD163+ macrophages upregulated on the surface of atherosclerotic plaques were assessed in multiple mouse atherosclerosis models. Immunostaining, flow cytometry, and single-cell RNA sequencing were performed to characterize the expression of CD163 on tissue-resident macrophages. Human carotid atherosclerotic plaques were used to measure the expression of CD163+ resident macrophages and test the binding specificity of [ 64 Cu]Cu-ICT-01. Results: [ 64 Cu]Cu-ICT-01 showed high binding affinity to U87 cells. The biodistribution study showed rapid blood and renal clearance with low retention in all major organs at 1, 2, and 4 h after injection. In an ApoE -/- mouse model, [ 64 Cu]Cu-ICT-01 demonstrated sensitive and specific detection of CD163+ macrophages and capability for tracking the progression of atherosclerotic lesions; these findings were further confirmed in Ldlr -/- and PCSK9 mouse models. Immunostaining showed elevated expression of CD163+ macrophages across the plaques. Flow cytometry and single-cell RNA sequencing confirmed the specific expression of CD163 on tissue-resident macrophages. Human tissue characterization demonstrated high expression of CD163+ macrophages on atherosclerotic lesions, and ex vivo autoradiography revealed specific binding of [ 64 Cu]Cu-ICT-01 to human CD163. Conclusion: This work reported the development of a PET radiotracer binding CD163+ macrophages. The elevated expression of CD163+ resident macrophages on human plaques indicated the potential of CD163 as a biomarker for vulnerable plaques. The sensitivity and specificity of [ 64 Cu]Cu-ICT-01 in imaging CD163+ macrophages warrant further investigation in translational settings., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

Background: Rapidly dividing cells are more sensitive to radiation therapy (RT) than quiescent cells. In the failing myocardium, macrophages and fibroblasts mediate collateral tissue injury, leading to progressive myocardial remodeling, fibrosis, and pump failure. Because these cells divide more rapidly than cardiomyocytes, we hypothesized that macrophages and fibroblasts would be more susceptible to lower doses of radiation and that cardiac radiation could therefore attenuate myocardial remodeling., Methods: In three independent murine heart failure models, including models of metabolic stress, ischemia, and pressure overload, mice underwent 5 Gy cardiac radiation or sham treatment followed by echocardiography. Immunofluorescence, flow cytometry, and non-invasive PET imaging were employed to evaluate cardiac macrophages and fibroblasts. Serial cardiac magnetic resonance imaging (cMRI) from patients with cardiomyopathy treated with 25 Gy cardiac RT for ventricular tachycardia (VT) was evaluated to determine changes in cardiac function., Findings: In murine heart failure models, cardiac radiation significantly increased LV ejection fraction and reduced end-diastolic volume vs. sham. Radiation resulted in reduced mRNA abundance of B-type natriuretic peptide and fibrotic genes, and histological assessment of the LV showed reduced fibrosis. PET and flow cytometry demonstrated reductions in pro-inflammatory macrophages, and immunofluorescence demonstrated reduced proliferation of macrophages and fibroblasts with RT. In patients who were treated with RT for VT, cMRI demonstrated decreases in LV end-diastolic volume and improvements in LV ejection fraction early after treatment., Conclusions: These results suggest that 5 Gy cardiac radiation attenuates cardiac remodeling in mice and humans with heart failure., Funding: NIH, ASTRO, AHA, Longer Life Foundation., Competing Interests: Declaration of interests A.J. has a pending patent for fusion protein nanodiscs for the treatment of heart failure and eye disease, is a member of the scientific advisory board of Mobius Scientific, and receives research funding from AstraZeneca and Bitterroot Bio, unrelated to the studies in this manuscript., (Published by Elsevier Inc.)

Solid organ transplant represents a potentially lifesaving procedure for patients suffering from end-stage heart, lung, liver, and kidney failure. However, rejection remains a significant source of morbidity and immunosuppressive medications have significant toxicities. Janus kinase (JAK) inhibitors are effective immunosuppressants in autoimmune diseases and graft versus host disease after allogeneic hematopoietic cell transplantation. Here we examine the role of JAK inhibition in preclinical fully major histocompatibility mismatched skin and heart allograft models. Baricitinib combined with cyclosporine A (CsA) preserved fully major histocompatibility mismatched skin grafts for the entirety of a 111-day experimental period. In baricitinib plus CsA treated mice, circulating CD4 + T-bet + T cells, CD8 + T-bet + T cells, and CD4 + FOXP3 + regulatory T cells were reduced. Single cell RNA sequencing revealed a unique expression profile in immune cells in the skin of baricitinib plus CsA treated mice, including decreased inflammatory neutrophils and increased CCR2 - macrophages. In a fully major histocompatibility mismatched mismatched heart allograft model, baricitinib plus CsA prevented graft rejection for the entire 28-day treatment period compared with 9 days in controls. Our findings establish that the combination of baricitinib and CsA prevents rejection in allogeneic skin and heart graft models and supports the study of JAK inhibitors in human solid organ transplantation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision, (Copyright © 2023 Abboud, Kim, Staser, Jayasinghe, Lim, Amatya, Frye, Kopecky, Ritchey, Gao, Lavine, Kreisel, DiPersio and Choi.)

Background: Cardiac inflammation in heart failure is characterized by the presence of damage-associated molecular patterns, myeloid cells, and T cells. Cardiac damage-associated molecular patterns provide continuous proinflammatory signals to myeloid cells through TLRs (toll-like receptors) that converge onto the adaptor protein MyD88 (myeloid differentiation response 88). These induce activation into efficient antigen-presenting cells that activate T cells through their TCR (T-cell receptor). T-cell activation results in cardiotropism, cardiac fibroblast transformation, and maladaptive cardiac remodeling. T cells rely on TCR signaling for effector function and survival, and while they express MyD88 and damage-associated molecular pattern receptors, their role in T-cell activation and cardiac inflammation is unknown., Methods: We performed transverse aortic constriction in mice lacking MyD88 in T cells and analyzed remodeling, systolic function, survival, and T-cell activation. We profiled wild type versus Myd88 -/- mouse T cells at the transcript and protein level and performed several functional assays., Results: Analysis of single-cell RNA-sequencing data sets revealed that MyD88 is expressed in mouse and human cardiac T cells. MyD88 deletion in T cells resulted in increased levels of cardiac T-cell infiltration and fibrosis in response to transverse aortic constriction. We discovered that TCR-activated Myd88 -/- T cells had increased proinflammatory signaling at the transcript and protein level compared with wild type, resulting in increased T-cell effector functions such as adhesion, migration across endothelial cells, and activation of cardiac fibroblast. Mechanistically, we found that MyD88 modulates T-cell activation and survival through TCR-dependent rather than TLR-dependent signaling., Conclusions: Our results outline a novel intrinsic role for MyD88 in limiting T-cell activation that is central to tune down cardiac inflammation during cardiac adaptation to stress., Competing Interests: Disclosures None.

The diversity of mononuclear phagocyte (MNP) subpopulations across tissues is one of the key physiological characteristics of the immune system. Here, we focus on understanding the metabolic variability of MNPs through metabolic network analysis applied to three large-scale transcriptional datasets: we introduce (1) an ImmGen MNP open-source dataset of 337 samples across 26 tissues; (2) a myeloid subset of ImmGen Phase I dataset (202 MNP samples); and (3) a myeloid mouse single-cell RNA sequencing (scRNA-seq) dataset (51,364 cells) assembled based on Tabula Muris Senis. To analyze such large-scale datasets, we develop a network-based computational approach, genes and metabolites (GAM) clustering, for unbiased identification of the key metabolic subnetworks based on transcriptional profiles. We define 9 metabolic subnetworks that encapsulate the metabolic differences within MNP from 38 different tissues. Obtained modules reveal that cholesterol synthesis appears particularly active within the migratory dendritic cells, while glutathione synthesis is essential for cysteinyl leukotriene production by peritoneal and lung macrophages., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Competing Interests: Dr Jimenez is supported by the National Institutes of Health (R25 HL105400). Dr. Mitchell has received modest consulting from Pfizer and BrigeBio; and research support from Pfizer, Myocardial Solutions, Abbott Laboratories, and Children's Discovery Institute. Dr Campbell is supported by the Amyloidosis Foundation. Dr Lavine is supported by grants from the National Institutes of Health (HL161185, HL150891 and HL151078), the Children’s Discovery Institute (PM-LI-2019-829), the Burroughs Welcome Fund (1014782), and the Leducq Foundation (20CVD02) and by generous gifts through Washington University and Barnes Jewish Hospital. Dr Lavine serves as a consultant for Implicit Biosciences and Medtronic; and is the recipient of sponsored research agreements with Amgen and Novartis; and has a pending patent entitled “Methods for detecting CCR2 receptors” (application number: US17/001,857). Dr Campbell has served on advisory boards for Alnylam Pharmaceuticals and Pfizer Inc; and has received research support from Alnylam Pharmaceuticals, Pfizer Inc, and Akari Therapeutics. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Background: Acute COVID-19 infection has been shown to have significant effects on the cardiovascular system. Post-acute sequelae of SARS-CoV-2 (PASC) are being identified in patients; however, the cardiovascular effects are yet to be well-defined. The Post-COVID Cardiology Clinic at Washington University evaluates and treats patients with ongoing cardiovascular PASC., Objectives: This investigation aims to describe the phenotypes of cardiovascular symptoms of PASC in patients presenting to the Post-COVID Cardiology Clinic, including their demographics, symptoms, and the clinical phenotypes observed., Methods: This was a retrospective analysis of symptoms, clinical findings, and test results from the first 100 consecutive adult patients who presented to the Post-COVID Cardiology Clinic at Washington University in St. Louis, between September 2020 to May 2021 with cardiovascular symptoms following COVID-19 infection., Results: The population (n = 100) had a mean age of 46.3 years and was 81% female. Most patients had mild acute illness, with only 23% of patients requiring hospitalization during acute COVID-19 infection. The most commonly reported PASC symptoms were chest pain (66%), palpitations (59%), and dyspnea on exertion (56%). Of those presenting with these symptoms, 74/98 patients (75.5%) were found to have a significant blood pressure elevation, considerable sinus tachycardia burden, reduced global longitudinal strain, increased indexed left-ventricular end-diastolic volume (LVEDVi) by echocardiogram, and/or cMRI findings consistent with possible active or healing myocarditis., Conclusions: Our findings highlight clinical phenotypes of the cardiovascular manifestations of PASC. Further studies are needed to evaluate the pathophysiology, treatment options and long-term outcomes for these patients., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Adipocytes transfer mitochondria to macrophages in white and brown adipose tissues to maintain metabolic homeostasis. In obesity, adipocyte-to-macrophage mitochondria transfer is impaired, and instead, adipocytes release mitochondria into the blood to induce a protective antioxidant response in the heart. We found that adipocyte-to-macrophage mitochondria transfer in white adipose tissue is inhibited in murine obesity elicited by a lard-based high-fat diet, but not a hydrogenated-coconut-oil-based high-fat diet, aging, or a corn-starch diet. The long-chain fatty acids enriched in lard suppress mitochondria capture by macrophages, diverting adipocyte-derived mitochondria into the blood for delivery to other organs, such as the heart. The depletion of macrophages rapidly increased the number of adipocyte-derived mitochondria in the blood. These findings suggest that dietary lipids regulate mitochondria uptake by macrophages locally in white adipose tissue to determine whether adipocyte-derived mitochondria are released into systemic circulation to support the metabolic adaptation of distant organs in response to nutrient stress., Competing Interests: Declaration of interests J.R.B. has a pending patent application related to intercellular mitochondria transfer for the treatment of mitochondrial disorders, is a consultant for DeciBio and Flagship Pioneering, and is a scientific advisor to LUCA Science, Inc., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Myocardial infarction is a leading cause of death worldwide 1 . Although advances have been made in acute treatment, an incomplete understanding of remodelling processes has limited the effectiveness of therapies to reduce late-stage mortality 2 . Here we generate an integrative high-resolution map of human cardiac remodelling after myocardial infarction using single-cell gene expression, chromatin accessibility and spatial transcriptomic profiling of multiple physiological zones at distinct time points in myocardium from patients with myocardial infarction and controls. Multi-modal data integration enabled us to evaluate cardiac cell-type compositions at increased resolution, yielding insights into changes of the cardiac transcriptome and epigenome through the identification of distinct tissue structures of injury, repair and remodelling. We identified and validated disease-specific cardiac cell states of major cell types and analysed them in their spatial context, evaluating their dependency on other cell types. Our data elucidate the molecular principles of human myocardial tissue organization, recapitulating a gradual cardiomyocyte and myeloid continuum following ischaemic injury. In sum, our study provides an integrative molecular map of human myocardial infarction, represents an essential reference for the field and paves the way for advanced mechanistic and therapeutic studies of cardiac disease., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

The heart, the first organ to develop in the embryo, undergoes complex morphogenesis that when defective results in congenital heart disease (CHD). With current therapies, more than 90% of patients with CHD survive into adulthood, but many suffer premature death from heart failure and non-cardiac causes 1 . Here, to gain insight into this disease progression, we performed single-nucleus RNA sequencing on 157,273 nuclei from control hearts and hearts from patients with CHD, including those with hypoplastic left heart syndrome (HLHS) and tetralogy of Fallot, two common forms of cyanotic CHD lesions, as well as dilated and hypertrophic cardiomyopathies. We observed CHD-specific cell states in cardiomyocytes, which showed evidence of insulin resistance and increased expression of genes associated with FOXO signalling and CRIM1. Cardiac fibroblasts in HLHS were enriched in a low-Hippo and high-YAP cell state characteristic of activated cardiac fibroblasts. Imaging mass cytometry uncovered a spatially resolved perivascular microenvironment consistent with an immunodeficient state in CHD. Peripheral immune cell profiling suggested deficient monocytic immunity in CHD, in agreement with the predilection in CHD to infection and cancer 2 . Our comprehensive phenotyping of CHD provides a roadmap towards future personalized treatments for CHD., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Tissue injury can drive secondary organ injury; however, mechanisms and mediators are not well understood. To identify interorgan cross-talk mediators, we used acute kidney injury (AKI)-induced acute lung injury (ALI) as a clinically important example. Using kidney and lung single-cell RNA sequencing after AKI in mice followed by ligand-receptor pairing analysis across organs, kidney ligands to lung receptors, we identify kidney-released circulating osteopontin (OPN) as a novel AKI-ALI mediator. OPN release from kidney tubule cells triggered lung endothelial leakage, inflammation, and respiratory failure. Pharmacological or genetic OPN inhibition prevented AKI-ALI. Transplantation of ischemic wt kidneys caused AKI-ALI, but not of ischemic OPN-global knockout kidneys, identifying kidney-released OPN as necessary interorgan signal to cause AKI-ALI. We show that OPN serum levels are elevated in patients with AKI and correlate with kidney injury. Our results demonstrate feasibility of using ligand-receptor analysis across organs to identify interorgan cross-talk mediators and may have important therapeutic implications in human AKI-ALI and multiorgan failure.

Crystal structures activate innate immune cells, especially macrophages and initiate inflammatory responses. We aimed to understand the role of the mechanosensitive TRPV4 channel in crystal-induced inflammation. Real-time RT-PCR, RNAscope in situ hybridisation, and Trpv4 eGFP mice were used to examine TRPV4 expression and whole-cell patch-clamp recording and live-cell Ca 2+ imaging were used to study TRPV4 function in mouse synovial macrophages and human peripheral blood mononuclear cells (PBMCs). Both genetic deletion and pharmacological inhibition approaches were used to investigate the role of TRPV4 in NLRP3 inflammasome activation induced by diverse crystals in vitro and in mouse models of crystal-induced pain and inflammation in vivo. TRPV4 was functionally expressed by synovial macrophages and human PBMCs and TRPV4 expression was upregulated by stimulation with monosodium urate (MSU) crystals and in human PBMCs from patients with acute gout flares. MSU crystal-induced gouty arthritis were significantly reduced by either genetic ablation or pharmacological inhibition of TRPV4 function. Mechanistically, TRPV4 mediated the activation of NLRP3 inflammasome by diverse crystalline materials but not non-crystalline NLRP3 inflammasome activators, driving the production of inflammatory cytokine interleukin-1β which elicited TRPV4-dependent inflammatory responses in vivo. Moreover, chemical ablation of the TRPV1-expressing nociceptors significantly attenuated the MSU crystal-induced gouty arthritis. In conclusion, TRPV4 is a common mediator of inflammatory responses induced by diverse crystals through NLRP3 inflammasome activation in macrophages. TRPV4-expressing resident macrophages are critically involved in MSU crystal-induced gouty arthritis. A neuroimmune interaction between the TRPV1-expressing nociceptors and the TRPV4-expressing synovial macrophages contributes to the generation of acute gout flares., Competing Interests: Competing interests: BK has served as a consultant for AbbVie, ABRAX Japan, Almirall, Cara Therapeutics, Maruho, Menlo Therapeutics, Pfizer, and Third Rock Ventures. BK is also founder, chief scientific officer, and stockholder of Nuogen Pharma and stockholder of Locus Biosciences., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

The coronavirus disease 2019 (COVID-19) pandemic is a rapidly evolving global emergency that continues to strain healthcare systems. Emerging research describes a plethora of patient factors-including demographic, clinical, immunologic, hematological, biochemical, and radiographic findings-that may be of utility to clinicians to predict COVID-19 severity and mortality. We present a synthesis of the current literature pertaining to factors predictive of COVID-19 clinical course and outcomes. Findings associated with increased disease severity and/or mortality include age > 55 years, multiple pre-existing comorbidities, hypoxia, specific computed tomography findings indicative of extensive lung involvement, diverse laboratory test abnormalities, and biomarkers of end-organ dysfunction. Hypothesis-driven research is critical to identify the key evidence-based prognostic factors that will inform the design of intervention studies to improve the outcomes of patients with COVID-19 and to appropriately allocate scarce resources., (© 2020 John Wiley & Sons, Ltd.)