Conditions Of Pressure Overload Research Articles

MYH11 rare variant augments aortic growth and induces cardiac hypertrophy and heart failure with pressure overload.

Smooth muscle cell-specific myosin heavy chain, encoded by MYH11, is selectively expressed in smooth muscle cells (SMCs). Pathogenic variants in MYH11 predispose to a number of disorders, including heritable thoracic aortic disease associated with patent ductus arteriosus, visceral myopathy, and megacystis-microcolon-intestinal hypoperistalsis syndrome. Rare variants of uncertain significance occur throughout the gene, including MYH11 p.Glu1892Asp, and we sought to determine if this variant causes thoracic aortic disease in mice. Genomic editing was used to generate Myh11 E1892D/E1892D mice. Wild-type (WT) and mutant mice underwent cardiovascular phenotyping and with transverse aortic constriction (TAC). Myh11 E1892D/E1892D and WT mice displayed similar growth, blood pressure, root and ascending aortic diameters, and cardiac function up to 13 months of age, along with similar contraction and relaxation on myographic testing. TAC induced hypertension similarly in Myh11 E1892D/E1892D and WT mice, but mutant mice showed augmented ascending aortic enlargement and increased elastic fragmentation on histology. Unexpectedly, male Myh11 E1892D/E1892D mice two weeks post-TAC had decreased ejection fraction, stroke volume, fractional shortening, and cardiac output compared to similarly treated male WT mice. Importantly, left ventricular mass increased significantly due to primarily posterior wall thickening, and cardiac histology confirmed cardiomyocyte hypertrophy and increased collagen deposition in the myocardium and surrounding arteries. These results further highlight the clinical heterogeneity associated with MYH11 rare variants. Given that MYH11 is selectively expressed in SMCs, these results implicate a role of vascular SMCs in the heart contributing to cardiac hypertrophy and failure with pressure overload.

Therapeutic Inhibition of LincRNA-p21 Protects Against Cardiac Hypertrophy.

Cardiac hypertrophy is an adaptive response to pressure overload aimed at maintaining cardiac function. However, prolonged hypertrophy significantly increases the risk of maladaptive cardiac remodeling and heart failure. Recent studies have implicated long noncoding RNAs in cardiac hypertrophy and cardiomyopathy, but their significance and mechanism(s) of action are not well understood. We measured lincRNA-p21 RNA and H3K27ac levels in the hearts of dilated cardiomyopathy patients. We assessed the functional role of lincRNA-p21 in basal and surgical pressure-overload conditions using loss-of-function mice. Genome-wide transcriptome analysis revealed dysregulated genes and pathways. We labeled proteins in proximity to full-length lincRNA-p21 using a novel BioID2-based system. We immunoprecipitated lincRNA-p21-interacting proteins and performed cell fractionation, ChIP-seq (chromatin immunoprecipitation followed by sequencing), and co-immunoprecipitation to investigate molecular interactions and underlying mechanisms. We used GapmeR antisense oligonucleotides to evaluate the therapeutic potential of lincRNA-p21 inhibition in cardiac hypertrophy and associated heart failure. lincRNA-p21 was induced in mice and humans with cardiomyopathy. Global and cardiac-specific lincRNA-p21 knockout significantly suppressed pressure overload-induced ventricular wall thickening, stress marker elevation, and deterioration of cardiac function. Genome-wide transcriptome analysis and transcriptional network analysis revealed that lincRNA-p21 acts in trans to stimulate the NFAT/MEF2 (nuclear factor of activated T cells/myocyte enhancer factor-2) pathway. Mechanistically, lincRNA-p21 is bound to the scaffold protein KAP1 (KRAB-associated protein-1). lincRNA-p21 cardiac-specific knockout suppressed stress-induced nuclear accumulation of KAP1, and KAP1 knockdown attenuated cardiac hypertrophy and NFAT activation. KAP1 positively regulates pathological hypertrophy by physically interacting with NFATC4 to promote the overactive status of NFAT/MEF2 signaling. GapmeR antisense oligonucleotide depletion of lincRNA-p21 similarly inhibited cardiac hypertrophy and adverse remodeling, highlighting the therapeutic potential of inhibiting lincRNA-p21. These findings advance our understanding of the functional significance of stress-induced long noncoding RNA in cardiac hypertrophy and demonstrate the potential of lincRNA-p21 as a novel therapeutic target for cardiac hypertrophy and subsequent heart failure.

Metformin induction of heat shock factor 1 activation and the mitochondrial unfolded protein response alleviate cardiac remodeling in spontaneously hypertensive rats.

Heart failure and cardiac remodeling are both characterized by mitochondrial dysfunction. Healthy mitochondria are required for adequate contractile activity and appropriate regulation of cell survival. In the mammalian heart, enhancement of the mitochondrial unfolded protein response (UPRmt) is cardioprotective under pressure overload conditions. We explored the UPRmt and the underlying regulatory mechanism in terms of hypertension-induced cardiac remodeling and the cardioprotective effect of metformin. Male spontaneously hypertensive rats and angiotensin II-treated neonatal rat cardiomyocytes were used to induce cardiac hypertrophy. The results showed that hypertension induced the formation of aberrant mitochondria, characterized by a reduced mtDNA/nDNA ratio and swelling, as well as lower levels of mitochondrial complexes I to V and inhibition of the expression of one protein subunit of each of complexes I to IV. Such changes eventually enlarged cardiomyocytes and increased cardiac fibrosis. Metformin treatment increased the mtDNA/nDNA ratio and regulated the UPRmt, as indicated by increased expression of activating transcription factor 5, Lon protease 1, and heat shock protein 60, and decreased expression of C/EBP homologous protein. Thus, metformin improved mitochondrial ultrastructure and function in spontaneously hypertensive rats. Invitro analyses revealed that metformin reduced the high levels of angiotensin II-induced mitochondrial reactive oxygen species in such animals and stimulated nuclear translocation of heat shock factor 1 (HSF1). Moreover, HSF1 small-interfering RNA reduced the metformin-mediated improvements in mitochondrial morphology and the UPRmt by suppressing hypertrophic signals and cardiomyocyte apoptosis. These results suggest that HSF1/UPRmt signaling contributes to the beneficial effects of metformin. Metformin-mediated targeting of mitochondrial protein homeostasis and modulation of HSF1 levels have potential therapeutic implications in terms of cardiac remodeling.

Titin's cardiac-specific N2B element is critical to mechanotransduction during volume overload of the heart

The heart has the ability to detect and respond to changes in mechanical load through a process called mechanotransduction. In this study, we focused on investigating the role of the cardiac-specific N2B element within the spring region of titin, which has been proposed to function as a mechanosensor. To assess its significance, we conducted experiments using N2B knockout (KO) mice and wildtype (WT) mice, subjecting them to three different conditions: 1) cardiac pressure overload induced by transverse aortic constriction (TAC), 2) volume overload caused by aortocaval fistula (ACF), and 3) exercise-induced hypertrophy through swimming. Under conditions of pressure overload (TAC), both genotypes exhibited similar hypertrophic responses. In contrast, WT mice displayed robust left ventricular hypertrophy after one week of volume overload (ACF), while the KO mice failed to undergo hypertrophy and experienced a high mortality rate. Similarly, swim exercise-induced hypertrophy was significantly reduced in the KO mice. RNA-Seq analysis revealed an abnormal β-adrenergic response to volume overload in the KO mice, as well as a diminished response to isoproterenol-induced hypertrophy. Because it is known that the N2B element interacts with the four-and-a-half LIM domains 1 and 2 (FHL1 and FHL2) proteins, both of which have been associated with mechanotransduction, we evaluated these proteins. Interestingly, while volume-overload resulted in FHL1 protein expression levels that were comparable between KO and WT mice, FHL2 protein levels were reduced by over 90% in the KO mice compared to WT. This suggests that in response to volume overload, FHL2 might act as a signaling mediator between the N2B element and downstream signaling pathways. Overall, our study highlights the importance of the N2B element in mechanosensing during volume overload, both in physiological and pathological settings.

An updated review of experimental rodent models of pulmonary hypertension and left heart disease.

Left heart disease (LHD) is the leading cause of pulmonary hypertension (PH). Its recent growth has not been matched by the design of therapeutic agents directly targeting the disease. Effective therapies approved for pulmonary arterial hypertension (PAH) have been shown to be inefficient in patients with PH-LHD. Hence, there is a need for an animal model that would closely mimic PH-LHD in preclinical experiments. The current study describes and compares a number of rodent models of left ventricular failure and their potential to induce PH. It also evaluates whether, and to what extent, common PH models could develop LV failure. Articles were identified in the Pubmed/Medline and Web of Science online electronic databases following the PRISMA Protocol between 1992 and 2022. Quality assessment was carried out using the SYRCLE risk-of-bias tool for animal studies. Publication bias across studies using Egger's regression test statistic, was performed together with sensitivity analysis. A wide spectrum of protocols-135 studies and 207 interventions, was examined, including systemic hypertensive models, pressure-overload-induced HF, model of ischemic heart failure, and metabolic approaches based on high fat diet or metabolic syndrome. The most pronounced alterations in PH-related parameters were demonstrated for the common PH models, but were also seen in animals with LV failure induced by ischemic conditions, pressure overload or metabolic conditions. Models based on aortic banding, transverse aortic constriction (TAC), or with myocardial infarction (MI) caused by coronary artery ligation, demonstrated more pronounced worsening in PH due to LV failure; however, they also demonstrated poor survival, especially the ischemic-HF model. Common PH models, excluding prolonged exposure to monocrotaline, do not promote LV hypertrophy. Prolonged exposure to a high-fat diet, or a two-hit model of an obese ZSF1 rat combined with SU5416-induced pulmonary endothelial impairment (a VEGF receptor antagonist) worsened PH and impaired diastolic dysfunction. Due to the limited number of protocols, further trials are needed to confirm the utility of such approaches for modeling PH in subjects with metabolic syndrome. This would provide a clearer insight into the complexity of LHD, PH and metabolic disorders in PH-LHD, and thus accelerate the development of new therapies in clinical trials.

Toll-like Receptor 4 Differentially Modulates Cardiac Function in Response to Chronic Exposure to High-Fat Diet and Pressure Overload.

The impact of myocardial stressors such as high-fat diet (HFD) and pressure overload has been extensively studied. Toll-like receptor 4 (TLR4) deficiency has been suggested to have a protective role in response to these stressors, although some conflicting data exist. Furthermore, there is limited information about the role of TLR4 on cardiac remodeling in response to long-term exposure to stressors. This study aims to investigate the effects of TLR4 deficiency on cardiac histology and physiology in response to chronic stressors. TLR4-deficient (TLR4-/-) and wild-type (WT) mice were subjected to either HFD or a normal diet (ND) for 28 weeks. Another group underwent abdominal aortic constriction (AAC) or a sham procedure and was monitored for 12 weeks. Inflammatory markers, histology, and echocardiography were used to assess the effects of these interventions. TLR4-/- mice exhibited reduced cardiac hypertrophy and fibrosis after long-term HFD exposure compared to ND without affecting cardiac function. On the other hand, TLR4 deficiency worsened cardiac function in response to AAC, leading to decreased ejection fraction (EF%) and increased end-systolic volume (ESV). TLR4 deficiency provided protection against HFD-induced myocardial inflammation but impaired hemodynamic cardiac function under pressure overload conditions. These findings highlight the crucial role of TLR4 and its downstream signaling pathway in maintaining cardiac output during physiologic cardiac hypertrophy in response to pressure overload.

Preprocedural global myocardial work index independently predicts NT-proBNP in patients undergoing transcatheter aortic valve replacement: a prospective study

Abstract Global myocardial work index is a novel echocardiographic parameter of the left ventricular (LV) function, which may overcome the load-sensitvity of the traditional functional measures by measuring LV deformation in the context of simultaneous pressures. This approach may gain particular importance in pressure overload states, such as patients with severe aortic stenosis. However, the longitudinal changes of this recently introduced measure are scarcely investigated in this population, and data are also lacking about its association with functional improvement following transcatheter aortic valve replacement (TAVR). Accordingly, our aim was to investigate the clinical determinants of preoperative and also postoperative GMWI in patients undergoing TAVR. Eighty-four patients (54%% male, age: 79±6 years) were enrolled. Prior to the procedure, subjects underwent echocardiographic investigation and the detailed medical history was also recorded. Serum NT-proBNP levels were also measured. We calculated LV ejection fraction and LV end-diastolic volume (EDV), and speckle-tracking analysis was performed to measure global longitudinal strain (GLS). As an accepted method of its estimation, LV pressure curve was generated by adding the mean aortic valve gradient to the systolic blood pressure. Using these measures, global myocardial work index (GMWI) was quantified by commercially available software. 12 months after the procedure, the patients underwent a follow-up echocardiographic examination, and at that time point we determined the same measures. At follow-up, GLS has significantly increased (-13.5±4.5 vs. -15.2±3.6%; p<0.001), while GMWI was significantly lower at the follow-up assessment (1913±786 vs. 1666±594 mmHg%, p<0.01). Compared to the preoperative values, LVEDV also showed a significant decrease at follow-up (115±46 vs. 105±41 mL, p<0.01). Using multivariable analysis, atrial fibrillation (β=0.36; p<0.001) ischemic heart disease (β=0.20; p<0.05) and also GMWI (β=-0.22; p<0.05) were found to be independent predictors of the postoperative NT-proBNP (R2=0.36; overall p<0.001). Importantly, by replacing GMWI to GLS, the latter did not enter the model as a predictor (β=0.17, p=0.11). TAVR significantly alters LV functional and morphological measures. Regarding the functional outcome of the patients, different clinical factors influence NT-proBNP after the procedure. Possibly due to its significant load dependency, preoperative GLS failed to predict NT-proBNP at follow-up, while GMWI was an independent precictor of NT-proBNP at follow up along with atrial fibrillation and ischemic heart disease. GMWI may serve as a useful imaging marker of preprocedural patient assessment before TAVR.

Right ventricular-pulmonary artery coupling and in-hospital mortality of patients with first acute coronary syndrome

Abstract Background Right ventricular-pulmonary artery (RV-PA) coupling is a means of indexing RV performance to the existent RV afterload. Although non-invasive analysis of RV-PA coupling is a well-recognized prognosticator in chronic RV pressure overload conditions such as heart failure and pulmonary hypertension, its impact in patients with myocardial infarction and acute elevations in RV afterload remains undetermined. Aim This study sought to investigate the associations and short term prognostic value of RV-PA coupling in patients with first acute coronary syndrome (ACS), as assessed by two standard echocardiographic measurements: tricuspid annular plane systolic excursion (TAPSE) and pulmonary artery systolic pressure (PASP). Methods A total of 300 consecutive patients with first ACS (mean age 61.2±11.8 years, 74% males) were prospectively enrolled. A comprehensive transthoracic echocardiographic assessment was undertaken within 24 hours after revascularization. In-hospital mortality was the study endpoint. The study population was dichotomized according to the optimal TAPSE/PASP cut-off, as determined by receiver-operating characteristic curve analysis. Univariable and multivariable logistic regression analysis was performed to determine predictors of impaired TPASE/PASP and the association of TAPSE/PASP with in-hospital mortality. To further assess the incremental prognostic value of TAPSE/PASP over a baseline model the change in x² was assessed using the likelihood ratio test. Results A total of 23 (7.7%) patients died in-hospital despite successful revascularization. The optimal cut-off value of TAPSE/PASP to determine in-hospital mortality was 0.49. Among others, univariable associates of impaired TAPSE/PASP were the Global Registry of Acute Coronary event (GRACE) risk score, Killip Class >2, late presentation after symptoms onset, NT-pro-BNP, and left ventricular ejection fraction (LVEF). In multivariable analysis LVEF was the only independent predictor of impaired TAPSE/PASP (OR 0.889, 95% CI [0.821-0.963], p=0.004). The subgroup of patients with LVEF<40% and TAPSE/PASP<0.49mm/mmHg exhibited the worst in-hospital mortality rate (Abstract Picture 1). TAPSE/PASP was significantly associated with in-hospital mortality (OR 0.037, 95% CI [0.009-0.153], p<0.001), and retained this association after adjusting for GRACE risk score and LVEF (OR 0.137, 95% CI [0.032-0.578], p=0.007). The incremental prognostic value of TAPSE/PASP<0.49mm/mmHg for in-hospital mortality was evaluated by adding it to a model including the GRACE risk-score, LVEF<40% and TAPSE<17mm. The further addition of impaired TAPSE/PASP significantly increased the x² of the model from 21.627 to 86.213, p<0.001 (Abstract Picture 2). Conclusion RV-PA coupling assessed non-invasively by echocardiography 24 hours after revascularization was an independent predictor of in-hospital mortality in patients with first ACS and may improve risk stratification.In hospital mortality ratesIncremental prognostic value

The role of androgens in pressure overload myocardial hypertrophy.

Pressure overload hypertrophy of the left ventricle is a common result of many cardiovascular diseases. Androgens show anabolic effects in skeletal muscles, but also in myocardial hypertrophy. We carefully reviewed literature regarding possible effects of androgens on specific left ventricular hypertrophy in pressure overload conditions excluding volume overload conditions or generel sex differences.

Clinical determinants of non-invasive global myocardial work index before and after transcatheter aortic valve implantation: a prospective study

Abstract The estimation of non-invasive global myocardial work indices is a novel method of the left ventricular (LV) functional assessment, which may overcome the load-sensitvity of the traditional functional measures. The diagnostic and prognostic role of this approach may gain particular importance in pressure overload states, such as in patients with severe aortic stenosis. However, the longitudinal changes of this recently introduced measure are scarcely investigated, and data are also lacking about the main determinants of these measures. Accordingly, our aim was to investigate the clinical determinants of preoperative and also postoperative GMWI in patients undergoing transcatheter aortic valve replacement (TAVR). Fifty patients (62% male, age: 78±5 years) were enrolled. Prior to the procedure, subjects underwent echocardiographic investigation and the detailed medical history was also recorded. Speckle-tracking analysis was performed and global longitudinal strain (GLS) was measured. LV pressure curve was estimated by adding the mean aortic valve gradient to the systolic blood pressure. Using these measures, global myocardial work index (GMWI) and global constructive work index (CMWI) was quantified by commercially available software. A 6 months follow-up examination was also performed and at that time point we determined the aforementioned parameters. At follow-up, GLS has significantly increased (−13.0±4.1 vs. −14.8±3.8%; p<0.001), while GMWI was significantly lower compared to baseline (1789±748 vs. 1506±561 mmHg%, p<0.01). CMWI did not differ between the two time points (2309±782 vs. 2086±609 mmHg%, p=0.11). Using multivariable analysis, age (β=0.30; p<0.05) preoperative New York Heart Association (NYHA) class (β=−0.48; p<0.001) and having a pacemaker (β=−0.44; p<0.01) were found to be independent predictors of the preoperative GMWI (R2=0.39; overall p<0.001). On the other hand, postoperative GMWI was determined (R2=0.48; overall p<0.001) by gender (β=−0.25; p<0.05), the presence of diabetes mellitus (β=−0.37; p<0.01) and also by having a pacemaker (β=−0.38; p<0.01). TAVR significantly alters LV functional measures. Different clinical factors influence GMWI before and after the procedure: age, NYHA class-based symptom severity and having a pacemaker were found to be independently associated with preoperative GMWI, while gender, the presence of diabetes mellitus and pacemaker device are the most important clinical determinants of the postoperative GMWI value. Funding Acknowledgement Type of funding sources: None.

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.

Cardiac Fibrosis in the Pressure Overloaded Left and Right Ventricle as a Therapeutic Target.

Myocardial fibrosis is a remodeling process of the extracellular matrix (ECM) following cardiac stress. “Replacement fibrosis” is a term used to describe wound healing in the acute phase of an injury, such as myocardial infarction. In striking contrast, ECM remodeling following chronic pressure overload insidiously develops over time as “reactive fibrosis” leading to diffuse interstitial and perivascular collagen deposition that continuously perturbs the function of the left (L) or the right ventricle (RV). Examples for pressure-overload conditions resulting in reactive fibrosis in the LV are systemic hypertension or aortic stenosis, whereas pulmonary arterial hypertension (PAH) or congenital heart disease with right sided obstructive lesions such as pulmonary stenosis result in RV reactive fibrosis. In-depth phenotyping of cardiac fibrosis has made it increasingly clear that both forms, replacement and reactive fibrosis co-exist in various etiologies of heart failure. While the role of fibrosis in the pathogenesis of RV heart failure needs further assessment, reactive fibrosis in the LV is a pathological hallmark of adverse cardiac remodeling that is correlated with or potentially might even drive both development and progression of heart failure (HF). Further, LV reactive fibrosis predicts adverse outcome in various myocardial diseases and contributes to arrhythmias. The ability to effectively block pathological ECM remodeling of the LV is therefore an important medical need. At a cellular level, the cardiac fibroblast takes center stage in reactive fibrotic remodeling of the heart. Activation and proliferation of endogenous fibroblast populations are the major source of synthesis, secretion, and deposition of collagens in response to a variety of stimuli. Enzymes residing in the ECM are responsible for collagen maturation and cross-linking. Highly cross-linked type I collagen stiffens the ventricles and predominates over more elastic type III collagen in pressure-overloaded conditions. Research has attempted to identify pro-fibrotic drivers causing fibrotic remodeling. Single key factors such as Transforming Growth Factor β (TGFβ) have been described and subsequently targeted to test their usefulness in inhibiting fibrosis in cultured fibroblasts of the ventricles, and in animal models of cardiac fibrosis. More recently, modulation of phenotypic behaviors like inhibition of proliferating fibroblasts has emerged as a strategy to reduce pathogenic cardiac fibroblast numbers in the heart. Some studies targeting LV reactive fibrosis as outlined above have successfully led to improvements of cardiac structure and function in relevant animal models. For the RV, fibrosis research is needed to better understand the evolution and roles of fibrosis in RV failure. RV fibrosis is seen as an integral part of RV remodeling and presents at varying degrees in patients with PAH and animal models replicating the disease of RV afterload. The extent to which ECM remodeling impacts RV function and thus patient survival is less clear. In this review, we describe differences as well as common characteristics and key players in ECM remodeling of the LV vs. the RV in response to pressure overload. We review pre-clinical studies assessing the effect of anti-fibrotic drug candidates on LV and RV function and their premise for clinical testing. Finally, we discuss the mode of action, safety and efficacy of anti-fibrotic drugs currently tested for the treatment of left HF in clinical trials, which might guide development of new approaches to target right heart failure. We touch upon important considerations and knowledge gaps to be addressed for future clinical testing of anti-fibrotic cardiac therapies.

Oxytocin Protects Against Isoproterenol-Induced Cardiac Hypertrophy by Inhibiting PI3K/AKT Pathway via a lncRNA GAS5/miR-375-3p/KLF4-Dependent Mechanism.

Cardiac hypertrophy is caused by cardiac volume or pressure overload conditions and ultimately leads to contractile dysfunction and heart failure. Oxytocin (OT), an endocrine nonapeptide, has been identified as a cardiovascular homeostatic hormone with anti-hypertrophic effects. However, the underlying mechanism remains elusive. In this study, we aimed to investigate the role and mechanism of OT in cardiac hypertrophy. The rats with cardiac hypertrophy induced by isoproterenol (ISO) were treated with or without oxytocin. Cardiac functional parameters were analyzed by echocardiography. The changes in cell surface area were observed using wheat germ agglutinin (WGA) or immunofluorescence staining. The expressions of cardiac hypertrophy markers (B-Natriuretic Peptide, BNP and β-myosin heavy chain, β-MHC), long non-coding RNA Growth (LcRNA) Arrest-Specific transcript 5 (lncRNA GAS5), miR-375-3p, and Kruppel-like factor 4 (Klf4) were detected by qRT-PCR. KLF4 protein and PI3K/AKT pathway related proteins were detected by Western blot. The interactions among lncRNA GAS5, miR-375-3p, and Klf4 were verified by dual-luciferase reporter assays. The findings showed that OT significantly attenuated cardiac hypertrophy, increased expressions of lncRNA GAS5 and KLF4, and decreased miR-375-3p expression. In vitro studies demonstrated that either knock-down of lncRNA GAS5 or Klf4, or over-expression of miR-375-3p blunted the anti-hypertrophic effects of OT. Moreover, down-regulation of lncRNA GAS5 promoted the expression of miR-375-3p and inhibited KLF4 expression. Similarly, over-expression of miR-375-3p decreased the expression of KLF4. Dual-luciferase reporter assays validated that lncRNA GAS5 could sponge miR-375-3p and Klf4 was a direct target gene of miR-375-3p. In addition, OT could inactivate PI3K/AKT pathway. The functional rescue experiments further identified OT regulated PI3K/AKT pathway through lncRNA GAS5/miR-375-3p/KLF4 axis. In summary, our study demonstrates that OT ameliorates cardiac hypertrophy by inhibiting PI3K/AKT pathway via lncRNA GAS5/miR-375-3p/KLF4 axis.

Cardiac function in fetal and infants born to mothers with gestational diabetes

Abstract Background The intraventricular pressure differences (IVPD) IVPD using color M-mode is a specific marker in infants of mothers with gestational diabetes mellitus (GDM). (Circulation R 2019, 378–388). Purpose This study investigated the myocardial performance of fetuses in mothers with GDM under the new GDM definition. Method The study population comprised of 27 mothers with GDM and the fetus. Women with GDM were defined as those with a glucose metabolism abnormality that existed before or began during the current pregnancy and was diagnosed using OGTTs. The 5 mothers with type 1 or type 2 DM were receiving insulin before their pregnancy. Fetal echo measurements were performed about median gestational age 35 weeks. The primary outcomes were comparisons of the fetal myocardial performance of GDM with insulin administration and without administration using echocardiography with IVPD, and IVPG. The secondary outcome has investigated the relationships between echocardiography parameters, IVPD, and IVPG, and maternal factors. For all statistical analyses, P<0.05 was considered significant. Result In the insulin group was higher RV output (Fig. 2A). Maternal max HbA1c was observed to have a positive correlation with fetal RV output, significantly (Fig. 2B). Maternal max fasting blood glucose was observed to have a negative correlation with the Total, Basal and Mid to apical IVPD, significantly, respectively. Serial change of LV Total IVPD from fetal to after birth shown in Slide. In both groups, LV Total IVPD was increasing from fetal and after birth significantly. Conclusion The mechanism associated with the favorable systolic and diastolic performances in IGDMs is suggested to involve metabolic adaptations in the heart. In diabetic mice, these adaptations seem to prevent the heart from failing during conditions of pressure overload, suggesting a restoration of the balance between glucose and fatty acid utilization is beneficial for cardiac function. In fetal LV and RV-IVPD might be interacted the mother's blood sugar control. These indexes can predict the sensitive fetal and infant's cardiac dysfunction for GDM. Funding Acknowledgement Type of funding sources: None.

Chondroitin sulfate n-acetylgalactosaminyltransferase-2 (ChGn-2) plays a significant role in cardiac remodeling and heart failure following pressure overload

Abstract Background Cardiac extracellular matrix (ECM) is critically involved in cardiac homeostasis by providing mechanical support as well as modulating growth factor signaling. Cardiac ECM dysregulation has been shown in heart failure pathogenesis, and accumulation of chondroitin sulfate glycosaminoglycans (CS-GAGs) was previously shown to exacerbate heart failure by augmenting inflammation and fibrosis at the chronic phase. However, it remains unclear whether and the mechanism by which CS-GAGs cause cardiac dysfunction, especially at the acute phase. Purpose The purpose of this study is to elucidate the role of CS-GAGs in heart failure. Methods In this study, we analyzed the role of CS-GAGs in heart failure using mice with target deletion of chondroitin sulfate N-acetylgalactosaminyltransferase (ChGn)-2 that elongates CS chains of GAGs. Heart failure was induced by transverse aortic constriction (TAC) in mice. Since cardiac fibroblasts (CFs) are the primary cells for ECM production in the heart, we explored the role of CF-derived ECM in cardiomyocyte apoptosis. CFs were given stretch stimuli that mimic pressure overload conditions. Results Significant CS-GAGs accumulation was detected in the heart of WT mice after TAC, which was substantially reduced in the heart of ChGn2−/− mice. Unexpectedly, loss of ChGn-2 deteriorated left ventricular systolic dysfunction accompanied by augmented cardiac hypertrophy and increased cardiomyocyte apoptosis. Stretch stimuli increased ChGn-2 expression and enhanced GAG production in CFs. Interestingly, only conditioned medium (CM) derived from stretched CFs showed protective effects on cardiomyocyte death induced by doxorubicin. Degradation of CS-GAGs in CFs-derived CM by using Chondroitinase ABC abolished its cardioprotective effect. Further experiments revealed that this cardioprotective effect is at least partially through CS-GAGs-derived PI3K/AKT pathway activation via CD44. Conclusion Our data revealed that CF-derived GAGs protect cardiomyocytes from death in the acute phase of heart failure due to pressure overload; thus, insufficient GAGs production caused by loss of ChGn-2 exacerbated heart failure. Funding Acknowledgement Type of funding sources: None.

The adult heart requires baseline expression of the transcription factor Hand2 to withstand right ventricular pressure overload.

AimsResearch on the pathophysiology of right ventricular (RV) failure has, in spite of the associated high mortality and morbidity, lagged behind compared to the left ventricle (LV). Previous work from our lab revealed that the embryonic basic helix-loop-helix transcription factor heart and neural crest derivatives expressed-2 (Hand2) is re-expressed in the adult heart and activates a ‘foetal gene programme’ contributing to pathological cardiac remodelling under conditions of LV pressure overload. As such, ablation of cardiac expression of Hand2 conferred protection to cardiac stress and abrogated the maladaptive effects that were observed upon increased expression levels. In this study, we aimed to understand the contribution of Hand2 to RV remodelling in response to pressure overload induced by pulmonary artery banding (PAB).Methods and resultsIn this study, Hand2F/F and MCM- Hand2F/F mice were treated with tamoxifen (control and knockout, respectively) and subjected to six weeks of RV pressure overload induced by PAB. Echocardiographic- and MRI-derived haemodynamic parameters as well as molecular remodelling were assessed for all experimental groups and compared to sham-operated controls. Six weeks after PAB, levels of Hand2 expression increased in the control-banded animals but, as expected, remained absent in the knockout hearts. Despite the dramatic differences in Hand2 expression, pressure overload resulted in impaired cardiac function independently of the genotype. In fact, Hand2 depletion seems to sensitize the RV to pressure overload as these mice develop more hypertrophy and more severe cardiac dysfunction. Higher expression levels of HAND2 were also observed in RV samples of human hearts from patients with pulmonary hypertension. In turn, the LV of RV pressure-overloaded hearts was also dramatically affected as reflected by changes in shape, decreased LV mass, and impaired cardiac function. RNA-sequencing revealed a distinct set of genes that are dysregulated in the pressure-overloaded RV, compared to the previously described pressure-overloaded LV.ConclusionCardiac-specific depletion of Hand2 is associated with severe cardiac dysfunction in conditions of RV pressure overload. While inhibiting Hand2 expression can prevent cardiac dysfunction in conditions of LV pressure overload, the same does not hold true for conditions of RV pressu re overload. This study highlights the need to better understand the molecular mechanisms driving pathological remodelling of the RV in contrast to the LV, in order to better diagnose and treat patients with RV or LV failure.

Characterization of Exercise-Induced Myocardium Growth Using Finite Element Modeling and Bayesian Optimization.

Cardiomyocyte growth can occur in both physiological (exercised-induced) and pathological (e.g., volume overload and pressure overload) conditions leading to left ventricular (LV) hypertrophy. Studies using animal models and histology have demonstrated the growth and remodeling process at the organ level and tissue–cellular level, respectively. However, the driving factors of growth and the mechanistic link between organ, tissue, and cellular growth remains poorly understood. Computational models have the potential to bridge this gap by using constitutive models that describe the growth and remodeling process of the myocardium coupled with finite element (FE) analysis to model the biomechanics of the heart at the organ level. Using subject-specific imaging data of the LV geometry at two different time points, an FE model can be created with the inverse method to characterize the growth parameters of each subject. In this study, we developed a framework that takes in vivo cardiac magnetic resonance (CMR) imaging data of exercised porcine model and uses FE and Bayesian optimization to characterize myocardium growth in the transverse and longitudinal directions. The efficacy of this framework was demonstrated by successfully predicting growth parameters of 18 synthetic LV targeted masks which were generated from three LV porcine geometries. The framework was further used to characterize growth parameters in 4 swine subjects that had been exercised. The study suggested that exercise-induced growth in swine is prone to longitudinal cardiomyocyte growth (58.0 ± 19.6% after 6 weeks and 79.3 ± 15.6% after 12 weeks) compared to transverse growth (4.0 ± 8.0% after 6 weeks and 7.8 ± 9.4% after 12 weeks). This framework can be used to characterize myocardial growth in different phenotypes of LV hypertrophy and can be incorporated with other growth constitutive models to study different hypothetical growth mechanisms.

Cardiac hypertrophy at autopsy

Since cardiac hypertrophy may be considered a cause of death at autopsy, its assessment requires a uniform approach. Common terminology and methodology to measure the heart weight, size, and thickness as well as a systematic use of cut off values for normality by age, gender, and body weight and height are needed. For these reasons, recommendations have been written on behalf of the Association for European Cardiovascular Pathology. The diagnostic work up implies the search for pressure and volume overload conditions, compensatory hypertrophy, storage and infiltrative disorders, and cardiomyopathies. Although some gross morphologic features can point to a specific diagnosis, systematic histologic analysis, followed by possible immunostaining and transmission electron microscopy, is essential for a final diagnosis. If the autopsy is carried out in a general or forensic pathology service without expertise in cardiovascular pathology, the entire heart (or pictures) together with mapped histologic slides should be sent for a second opinion to a pathologist with such an expertise. Indication for postmortem genetic testing should be integrated into the multidisciplinary management of sudden cardiac death.

Regional shape, global function and mechanics in right ventricular volume and pressure overload conditions: a three-dimensional echocardiography study

Our aim was to assess the regional right ventricular (RV) shape changes in pressure and volume overload conditions and their relations with RV function and mechanics. The end-diastolic and end-systolic RV endocardial surfaces were analyzed with three-dimensional echocardiography (3DE) in 33 patients with RV volume overload (rToF), 31 patients with RV pressure overload (PH), and 60 controls. The mean curvature of the RV inflow (RVIT) and outflow (RVOT) tracts, RV apex and body (both divided into free wall (FW) and septum) were measured. Zero curvature defined a flat surface, whereas positive or negative curvature indicated convexity or concavity, respectively. The longitudinal and radial RV wall motions were also obtained. rToF and PH patients had flatter FW (body and apex) and RVIT, more convex interventricular septum (body and apex) and RVOT than controls. rToF demonstrated a less bulging interventricular septum at end-systole than PH patients, resulting in a more convex shape of the RVFW (r = − 0.701, p < 0.0001), and worse RV longitudinal contraction (r = − 0.397, p = 0.02). PH patients showed flatter RVFW apex at end-systole compared to rToF (p < 0.01). In both groups, a flatter RVFW apex was associated with worse radial RV contraction (r = 0.362 in rToF, r = 0.482 in PH at end-diastole, and r = 0.555 in rToF, r = 0.379 in PH at end-systole, respectively). In PH group, the impairment of radial contraction was also related to flatter RVIT (r = 0.407) and more convex RVOT (r = − 0.525) at end-systole (p < 0.05). In conclusion, different loading conditions are associated to specific RV curvature changes, that are related to longitudinal and radial RV dysfunction.

Carnosic acid protects against pressure overload-induced cardiac remodelling by inhibiting the AKT/GSK3β/NOX4 signalling pathway.

Oxidative stress and apoptosis serve an important role in the development of pressure overload-induced cardiac remodelling. Carnosic acid (CA) has been found to exert antioxidant and anti-apoptotic effects. The present study investigated the underlying mechanism of CA protection and whether this effect was exerted against pressure overload-induced cardiac remodelling. Aortic banding (AB) surgery was performed to induce cardiac remodelling. Mice were randomly divided into four groups (n=15/group): i) Sham + vehicle; ii) sham + CA; iii) AB + vehicle; and iv) AB + CA. After 2 days of AB, 50 mg kg CA was administered orally for 12 days. Echocardiography, histological analysis and molecular biochemistry techniques were performed to evaluate the roles of CA. CA treatment decreased cardiac hypertrophy, fibrosis, oxidative stress and apoptosis in mice challenged with pressure overload. CA also decreased the cross-sectional area of cardiomyocytes and the mRNA and protein expression levels of hypertrophic markers. Furthermore, CA treatment decreased collagen deposition, α-smooth muscle actin expression and the mRNA and protein expression of various fibrotic markers. Additionally, CA reversed the AB-mediated increase in NAPDH oxidase (NOX) 2, NOX4 and 4-hydroxynonenal levels. The number of apoptotic cells was decreased following CA treatment following under conditions of pressure overload. CA also suppressed the activation of AKT and glycogen synthase kinase 3 β (GSK3β) in mice challenged with AB. The present results suggested that CA could inhibit pressure overload-induced cardiac hypertrophy and fibrosis by suppressing the AKT/GSK3β/NOX4 signalling pathway. Therefore, CA may be a promising therapy for cardiac remodelling.