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Over 10 million doses of COVID‐19 vaccines based on RNA technology, viral vectors, recombinant protein, and inactivated virus have been administered worldwide. Although generally very safe, post‐vaccine myocarditis can result from adaptive humoral and cellular, cardiac‐specific inflammation within days and weeks of vaccination. Rates of vaccine‐associated myocarditis vary by age and sex with the highest rates in males between 12 and 39 years. The clinical course is generally mild with rare cases of left ventricular dysfunction, heart failure and arrhythmias. Mild cases are likely underdiagnosed as cardiac magnetic resonance imaging (CMR) is not commonly performed even in suspected cases and not at all in asymptomatic and mildly symptomatic patients. Hospitalization of symptomatic patients with electrocardiographic changes and increased plasma troponin levels is considered necessary in the acute phase to monitor for arrhythmias and potential decline in left ventricular function. In addition to evaluation for symptoms, electrocardiographic changes and elevated troponin levels, CMR is the best non‐invasive diagnostic tool with endomyocardial biopsy being restricted to severe cases with heart failure and/or arrhythmias. The management beyond guideline‐directed treatment of heart failure and arrhythmias includes non‐specific measures to control pain. Anti‐inflammatory drugs such as non‐steroidal anti‐inflammatory drugs, and corticosteroids have been used in more severe cases, with only anecdotal evidence for their effectiveness. In all age groups studied, the overall risks of SARS‐CoV‐2 infection‐related hospitalization and death are hugely greater than the risks from post‐vaccine myocarditis. This consensus statement serves as a practical resource for physicians in their clinical practice, to understand, diagnose, and manage affected patients. Furthermore, it is intended to stimulate research in this area. [ABSTRACT FROM AUTHOR]

Background: Microvesicles are vesicles shed by plasma membranes following cell activation and apoptosis. The role of lymphocyte‐derived microvesicles in endothelial function remains poorly understood. Methods: CD4+ T cells isolated from peripheral blood of healthy human donors were stimulated using anti‐CD3/anti‐CD28‐coated beads. Proteomic profiling of microvesicles was performed using linear discriminant analysis (LDA) from activated T cells (MV.Act) and nonactivated T cells (MV.NAct). In addition, data processing analysis was performed using MaxQUANT workflow. Differentially expressed proteins found in MV.Act or MV.NAct samples with identification frequency = 100%, which were selected by both LDA (p <.01) and MaxQUANT (p <.01) workflows, were defined as "high‐confidence" differentially expressed proteins. Functional effects of MV.Act on human primary microvascular endothelial cells were analysed. Results: T cells released large amounts of microvesicles upon stimulation. Proteomic profiling of microvesicles using LDA identified 2279 proteins (n = 2110 and n = 851 proteins in MV.Act and MV.NAct, respectively). Protein–protein interaction network models reconstructed from both differentially expressed proteins (n = 594; LDA p ≤.01) and "high‐confidence" differentially expressed proteins (n = 98; p ≤.01) revealed that MV.Act were enriched with proteins related to immune responses, protein translation, cytoskeleton organisation and TNFα‐induced apoptosis. For instance, MV.Act were highly enriched with IFN‐γ, a key proinflammatory pathway related to effector CD4+ T cells. Endothelial cell incubation with MV.Act induced superoxide generation, apoptosis, endothelial wound healing impairment and endothelial monolayer barrier disruption. Conclusions: T cell receptor‐mediated activation of CD4+ T cells stimulates the release of microvesicles enriched with proteins involved in immune responses, inflammation and apoptosis. T cell‐derived microvesicles alter microvascular endothelial function and barrier permeability, potentially promoting tissue inflammation. [ABSTRACT FROM AUTHOR]

Aims Angiotensin (Ang) II signalling has been suggested to promote cardiac fibrosis in inflammatory heart diseases; however, the underlying mechanisms remain obscure. Using Agtr1a -/- mice with genetic deletion of angiotensin receptor type 1 (ATR1) and the experimental autoimmune myocarditis (EAM) model, we aimed to elucidate the role of Ang II-ATR1 pathway in development of heart-specific autoimmunity and post-inflammatory fibrosis. Methods and results EAM was induced in wild-type (WT) and Agtr1a -/- mice by subcutaneous injections with alpha myosin heavy chain peptide emulsified in complete Freund's adjuvant. Agtr1a -/- mice developed myocarditis to a similar extent as WT controls at day 21 but showed reduced fibrosis and better systolic function at day 40. Crisscross bone marrow chimaera experiments proved that ATR1 signalling in the bone marrow compartment was critical for cardiac fibrosis. Heart infiltrating, bone-marrow-derived cells produced Ang II, but lack of ATR1 in these cells reduced transforming growth factor beta (TGF-β)-mediated fibrotic responses. At the molecular level, Agtr1a -/- heart-inflammatory cells showed impaired TGF-β-mediated phosphorylation of Smad2 and TAK1. In WT cells, TGF-β induced formation of RhoA-GTP and RhoA-A-kinase anchoring protein-Lbc (AKAP-Lbc) complex. In Agtr1a-/- cells, stabilization of RhoA-GTP and interaction of RhoA with AKAP-Lbc were largely impaired. Furthermore, in contrast to WT cells, Agtr1a-/- cells stimulated with TGF-β failed to activate canonical Wnt pathway indicated by suppressed activity of glycogen synthase kinase-3 (GSK-3)β and nuclear β-catenin translocation and showed reduced expression of Wnts. In line with these in vitro findings, β-catenin was detected in inflammatory regions of hearts of WT, but not Agtr1a-/- mice and expression of canonical Wnt1 and Wnt10b were lower in Agtr1a-/- hearts. Conclusion Ang II-ATR1 signalling is critical for development of post-inflammatory fibrotic remodelling and dilated cardiomyopathy. Our data underpin the importance of Ang II-ATR1 in effective TGF-β downstream signalling response including activation of profibrotic Wnt/β-catenin pathway. [ABSTRACT FROM AUTHOR]

Cardiac hypertrophic stimuli induce both adaptive and maladaptive growth response pathways in heart. A study showing that the mice lacking junD develop less adaptive hypertrophy in heart after mechanical pressure overload, while cardiomyocyte-specific expression of junD in mice results in spontaneous ventricular dilation and decreased contractility is detailed.