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Background Sarcoidosis is an inflammatory, granulomatous disease of unknown cause affecting multiple organs, including the heart. Untreated, unresolved granulomatous inflammation can lead to cardiac fibrosis, arrhythmias, and eventually heart failure. Here we characterize the cardiac phenotype of mice with chronic activation of mammalian target of rapamycin (mTOR) complex 1 signaling in myeloid cells known to cause spontaneous pulmonary sarcoid‐like granulomas. Methods and Results The cardiac phenotype of mice with conditional deletion of the tuberous sclerosis 2 (TSC2) gene in CD11c+ cells (TSC2fl/flCD11c‐Cre; termed TSC2KO) and controls (TSC2fl/fl) was determined by histological and immunological stains. Transthoracic echocardiography and invasive hemodynamic measurements were performed to assess myocardial function. TSC2KO animals were treated with either everolimus, an mTOR inhibitor, or Bay11‐7082, a nuclear factor‐kB inhibitor. Activation of mTOR signaling was evaluated on myocardial samples from sudden cardiac death victims with a postmortem diagnosis of cardiac sarcoidosis. Chronic activation of mTORC1 signaling in CD11c+ cells was sufficient to initiate progressive accumulation of granulomatous infiltrates in the heart, which was associated with increased fibrosis, impaired cardiac function, decreased plakoglobin expression, and abnormal connexin 43 distribution, a substrate for life‐threatening arrhythmias. Mice treated with the mTOR inhibitor everolimus resolved granulomatous infiltrates, prevented fibrosis, and improved cardiac dysfunction. In line, activation of mTOR signaling in CD68+ macrophages was detected in the hearts of sudden cardiac death victims who suffered from cardiac sarcoidosis. Conclusions To our best knowledge this is the first animal model of cardiac sarcoidosis that recapitulates major pathological hallmarks of human disease. mTOR inhibition may be a therapeutic option for patients with cardiac sarcoidosis.

Abstract The muscular dystrophies caused by dystrophin deficiency, the so‐called dystrophinopathies, are associated with impaired cardiac contractility and arrhythmias, which considerably contribute to disease morbidity and mortality. Impaired Ca handling in ventricular cardiomyocytes has been identified as a causative factor for complications in the dystrophic heart, and restoration of normal Ca handling in myocytes has emerged as a promising new therapeutic strategy. In the present study, we explored the hypothesis that ivabradine, a drug clinically approved for the treatment of heart failure and stable angina pectoris, improves Ca handling in dystrophic cardiomyocytes and thereby enhances contractile performance in the dystrophic heart. Therefore, ventricular cardiomyocytes were isolated from the hearts of adult dystrophin‐deficient DMDmdx rats, and the effects of acutely applied ivabradine on intracellular Ca transients were tested. In addition, the drug's acute impact on cardiac function in DMDmdx rats was assessed by transthoracic echocardiography. We found that administration of ivabradine to DMDmdx rats significantly improved cardiac function. Moreover, the amplitude of electrically induced intracellular Ca transients in ventricular cardiomyocytes isolated from DMDmdx rats was increased by the drug. We conclude that ivabradine enhances Ca release from the sarcoplasmic reticulum in dystrophic cardiomyocytes and thereby improves contractile performance in the dystrophic heart.

Background: Saline is still the most widely used storage and rinsing solution for vessel grafts during cardiac surgery despite knowing evidence of its negative influence on the human endothelial cell function. Aim of this study was to assess the effect of DuraGraft©, an intraoperative graft treatment solution, on human saphenous vein segments and further elaborate the vasoprotective effect on rat aortic segments in comparison to saline. Methods: Human Saphenous vein (HSV) graft segments from patients undergoing aortocoronary bypass surgery (n = 15), were randomized to DuraGraft© (n = 15) or saline (n = 15) solution before intraoperative storage. Each segment was divided into two subsegmental parts for evaluation. These segments as well as rat aortic segments stored in DuraGraft© underwent assessment of vascular function in a multichamber isometric myograph system in comparison to Krebs-Henseleit solution (KHS), a physiologic organ buffer solution. Results: Potassium-Chloride (KCL)-induced contraction depicted a tendency towards increase when treated with DuraGraft© compared to saline preservation of HSV segments (23.02 ± 14.77 vs 14.44 ± 9.13 mN, p = 0.0571). Vein segments preserved with DuraGraft© showed a significant improvement of endothelium-dependent vasorelaxation in response to cumulative concentrations of bradykinin compared to saline treated segments (p < 0.05). Rat aortic segments stored in saline showed significantly impaired vasoconstriction (3.59 ± 4.20, p < 0.0001) and vasorelaxation when compared to KHS and DuraGraft© (p < 0.0001). Conclusions: DuraGraft© demonstrated a favorable effect on graft relaxation and contraction indicating preservation of vascular endothelial function. Clinical Trial Registration Number: NCT04614077.

Background: Tenascin-C (TN-C) plays a maladaptive role in left ventricular (LV) hypertrophy following pressure overload. However, the role of TN-C in LV regression following mechanical unloading is unknown. Methods: LV hypertrophy was induced by transverse aortic constriction for 10 weeks followed by debanding for 2 weeks in wild type (Wt) and TN-C knockout (TN-C KO) mice. Cardiac function was assessed by serial magnetic resonance imaging. The expression of fibrotic markers and drivers (angiotensin-converting enzyme-1, ACE-1) was determined in LV tissue as well as human cardiac fibroblasts (HCFs) after TN-C treatment. Results: Chronic pressure overload resulted in a significant decline in cardiac function associated with LV dilation as well as upregulation of TN-C, collagen 1 (Col 1), and ACE-1 in Wt as compared to TN-C KO mice. Reverse remodeling in Wt mice partially improved cardiac function and fibrotic marker expression; however, TN-C protein expression remained unchanged. In HCF, TN-C strongly induced the upregulation of ACE 1 and Col 1. Conclusions: Pressure overload, when lasting long enough to induce HF, has less potential for reverse remodeling in mice. This may be due to significant upregulation of TN-C expression, which stimulates ACE 1, Col 1, and alpha-smooth muscle actin (α-SMA) upregulation in fibroblasts. Consequently, addressing TN-C in LV hypertrophy might open a new window for future therapeutics.

Duchenne muscular dystrophy (DMD) is characterized by wasting of muscles that leads to difficulty moving and premature death, mainly from heart failure. Glucocorticoids are applied in the management of the disease, supporting the hypothesis that inflammation may be driver as well as target. However, the inflammatory mechanisms during progression of cardiac and skeletal muscle dysfunction are still not well characterized. Our objective was to characterize the inflammasomes in myocardial and skeletal muscle in rodent models of DMD. Gastrocnemius and heart samples were collected from mdx mice and DMDmdx rats (3 and 9–10 months). Inflammasome sensors and effectors were assessed by immunoblotting. Histology was used to assess leukocyte infiltration and fibrosis. In gastrocnemius, a tendency towards elevation of gasdermin D irrespective of the age of the animal was observed. The adaptor protein was elevated in the mdx mouse skeletal muscle and heart. Increased cleavage of the cytokines was observed in the skeletal muscle of the DMDmdx rats. Sensor or cytokine expression was not changed in the tissue samples of the mdx mice. In conclusion, inflammatory responses are distinct between the skeletal muscle and heart in relevant models of DMD. Inflammation tends to decrease over time, supporting the clinical observations that the efficacy of anti-inflammatory therapies might be more prominent in the early stage.

Background: Geometrical alterations in the coronary resistance artery network and the potential involvement of Tenascin C (TNC) extracellular matrix protein were investigated in diabetic and control mice. Methods: Diabetes was induced by streptozotocin (STZ) injections (n = 7–11 animals in each group) in Tenascin C KO (TNC KO) mice and their Wild type (A/J) littermates. After 16–18 weeks the heart was removed and the whole subsurface network of the left coronary artery was prepared (down to branches of 40 μm outer diameter), in situ pressure-perfused and studied using video-microscopy. Outer and inner diameters, wall thicknesses and bifurcation angles were measured on whole network pictures reconstructed into collages at 1.7 μm pixel resolutions. Results: Diabetes induced abnormal morphological alterations including trifurcations, sharp bends of larger branches, and branches directed retrogradely (p < 0.001 by the χ2 test). Networks of TNC KO mice tended to form early divisions producing parallelly running larger branches (p < 0.001 by the χ2 probe). Networks of coronary resistance arteries were substantially more abundant in 100–180 μm components, appearing in 2–5 mm flow distance from orifice in diabetes. This was accompanied by thickening of the wall of larger arterioles (>220 μm) and thinning of the wall of smaller (100–140 μm) arterioles (p < 0.001). Blood flow should cover larger distances in diabetic networks, but interestingly STZ-induced diabetes did not generate further geometrical changes in TNC KO mice. Conclusions: Diabetes promotes hypertrophic and hypotrophic vascular remodeling and induces vasculogenesis at well defined, specific positions of the coronary vasculature. TNC plays a pivotal role in the formation of coronary network geometry, and TNC deletion causes parallel fragmentation preventing diabetes-induced abnormal vascular morphologies.

Besides skeletal muscle abnormalities, Duchenne muscular dystrophy (DMD) patients present with dilated cardiomyopathy development, which considerably contributes to morbidity and mortality. Because the mechanisms responsible for the cardiac complications in the context of DMD are largely unknown, evidence-based therapy approaches are still lacking. This has increased the need for basic research efforts into animal models for DMD. Here, we characterized in detail the cardiovascular abnormalities of Dmdmdx rats, with the aim of determining the suitability of this recently established dystrophin-deficient small animal as a model for DMD. Various methods were applied to compare cardiovascular properties between wild-type and Dmdmdx rats, and to characterize the Dmdmdx cardiomyopathy. These methods comprised echocardiography, invasive assessment of left ventricular hemodynamics, examination of adverse remodeling and endothelial cell inflammation, and evaluation of vascular function, employing wire myography. Finally, intracellular Ca2+ transient measurements, and recordings of currents through L-type Ca2+ channels were performed in isolated single ventricular cardiomyocytes. We found that, similar to respective observations in DMD patients, the hearts of Dmdmdx rats show significantly impaired cardiac function, fibrosis and inflammation, consistent with the development of a dilated cardiomyopathy. Moreover, in Dmdmdx rats, vascular endothelial function is impaired, which may relate to inflammation and oxidative stress, and Ca2+ handling in Dmdmdx cardiomyocytes is abnormal. These findings indicate that Dmdmdx rats represent a promising small-animal model to elucidate mechanisms of cardiomyopathy development in the dystrophic heart, and to test mechanism-based therapies aiming to combat cardiovascular complications in DMD.