Mouse Model Of Transverse Aortic Constriction Research Articles

SIRT6 mediated histone H3K9ac deacetylation involves myocardial remodelling through regulating myocardial energy metabolism in TAC mice.

Pathological myocardial remodelling is the initial factor of chronic heart failure (CHF) and is induced by multiple factors. We previously demonstrated that histone acetylation is involved in CHF in transverse aortic constriction (TAC) mice, a model for pressure overload-induced heart failure. In this study, we investigated whether the histone deacetylase Sirtuin 6 (SIRT6), which mediates deacetylation of histone 3 acetylated at lysine 9 (H3K9ac), is involved pathological myocardial remodelling by regulating myocardial energy metabolism and explored the underlying mechanisms. We generated a TAC mouse model by partial thoracic aortic banding. TAC mice were injected with the SIRT6 agonist MDL-800 at a dose of 65 mg/kg for 8 weeks. At 4, 8 and 12 weeks after TAC, the level of H3K9ac increased gradually, while the expression of SIRT6 and vascular endothelial growth factor A (VEGFA) decreased gradually. MDL-800 reversed the effects of SIRT6 on H3K9ac in TAC mice and promoted the expression of VEGFA in the hearts of TAC mice. MDL-800 also attenuated mitochondria damage and improved mitochondrial respiratory function through upregulating SIRT6 in the hearts of TAC mice. These results revealed a novel mechanism in which SIRT6-mediated H3K9ac level is involved pathological myocardial remodelling in TAC mice through regulating myocardial energy metabolism. These findings may assist in the development of novel methods for preventing and treating pathological myocardial remodelling.

Identification of TGF-β-related genes in cardiac hypertrophy and heart failure based on single cell RNA sequencing.

Heart failure (HF) remains a huge medical burden worldwide. Pathological cardiac hypertrophy is one of the most significant phenotypes of HF. Several studies have reported that the TGF-β pathway plays a double-sided role in HF. Therefore, TGF-β-related genes (TRGs) may be potential therapeutic targets for cardiac hypertrophy and HF. However, the roles of TRGs in HF at the single-cell level remain unclear. In this study, to analyze the expression pattern of TRGs during the progress of cardiac hypertrophy and HF, we used three public single-cell RNA sequencing datasets for HF (GSE161470, GSE145154, and GSE161153), one HF transcriptome data (GSE57338), and one hypertrophic cardiomyopathy transcriptome data (GSE141910). Weighted gene co-expression network analysis (WGCNA), functional enrichment analysis and machine learning algorithms were used to filter hub genes. Transverse aortic constriction mice model, CCK-8, wound healing assay, quantitative real-time PCR and western blotting were used to validate bioinformatics results. We observed that cardiac fibroblasts (CFs) and endothelial cells showed high TGF-β activity during the progress of HF. Three modules (royalblue, brown4, and darkturquoize) were identified to be significantly associated with TRGs in HF. Six hub genes (TANC2, ADAMTS2, DYNLL1, MRC2, EGR1, and OTUD1) showed anomaly trend in cardiac hypertrophy. We further validated the regulation of the TGF-β-MYC-ADAMTS2 axis on CFs activation in vitro. This study identified six hub genes (TANC2, ADAMTS2, DYNLL1, MRC2, EGR1, and OTUD1) by integrating scRNA and transcriptome data. These six hub genes might be therapeutic targets for cardiac hypertrophy and HF.

Divergent effects of myostatin inhibition on cardiac and skeletal muscles in a mouse model of pressure overload.

The transforming growth factor-β (TGF-β) superfamily member, myostatin, is a negative regulator of muscle growth and may contribute to adverse cardiac remodeling. Whether suppressing myostatin could benefit pressure-overloaded heart remains unclear. We investigated the effects of pharmacological inhibition of myostatin on cardiac fibrosis and hypertrophy in a mouse model of pressure overload induced by transverse aortic constriction (TAC). Two weeks after the surgery, TAC and sham mice were randomly divided into groups receiving mRK35, a monoclonal anti-myostatin antibody, or vehicle (PBS) for 8 wk. Significant progressive cardiac hypertrophy was observed in TAC mice, as reflected by the increased wall thickness, ventricular weight, and cross-sectional area of cardiomyocytes. In the groups treated with mRK35, compared with sham mice, cardiac fibrosis was increased in TAC mice, accompanied with elevated mRNA expression of fibrotic genes. However, among the TAC mice, mRK35 did not reduce cardiac hypertrophy or fibrosis. Body weight, lean mass, and wet weights of tibialis anterior and gastrocnemius muscle bundle were increased by mRK35. When compared with the TAC-PBS group, the TAC mice treated with mRK35 demonstrated greater forelimb grip strength and a larger mean size of gastrocnemius fibers. Our data suggest that mRK35 does not attenuate cardiac hypertrophy and fibrosis in a TAC mouse model but has positive effects on muscle mass and muscle strength. Anti-myostatin treatment may have therapeutic value against muscle wasting in cardiac vascular disease.NEW & NOTEWORTHY Recent research has highlighted the importance of inhibiting TGF-β signaling in mitigating cardiac dysfunction and remodeling. As myostatin belongs to the TGF-β family, we evaluated the impact of myostatin inhibition using mRK35 in TAC-operated mice. Our data demonstrate that mRK35 significantly increased body weight, muscle mass, and muscle strength but did not attenuate cardiac hypertrophy or fibrosis. Pharmacological inhibition of myostatin may provide therapeutic benefits for the management of muscle wasting in cardiovascular diseases.

A time-series minimally invasive transverse aortic constriction mouse model for pressure overload-induced cardiac remodeling and heart failure.

Transverse aortic constriction (TAC) is a widely-used animal model for pressure overload-induced cardiac hypertrophy and heart failure (HF). The severity of TAC-induced adverse cardiac remodeling is correlated to the degree and duration of aorta constriction. Most studies of TAC are performed with a 27-gauge needle, which is easy to cause a tremendous left ventricular overload and leads to a rapid HF, but it is accompanied by higher mortality attributed to tighter aortic arch constriction. However, a few studies are focusing on the phenotypes of TAC applied with a 25-gauge needle, which produces a mild overload to induce cardiac remodeling and has low post-operation mortality. Furthermore, the specific timeline of HF induced by TAC applied with a 25-gauge needle in C57BL/6 J mice remains unclear. In this study, C57BL/6 J mice were randomly subjected to TAC with a 25-gauge needle or sham surgery. Echocardiography, gross morphology, and histopathology were applied to evaluate time-series phenotypes in the heart after 2, 4, 6, 8, and 12 weeks. The survival rate of mice after TAC was more than 98%. All mice subjected to TAC maintained compensated cardiac remodeling during the first two weeks and began to exhibit heart failure characteristics after 4 weeks upon TAC. At 8 weeks post-TAC, the mice showed severe cardiac dysfunction, hypertrophy, and cardiac fibrosis compared to sham mice. Moreover, the mice raised a severe dilated HF at 12 weeks. This study provides an optimized method of the mild overload TAC-induced cardiac remodeling from the compensatory period to decompensatory HF in C57BL/6 J mice.

BAY-7081: A Potent, Selective, and Orally Bioavailable Cyanopyridone-Based PDE9A Inhibitor.

Despite advances in the treatment of heart failure in recent years, options for patients are still limited and the disease is associated with considerable morbidity and mortality. Modulating cyclic guanosine monophosphate levels within the natriuretic peptide signaling pathway by inhibiting PDE9A has been associated with beneficial effects in preclinical heart failure models. We herein report the identification of BAY-7081, a potent, selective, and orally bioavailable PDE9A inhibitor with very good aqueous solubility starting from a high-throughput screening hit. Key aspect of the optimization was a switch in metabolism of our lead structures from glucuronidation to oxidation. The switch proved being essential for the identification of compounds with improved pharmacokinetic profiles. By studying a tool compound in a transverse aortic constriction mouse model, we were able to substantiate the relevance of PDE9A inhibition in heart diseases.

Mitochondrial derived peptide MOTS-c prevents the development of heart failure under pressure overload conditions in mice.

MOTS-c, a mitochondrial-derived peptide (MDP), has been shown to have multiple biological activities such as antioxidation, anti-inflammation, and anti-apoptosis properties. In the present study, we aimed at evaluating the therapeutic effect of MOTS-c peptide in an animal model of heart failure. The heart failure mouse model was made by transverse aortic constriction (TAC) operations. The MOTS-c peptide was administrated subcutaneously by using an osmotic pump. At the end of the animal experiment, cardiac function was evaluated by echocardiography, and heart tissues were subjected to histological and molecular analysis. In vitro cultured H9C2 cells were used to test the effects of MOTS-c overexpression on cell death in response to H2 O2 stimulation. Our study showed that MOTS-c peptide attenuated TAC-induced cardiac dysfunction and remodelling. In addition, the MOTS-c peptide reduced the inflammatory response and upregulated the antioxidant capacity, coupled with the activation of the AMPK pathway in the heart of the TAC mouse model. In in vitro cultured cardiac cells, overexpression of MOTS-c was shown to activate the AMPK pathway and protect cell apoptosis in response to H2 O2 stimulation. Taken together, our study suggested that MOTS-c peptides may have therapeutic potential in treating HF.

A Simplified Herbal Formula Improves Cardiac Function and Reduces Inflammation in Mice Through the TLR-Mediated NF-κB Signaling Pathway.

Nuanxinkang tablet (NXK), a Chinese herbal formula, can improve heart function and quality of life in patients with chronic heart failure (CHF). However, the mechanisms of action of NXK are not fully understood. In this study, we investigated the effects of NXK on inflammation in the CHF mouse model. This model was established by transverse aortic constriction (TAC) and treated with NXK for 8 weeks. Then, the cardiac function and myocardial fibrosis were evaluated. The monocytes/macrophages were evaluated by immunofluorescence. The mRNA levels of IL-1β, IL-6, TNF-α, ICAM-1, and VCAM-1 were measured by quantitative real-time polymerase chain reaction (qRT-PCR), while TLR4, MyD88, NF-κB p65, P-IκBα, TLR2, TLR7 and TLR9 protein levels were evaluated by Western blot. The results showed that NXK improved the left ventricular ejection fraction (LVEF) and left ventricular end-systolic dimension, reversed myocardial fibrosis, and inhibited pro-inflammatory (CD11b + Ly6C+) monocytes/macrophages in the TAC mouse model. NXK also reduced the mRNA and protein levels of the above markers. Taken together, NXK improved heart function and reduced inflammation through the TLR-mediated NF-κB signaling pathway, suggesting that it might be used as an innovative treatment strategy for CHF.

EGCG prevents pressure overload‑induced myocardial remodeling by downregulating overexpression of HDAC5 in mice.

Myocardial remodeling is a complex pathological process and its mechanism is unclear. The present study investigated whether epigallocatechin gallate (EGCG) prevents myocardial remodeling by regulating histone acetylation and explored the mechanisms underlying this effect in the heart of a mouse model of transverse aortic constriction (TAC). A TAC mouse model was created by partial thoracic aortic banding (TAB). Subsequently, TAC mice were injected with EGCG at a dose of 50 mg/kg/day for 12 weeks. The hearts of mice were collected for analysis 4, 8 and 12 weeks after TAC. Histopathological changes in the heart were observed by hematoxylin and eosin, Masson trichrome and wheat germ agglutinin staining. Protein expression levels were investigated using western blotting. Cardiac function of mice was detected by echocardiography. The level of histone acetylated lysine 27 on histone H3 (H3K27ac) first increased and then decreased in the hearts of mice at 4, 8 and 12 weeks after TAC. The expression levels of two genes associated with pathological myocardial remodeling, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), also increased initially but then decreased. The expression levels of histone deacetylase 5 (HDAC5) gradually increased in the hearts of mice at 4, 8 and 12 weeks after TAC. Furthermore, EGCG increased acetylation of H3K27ac by inhibiting HDAC5 in the heart of TAC mice treated with EGCG for 12 weeks. EGCG normalized the transcriptional activity of heart nuclear transcription factor myocyte enhancer factor 2A in TAC mice treated for 12 weeks. The low expression levels of myocardial remodeling-associated genes (ANP and BNP) were reversed by EGCG treatment for 12 weeks in TAC mice. In addition, EGCG reversed cardiac enlargement and improved cardiac function and survival in TAC mice when treated with EGCG for 12 weeks. Modification of the HDAC5-mediated imbalance in histone H3K27ac served a key role in pathological myocardial remodeling. The present results show that EGCG prevented and delayed myocardial remodeling in TAC mice by inhibiting HDAC5.

Analysis on the expression profile of circRNAs in hypertrophic myocardium mice

Objective: To explore the differential expression of circRNAs and their potential impact on the pathophysiological process in cardiac hypertrophy. Methods: Six SPF C57BL/6J male mice, aged 8 to 10 weeks, were randomly divided into transverse aortic constriction (TAC) group (n=3) or sham operation(sham) group (n=3) according to random number table method. TAC mouse model was used to induce cardiac hypertrophy. Four weeks after surgery, high-throughput sequencing analysis was performed to detect differentially expressed circRNA in left myocardial tissues of mice between TAC group and sham group, and principal component analysis of circRNA was performed by R language software. Enrichment analysis was performed by GO and KEGG databases to predict the basic functions of differentially expressed circRNA-derived genes and their biological pathways. The differentially expressed circRNAs in the sequencing results were verified by real-time fluorescence quantitative polymerase chain reaction. Cytoscape software was used to construct circRNA-microRNA (miRNA) network maps to predict their interactions by combining differentially expressed circRNA and TargetScan predicted miRNA sites. Results: Principal component analysis was performed on 4 580 circRNAs detected from 6 samples of mice in TAC group and sham group. The results of R language software indicated that the variance contribution rate of the first 3 principal components, namely the first, second and third principal components, was 91.01%, 3.19% and 2.01%, respectively, and the cumulative variance contribution rate of the 3 components was 96.21%. Among the differentially expressed circRNAs, 6 (19%) were up-regulated and 25 (81%) were down-regulated in the TAC group. GO analysis showed that differentially expressed circRNA was closely related to the occurrence and development of cardiac hypertrophy, and KEGG pathway analysis suggested that downregulated circRNA expression was involved in the regulation of actin cytoskeleton. Fifteen out of the 31 differentially expressed circRNAs were selected for real-time fluorescence quantitative polymerase chain reaction verification, and the results showed that 8 circRNAs were consistent with sequencing results. circRNA-miRNA co-expression network analysis results showed that chr11:65218529-65233184-interacts with mmu-miRNA-30e-3p and mmu-miRNA-30a-3p. Conclusions The differential expression of circRNA in hypertrophic myocardium mice is evidenced in TAC mouse model. circRNA may interact with the corresponding miRNA to influence the occurrence and development of cardiac hypertrophy through autophagy-related cellular hypertrophy pathway or apoptosis-related pathological phenotypes.

Abstract 9508: The Natural Product Zerumbone Suppresses Pressure Overload-Induced Cardiac Dysfunction by Inhibiting Cardiac Hypertrophy and Fibrosis

Introduction: Cardiac hypertrophy and fibrosis are hallmarks of cardiac remodeling and are involved functionally in the development of heart failure (HF). Various food components effectively prevent cardiovascular diseases. However, it is unknown whether zerumbone (ZER), a major active terpene found in endemic wild ginger species, suppresses cardiac hypertrophy, fibrosis, and dysfunction. Hypothesis: We assessed the hypothesis that ZER suppresses cardiac hypertrophy and fibrosis in vitro and in vivo . Methods: The effects of ZER on phenylephrine (PE)-induced hypertrophic responses and on transforming growth factor beta (TGF-β)-induced fibrotic responses were examined in primary cultured cardiomyocytes and fibroblasts from neonatal rats. To determine whether ZER prevents the development of pressure overload-induced HF in vivo , a transverse aortic constriction mouse model was utilized (n=6-10). One day after surgery, mice were randomly divided into two groups and orally administered with ZER 20 mg / kg or vehicle for 8 weeks. Cardiac function was evaluated by echocardiography. Changes in cardiomyocyte surface area and degree of fibrosis were observed by histological analysis (HE and WGA staining). The total mRNA levels of the genes associated with hypertrophy and fibrosis were measured by qRT-PCR. Protein expression (Akt phosphorylation and α-SMA) were assessed by western blotting. Results: ZER significantly suppressed PE-induced increases in cell size, hypertrophic gene expression (ANF and BNP), and Akt phosphorylation in cardiomyocytes. TGF-β-induced increases in collagen synthesis, mRNA levels of POSTN and α-SMA, and protein expression of α-SMA were lower in the ZER-treated cultured cardiac fibroblasts. Echocardiography results showed that left ventricular fractional shortening was increased and wall thickness was reduced in the ZER group compared with the vehicle group. Histological analysis showed that pressure overload-induced cardiac hypertrophy and cardiac fibrosis were inhibited in the ZER group compared with the vehicle group. Conclusions: These results suggest that zerumbone ameliorates pressure overload-induced cardiac dysfunction, at least in part by suppressing both cardiac hypertrophy and fibrosis.

A New Minimally Invasive Method of Transverse Aortic Constriction in Mice

Transverse aortic constriction (TAC) in mice is the most popular model to mimic pressure overload heart disease. In this study, we developed a convenient, quick, and less invasive new TAC mice model. Briefly, after anesthetization, endotracheal intubation was then performed, and the endotracheal tube was connected to a ventilator. The second intercostal space was opened and then the home-made retractors were used to push aside the thymus gently. A tunnel under the aortic arch was made and a segment of 6-0 monofilament polypropylene suture which had been threaded through a specifically modified blunted 26-gauge syringe needle was passed through the tunnel.A blunted 27-gauge needle was placed parallel to the transverse aorta and then three knots were tied quickly. After ligation, the spacer was removed promptly and gently to achieve a constriction of 0.4mm in diameter. Five weeks after TAC, cardiac hypertrophy, fibrosis, and left ventricular dysfunction were observed. The mouse was anesthetized with pentobarbital (50mg/kg) via intraperitoneal injection. Endotracheal intubation under direct vision was then performed and the endotracheal tube was connected to a ventilator. The second intercostal space was opened and then the home-made retractors were used to push aside the thymus gently. A tunnel under the aortic arch was made and a segment of 6-0 monofilament polypropylene suture which had been threaded through a specifically modified blunted 26-gauge syringe needle was passed through the tunnel.

Ndufs1 Deficiency Aggravates the Mitochondrial Membrane Potential Dysfunction in Pressure Overload-Induced Myocardial Hypertrophy.

Mitochondrial dysfunction has been suggested to be the key factor in the development and progression of cardiac hypertrophy. The onset of mitochondrial dysfunction and the mechanisms underlying the development of cardiac hypertrophy (CH) are incompletely understood. The present study is based on the use of multiple bioinformatics analyses for the organization and analysis of scRNA-seq and microarray datasets from a transverse aortic constriction (TAC) model to examine the potential role of mitochondrial dysfunction in the pathophysiology of CH. The results showed that NADH:ubiquinone oxidoreductase core subunit S1- (Ndufs1-) dependent mitochondrial dysfunction plays a key role in pressure overload-induced CH. Furthermore, in vivo animal studies using a TAC mouse model of CH showed that Ndufs1 expression was significantly downregulated in hypertrophic heart tissue compared to that in normal controls. In an in vitro model of angiotensin II- (Ang II-) induced cardiomyocyte hypertrophy, Ang II treatment significantly downregulated the expression of Ndufs1 in cardiomyocytes. In vitro mechanistic studies showed that Ndufs1 knockdown induced CH; decreased the mitochondrial DNA content, mitochondrial membrane potential (MMP), and mitochondrial mass; and increased the production of mitochondrial reactive oxygen species (ROS) in cardiomyocytes. On the other hand, Ang II treatment upregulated the expression levels of atrial natriuretic peptide, brain natriuretic peptide, and myosin heavy chain beta; decreased the mitochondrial DNA content, MMP, and mitochondrial mass; and increased mitochondrial ROS production in cardiomyocytes. The Ang II-mediated effects were significantly attenuated by overexpression of Ndufs1 in rat cardiomyocytes. In conclusion, our results demonstrate downregulation of Ndufs1 in hypertrophic heart tissue, and the results of mechanistic studies suggest that Ndufs1 deficiency may cause mitochondrial dysfunction in cardiomyocytes, which may be associated with the development and progression of CH.

Dec1 deficiency protects the heart from fibrosis, inflammation, and myocardial cell apoptosis in a mouse model of cardiac hypertrophy

Cardiac inflammation and fibrosis triggered by left ventricular pressure overload are the major causes of heart dysfunction. Differentiated embryonic chondrocyte gene 1 (Dec1) is a basic helix-loop-helix transcription factor that is comprehensively involved in inflammation and tissue fibrosis, but its role in cardiac hypertrophy remains unclear. This study explored the effects of Dec1 on cardiac fibrosis, inflammation, and apoptosis in hypertrophic conditions. Transverse aortic constriction (TAC) was performed to induce cardiac hypertrophy in wild-type (WT) mice and in Dec1 knock out (KO) mice for 4 weeks. Using the TAC mouse model, prominent differences in cardiac hypertrophy at the morphological, functional, and molecular levels were delineated by Masson’s Trichrome and TUNEL staining, immunohistochemistry, RT-PCR and Western Blot. DNA microarray and microRNA (miRNA) array analyses were carried out to identify gene and miRNA expression patterns. Dec1KO mice exhibited a more severe hypertrophic heart, whereas WT mice showed a more pronounced perivascular fibrosis after TAC at 4 weeks. The Dec1 deficiency promoted M2 phenotype macrophages. Dec1KO TAC mice showed fewer apoptotic cells than WT TAC mice. APEX1, WNT16, FGF10 and MMP-10 were differentially expressed according to DNA microarray analysis and expression levels of those genes and the corresponding miRNAs (miR-295, miR-200 b, miR-130a, miR-92a) showed the same trends. Furthermore, luciferase reporter assay confirmed that FGF10 is the direct target gene of miR-130. In conclusion, a Dec1 deficiency protects the heart from perivascular fibrosis, regulates M1/M2 macrophage polarization and reduces cell apoptosis, which may provide a novel insight for the treatment of cardiac hypertrophy.

The potential role of calnexin in the activation of cardiac fibroblasts

Calnexin is a lectin-like molecular chaperone protein on the endoplasmic reticulum, mediating unfolded protein responses, the endoplasmic reticulum Ca 2+ homeostasis, and Ca 2+ signals conduction. In recent years, studies have found that calnexin plays a key role in the heart diseases. This study aims to explore the role of calnexin in the activation of cardiac fibroblasts. A transverse aortic constriction (TAC) mouse model was established to observe the activation of cardiac fibroblasts in vivo, and the in vitro cardiac fibroblasts activation model was established by transforming growth factor β1 (TGFβ1) stimulation. The adenovirus was respectively used to gene overexpression and silencing calnexin in cardiac fibroblasts to elucidate the relationship between calnexin and cardiac fibroblasts activation, as well as the possible underlying mechanism. We confirmed the establishment of TAC model by echocardiography, hematoxylin-eosin, Masson, and Sirius red staining, and detecting the expression of cardiac fibrosis markers in cardiac tissues. After TGFβ1 stimulation, markers of the activation of cardiac fibroblast, and proliferation and migration of cardiac fibroblast were detected by quantitative PCR, Western blot, EdU assay, and wound healing assay respectively. The results showed that the calnexin expression was reduced in both the TAC mice model and the activated cardiac fibroblasts. The overexpression of calnexin relieved cardiac fibroblasts activation, in contrast, the silencing of calnexin promoted cardiac fibroblasts activation. Furthermore, we found that the endoplasmic reticulum stress was activated during cardiac fibroblasts activation, and endoplasmic reticulum stress was relieved after overexpression of calnexin. Conversely, after the silencing of calnexin, endoplasmic reticulum stress was further aggravated, accompanying with the activation of cardiac fibroblasts. Our data suggest that the overexpression of calnexin may prevent cardiac fibroblasts against activation by alleviating endoplasmic reticulum stress.

Dapagliflozin Attenuates Cardiac Remodeling in Mice Model of Cardiac Pressure Overload

Dapagliflozin (DAPA) is an inhibitor of sodium-glucose cotransporter 2 prescribed for type 2 diabetes mellitus. DAPA plays a protective role against cardiovascular diseases. Nevertheless, the effect and mechanism of DAPA on pressure-overload-induced cardiac remodeling has not been determined. We used a transverse aortic constriction (TAC) induced cardiac remodeling model to evaluate the effect of DAPA. Twenty-four C57BL/6J mice were divided into 3 groups: Sham, TAC, and TAC + DAPA groups (n = 8, each). DAPA was administered by gavage (1.0 mg/kg/day) for 4 weeks in the TAC + DAPA group, and then the myocardial hypertrophy, cardiac systolic function, myocardial fibrosis, and cardiomyocyte apoptosis were evaluated. Mice in TAC group showed increased heart weight/body weight, left ventricular (LV) diameter, LV posterior wall thickness, and decreased LV ejection fraction and LV fractional shortening. The collagen volume fraction and perivascular collagen area/luminal area ratio were significantly greater in the TAC group; the TUNEL-positive cell number and PARP level were also increased. We found that DAPA treatment reduced myocardial hypertrophy, myocardial interstitial and perivascular fibrosis, and cardiomyocyte apoptosis. Furthermore, DAPA administration inhibited phosphorylation of P38 and JNK in TAC group. In addition, the inhibited phosphorylation of FoxO1 in the TAC mice was upregulated by DAPA administration. DAPA administration had a cardioprotective effect by improving cardiac systolic function, inhibiting myocardial fibrosis and cardiomyocyte apoptosis in a TAC mouse model, indicating that it could serve as a new therapy to prevent pathological cardiac remodeling in nondiabetics.

Ivabradine improved left ventricular function and pressure overload-induced cardiomyocyte apoptosis in a transverse aortic constriction mouse model.

This study aimed to investigate the effects and molecular mechanisms of ivabradine in preventing cardiac hypertrophy in an established transverse aortic constriction (TAC) mouse model. A total of 56 male C57BL/6 mice were randomly assigned into the following seven groups (8 mice per group): sham, TAC model, Iva-10 (10mg/kg/day ivabradine), Iva-20 (20mg/kg/day ivabradine), Iva-40 (40mg/kg/day ivabradine), Iva-80 (80mg/kg/day ivabradine), and Rap (rapamycin, a positive control). Echocardiography and left ventricular hemodynamics were performed. Hematoxylin-eosin (H&E), Masson's trichome staining, and TUNEL assays were conducted to evaluate cardiac hypertrophy, fibrosis, and apoptosis, respectively. Western blotting was performed to detect the expression of proteins related to the PI3K/Akt/mTOR/p70S6K pathway. Ivabradine could effectively improve left ventricular dysfunction and hypertrophy induced by TAC in a dose-independent manner. Moreover, no obvious change in heart rate (HR) was observed in the TAC and Rap groups, whereas a significant decrease in HR was found after ivabradine treatment (P < 0.05). Cardiac hypertrophy, fibrosis, and apoptosis induced by TAC were notably suppressed after either rapamycin or ivabradine treatment (P < 0.05). Ivabradine and rapamycin also decreased the expression of PI3K/Akt and mTOR induced by TAC. Ivabradine improved cardiac hypertrophy and fibrosis as well as reduced cardiomyocyte apoptosis via the PI3K/Akt/mTOR/p70S6K pathway in TAC model mice.

Abstract 115: AT2 Receptor Regulates Ascending Aortic Dilation during AT1 Receptor Blockade in Transverse Aortic Constriction Mouse Model

Introduction: The angiotensin II (Ang II) type 1 receptor (AT1R) antagonist losartan can slow aortic enlargement in mouse models and patients with Marfan syndrome. We have previously shown that losartan attenuates aortic enlargement and remodeling induced by thoracic aortic constriction (TAC). Objective: We investigated the role of the Ang II type 2 receptor (AT2R) in an acute hypertensive remodeling of the ascending aorta induced by TAC. Methods: 160 male C57BL/6J mice were subjected to TAC surgeries with 27-gauge needle or sham surgery. Echocardiography measurements were performed 2 weeks post-operation using the Vevo 3100 imaging system. Blood pressure was measured in the ascending aorta using a Millar catheter introduced through the right common carotid artery. Results: TAC induced significant enlargement in aortic root and ascending aorta two weeks after surgery. The angiotensin converting enzyme inhibitor, captopril, decreased intraluminal systolic blood pressure (SBP) to the same degree as losartan, but did not prevent the increased aortic dilation, adventitial inflammation, medial elastin breakage, or Mmp9 expression compared with TAC mice. Captopril plus an AT2R agonist, compound 21 (C21) attenuated TAC-indcued aortic dilation, elastin break numbers and Mmp9 expression similar to losartan, despite an increase in SBP compared with captopril-treated TAC mice. Consistent with these results, treatment with losartan and an AT2R antagonist, PD123319, reversed the protective effects of losartan on TAC-induced aortic enlargement and remodeling. Note that treating with captopril and a Mas receptor agonist AVE0991 did not prevent TAC-induced aortic enlargement. Importantly, treating with C21 alone did not prevent TAC-induced aortic dilation, elastin breakage or Mmp9 expression despite significantly decreased SBP. Conclusions: These data indicate signaling through both AT1R and AT2R are key modulators in aortic dilation and remodeling with acute increases in biomechanical forces induced by TAC and these protective effects are independent of alterations in blood pressure.

Monitoring of Cardiac Remodeling in a Mouse Model of Pressure-Overload Left Ventricular Hypertrophy with [18F]FDG MicroPET.

This study aims to analyze the left ventricular function parameters, scar load, and hypertrophy in a mouse model of pressure-overload left ventricular (LV) hypertrophy over the course of 8weeks using 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) micro-positron emission tomography (microPET) imaging. LV hypertrophy was induced in C57BL/6 mice by transverse aortic constriction (TAC). Myocardial hypertrophy developed after 2-4weeks. ECG-gated microPET scans with [18F]FDG were performed 4 and 8weeks after surgery. The extent of fibrosis was measured by histopathologic analysis. LV function parameters and scar load were calculated using QGS®/QPS®. LV metabolic volume (LVMV) and percentage injected dose per gram were estimated by threshold-based analysis. The fibrotic tissue volume increased significantly from 4 to 8weeks after TAC (​1.67 vs. 3.91mm3; P=0.044). There was a significant increase of the EDV (4weeks: 54±15μl, 8weeks: 79±32μl, P<0.01) and LVMV (4weeks: 222±24μl, 8weeks: 276±52μl, P<0.01) as well as a significant decrease of the LVEF (4weeks: 56±17%, 8weeks: 44±20%, P<0.01). The increase of LVMV had a high predictive value regarding the amount of ex vivo measured fibrotic tissue (R=0.905, P<0.001). The myocardial metabolic defects increased within 4weeks (P=0.055) but only moderately correlated with the fibrosis volume (R=0.502, P=0.021). The increase in end-diastolic volume showed a positive correlation with the fibrosis at 8weeks (R=0.763, P=0.017). [18F]FDG-PET is applicable for serial in vivo monitoring of the TAC mouse model. Myocardial hypertrophy, the dilation of the left ventricle, and the decrease in LVEF could be reliably quantified over time, as well as the developing localized scar. The increase in volume over time is predictive of a high fibrosis load.

Overexpression of SerpinE2/protease nexin-1 Contribute to Pathological Cardiac Fibrosis via increasing Collagen Deposition.

Although increases in cardiovascular load (pressure overload) are known to elicit ventricular remodeling including cardiomyocyte hypertrophy and interstitial fibrosis, the molecular mechanisms of pressure overload or AngII -induced cardiac interstitial fibrosis remain elusive. In this study, serpinE2/protease nexin-1 was over-expressed in a cardiac fibrosis model induced by pressure-overloaded via transverse aortic constriction (TAC) in mouse. Knockdown of serpinE2 attenuates cardiac fibrosis in a mouse model of TAC. At meantime, the results showed that serpinE2 significantly were increased with collagen accumulations induced by AngII or TGF-β stimulation in vitro. Intriguingly, extracellular collagen in myocardial fibroblast was reduced by knockdown of serpinE2 compared with the control in vitro. In stark contrast, the addition of exogenous PN-1 up-regulated the content of collagen in myocardial fibroblast. The MEK1/2- ERK1/2 signaling probably promoted the expression of serpinE2 via transcription factors Elk1 in myocardial fibroblast. In conclusion, stress-induced the ERK1/2 signaling pathway activation up-regulated serpinE2 expression, consequently led accumulation of collagen protein, and contributed to cardiac fibrosis.

Cardioprotective Effects of Radix on the Pressure Overloaded Heart Failure Model by Transverse Aortic Constriction-induced Mice

Objectives: The objective of this study is to demonstrate the cardioprotective effects of Salvia Miltiorrhiza Radix (SMR) on the pressure overload (PO)-induced heart failure (HF) by transverse aortic constriction (TAC) in C57BL/6 mice through possible antioxidant effects. Methods: The mortality, body and heart weights, antioxidant defense system of the heart and histopathology of heart were analyzed. The obtained results were compared with resveratrol, in which potent cardioprotective effects on TAC mice model were already proved at a dose level of 10 mg/kg by antioxidant effects, as reference in this experiment. Results: Significant increases of mortalities, heart weights, and hypertrophic, lytic and focal fibrotic histological changes in the left ventricles were found with defects of heart antioxidant defense systems – the increases of heart cortex MDA contents, decreases of GSH contents, SOD and CAT activities in TAC control mice as compared with sham vehicle control mice, respectively. However, these HF signs induced by TAC surgery through PO and destroys heart antioxidant defense systems were significantly and dose-dependently inhibited by 14 days continuous oral treatment of SMR 500, 250 and 125 mg/kg, similar to those of resveratrol 10 mg/kg in SMR 125 mg/kg. Conclusions: The results obtained in this study propose that oral administration of SMR potently alleviates PO-induced HF by TAC, through augmentation of heart antioxidant defense system.