Increase In Myocardial Fibrosis Research Articles

Vagus nerve stimulation alleviates cardiac dysfunction and inflammatory markers during heart failure in rats

Vagus nerve stimulation (VNS) is under clinical investigation as a therapy for heart failure with reduced ejection fraction (HFrEF). This study aimed to investigate its therapeutic effects on three main components of heart failure: cardiac function, cardiac remodeling and central neuroinflammation using a pressure overload (PO) rat model. Male Sprague-Dawley rats were divided into four groups: PO, PO + VNS, PO + VNS sham, and controls. All rats, except controls, underwent a PO surgery to constrict the thoracic aorta (~50 %) to induce HFrEF. Open loop VNS therapy was continuously administered to PO + VNS rats at 20 Hz, 1.0 mA for 60 days. Evaluation of cardiac function and structure via echocardiograms showed decreases in stroke volume and relative ejection fraction and increases in the internal diameter of the left ventricle during systole and diastole in PO rats (p < 0.05). However, these PO-induced adverse changes were alleviated with VNS therapy. Additionally, PO rats exhibited significant increases in myocyte cross sectional areas indicating hypertrophy, along with significant increases in myocardial fibrosis and apoptosis, all of which were reversed by VNS therapy (p < 0.05). Furthermore, VNS mitigated microglial activation in two central autonomic nuclei: the paraventricular nucleus of the hypothalamus and locus coeruleus. These findings demonstrate that when VNS therapy is initiated at an early stage of HFrEF progression (<10 % reduction in relative ejection fraction), the supplementation of vagal activity is effective in restoring multi organ homeostasis in a PO model.

Multimodality imaging methods and systemic biomarkers in classical low-flow low-gradient aortic stenosis: Key findings for risk stratification.

The aim of the present study is to assess multimodality imaging findings according to systemic biomarkers, high-sensitivity troponin I (hsTnI) and B-type natriuretic peptide (BNP) levels, in low-flow, low-gradient aortic stenosis (LFLG-AS). Elevated levels of BNP and hsTnI have been related with poor prognosis in patients with LFLG-AS. Prospective study with LFLG-AS patients that underwent hsTnI, BNP, coronary angiography, cardiac magnetic resonance (CMR) with T1 mapping, echocardiogram and dobutamine stress echocardiogram. Patients were divided into 3 groups according to BNP and hsTnI levels: Group 1 (n = 17) when BNP and hsTnI levels were below median [BNP < 1.98 fold upper reference limit (URL) and hsTnI < 1.8 fold URL]; Group 2 (n = 14) when BNP or hsTnI were higher than median; and Group 3 (n = 18) when both hsTnI and BNP were higher than median. 49 patients included in 3 groups. Clinical characteristics (including risk scores) were similar among groups. Group 3 patients had lower valvuloarterial impedance (P = 0.03) and lower left ventricular ejection fraction (P = 0.02) by echocardiogram. CMR identified a progressive increase of right and left ventricular chamber from Group 1 to Group 3, and worsening of left ventricular ejection fraction (EF) (40 [31-47] vs. 32 [29-41] vs. 26 [19-33]%; p < 0.01) and right ventricular EF (62 [53-69] vs. 51 [35-63] vs. 30 [24-46]%; p < 0.01). Besides, there was a marked increase in myocardial fibrosis assessed by extracellular volume fraction (ECV) (28.4 [24.8-30.7] vs. 28.2 [26.9-34.5] vs. 31.8 [28.9-35.5]%; p = 0.03) and indexed ECV (iECV) (28.7 [21.2-39.1] vs. 28.8 [25.4-39.9] vs. 44.2 [36.4-51.2] ml/m2, respectively; p < 0.01) from Group 1 to Group 3. Higher levels of BNP and hsTnI in LFLG-AS patients are associated with worse multi-modality evidence of cardiac remodeling and fibrosis.

Post-ischemic cardioprotective potential of exogenous ubiquitin in myocardial remodeling late after ischemia/reperfusion injury

AimsPretreatment with ubiquitin (UB) associates with preservation of heart function 3 days post-ischemia/reperfusion (I/R) injury. This study investigated the cardioprotective potential of exogenous UB late after myocardial I/R injury. To enhance the clinical relevance, UB treatment was started at the time of reperfusion and continued for 28 days post-I/R. Main methodsMice underwent ligation of the left anterior descending coronary artery for 45 min. At the time of reperfusion, mice were treated with UB or saline which was continued until 28 days post-I/R. Heart function was measured at 3, 7, 14 and 28 days post-I/R using echocardiography. Biochemical parameters of the heart and serum cytokines/chemokines levels were measured 28 days post-I/R. Key findingsI/R decreased heart function and induced LV dilation at all time points post-I/R. However, I/R + UB exhibited improved heart function throughout the observation period, while LV dilation was lower in I/R + UB group at 3, 14 and 28 days post-I/R. I/R-mediated increase in myocardial fibrosis, hypertrophy and apoptosis were significantly lower in I/R + UB vs. I/R. Collagen-1α1 and MMP-2 expression was lower, while MMP-9 and TIMP-2 expression was higher in I/R + UB vs. I/R. MYH-7B (hypertrophy marker) expression was lower in I/R + UB vs. I/R. GSK3β activation was lower (vs. Sham), while activation of ERK1/2 (vs. I/R) and AKT (vs. Sham) was higher in I/R + UB. Serum levels of IL-6, G-CSF and IL-2 were lower in I/R + UB vs. I/R. SignificancePost-ischemic UB treatment improves heart function, and associates with decreased myocardial fibrosis, apoptosis, hypertrophy and serum cytokine/chemokine levels.

Chronic high-rate pacing induces heart failure with preserved ejection fraction-like phenotype in Ossabaw swine.

The lack of pre-clinical large animal models of heart failure with preserved ejection fraction (HFpEF) remains a growing, yet unmet obstacle to improving understanding of this complex condition. We examined whether chronic cardiometabolic stress in Ossabaw swine, which possess a genetic propensity for obesity and cardiovascular complications, produces an HFpEF-like phenotype. Swine were fed standard chow (lean; n = 13) or an excess calorie, high-fat, high-fructose diet (obese; n = 16) for ~ 18weeks with lean (n = 5) and obese (n = 8) swine subjected to right ventricular pacing (180 beats/min for ~ 4weeks) to induce heart failure (HF). Baseline blood pressure, heart rate, LV end-diastolic volume, and ejection fraction were similar between groups. High-rate pacing increased LV end-diastolic pressure from ~ 11 ± 1mmHg in lean and obese swine to ~ 26 ± 2mmHg in lean HF and obese HF swine. Regression analyses revealed an upward shift in LV diastolic pressure vs. diastolic volume in paced swine that was associated with an ~ twofold increase in myocardial fibrosis and an ~ 50% reduction in myocardial capillary density. Hemodynamic responses to graded hemorrhage revealed an ~ 40% decrease in the chronotropic response to reductions in blood pressure in lean HF and obese HF swine without appreciable changes in myocardial oxygen delivery or transmural perfusion. These findings support that high-rate ventricular pacing of lean and obese Ossabaw swine initiates underlying cardiac remodeling accompanied by elevated LV filling pressures with normal ejection fraction. This distinct pre-clinical tool provides a unique platform for further mechanistic and therapeutic studies of this highly complex syndrome.

MicroRNA-122-5p Aggravates Angiotensin II-Mediated Myocardial Fibrosis and Dysfunction in Hypertensive Rats by Regulating the Elabela/Apelin-APJ and ACE2-GDF15-Porimin Signaling.

Hypertension is the leading risk factor for cardiovascular disorders. This study aimed to explore roles of microRNA (miR)-122-5p in hypertension. Angiotensin II (Ang II; 1.5 mg/kg/day) with an osmotic minipump was used to induce hypertensive rats pretreated by rAAV-miR-122-5p or rAAV-GFP, respectively. Notably, Ang II infusion caused marked increases in myocardial fibrosis, inflammation, oncosis, and oxidant injury in rats, which were aggravated by rAAV-miR-122-5p. RAAV-miR-122-5p exacerbated Ang II–mediated cardiac dysfunction and structural injury in hypertensive rats, with downregulated levels of apelin, elabela, ACE2, and GDF15, as well as upregulated expression of porimin and CTGF. In cultured rat cardiac fibroblasts, Ang II contributed to augmentation of cellular oncosis, migration, inflammation, and oxidative stress, with reduction of apelin, elabela, ACE2, and GDF15 levels, which were rescued by miR-122 inhibitor. In summary, miR-122-5p exacerbates myocardial fibrosis and dysfunction in hypertensive rats by modulating the elabela/apelin-ACE2-GDF15 signaling. MiR-122-5p has potential therapeutic significance for hypertension and hypertensive cardiac injury.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s12265-022-10214-3.

Multimodality imaging and systemic biomarkers in classical low-flow low-gradient aortic stenosis: key findings for cardiac remodeling evaluation

Abstract Background Elevated levels of troponin I (hsTnT) and B-type natriuretic peptide (BNP) have been related with poor prognosis in patients with LFLG-AS. Biomarkers are less expensive, more practical and more accessible than imaging tests, so their use can be an alternative to imaging in the evaluation of patients with LFLG-AS. Purpose The aim of the present study is to assess multimodality imaging findings according to systemic biomarkers (i.e. hsTnT and BNP) in Low-Flow, Low-Gradient Aortic Stenosis (LFLG-AS) and reduced left ventricular ejection fraction (LVEF) patients. Methods Prospective study with LFLG-AS patients (LVEF &amp;lt;50%, aortic valve area ≤1,0 cm2 and mean gradient &amp;lt;40 mmHg) that underwent hsTNnT, BNP, cardiac magnetic resonance (CMR) with T1 mapping and 2 dimensional echocardiogram (2DEcho). All patients also underwent dobutamine stress echocardiogram to define aortic stenosis severity. Patients were divided into 3 groups according to BNP and hsTnT levels: Group 1: BNP and hsTnT levels below median (BNP &amp;lt;395 pg/ml and TnI-Ultra &amp;lt;0.042 ng/ml); Group 2: BNP or hsTnT higher than median; and Group 3: both hsTnT and BNP higher than median. Results 49 patients with LFLG-AS were included (Group 1: 17 patients, Group 2: 14 patients and Group 3: 18 patients). Clinical characteristics (including risk scores) were not able to stratify these groups. Patients with elevation of both biomarkers had lower valvuloarterial impedance (P=0.03), lower LVEF (P=0.02), less moderate/severe mitral (P=0.01) and tricuspid regurgitation (P&amp;lt;0.01) by 2DEcho. CMR identified a progressive increase (from Group 1 to 3) of right and left chamber volumes; reduction in right and left ejection fraction and a marked increase in myocardial fibrosis assessed by extracellular volume (ECV) and indexed extracellular volume (iECV) (Figure 1). Conclusion Higher levels of BNP and hsTnT in LFLG-AS patients were associated with worse multi-modality imaging parameters and can be a surrogate of cardiac remodeling. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): No funding

Cardiac Fibrosis and Changes in Left Ventricle Function in Patients with Chronic Chagas Heart Disease.

ResumoFundamento A cardiopatia chagásica (CC) é uma condição de progressão lenta, cujo principal achado histopatológico é fibrose.Objetivos Avaliar se a fibrose cardíaca aumenta ao longo do tempo e se correlaciona com aumento no tamanho do ventrículo esquerdo (CE) e redução na fração de ejeção (FE) na CC crônica.Métodos Estudo retrospectivo que incluiu 20 indivíduos (50% homens; 60±10 anos) com CC crônica que se submeteram a dois exames de ressonância magnética cardíaca (RMC) com realce tardio com gadolínio em um intervalo mínimo de quatro anos entre os exames. Volume, FE e massa de fibrose do ventrículo esquerdo (VE) foram determinados por RMC. Associações da massa de fibrose na primeira RMC com alterações no volume do VE e FE ventricular esquerda na segunda RMC foram testadas por análise de regressão logística. Valores p<0,05 foram considerados significativos.Resultados Os pacientes foram classificados em: A (n=13; alterações típicas de CC no eletrocardiograma e função sistólica global e segmentar do VE normal) e B1 (n=7; alteração na motilidade da parede do VE e FE ≥45%). O tempo médio entre os dois estudos de RMC foi de 5,4±0,5 anos. Fibrose do VE (em % massa do VE) aumentou de 12,6±7.9% para 18,0±14,1% entre os exames de RMC (p=0,02). A massa de fibrose cardíaca no basal associou-se com uma diminuição > cinco unidades absolutas na FE ventricular esquerda da primeira para a segunda RMC (OR 1,48; IC95% 1,03-2,13; p=0,03). A massa de fibrose do VE foi maior e aumentou entre os dois estudos de RMC no grupo de pacientes que apresentaram diminuição na FE entre os testes.Conclusões Mesmo pacientes em estágios iniciais da CC apresentam um aumento na fibrose do miocárdio ao longo do tempo, e a presença de fibrose do VE no basal está associada a uma diminuição da função sistólica do VE.

Effect of sarcomere and mitochondria-related mutations on myocardial fibrosis in patients with hypertrophic cardiomyopathy

BackgroundMyocardial fibrosis is an important prognostic factor in hypertrophic cardiomyopathy (HCM). However, the contribution from a wide spectrum of genetic mutations has not been well defined. We sought to investigate effect of sarcomere and mitochondria-related mutations on myocardial fibrosis in HCM.MethodsIn 133 HCM patients, comprehensive genetic analysis was performed in 82 nuclear DNA (33 sarcomere-associated genes, 5 phenocopy genes, and 44 nuclear genes linked to mitochondrial cardiomyopathy) and 37 mitochondrial DNA. In all patients, cardiovascular magnetic resonance (CMR) was performed, including 16-segmental thickness, late gadolinium enhancement (LGE), native and post-T1, extracellular volume fraction (ECV), and T2, along with echo-Doppler evaluations.ResultsPatients with sarcomere mutation (SM, n = 41) had higher LGE involved segment, % LGE mass, ECV and lower post-T1 compared to patients without SM (n = 92, all p < 0.05). When classified into, non-mutation (n = 67), only mitochondria-related mutation (MM, n = 24), only-SM (n = 36) and both SM and MM (n = 5) groups, only-SM group had higher ECV and LGE than the non-mutation group (all p < 0.05). In non-LGE-involved segments, ECV was significantly higher in patients with SM. Within non-SM group, patients with any sarcomere variants of uncertain significance had higher echocardiographic Doppler E/e’ (p < 0.05) and tendency of higher LGE amount and ECV (p > 0.05). However, MM group did not have significantly higher ECV or LGE amount than non-mutation group.ConclusionsSMs are significantly related to increase in myocardial fibrosis. Although, some HCM patients had pathogenic MMs, it was not associated with an increase in myocardial fibrosis.

Characterization of cardiovascular injury in mice following partial-heart irradiation with clinically relevant dose and fractionation

Background and purposeLate cardiac toxicity is a major side effect of radiation therapy (RT) for breast cancer. We developed and characterized a mouse model of radiation-induced heart disease that mimics the dose, fractionation, and beam arrangement of left breast and chest wall RT. Material and methodsFemale wild-type (C57BL6/J) and atherosclerosis-prone apolipoprotein E-deficient (ApoE−/−) mice (on a C57BL/6J background) on regular chow were treated with 2 Gy × 25 fractions of partial-heart irradiation via opposed tangential beams to the left chest wall. The changes in myocardial perfusion and cardiac function of C57BL/6J mice were examined by single-photon emission computed tomography (SPECT) and echocardiography, respectively. In addition to SPECT and echocardiography, the formation of calcified plaques and changes in cardiac function of ApoE−/− mice were examined by dual-energy microCT (DE-CT) and pressure–volume (PV) loop analysis, respectively. The development of myocardial fibrosis was examined by histopathology. ResultsCompared to unirradiated controls, irradiated C57BL/6J mice showed no significant changes by SPECT or echocardiography up to 18 months after 2 Gy × 25 partial-heart irradiation even though irradiated mice exhibited a modest increase in myocardial fibrosis. For ApoE−/− mice, 2 Gy × 25 partial-heart irradiation did not cause significant changes by SPECT, DE-CT, or echocardiography. However, PV loop analysis revealed a significant decrease in load-dependent systolic and diastolic function measures including cardiac output, dV/dtmax and dV/dt min 12 months after RT. ConclusionsFollowing clinically relevant doses of partial-heart irradiation in C57BL/6J and ApoE−/− mice, assessment with noninvasive imaging modalities such as echocardiography, SPECT, and DE-CT yielded no evidence of decreased myocardial perfusion and cardiac dysfunction related to RT. However, invasive hemodynamic assessment with PV loop analysis indicated subtle, but significant, changes in cardiac function of irradiated ApoE−/− mice. PV loop analysis may be useful for future preclinical studies of radiation-induced heart disease, especially if subtle changes in cardiac function are expected.

Characterising an Alternative Murine Model of Diabetic Cardiomyopathy.

The increasing burden of heart failure globally can be partly attributed to the increased prevalence of diabetes, and the subsequent development of a distinct form of heart failure known as diabetic cardiomyopathy. Despite this, effective treatment options have remained elusive, due partly to the lack of an experimental model that adequately mimics human disease. In the current study, we combined three consecutive daily injections of low-dose streptozotocin with high-fat diet, in order to recapitulate the long-term complications of diabetes, with a specific focus on the diabetic heart. At 26 weeks of diabetes, several metabolic changes were observed including elevated blood glucose, glycated haemoglobin, plasma insulin and plasma C-peptide. Further analysis of organs commonly affected by diabetes revealed diabetic nephropathy, underlined by renal functional and structural abnormalities, as well as progressive liver damage. In addition, this protocol led to robust left ventricular diastolic dysfunction at 26 weeks with preserved systolic function, a key characteristic of patients with type 2 diabetes-induced cardiomyopathy. These observations corresponded with cardiac structural changes, namely an increase in myocardial fibrosis, as well as activation of several cardiac signalling pathways previously implicated in disease progression. It is hoped that development of an appropriate model will help to understand some the pathophysiological mechanisms underlying the accelerated progression of diabetic complications, leading ultimately to more efficacious treatment options.

Myocardial Fibrosis and Prognosis in Heart Transplant Recipients.

Myocardial fibrosis is a well-described histopathologic feature in heart transplant recipients. Whether myocardial fibrosis in heart transplant recipients is independently associated with clinical outcomes is unclear. We sought to determine whether myocardial fibrosis on late gadolinium enhancement cardiovascular magnetic resonance imaging in heart transplant recipients was independently associated with all-cause death or major adverse cardiac outcomes in the long-term. Using a cohort of consecutive heart transplant recipients that had cardiovascular magnetic resonance imaging, we determined the prevalence and the patterns of myocardial fibrosis and analyzed associations between myocardial fibrosis and a composite end point of all-cause death or major adverse cardiac events: retransplantation, nonfatal myocardial infarction, coronary revascularization, and heart failure hospitalization. One hundred and fifty-two heart transplant recipients (age, 54±15 years; 29% women; 5.0±5.4 years after heart transplantation) were included. Myocardial fibrosis was present in 18% (37% infarct pattern, 41% noninfarct pattern, and 22% both). Its prevalence was positively associated with cardiac allograft vasculopathy grade. With a median follow-up of 2.6 years, myocardial fibrosis was independently associated with all-cause death or major adverse cardiac events (hazard ratio, 2.88; 95% CI, 1.59-5.23; P<0.001) after adjustment for cardiac allograft vasculopathy, history of rejection, time since transplantation, left ventricular ejection fraction, and indexed right ventricular end-diastolic volume. Every 1% increase in myocardial fibrosis was independently associated with a 6% higher hazard for all-cause death or major adverse cardiac events (hazard ratio, 1.06; 95% CI, 1.03-1.09; P<0.001). The addition of myocardial fibrosis variables to models with cardiac allograft vasculopathy, history of rejection, time since transplantation, left ventricular ejection fraction, and indexed right ventricular end-diastolic volume resulted in significant improvements in model fit, suggesting incremental prognostic value. In heart transplant recipients, myocardial fibrosis is seen on late gadolinium enhancement cardiovascular magnetic resonance imaging in 18%. Both the presence and the extent of myocardial fibrosis are independently associated with the long-term risk of all-cause death or major adverse cardiac events.

Human Umbilical Cord Mesenchymal Stem Cells Alleviate Myocardial Endothelial-Mesenchymal Transition in a Rat Dilated Cardiomyopathy Model

BackgroundHuman umbilical cord–derived mesenchymal stem cells (HuMSCs) have been shown to suppress cardiac fibrosis; however, the underlying mechanisms are not fully understood. Recent studies have shown that endothelial-mesenchymal transition (EndMT) plays a crucial part in myocardial fibrosis. In the present study, we investigated the suppressive role of HuMSCs in cardiac fibrosis and related mechanisms in a rat dilated cardiomyopathy (DCM) model. MethodsMale Lewis rats were randomly divided into 3 groups. Rats without any treatment served as a negative control group, while the DCM rats, which were generated by immunization with porcine myosin, were divided into 2 groups: a HuMSC group, in which HuMSCs (1 × 106 cells/rat) were injected intravenously, and a vehicle group, in which rats were injected with volume-matched solution containing no HuMSCs. Histologic and immunofluorescent measurements were used to evaluate the effects of HuMSCs on cardiac fibrosis and EndMT. ResultsWe observed a significant increase in myocardial fibrosis, and elevated EndMT in rats of the vehicle group were observed compared with those in the negative control group along with the increased activity of transforming growth factor (TGF)-β1/extracellular signal-regulated kinase (ERK) 1/2 signaling. Treatment with HuMSCs repressed the increase in myocardial fibrosis and EndMT observed in DCM rats, which correlated with decreased activity of TGF-β1/ERK1/2 signaling. ConclusionThe HuMSCs attenuated cardiac fibrosis at least partly through the inhibition of TGF-β/ERK-induced EndMT.

Poor Glycemic Control Is Associated With Increased Extracellular Volume Fraction in Diabetes.

We assessed whether poor glycemic control is associated with an increase in myocardial fibrosis among adults with diabetes. We studied 47 adults with type 2 diabetes and stratified them into three groups according to their hemoglobin A1c (HbA1c) level: <6.5% (group 1; n = 12), 6.5-7.5% (group 2; n = 20), and >7.5% (group 3; n = 15). Left ventricular (LV) mass was assessed using cardiac MRI. The extracellular volume fraction (ECVF), an index of myocardial fibrosis, was measured by using myocardial T1 mapping before and after the administration of a gadolinium-based contrast agent. Mean HbA1c was 5.84 ± 0.16%, 6.89 ± 0.14%, and 8.57 ± 0.2% in groups 1, 2, and 3, respectively. LV mass was not significantly different between the groups. The myocardial ECVF was significantly greater in groups 2 (mean 27.6% [95% CI 24.8-30.3]) and 3 (27.6% [24.4-30.8]) than in group 1 (21.1% [17.5-24.7]; P = 0.015). After adjusting for age, sex, BMI, blood pressure, and estimated glomerular filtration rate, the myocardial ECVF was significantly greater in groups 2 (27.4% [24.4-30.4]) and 3 (28% [24.5-31.5]) than in group 1 (20.9% [17.1-24.6]; P = 0.0156, ANCOVA). An increased myocardial ECVF, suggesting myocardial fibrosis, is independently associated with poor glycemic control among adults with diabetes. Further research should assess whether tight glycemic control can revert fibrosis to healthy myocardium or ameliorate it and its adverse clinical consequences.

RITONAVIR-BASED ANTI-RETROVIRAL THERAPY IS ASSOCIATED WITH A LOWER EJECTION FRACTION AND AN INCREASED RISK FOR DECOMPENSATED HEART FAILURE AND CARDIOVASCULAR MORTALITY AMONG PERSONS LIVING WITH HIV

Persons with HIV are at an increased risk of heart failure (HF). Ritonavir-based therapy (RBT) is associated with an increase in myocardial fibrosis; however, there are no data testing the effect of RBT on clinical outcomes among patients with HF. We retrospectively analyzed 160 people on ART

Cyclosporin A induces autophagy in cardiac fibroblasts through the NRP-2/WDFY-1 axis

Cyclosporin A (CsA) is an effective immunosuppressive agent, but its myocardial toxicity limits its widespread and long-term clinical application. In this study, CsA treatment led to damages in myocardial fiber structure, an increase in myocardial fibrosis, and changes in heart size and shape; moreover, the degree of damage was exacerbated with prolonged drug application and increases in dose. However, the mechanism is not clear; therefore, the purpose of this study was to reveal the mechanism of CsA-induced myocardial fibrosis and identify a new target for the prevention and treatment of CsA-induced myocardial injury. Cardiac fibroblasts were treated with CsA (5, 10, or 20 μg/mL) for 24 h. Autophagy was observed by electron microscopy and immunofluorescence. The expression of NRP-2/WDFY-1, autophagy-related proteins (Beclin1 and LC3B), fibrosis-related proteins (MMP2/9), and fibroblast phenotype conversion factor (α-SMA) was evaluated by Western blot. The expression of collagen I was determined by ELISA. Then, we used the gene interference technique to alter WDFY-1 expression with or without CsA or 3-MA treatment for 24 h, and the effects on autophagy and the expression of autophagy-related proteins, fibrosis-associated proteins, IFN-α, TNF-α, and IL-6 were determined. The results showed the following: (1) CsA induced fibrosis-related protein (MMP2/9), fibroblast phenotype conversion factor (α-SMA), and collagen I up-regulation in a dose-dependent manner. (2) CsA induced the formation of autophagosomes and up-regulated the expression of Beclin1, LC3B, and the ERK/MAPK pathway in cardiac fibroblasts. (3) CsA induced NRP-2 down-regulation and WDFY-1 up-regulation. (4) Depletion of WDFY-1 inhibited CsA-induced autophagy, TNF-α and IFN-α up-regulation, and fibrosis. (5) The autophagy inhibitor 3-MA inhibited CsA-induced TNF-α and IFN-α up-regulation and fibrosis. Overall, cyclosporin A induces autophagy in cardiac fibroblasts through the NRP-2/WDFY-1 axis, which promotes the progression of myocardial fibrosis.

Characterization of the Changes in Cardiac Structure and Function in Mice Treated With Anthracyclines Using Serial Cardiac Magnetic Resonance Imaging.

Anthracyclines are cardiotoxic; however, there are limited data characterizing the serial changes in cardiac structure and function after anthracyclines. The aim of this study was to use cardiac magnetic resonance to characterize anthracycline-induced cardiotoxicity in mice. This was a longitudinal cardiac magnetic resonance and histological study of 45 wild-type male mice randomized to doxorubicin (n=30, 5 mg/kg of doxorubicin/week for 5 weeks) or placebo (n=15). A cardiac magnetic resonance was performed at baseline and at 5, 10, and 20 weeks after randomization. Measures of primary interest included left ventricular ejection fraction, myocardial edema (multiecho short-axis spin-echo acquisition), and myocardial fibrosis (Look-Locker gradient echo). In doxorubicin-treated mice versus placebo, there was an increase in myocardial edema at 5 weeks (T2 values of 32±4 versus 21±3 ms; P<0.05), followed by a reduction in left ventricular ejection fraction (54±6 versus 63±5%; P<0.05) and an increase in myocardial fibrosis (extracellular volume of 0.34±0.03 versus 0.27±0.03; P<0.05) at 10 weeks. There was a strong association between the early (5 weeks) increase in edema and the subacute (10 weeks) increase in fibrosis (r=0.90; P<0.001). Both the increase in edema and fibrosis predicted the late doxorubicin-induced mortality in mice (P<0.001). Our data suggest that, in mice, anthracycline-induced cardiotoxicity is associated with an early increase in cardiac edema and a subsequent increase in myocardial fibrosis. The early increase in edema and subacute increase in fibrosis are strongly linked and are both predictive of late mortality.

Abstract 13220: Distinct Disease Mechanisms Drive Pediatric and Adult Dilated Cardiomyopathy

Background: Numerous clinical studies have suggested that adult heart failure (HF) therapies are less effective in children with dilated cardiomyopathy (DCM). The mechanistic basis for this phenomenon is poorly defined. Collectively, adult HF therapeutics target a process termed adverse remodeling, a common pathway by which the adult heart responds to injury. We hypothesized that pediatric and adult DCM comprise distinct pathological entities in that children do not undergo adverse remodeling. Methods: LV specimens were obtained from donor pediatric and adult controls (24), pediatric DCM (31) and adult DCM patients (33). Pathological evidence of adverse remodeling including myocardial fibrosis, cardiomyocyte hypertrophy, and gene expression was examined using immunostaining, electron microscopy and RNA sequencing. Results: Consistent with the established pathophysiology of adult HF, adults with DCM displayed marked increases in myocardial fibrosis compared to donor controls (both p&lt;0.01)(Figure). In contrast, pediatric DCM had minimal evidence of fibrosis compared to both aged-matched controls and adults with DCM. Examination of cardiomyocyte hypertrophy and capillary density demonstrated less extensive cardiomyocyte hypertrophy and capillary rarefaction in pediatric compared to adult DCM patients. Electron microscopy revealed similar sarcomere thickness and length between control and pediatric DCM specimens. RNA sequencing demonstrated that genes associated with adverse remodeling were not up-regulated in pediatric DCM specimens. Conclusions: These findings demonstrate that children with DCM display minimal evidence of adverse remodeling; suggesting pediatric and adult DCM may represent different pathological entities. Collectively, these data provide a mechanistic basis to understand why adult HF therapeutics may not work in children, and suggest the possibility that distinct therapies may be needed for pediatric DCM.

Losartan Attenuates Myocardial Endothelial-To-Mesenchymal Transition in Spontaneous Hypertensive Rats via Inhibiting TGF-β/Smad Signaling

BackgroundLosartan plays an important role in the inhibition of myocardial fibrosis. But the underlying mechanism is not entirely clear. Emerging evidences have indicated that endothelial-to-mesenchymal transition (EndMT) plays a crucial role in cardiac fibrosis. Here the present study aims to first investigated the effect of Losartan on EndMT in cardiac fibrosis of spontaneous hypertensive rats (SHRs).MethodsMale SHRs were randomly divided into three groups and fed for 12 weeks, namely the SHR group (Group S), the Losartan-treated group (Group L) and the Prazosin-treated group (Group P). Wistar-Kyoto rats served as controls (Group W). The histological changes were evaluated by Masson’s trichrome. Co-expression of CD31 and fibroblast-specific protein 1 (FSP1) were used as the markers of EndMT through immunofluorescence. The expressions of FSP1, CD31, TGF-β, Smad were detected by Western blot analysis.ResultsIt was identified that elevated blood pressure induced a significant increase in myocardial fibrosis and EndMT in SHRs, which was reversed by Losartan and Prazosin treatment. Furthermore, the activity of TGF-β/Smad signaling was detected in the four groups. TGF-β/Smad signaling was activated in SHRs and suppressed by Losartan or Prazosin treatment. Losartan exhibited more efficiently than Prazosin in inhibiting TGF-β/Smad signaling activation, EndMT and myocardial fibrosis.ConclusionThese results showed that EndMT played an important role in promoting hypertensive cardiac fibrosis, and that losartan could suppress cardiac fibrosis through the inhibition of EndMT via classical TGF-β/Smad pathway.

Cardiac Fibrosis Alters Calcium Sensitivity and Myofilament Relaxation

Heart failure with preserved ejection fraction (HFpEF) accounts for at least half of the patients with heart failure, but there are no proven therapies for these patients. There is a need to better understand the molecular mechanisms involved in this heterogeneous patient population. Studies have shown an increase in myocardial fibrosis and collagen content in patients with HFpEF. It is not clear whether or how fibrosis alters myocyte cellular contraction. We used a previously published model of cardiac fibrosis with macrophage-targeted overexpression of urokinase plasminogen activator (SR-uPA mice) to determine the effect of fibrosis on myofilament function and cardiomyocyte contraction. We measured the passive stiffness and contractile properties of demembranated papillary muscle preparations as well as activation and relaxation parameters of isolated myofibrils from WT and SR-uPA mice. Our results showed an increase in passive stiffness in SR-uPA compared to WT mice when the demembranated preparations were stretched to 24% from baseline length (∼SL=2.0 μM). The SR-uPA +/o mice also show an increase in Ca2+ sensitivity (pCa50=5.69±0.04 vs. 5.55±0.03, P<0.05) compared to WT mice. Myofibrils from these mice show preserved tension and rate of activation. However, there is prolonged slow phase of relaxation (69±3 vs. 58±2 ms, P<0.05) with reduced rates of both slow (1.6±0.2 vs. 1.2±0.2 s-1, P<0.05) and fast (15.1±1.8 vs. 7.0±0.6 s-1, P<0.05) phases of relaxation. In order to elicit the mechanism of this difference we performed western blot analysis and there were no differences in myosin isoform or troponin I phosphorylation level at Ser23/24. Our preliminary data suggest slower relaxation of myofibrils could be compensatory for the increased stiffness, to maintain ventricular relaxation kinetics. We are currently collecting data to characterize the contraction and relaxation parameters of intact cells.

Abstract 10378: Characterization of Changes in Cardiac Structure and Function in Mice Treated With Anthracyclines Using Serial Cardiac Magnetic Resonance Imaging

Introduction: Anthracyclines are a standard chemotherapeutic agent. However, the anthracyclines are associated with a late reduction in left ventricular ejection fraction (LVEF) and heart failure. Pathologically, anthracycline-induced cardiotoxicity (AIC) is characterized by the development of cardiac edema and fibrosis and cardiac magnetic resonance (CMR) is the gold-standard imaging technique for edema and fibrosis. Hypothesis: We hypothesized that a) cardiac edema and fibrosis would be detected by CMR after anthracyclines and b) edema and fibrosis would provide prognostic information. Methods: We performed a longitudinal CMR and histological study of 45 wild-type mice randomized to doxorubicin (DOX, n=30, 5 mg/kg/week for 5 weeks) or placebo (n=15). Measurements were performed at baseline, 5, 10, and 20 weeks after DOX or placebo. Measures of interest were LVEF, myocardial edema and fibrosis. Edema was assessed by T2 mapping, fibrosis by calculating the extracellular volume (ECV) from pre- and post-contrast T1 measurements. Results: In DOX-treated mice vs. placebo, myocardial edema at 5 weeks was increased (T2 values of 32±4 vs. 21±3 ms, P&lt;0.05, Fig. A), while LVEF was unchanged. At 10 weeks, there was a reduction in LVEF (54±6 vs. 63±5% μL, P&lt;0.05) and an increase in myocardial fibrosis (ECV of 0.34±0.03 vs. 0.27±0.03, P&lt;0.05, Fig. B). There was a correlation between T2 measures and cardiac water weight (r=0.79, P=0.007, Fig. C) and between the ECV and histological myocardial fibrosis (r=0.90, P&lt;0.001; Fig. D). Both the early increase in edema and the sub-acute increase in fibrosis predicted the late DOX-induced mortality (P&lt;0.001, Fig. E and F). Conclusions: Our data suggest that, in mice, CMR can detect the early increase in edema and sub-acute increase in fibrosis after anthracyclines, that an increase in edema precedes a reduction in LVEF, that the increase in edema and fibrosis are linked and both are predictive of late animal mortality.