Cardiac Hypertrophy Phenotype Research Articles

Acromegaly in Speckle Tracking Echocardiography-A New Cardiac Hypertrophy Phenotype? Case Report and Review.

This study aims to provide a comprehensive overview of speckle tracking echocardiography (STE) findings in patients diagnosed with acromegaly, exploring a potential application for the differential diagnosis of cardiac hypertrophy and guiding clinicians in patient management. To our knowledge, this is the first review showcasing changes in the bull's-eye pattern in myocardial function after acromegaly treatment, suggesting a possible pattern in this aetiology of left ventricular hypertrophy. A review of PubMed articles using the search term "speckle tracking echocardiography acromegaly" yielded 11 relevant papers published between 2017 and 2023. The final analysis evaluated each paper's substantial value and summarised pertinent information. A clinical case of myocardial strain changes before and after pharmacological and neurosurgical treatment is also described. The 11 analysed papers, with patient groups ranging from 19 to 50 individuals, revealed varying results in STE parameters between acromegalic and control groups. Left ventricular strain parameters were commonly assessed, showing discrepancies in different studies. Notably, the MAGYAR-Path Study emphasised left ventricular twist and radial strain abnormalities in acromegaly patients. Furthermore, the interplay between acromegaly and diabetes influenced myocardial function. Drug treatment with somatostatin receptor ligands demonstrated a favourable impact on left ventricular systolic function. The case study we describe in this manuscript showed changes in the posterior basal LV segment, which may be a specific pattern of acromegaly remodelling. Somatostatin therapy and neurosurgery led to the normalisation of global longitudinal strain (GLS) and improvement in myocardial work, as well as improved diastolic function, including enhanced left atrial strain (LAS) as well as a visible elastic recoil sign (ERS). While the available literature on STE in acromegaly is limited, our analysis suggests potential applications in differentiating hypertrophy aetiologies and monitoring cardiac function post-treatment. The results underscore the need for more interdisciplinary research to optimise patient management. The bull's-eye pattern with posterior basal segment strain impairment we describe may be used to differentiate this entity.

The Relationship between Changes in MYBPC3 Single-Nucleotide Polymorphism-Associated Metabolites and Elite Athletes' Adaptive Cardiac Function.

Athletic performance is a multifactorial trait influenced by a complex interaction of environmental and genetic factors. Over the last decades, understanding and improving elite athletes' endurance and performance has become a real challenge for scientists. Significant tools include but are not limited to the development of molecular methods for talent identification, personalized exercise training, dietary requirements, prevention of exercise-related diseases, as well as the recognition of the structure and function of the genome in elite athletes. Investigating the genetic markers and phenotypes has become critical for elite endurance surveillance. The identification of genetic variants contributing to a predisposition for excellence in certain types of athletic activities has been difficult despite the relatively high genetic inheritance of athlete status. Metabolomics can potentially represent a useful approach for gaining a thorough understanding of various physiological states and for clarifying disorders caused by strength-endurance physical exercise. Based on a previous GWAS study, this manuscript aims to discuss the association of specific single-nucleotide polymorphisms (SNPs) located in the MYBPC3 gene encoding for cardiac MyBP-C protein with endurance athlete status. MYBPC3 is linked to elite athlete heart remodeling during or after exercise, but it could also be linked to the phenotype of cardiac hypertrophy (HCM). To make the distinction between both phenotypes, specific metabolites that are influenced by variants in the MYBPC3 gene are analyzed in relation to elite athletic performance and HCM. These include theophylline, ursodeoxycholate, quinate, and decanoyl-carnitine. According to the analysis of effect size, theophylline, quinate, and decanoyl carnitine increase with endurance while decreasing with cardiovascular disease, whereas ursodeoxycholate increases with cardiovascular disease. In conclusion, and based on our metabolomics data, the specific effects on athletic performance for each MYBPC3 SNP-associated metabolite are discussed.

Cardioprotective Role for Paraoxonase-1 in Chronic Kidney Disease.

Paraoxonase-1 (PON-1) is a hydrolytic enzyme associated with HDL, contributing to its anti-inflammatory, antioxidant, and anti-atherogenic properties. Deficiencies in PON-1 activity result in oxidative stress and detrimental clinical outcomes in the context of chronic kidney disease (CKD). However, it is unclear if a decrease in PON-1 activity is mechanistically linked to adverse cardiovascular events in CKD. We investigated the hypothesis that PON-1 is cardioprotective in a Dahl salt-sensitive model of hypertensive renal disease. Experiments were performed on control Dahl salt-sensitive rats (SSMcwi, hereafter designated SS-WT rats) and mutant PON-1 rats (SS-Pon1em1Mcwi, hereafter designated SS-PON-1 KO rats) generated using CRISPR gene editing technology. Age-matched 10-week-old SS and SS-PON-1 KO male rats were maintained on high-salt diets (8% NaCl) for five weeks to induce hypertensive renal disease. Echocardiography showed that SS-PON-1 KO rats but not SS-WT rats developed compensated left ventricular hypertrophy after only 4 weeks on the high-salt diet. RT-PCR analysis demonstrated a significant increase in the expression of genes linked to cardiac hypertrophy, inflammation, and fibrosis, as well as a significant decrease in genes essential to left ventricular function in SS-PON-1 KO rats compared to SS-WT rats. A histological examination also revealed a significant increase in cardiac fibrosis and immune cell infiltration in SS-PON-1 KO rats, consistent with their cardiac hypertrophy phenotype. Our data suggest that a loss of PON-1 in the salt-sensitive hypertensive model of CKD leads to increased cardiac inflammation and fibrosis as well as a molecular and functional cardiac phenotype consistent with compensated left ventricular hypertrophy.

Gut microbiota production of trimethyl-5-aminovaleric acid reduces fatty acid oxidation and accelerates cardiac hypertrophy

Numerous studies found intestinal microbiota alterations which are thought to affect the development of various diseases through the production of gut-derived metabolites. However, the specific metabolites and their pathophysiological contribution to cardiac hypertrophy or heart failure progression still remain unclear. N,N,N-trimethyl-5-aminovaleric acid (TMAVA), derived from trimethyllysine through the gut microbiota, was elevated with gradually increased risk of cardiac mortality and transplantation in a prospective heart failure cohort (n = 1647). TMAVA treatment aggravated cardiac hypertrophy and dysfunction in high-fat diet-fed mice. Decreased fatty acid oxidation (FAO) is a hallmark of metabolic reprogramming in the diseased heart and contributes to impaired myocardial energetics and contractile dysfunction. Proteomics uncovered that TMAVA disturbed cardiac energy metabolism, leading to inhibition of FAO and myocardial lipid accumulation. TMAVA treatment altered mitochondrial ultrastructure, respiration and FAO and inhibited carnitine metabolism. Mice with γ-butyrobetaine hydroxylase (BBOX) deficiency displayed a similar cardiac hypertrophy phenotype, indicating that TMAVA functions through BBOX. Finally, exogenous carnitine supplementation reversed TMAVA induced cardiac hypertrophy. These data suggest that the gut microbiota-derived TMAVA is a key determinant for the development of cardiac hypertrophy through inhibition of carnitine synthesis and subsequent FAO.

MicroRNA miR-27a-3p accelerates cardiac hypertrophy by targeting neuro-oncological ventral antigen 1

ABSTRACT MiRNAs are a class of small non-coding RNAs (ncRNAs) responsible for post-transcriptional regulation of target genes. Accumulating evidence indicates that miRNAs are implicated in the progression of cardiac hypertrophy. Therefore, understanding the molecular mechanisms how these miRNAs regulate cardiac hypertrophy is useful for diagnosis and monitoring of disease progression. In this study, to investigate the effect of miR-27a-3p, we established an in vitro cardiac hypertrophy model by treating H9c2 cardiomyocytes with angiotensin II (Ang II) and an in vivo model through the chronic infusion of Ang II into mice. As revealed by our experimental results, miR-27a-3p expression was significantly increased in clinical samples, animal and cell models of cardiac hypertrophy. Inhibiting miR-27a-3p mitigated cardiac hypertrophy phenotype induced by Ang II. Additionally, our work identified NOVA1 (neuro-oncological ventral antigen 1) as a downstream target of miR-27a-3p. miR-27a-3p overexpression reduced NOVA1 protein level and mRNA expression. Consistently, NOVA1 silencing promoted cardiac hypertrophy phenotype induced by Ang II. In summary, these results suggest that the upregulation of miR-27a-3p may serve as a diagnostic factor for cardiac hypertrophy, and miR-27a-3p upregulation promotes cardiac hypertrophy by targeting NOVA1.

ANP32A represses Wnt signaling across tissues thereby protecting against osteoarthritis and heart disease

To investigate how ANP32A, previously linked to the antioxidant response, regulates Wnt signaling as unraveled by transcriptome analysis of Anp32a-deficient mouse articular cartilage, and its implications for osteoarthritis (OA) and diseases beyond the joint. Anp32a knockdown chondrogenic ATDC5 cells were cultured in micromasses. Wnt target genes, differentiation markers and matrix deposition were quantified. Wnt target genes were determined in articular cartilage from Anp32a-deficient mice and primary human articular chondrocytes upon ANP32A silencing, using qPCR, luciferase assays and immunohistochemistry. Co-immunoprecipitation, immunofluorescence and chromatin-immunoprecipitation quantitative PCR probed the molecular mechanism via which ANP32A regulates Wnt signaling. Anp32a-deficient mice were subjected to the destabilization of the medial meniscus (DMM) OA model and treated with a Wnt inhibitor and an antioxidant. Severity of OA was assessed by cartilage damage and osteophyte formation. Human Protein Atlas data analysis identified additional organs where ANP32A may regulate Wnt signaling. Wnt target genes were determined in heart and hippocampus from Anp32a-deficient mice, and cardiac hypertrophy and fibrosis quantified. Anp32a loss triggered Wnt signaling hyper-activation in articular cartilage. Mechanistically, ANP32A inhibited target gene expression via histone acetylation masking. Wnt antagonist treatment reduced OA severity in Anp32a-deficient mice by preventing osteophyte formation but not cartilage degradation, contrasting with antioxidant treatment. Dual therapy ameliorated more OA features than individual treatments. Anp32a-deficient mice also showed Wnt hyper-activation in the heart, potentially explaining the cardiac hypertrophy phenotype found. ANP32A is a novel translationally relevant repressor of Wnt signaling impacting osteoarthritis and cardiac disease.

Interplay between mineral bone disorder and cardiac damage in acute kidney injury: from Ca2+ mishandling and preventive role of Klotho in mice to its potential mortality prediction in human

Biomarkers of mineral bone disorders (MBD) including phosphorus, fibroblast growth factor (FGF)-23 and Klotho are strongly altered in patients with acute kidney injury (AKI) who have high cardiac outcomes and mortality rates. However, the crosslink between MBD and cardiac damage after an AKI episode still remains unclear. We tested MBD and cardiac biomarkers in an experimental AKI model after 24 or 72 hours of folic acid injection and we analyzed structural cardiac remodeling, intracellular calcium (Ca2+) dynamics in cardiomyocytes and cardiac rhythm. AKI mice presented high levels of FGF-23, phosphorus and cardiac troponin T and exhibited a cardiac hypertrophy phenotype accompanied by an increase in systolic Ca2+ release 24 hours after AKI. Ca2+ transients and contractile dysfunction were reduced 72 hours after AKI while diastolic sarcoplasmic reticulum Ca2+ leak, pro-arrhythmogenic Ca2+ events and ventricular arrhythmias were increased. These cardiac events were linked to the activation of the calcium/calmodulin-dependent kinase II pathway through the increased phosphorylation of ryanodine receptors and phospholamban specific sites after AKI. Cardiac hypertrophy and the altered intracellular Ca2+ dynamics were prevented in transgenic mice overexpressing Klotho after AKI induction. In a translational retrospective longitudinal clinical study, we determined that combining FGF-23 and phosphorus with cardiac troponin T levels achieved a better prediction of mortality in AKI patients at hospital admission. Thus, monitoring MBD and cardiac damage biomarkers could be crucial to prevent mortality in AKI patients. In this setting, Klotho might be considered as a new cardioprotective therapeutic tool to prevent deleterious cardiac events in AKI conditions.

Myeloid MKL1 Disseminates Cues to Promote Cardiac Hypertrophy in Mice.

Cardiac hypertrophy is a key pathophysiological process in the heart in response to stress cues. Although taking place in cardiomyocytes, the hypertrophic response is influenced by other cell types, both within the heart and derived from circulation. In the present study we investigated the myeloid-specific role of megakaryocytic leukemia 1 (MKL1) in cardiac hypertrophy. Following transverse aortic constriction (TAC), myeloid MKL1 conditional knockout (MFCKO) mice exhibit an attenuated phenotype of cardiac hypertrophy compared to the WT mice. In accordance, the MFCKO mice were protected from excessive cardiac inflammation and fibrosis as opposed to the WT mice. Conditioned media collected from macrophages enhanced the pro-hypertrophic response in cardiomyocytes exposed to endothelin in an MKL1-dependent manner. Of interest, expression levels of macrophage derived miR-155, known to promote cardiac hypertrophy, were down-regulated in the MFCKO mice compared to the WT mice. MKL1 depletion or inhibition repressed miR-155 expression in macrophages. Mechanistically, MKL1 interacted with NF-κB to activate miR-155 transcription in macrophages. In conclusion, our data suggest that MKL1 may contribute to pathological hypertrophy via regulating macrophage-derived miR-155 transcription.

Myocardin-related transcription factor A regulates integrin beta 2 transcription to promote macrophage infiltration and cardiac hypertrophy in mice.

Macrophage-mediated inflammatory response represents a key pathophysiological process in a host of cardiovascular diseases including heart failure. Regardless of aetiology, heart failure is invariably preceded by cardiac hypertrophy. In the present study, we investigated the effect of macrophage-specific deletion of myocardin-related transcription factor A (MRTF-A) on cardiac hypertrophy and the underlying mechanism. We report that when subjected to transverse aortic constriction (TAC), macrophage MRTF-A conditional knockout (CKO) mice developed a less severe phenotype of cardiac hypertrophy compared to wild-type (WT) littermates and were partially protected from the loss of heart function. In addition, there was less extensive cardiac fibrosis in the CKO mice than WT mice following the TAC procedure. Further analysis revealed that cardiac inflammation, as assessed by levels of pro-inflammatory cytokines and chemokines, was dampened in CKO mice paralleling reduced infiltration of macrophages in the heart. Mechanistically, MRTF-A deficiency attenuated the expression of integrin beta 2 (ITGB2/CD18) in macrophage thereby disrupting adhesion of macrophages to vascular endothelial cells. MRTF-A was recruited by Sp1 to the ITGB2 promoter and cooperated with Sp1 to activate ITGB2 transcription in macrophages. Administration of a CD18 blocking antibody attenuated TAC-induced cardiac hypertrophy in mice. Interaction between MRTF-A and the histone demethylase KDM3A likely contributed to IGTB2 transcription and consequently adhesion of macrophages to endothelial cells. Our data suggest that MRTF-A may regulate macrophage trafficking and contribute to the pathogenesis of cardiac hypertrophy by activating ITGB2 transcription.

Abstract 13451: Upregulation of CaMKII and Contrast Changes of Cardiac β 1 - and β 3 -Adrenergic Signaling Pathways in a Humanized Angiotensinogen Model of Hypertension

Background: The transgenic rats expressing the human AGT gene [TGR (hAGT) L1623] (hAogen) is an established humanized model of hypertension. Recently we further found that this model is associated with declines in cardiac contractile function and β-adrenergic receptor (AR) reserve. However, the molecular basis is unclear. It has been suggested that pivotal restructuring of β-AR system is a critical determinant of the dysfunctional β-AR regulation in several cardiovascular diseases, including hypertension. But the alterations of subtypes of β-ARs have not been systemically evaluated in this model. Furthermore, there is significant crosstalk between β-AR signaling and CaMKII activation presenting CaMKII as a possible downstream mediator of detrimental β-AR signaling in the abnormal contractile phenotype of cardiac hypertrophy. However, the changes in cardiac CaMKII in this model are unknown. We tested the hypothesis that in hAogen, CaMKII and β 3 -AR are upregulated in the myocardium, but β 1 -AR is down-regulated, which are important causes of cardiac dysfunction and β-AR desensitization. Methods: We compared LV myocyte CaMKIIδ expression and activity and β 1 - and β 3 -AR expression and determined myocyte functional performance and [Ca 2+ ] i transient ([Ca 2+ ] iT) response to β -AR stimulation in myocytes obtained from 6 Sprague Dawley (SD) control and 6 haogen male adult rats. Results: Compared with SD, in hAogen LV myocytes, β 3 -AR protein level significantly increased (26%, 0.29 vs 0.23), but β 1 -AR protein level (26%, 0.4 vs 0.54) significantly decreased. The CaMKIIδ protein levels (16%, 0.50 vs 0.43) and CaMKIIδ phosphorylation (at Thr287) (35%, 0.27 vs 0.20) were significantly increased. These changes were followed by significantly reduced cell contraction (dL/dt max , 102.1vs 138.8μm/s), relaxation (dR/dt max , 94.0 vs 104.7 μm/s) and [Ca 2+ ] iT (0.15 vs 0.21). ISO-stimulated increases in dL/dt max (42% vs 60%), dR/dt max (36% vs 51%) and [Ca 2+ ] iT (20% vs 31%) were also significantly reduced. Conclusions: The upregulation of LV myocyte CaMKIIδ and contrast changes in β 3 -AR and β 1 -AR may be the important cause of the abnormal contractile phenotype and β-AR desensitization in this humanized angiotensinogen model of hypertension of TGR (hAGT) L1623.

Leech extract: A candidate cardioprotective against hypertension-induced cardiac hypertrophy and fibrosis

The prevalence of cardiovascular diseases (CVDs) has been increasing worldwide. Despite significant improvements in therapeutics and on-going developments of novel targeted-treatment regimens, cardiac diseases lack effective preventive and curative therapies with minimal side effects. Therefore, there is an urgent need to identify and propagate alternative and complementary therapies against cardiovascular diseases. Some traditional Chinese medicines can contribute to the prevention and treatment of CVDs and other chronic diseases, with few side effects. Hirudo, a medicinal leech, has been acclaimed for improving blood circulation and overcoming blood stagnation; however, the precise molecular mechanisms of leech extract treatment against pathological cardiac remodeling remain elusive. In this study, we aimed to delineate the molecular mechanisms of medicinal leech extract in the treatment of cardiac hypertrophy and fibrosis, using both in vitro and in vivo assessments. We conducted in vitro and in vivo animal experiments, including cell-viability assays, fluorescence microscopy, immunoblotting, immunohistochemistry, and Masson's trichrome staining. Pre-treatment with leech extract conferred a survival benefit to spontaneously-hypertensive rats (SHRs) and significantly reduced angiotensin II (ANG II)-induced cardiac hypertrophy and fibrosis. ANG II-stimulated cardiac hypertrophy markers were attenuated by leech extract treatment, versus controls. Translational expression of stress-associated mitogen-activated protein kinases (MAPKs) was also repressed. In vivo, leech extract treatment significantly ameliorated the cardiac hypertrophy phenotype in SHRs and diminished interstitial fibrosis, accompanied with reduced fibrosis markers. Leech extract treatment under a hypertensive condition exerted significant cardio-protective benefits by reducing the expression of cardiac hypertrophy-related transcription factors, stress-associated MAPKs, and fibrosis mediators. Our findings imply that medicinal leach extract may be effective against hypertension-induced cardiac hypertrophy and fibrosis.

Impact of hyperthyroidism on cardiac hypertrophy.

The cardiac growth process (hypertrophy) is a crucial phenomenon conserved across a wide array of species and is critically involved in the maintenance of cardiac homeostasis. This process enables an organism to adapt to changes in systemic demand and occurs due to a plethora of responses, depending on the type of signal or stimuli received. The growth of cardiac muscle cells in response to environmental conditions depends on the type, strength and duration of stimuli, and results in adaptive physiological responses or non-adaptive pathological responses. Thyroid hormones (TH) have a direct effect on the heart and induce a cardiac hypertrophy phenotype, which may evolve to heart failure. In this review, we summarize the literature on TH function in the heart by presenting results from experimental studies. We discuss the mechanistic aspects of TH associated with cardiac myocyte hypertrophy, increased cardiac myocyte contractility and electrical remodeling, as well as the associated signaling pathways. In addition to classical crosstalk with the sympathetic nervous system (SNS), emerging work pointing to the new endocrine interaction between TH and the renin-angiotensin system (RAS) is also explored. Given the inflammatory potential of the angiotensin II peptide, this new interaction may open the door for new therapeutic approaches which target the key mechanisms responsible for TH-induced cardiac hypertrophy.

Myotubularin-related protein 14 suppresses cardiac hypertrophy by inhibiting Akt

Cardiac hypertrophy (CH) is an independent risk factor for many cardiovascular diseases, and is one of the primary causes of morbidity and mortality in elderly people. Pathological CH involves excessive protein synthesis, increased cardiomyocyte size, and ultimately the development of heart failure. Myotubularin-related protein 14 (MTMR14) is a member of the myotubularin (MTM)-related protein family, which is involved in apoptosis, aging, inflammation, and autophagy. However, its exact function in CH is still unclear. Herein, we investigated the roles of MTMR14 in CH. We show that MTMR14 expression was increased in hypertrophic mouse hearts. Mice deficient in heart MTMR14 exhibited an aggravated aortic-banding (AB)-induced CH phenotype. In contrast, MTMR14 overexpression prevented pressure overload-induced hypertrophy. At the molecular level, prevention of CH in the absence of MTMR14 involved elevations in Akt pathway components, which are key elements that regulate apoptosis and cell proliferation. These results demonstrate that MTMR14 is a new molecular target for the treatment of CH.

The Mechanism of High-Output Cardiac Hypertrophy Arising From Potassium Channel Gain-of-Function in Cantú Syndrome.

Dramatic cardiomegaly arising from gain-of-function (GoF) mutations in the ATP-sensitive potassium (KATP) channels genes, ABCC9 and KCNJ8, is a characteristic feature of Cantú syndrome (CS). How potassium channel over-activity results in cardiac hypertrophy, as well as the long-term consequences of cardiovascular remodeling in CS, is unknown. Using genome-edited mouse models of CS, we therefore sought to dissect the pathophysiological mechanisms linking KATP channel GoF to cardiac remodeling. We demonstrate that chronic reduction of systemic vascular resistance in CS is accompanied by elevated renin–angiotensin signaling, which drives cardiac enlargement and blood volume expansion. Cardiac enlargement in CS results in elevation of basal cardiac output, which is preserved in aging. However, the cardiac remodeling includes altered gene expression patterns that are associated with pathological hypertrophy and are accompanied by decreased exercise tolerance, suggestive of reduced cardiac reserve. Our results identify a high-output cardiac hypertrophy phenotype in CS which is etiologically and mechanistically distinct from other myocardial hypertrophies, and which exhibits key features of high-output heart failure (HOHF). We propose that CS is a genetically-defined HOHF disorder and that decreased vascular smooth muscle excitability is a novel mechanism for HOHF pathogenesis.

CRISPR-Mediated Activation of Endogenous Gene Expression in the Postnatal Heart.

Genome editing by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 is evolving rapidly. Recently, second-generation CRISPR/Cas9 activation systems based on nuclease inactive dead (d)Cas9 fused to transcriptional transactivation domains were developed for directing specific guide (g)RNAs to regulatory regions of any gene of interest, to enhance transcription. The application of dCas9 to activate cardiomyocyte transcription in targeted genomic loci in vivo has not been demonstrated so far. We aimed to develop a mouse model for cardiomyocyte-specific, CRISPR-mediated transcriptional modulation, and to demonstrate its versatility by targeting Mef2d and Klf15 loci (2 well-characterized genes implicated in cardiac hypertrophy and homeostasis) for enhanced transcription. A mouse model expressing dCas9 with the VPR transcriptional transactivation domains under the control of the Myh (myosin heavy chain) 6 promoter was generated. These mice innocuously expressed dCas9 exclusively in cardiomyocytes. For initial proof-of-concept, we selected Mef2d, which when overexpressed, led to hypertrophy and heart failure, and Klf15, which is lowly expressed in the neonatal heart. The most effective gRNAs were first identified in fibroblast (C3H/10T1/2) and myoblast (C2C12) cell lines. Using an improved triple gRNA expression system (TRISPR [triple gRNA expression construct]), up to 3 different gRNAs were transduced simultaneously to identify optimal conditions for transcriptional activation. For in vivo delivery of the validated gRNA combinations, we employed systemic administration via adeno-associated virus serotype 9. On gRNA delivery targeting Mef2d expression, we recapitulated the anticipated cardiac hypertrophy phenotype. Using gRNA targeting Klf15, we could enhance its transcription significantly, although Klf15 is physiologically silenced at that time point. We further confirmed specific and robust dCas9VPR on-target effects. The developed mouse model permits enhancement of gene expression by using endogenous regulatory genomic elements. Proof-of-concept in 2 independent genomic loci suggests versatile applications in controlling transcription in cardiomyocytes of the postnatal heart.

Ubiquitin-Specific Protease 10 Suppresses Cardiac Hypertrophy by Inhibiting Sirt6

Background and Purpose: Cardiac hypertrophy (CH) is a physiological response that compensates for blood pressure overload. Under pathological conditions, hypertrophy can evolve to heart failure as a consequence of the disorganized growth of cardiomyocytes and cardiac tissue. Ubiquitin-specific protease 10 (USP10) is a member of the ubiquitin-specific protease family of cysteine proteases, which are involved in viral infection, oxidative stress, lipid drop formation and heat shock. However, the role of USP10 in CH remains largely unclear. Here, we investigated the roles of USP10 in CH. Experimental Approach: In this study, by utilizing conditional cardiac-specific USP10 knockout (USP10-CKO) mice and USP10- transgenic(USP10-TG) mice, we examined the role of USP10 in hypertrophic hearts. We further examined the specific function of USP10 in cardiomyocytes. Key Results: We show that USP10 expression increased in murine hypertrophic hearts. Mice deficient in USP10 in the heart exhibited an aggravated aortic banding (AB)-induced CH phenotype. However, overexpression of USP10 protected against pressure overload-induced hypertrophy. At the molecular level, the prevention of CH in the absence of USP10 involves elevated Akt pathway components, which are key elements that regulate cell apoptosis and proliferation. Moreover, USP10 physically binds to Sirt6 and inhibits Akt phosphorylation. Conclusion and Implications: These observations demonstrate that USP10 functions as a positive switch in CH. Funding Statement: This work was supported by grants from National Natural Science Foundation of China (81770048;81970242); Cooperative Project of Academy training Foundation of Zhengzhou University(2016-BSTDJJ-13). Declaration of Interests: The authors stated: None. Ethics Approval Statement: All animal use protocols were approved by the Animal Care and Use Committee of The First Affiliated Hospital of Zhengzhou University. The related procedures were conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals.

6090Conditional ablation of SDF-1/CXCL12 in smooth muscle cells leads to severe cardiac hypertrophy and aortic valve stenosis

Abstract Background Stromal cell derived factor-1 (SDF-1) and its corresponding receptors CXCR4 & CXCR7 have been shown to play pivotal roles during cardiovascular development, cardiac repair and tissue homeostasis after ischemia. Stabilization of the SDF-1/CXCR4+ axis has been shown to provide beneficial effects on myocardial repair. Nevertheless, detailed mechanisms of the cell specific role of SDF-1 are poorly understood. Since SDF-1-EGFP lineage tracking revealed high expression of SDF-1 in smooth muscle cells, we aimed to investigate the cell specific role by generating a smooth muscle cell specific SDF-1 (SM-SDF-1 KO) knockout mouse model. Methods SDF-1 expression was analyzed utilizing SDF-1-EGFP reporter mice. SM-SDF-1 KO mice were generated using Cre/LoxP technology (SM22a-Cre; SDF-1fl/fl). Morphology was analysed with immunohistochemistry and immunofluorescence. Cardiac function was assessed utilizing echocardiography and millar tip catheterization. Whole transcriptome analysis, qRT-PCR and western blotting were performed. Further, apoptotic index and cell proliferation were quantified by TUNEL assay and PH3 immunostaining, respectively. Results SDF-1-EGFP lineage tracking and immunofluorescence analysis revealed high expression of SDF-1 particularly in smooth muscle cells and less frequently in perivascular and endothelial cells. Conditional SM-SDF-1 KO mice showed a high pre- and perinatal mortality (50%). Immunohistochemistry in surviving adult SM-SDF-1 KO mice revealed a severe cardiac hypertrophy phenotype, associated with increased cardiac fibrosis and apoptotic cell death. SM-SDF-1 KO mice revealed very thin and dilated arteries. Echocardiography measurements confimed concentric hypertrophy, and decreased stroke volume reflecting restrictive hypertrophic cardiomyopathy. Immunohistochemistry confirmed pronounced hypertrophy of cardiomyocytes. Additionally, we found evidence for enhanced proliferation markers in cardiomyocytes of SM-SDF-1 KO mice. Transcriptome analyses from KO hearts vs. non-ablated littermates identified over 150 significantly up- and downregulated genes. Western blot analysis for HIF-1α, AKT and ERK cell-signalling pathways were significantly elevated, whereas Rho Kinase signalling was specifically downregulated in SM-SDF-1 KO mice. As a possible reason for the hypertrophic phenotype, SDF-1 mutants exhibited aortic stenosis due to aortic valve thickening associated with upregulation of the extracellular proteoglycan versican anddownregulation of the SDF-1 co-receptor CXCR7. We further noticed increased plasma levels of SDF-1 in aortic stenosis patients suggesting a cardioprotective role. Conclusion Our data suggest that smooth muscle cell specific expression of SDF-1 plays a prominent role in cardiovascular development leadingto cardiac hypertrophy in adult animals. Our data further suggest that SDF-1 is involved in maintaining the homeostasis of the aortic valve, possibly by regulating versican. Acknowledgement/Funding FWF Austria

Cardiac hypertrophy in mice submitted to a swimming protocol: influence of training volume and intensity on myocardial renin-angiotensin system.

Exercise promotes physiological cardiac hypertrophy and activates the renin-angiotensin system (RAS), which plays an important role in cardiac physiology, both through the classical axis [angiotensin II type 1 receptor (AT1R) activated by angiotensin II (ANG II)] and the alternative axis [proto-oncogene Mas receptor (MASR) activated by angiotensin-(1-7)]. However, very intense exercise could have deleterious effects on the cardiovascular system. We aimed to analyze the cardiac hypertrophy phenotype and the classical and alternative RAS axes in the myocardium of mice submitted to swimming exercises of varying volume and intensity for the development of cardiac hypertrophy. Male Balb/c mice were divided into three groups, sedentary, swimming twice a day without overload (T2), and swimming three times a day with a 2% body weight overload (T3), totaling 6 wk of training. Both training groups developed similar cardiac hypertrophy, but only T3 mice improved their oxidative capacity. We observed that T2 had increased levels of MASR, which was followed by the activation of its main downstream protein AKT; meanwhile, AT1R and its main downstream protein ERK remained unchanged. Furthermore, no change was observed regarding the levels of angiotensin peptides, in either group. In addition, we observed no change in the ratio of expression of the myosin heavy chain β-isoform to that of the α-isoform. Fibrosis was not observed in any of the groups. In conclusion, our results suggest that increasing exercise volume and intensity did not induce a pathological hypertrophy phenotype, but instead improved the oxidative capacity, and this process might have the participation of the RAS alternative axis.

Tsg101 positively regulates physiologic-like cardiac hypertrophy through FIP3-mediated endosomal recycling of IGF-1R.

Development of physiologic cardiac hypertrophy has primarily been ascribed to the IGF-1 and its receptor, IGF-1 receptor (IGF-1R), and subsequent activation of the protein kinase B (Akt) pathway. However, regulation of endosome-mediated recycling and degradation of IGF-1R during physiologic hypertrophy has not been investigated. In a physiologic hypertrophy model of treadmill-exercised mice, we observed that levels of tumor susceptibility gene 101 (Tsg101), a key member of the endosomal sorting complex required for transport, were dramatically elevated in the heart compared with sedentary controls. To determine the role of Tsg101 on physiologic hypertrophy, we generated a transgenic (TG) mouse model with cardiac-specific overexpression of Tsg101. These TG mice exhibited a physiologic-like cardiac hypertrophy phenotype at 8 wk evidenced by: 1) the absence of cardiac fibrosis, 2) significant improvement of cardiac function, and 3) increased total and plasma membrane levels of IGF-1R and increased phosphorylation of Akt. Mechanistically, we identified that Tsg101 interacted with family-interacting protein 3 (FIP3) and IGF-1R, thereby stabilizing FIP3 and enhancing recycling of IGF-1R. In vitro, adenovirus-mediated overexpression of Tsg101 in neonatal rat cardiomyocytes resulted in cell hypertrophy, which was blocked by addition of monensin, an inhibitor of endosome-mediated recycling, and by small interfering RNA-mediated knockdown (KD) of FIP3. Furthermore, cardiac-specific KD of Tsg101 showed a significant reduction in levels of endosomal recycling compartment members (Rab11a and FIP3), IGF-1R, and Akt phosphorylation. Most interestingly, Tsg101-KD mice failed to develop cardiac hypertrophy after intense treadmill training. Taken together, our data identify Tsg101 as a novel positive regulator of physiologic cardiac hypertrophy through facilitating the FIP3-mediated endosomal recycling of IGF-1R.-Essandoh, K., Deng, S., Wang, X., Jiang, M., Mu, X., Peng, J., Li, Y., Peng, T., Wagner, K.-U., Rubinstein, J., Fan, G.-C. Tsg101 positively regulates physiologic-like cardiac hypertrophy through FIP3-mediated endosomal recycling of IGF-1R.

Caveolin-1 Deletion Prevents Hypertensive Vascular Remodeling Induced by Angiotensin II.

It has been proposed that membrane microdomains, caveolae, in vascular cells are critical for signal transduction and downstream functions induced by angiotensin II (AngII). We have tested our hypothesis that caveolin-1 (Cav1), a major structural protein of vascular caveolae, plays a critical role in the development of vascular remodeling by AngII via regulation of epidermal growth factor receptor and vascular endothelial adhesion molecule-1. Cav1-/- and control Cav+/+ mice were infused with AngII for 2 weeks to induce vascular remodeling and hypertension. On AngII infusion, histological assessments demonstrated medial hypertrophy and perivascular fibrosis of aorta and coronary and renal arteries in Cav1+/+ mice compared with sham-operated Cav1+/+ mice. AngII-infused Cav1+/+ mice also showed a phenotype of cardiac hypertrophy with increased heart weight to body weight ratio compared with control Cav1+/+ mice. In contrast, Cav1-/- mice infused with AngII showed attenuation of vascular remodeling but not cardiac hypertrophy. Similar levels of AngII-induced hypertension were found in both Cav1+/+ and Cav1-/- mice as assessed by telemetry. In Cav1+/+ mice, AngII enhanced tyrosine-phosphorylated epidermal growth factor receptor staining in the aorta, which was attenuated in Cav1-/- mice infused with AngII. Enhanced Cav1 and vascular endothelial adhesion molecule-1 expression was also observed in aorta from AngII-infused Cav1+/+ mice but not in Cav1-/- aorta. Experiments with vascular cells further provided a potential mechanism for our in vivo findings. These data suggest that Cav1, and presumably caveolae, in vascular smooth muscle and the endothelium plays a critical role in vascular remodeling and inflammation independent of blood pressure or cardiac hypertrophy regulation.