Lumican-null mice are susceptible to aging and isoproterenol-induced myocardial fibrosis

Cardiac Molecular Analysis Reveals Aging-Associated Metabolic Alterations Promoting Glycosaminoglycans Accumulation via Hexosamine Biosynthetic Pathway

Age is a prominent risk factor for cardiometabolic disease, often leading to heart structural and functional changes. However, precise molecular mechanisms underlying cardiac remodeling and dysfunction exclusively resulting from physiological aging remain elusive. Previous research demonstrated age-related functional alterations in baboons, analogous to humans. The goal of this study is to identify early cardiac molecular alterations preceding functional adaptations, shedding light on the regulation of age-associated changes. Unbiased transcriptomics of left ventricle samples are performed from female baboons aged 7.5-22.1 years (human equivalent ≈30-88 years). Weighted-gene correlation network and pathway enrichment analyses are performed, with histological validation. Modules of transcripts negatively correlated with age implicated declined metabolism-oxidative phosphorylation, tricarboxylic acid cycle, glycolysis, and fatty-acid β-oxidation. Transcripts positively correlated with age suggested a metabolic shift toward glucose-dependent anabolic pathways, including hexosamine biosynthetic pathway (HBP). This shift is associated with increased glycosaminoglycan synthesis, modification, precursor synthesis via HBP, and extracellular matrix accumulation, verified histologically. Upregulated extracellular matrix-induced signaling coincided with glycosaminoglycan accumulation, followed by cardiac hypertrophy-related pathways. Overall, these findings revealed a transcriptional shift in metabolism favoring glycosaminoglycan accumulation through HBP before cardiac hypertrophy. Unveiling this metabolic shift provides potential targets for age-related cardiac diseases, offering novel insights into early age-related mechanisms.

Single cell sequencing data identify distinct B cell and fibroblast populations in stricturing Crohn's disease

Single cell RNA sequencing of human full thickness Crohn's disease (CD) small bowel resection specimens was used to identify potential therapeutic targets for stricturing (S) CD. Using an unbiased approach, 16 cell lineages were assigned within 14,539 sequenced cells from patient-matched SCD and non-stricturing (NSCD) preparations. SCD and NSCD contained identical cell types. Amongst immune cells, B cells and plasma cells were selectively increased in SCD samples. B cell subsets suggested formation of tertiary lymphoid tissue in SCD and compared with NSCD there was an increase in IgG, and a decrease in IgA plasma cells, consistent with their potential role in CD fibrosis. Two Lumican-positive fibroblast subtypes were identified and subclassified based on expression of selectively enriched genes as fibroblast clusters (C) 12 and C9. Cells within these clusters expressed the profibrotic genes Decorin (C12) and JUN (C9). C9 cells expressed ACTA2; ECM genes COL4A1, COL4A2, COL15A1, COL6A3, COL18A1 and ADAMDEC1; LAMB1 and GREM1. GO and KEGG Biological terms showed extracellular matrix and stricture organization associated with C12 and C9, and regulation of WNT pathway genes with C9. Trajectory and differential gene analysis of C12 and C9 identified four sub-clusters. Intra sub-cluster gene analysis detected 13 co-regulated gene modules that aligned along predicted pseudotime trajectories. CXCL14 and ADAMDEC1 were key markers in module 1. Our findings support further investigation of fibroblast heterogeneity and interactions with local and circulating immune cells at earlier time points in fibrosis progression. Breaking these interactions by targeting one or other population may improve therapeutic management for SCD.

Extracellular Matrix Instability and Chronic Inflammation Underlie Maladaptive Right Ventricular Pressure Overload Remodeling and Failure in Male Mice

Background

Right ventricular dysfunction (RVD) portends increased death risk for heart failure (HF) and pulmonary arterial hypertension (PAH) patients, regardless of left ventricular function or etiology. In both, RVD arises from the chronic RV pressure overload, and represents advanced cardiopulmonary disease. RV remodeling responses and survival rates of HF and PAH patients, however, differ by sex. Men develop more severe RVD and die at younger ages than do women. Mechanistic details of this sexual dimorphism in RV remodeling are incompletely understood. We sought to elucidate the cardiac pathophysiology underlying the sex-specific RV remodeling phenotypes, RV failure (RVF) versus compensated RVD.

Methods

We subjected male (M-) and female (F-) adult mice to moderate pulmonary artery banding (PAB) for 9wks. Mice underwent serial echocardiography, cardiac MRI, RV pressure-volume loop recordings, histologic and molecular analyses.

Results

M-PAB developed severe RVD with RVF, increased RV collagen deposition and degradation, extracellular matrix (ECM) instability, and activation and recruitment of macrophages. Despite the same severity and chronicity of RV pressure overload, F-PAB had more stable ECM, lacked chronic inflammation, and developed mild RVD without RVF.

Conclusions

ECM destabilization and chronic activation of recruited macrophages are associated with maladaptive RV remodeling and RVF in male PAB mice. Adaptive RV remodeling of female PAB mice lacked these histopathologic changes. Our findings suggest that these two pathophysiologic processes likely contribute to the sexual dimorphism of RV pressure overload remodeling. Further mechanistic studies are needed to assess their pathogenic roles and potential as targets for RVD therapy and RVF prevention.

CLINICAL PERSPECTIVE

What is new?: In a mouse model of pure PH, males but not females showed an association between ECM instability, chronic inflammation with activation of recruited macrophages, and severe RV dysfunction and failure.What are the clinical implications?: In male HF and PH patients, enhancing ECM stability and countering the recruitment and activation of macrophages may help preserve RV function such that RVF can be prevented or delayed. Further preclinical mechanistic studies are needed to assess the therapeutic potential of such approaches.

RESEARCH PERSPECTIVE

What new question does this study raise? What question should be addressed next?: What mechanisms regulate RV ECM stability and macrophage recruitment and activation in response to chronic RV pressure overload? Are these regulatory mechanisms dependent upon or independent of sex hormone signaling?

Cardiac Molecular Analysis Reveals Aging-Associated Metabolic Alterations Promoting Glycosaminoglycans Accumulation Via Hexosamine Biosynthetic Pathway

Age is a prominent risk factor for cardiometabolic disease, and often leads to heart structural and functional changes. However, precise molecular mechanisms underlying cardiac remodeling and dysfunction resulting from physiological aging per se remain elusive. Understanding these mechanisms requires biological models with optimal translation to humans. Previous research demonstrated that baboons undergo age-related reduction in ejection fraction and increased heart sphericity, mirroring changes observed in humans. The goal of this study was to identify early cardiac molecular alterations that precede functional adaptations, shedding light on the regulation of age-associated changes. We performed unbiased transcriptomics of left ventricle (LV) samples from female baboons aged 7.5-22.1 years (human equivalent ~30-88 years). Weighted-gene correlation network and pathway enrichment analyses were performed to identify potential age-associated mechanisms in LV, with histological validation. Myocardial modules of transcripts negatively associated with age were primarily enriched for cardiac metabolism, including oxidative phosphorylation, tricarboxylic acid cycle, glycolysis, and fatty-acid β-oxidation. Transcripts positively correlated with age suggest upregulation of glucose uptake, pentose phosphate pathway, and hexosamine biosynthetic pathway (HBP), indicating a metabolic shift towards glucose-dependent anabolic pathways. Upregulation of HBP commonly results in increased glycosaminoglycan precursor synthesis. Transcripts involved in glycosaminoglycan synthesis, modification, and intermediate metabolism were also upregulated in older animals, while glycosaminoglycan degradation transcripts were downregulated with age. These alterations would promote glycosaminoglycan accumulation, which was verified histologically. Upregulation of extracellular matrix (ECM)-induced signaling pathways temporally coincided with glycosaminoglycan accumulation. We found a subsequent upregulation of cardiac hypertrophy-related pathways and an increase in cardiomyocyte width. Overall, our findings revealed a transcriptional shift in metabolism from catabolic to anabolic pathways that leads to ECM glycosaminoglycan accumulation through HBP prior to upregulation of transcripts of cardiac hypertrophy-related pathways. This study illuminates cellular mechanisms that precede development of cardiac hypertrophy, providing novel potential targets to remediate age-related cardiac diseases.

Lumican accumulates with fibrillar collagen in fibrosis in hypertrophic cardiomyopathy

AIMS

Familial hypertrophic cardiomyopathy (HCM) is the most common form of inherited cardiac disease. It is characterized by myocardial hypertrophy and diastolic dysfunction, and can lead to severe heart failure, arrhythmias, and sudden cardiac death. Cardiac fibrosis, defined by excessive accumulation of extracellular matrix (ECM) components, is central to the pathophysiology of HCM. The ECM proteoglycan lumican is increased during heart failure and cardiac fibrosis, including HCM, yet its role in HCM remains unknown. We provide an in-depth assessment of lumican in clinical and experimental HCM.

METHODS

Left ventricular (LV) myectomy specimens were collected from patients with hypertrophic obstructive cardiomyopathy (n = 15), and controls from hearts deemed unsuitable for transplantation (n = 8). Hearts were harvested from a mouse model of HCM; Myh6 R403Q mice administered cyclosporine A and wild-type littermates (n = 8-10). LV tissues were analysed for mRNA and protein expression. Patient myectomy or mouse mid-ventricular sections were imaged using confocal microscopy, direct stochastic optical reconstruction microscopy (dSTORM), or electron microscopy. Human foetal cardiac fibroblasts (hfCFBs) were treated with recombinant human lumican (n = 3) and examined using confocal microscopy.

RESULTS

Lumican mRNA was increased threefold in HCM patients (P < 0.05) and correlated strongly with expression of collagen I (R²  = 0.60, P < 0.01) and III (R²  = 0.58, P < 0.01). Lumican protein was increased by 40% in patients with HCM (P < 0.01) and correlated with total (R²  = 0.28, P = 0.05) and interstitial (R²  = 0.30, P < 0.05) fibrosis. In mice with HCM, lumican mRNA increased fourfold (P < 0.001), and lumican protein increased 20-fold (P < 0.001) in insoluble ECM lysates. Lumican and fibrillar collagen were located together throughout fibrotic areas in HCM patient tissue, with increased co-localization measured in patients and mice with HCM (patients: +19%, P < 0.01; mice: +13%, P < 0.01). dSTORM super-resolution microscopy was utilized to image interstitial ECM which had yet to undergo overt fibrotic remodelling. In these interstitial areas, collagen I deposits located closer to (-15 nm, P < 0.05), overlapped more frequently with (+7.3%, P < 0.05) and to a larger degree with (+5.6%, P < 0.05) lumican in HCM. Collagen fibrils in such deposits were visualized using electron microscopy. The effect of lumican on collagen fibre formation was demonstrated by adding lumican to hfCFB cultures, resulting in thicker (+53.8 nm, P < 0.001), longer (+345.9 nm, P < 0.001), and fewer (-8.9%, P < 0.001) collagen fibres.

CONCLUSIONS

The ECM proteoglycan lumican is increased in HCM and co-localizes with fibrillar collagen throughout areas of fibrosis in HCM. Our data suggest that lumican may promote formation of thicker collagen fibres in HCM.

Remodeling and Fibrosis of the Cardiac Muscle in the Course of Obesity-Pathogenesis and Involvement of the Extracellular Matrix

Obesity is a growing epidemiological problem, as two-thirds of the adult population are carrying excess weight. It is a risk factor for the development of cardiovascular diseases (hypertension, ischemic heart disease, myocardial infarct, and atrial fibrillation). It has also been shown that chronic obesity in people may be a cause for the development of heart failure with preserved ejection fraction (HFpEF), whose components include cellular hypertrophy, left ventricular diastolic dysfunction, and increased extracellular collagen deposition. Several animal models with induced obesity, via the administration of a high-fat diet, also developed increased heart fibrosis as a result of extracellular collagen accumulation. Excessive collagen deposition in the extracellular matrix (ECM) in the course of obesity may increase the stiffness of the myocardium and thereby deteriorate the heart diastolic function and facilitate the occurrence of HFpEF. In this review, we include a rationale for that process, including a discussion about possible putative factors (such as increased renin–angiotensin–aldosterone activity, sympathetic overdrive, hemodynamic alterations, hypoadiponectinemia, hyperleptinemia, and concomitant heart diseases). To address the topic clearly, we include a description of the fundamentals of ECM turnover, as well as a summary of studies assessing collagen deposition in obese individuals.

Molecular alterations due to Col5a1 haploinsufficiency in a mouse model of classic Ehlers-Danlos syndrome

Type V collagen is a regulatory fibrillar collagen essential for type I collagen fibril nucleation and organization and its deficiency leads to structurally abnormal extracellular matrix (ECM). Haploinsufficiency of the Col5a1 gene encoding α(1) chain of type V collagen is the primary cause of classic Ehlers-Danlos syndrome (EDS). The mechanisms by which this initial insult leads to the spectrum of clinical presentation are not fully understood. Using transcriptome analysis of skin and Achilles tendons from Col5a1 haploinsufficient (Col5a1+/-) mice, we recognized molecular alterations associated with the tissue phenotypes. We identified dysregulation of ECM components including thrombospondin-1, lysyl oxidase, and lumican in the skin of Col5a1+/- mice when compared with control. We also identified upregulation of transforming growth factor β1 (Tgf-β) in serum and increased expression of pSmad2 in skin from Col5a1+/- mice, suggesting Tgf-β dysregulation is a contributor to abnormal wound healing and atrophic scarring seen in classic EDS. Together, these findings support altered matrix to cell signaling as a component of the pathogenesis of the tissue phenotype in classic EDS and point out potential downstream signaling pathways that may be targeted for the treatment of this disease.

Bioinformatics Analysis and Identification of Genes and Pathways in Ischemic Cardiomyopathy

Purpose

Ischemic cardiomyopathy (ICM) is considered to be the most common cause of heart failure, with high prevalence and mortality. This study aimed to investigate the different expressed genes (DEGs) and pathways in the pathogenesis of ICM using bioinformatics analysis.

Methods

The control and ICM datasets GSE116250, GSE46224 and GSE5406 were collected from the gene expression omnibus (GEO) database. DEGs were identified using limma package of R software, and co-expressed genes were identified using Venn diagrams. Then, the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to explore the biological functions and signaling pathways. Protein-protein interaction (PPI) networks were assembled with Cytoscape software to identify hub genes related to the pathogenesis of ICM. RT-PCR of Heart tissues (n=2 for non-failing controls and n=4 for ischemic cardiomyopathy patients) was used to validate the bioinformatic results.

Results

A total of 844 DEGs were screened from GSE116250, of which 447 were up-regulated genes and 397 were down-regulated genes, respectively. A total of 99 DEGs were singled out from GSE46224, of which 58 were up-regulated genes and 41 were down-regulated genes, respectively. Thirty DEGs were screened from GSE5406, including 10 genes with up-regulated expression and 20 genes with down-regulated expression. Five up-regulated and 3 down-regulated co-expressed DEGs were intersected in three datasets. GO and KEGG pathway analyses revealed that DEGs are mainly enriched in collagen fibril organization, protein digestion and absorption, AGE-RAGE signaling pathway and other related pathways. Collagen alpha-1(III) chain (COL3A1), collagen alpha-2(I) chain (COL1A2) and lumican (LUM) are the three hub genes in all three datasets through PPI network analysis. The expression of 5 DEGs (SERPINA3, FCN3, COL3A1, HBB, MXRA5) in heart tissues by qRT-PCR results was consistent with our GEO analysis, while expression of 3 DEGs (ASPN, LUM, COL1A2) was opposite with GEO analysis.

Conclusion

These findings from this bioinformatics network analysis investigated key hub genes, which contributed to better understanding the mechanism and new therapeutic targets of ICM.

Expression and role of lumican in acute aortic dissection: A human and mouse study

Introduction

Aortic dissection (AD) is a life-threatening emergency, and lumican (LUM) is a potential Biomarker for AD diagnosis. We investigated LUM expression patterns in patients with AD and explored the molecular functions of Lum in AD mice model.

Methods

LUM expression patterns were analyzed using aortic tissues of AD patients, and serum soluble LUM (s-LUM) levels were compared between patients with acute AD (AAD) and chronic AD (CAD). Lum-knockout (Lum^−/−) mice were challenged with β-aminopropionitrile (BAPN) and angiotensin II (Ang II) to induce AD. The survival rate, AD incidence, and aortic aneurysm (AA) in these mice were compared with those in BAPN–Ang II–challenged wildtype (WT) mice. Tgf-β/Smad2, Mmps, Lum, and Nox expression patterns were examined.

Results

LUM expression was detected in the intima and media of the ascending aorta in patients with AAD. Serum s-LUM levels were significantly higher in patients with AAD than CAD. Furthermore, AD-associated mortality and thoracic aortic rupture incidence were significantly higher in the Lum^−/− AD mice than in the WT AD mice. However, no significant pathologic changes in AA were observed in the Lum^−/− AD mice compared with the WT AD mice. The BAPN–Ang II–challenged WT and Lum^−/− AD mice had higher Tgf-β, p-Smad2, Mmp2, Mmp9, and Nox4 levels than those of non-AD mice. We also found that Lum expression was significantly higher in the BAPN-Ang II–challenged WT in comparison to the unchallenged WT mice.

Conclusion

LUM expression was altered in patients with AD display increased s-LUM in blood, and Lum^−/− mice exhibited augmented AD pathogenesis. These findings support the notion that LUM is a biomarker signifying the pathogenesis of injured aorta seen in AAD. The presence of LUM is essential for maintenance of connective tissue integrity. Future studies should elucidate the mechanisms underlying LUM association in aortic changes.

Boeravinone B alleviates gut dysbiosis during myocardial infarction-induced cardiotoxicity in rats

Myocardial infarction (MI) is the most common heart disease, and also, it is one of the leading causes of death from cardiovascular disease. It is well known that MI causes additional injury during blood flow restoration in ischaemic myocardium. Boeravinone B (BB) is a well-known antioxidant and anti-inflammatory drug. We investigated the cardioprotective effect of BB drug against isoproterenol (ISO)-induced MI in rats in this experimental study, along with we analysed its underlying mechanism. Adult Sprague Dawley (SD) rats were treated subcutaneously with ISO (45 mg/kg), then divided into groups and then given BB drug was administered orally. The cardioprotective effect of BB on ISO-induced MI rats was analysed by estimating the heart injury markers, antioxidant pro-inflammatory cytokines and inflammatory parameters. We also detected quantified expression of inflammation and apoptosis-related marker protein family. We estimated the effect of BB drug on GUT microbiota in ISO-induced MI rats and scrutinized the histopathological variations in heart tissues. BB treatment significantly (P < .001) diminished the level of heart markers such as lactate dehydrogenase (LDH), troponin (TnT), creatine kinase (CK) and creatine kinase isoenzymes MB (CK-MB). BB treatment also altered the antioxidant parameters and reduced the pro-inflammatory cytokines in the serum and tissues. Additionally, the histopathological aspects demonstrated that the pathological changes observed in the heart tissue of the ISO group rats were suppressed by the BB treatment to varying degrees. Furthermore, the expressions of caspase-3, p53, caspase-9, Bax, interleukin-6 (IL-6), cytochrome C, neutrophil gelatinase-associated lipocalin (NGAL), tumour necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB) and interleukin-1β (IL-1β) in the heart tissue were down-regulated whereas the Bcl-2 expression seemed to be enhanced. BB treatment not only alleviated ISO-induced gut dysbiosis by its enhanced specified Firmicutesto-Bacteroidetes (F/B) ratio but also maintained the relative abundance of major bacteria such as Clostridium IV, Butyricicoccus, Clostridium XIVs, Akkermansia and Roseburia. Collectively, our findings showed that the BB drug acted against myocardial infraction and prevented the damage by reducing the oxidative stress and controlling the inflammatory pathways, and gut microbiota.

Cardiac fibrosis

Myocardial fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix proteins, is a common pathophysiologic companion of many different myocardial conditions. Fibrosis may reflect activation of reparative or maladaptive processes. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. Immune cells, vascular cells and cardiomyocytes may also acquire a fibrogenic phenotype under conditions of stress, activating fibroblast populations. Fibrogenic growth factors (such as transforming growth factor-β and platelet-derived growth factors), cytokines [including tumour necrosis factor-α, interleukin (IL)-1, IL-6, IL-10, and IL-4], and neurohumoral pathways trigger fibrogenic signalling cascades through binding to surface receptors, and activation of downstream signalling cascades. In addition, matricellular macromolecules are deposited in the remodelling myocardium and regulate matrix assembly, while modulating signal transduction cascades and protease or growth factor activity. Cardiac fibroblasts can also sense mechanical stress through mechanosensitive receptors, ion channels and integrins, activating intracellular fibrogenic cascades that contribute to fibrosis in response to pressure overload. Although subpopulations of fibroblast-like cells may exert important protective actions in both reparative and interstitial/perivascular fibrosis, ultimately fibrotic changes perturb systolic and diastolic function, and may play an important role in the pathogenesis of arrhythmias. This review article discusses the molecular mechanisms involved in the pathogenesis of cardiac fibrosis in various myocardial diseases, including myocardial infarction, heart failure with reduced or preserved ejection fraction, genetic cardiomyopathies, and diabetic heart disease. Development of fibrosis-targeting therapies for patients with myocardial diseases will require not only understanding of the functional pluralism of cardiac fibroblasts and dissection of the molecular basis for fibrotic remodelling, but also appreciation of the pathophysiologic heterogeneity of fibrosis-associated myocardial disease.

Lumican promotes joint fibrosis through TGF-β signaling

Joint contracture (also known as arthrofibrosis) is a fibrotic joint disorder characterized by excessive collagen production to form fibrotic scar tissue and adhesions within joint capsules. This can severely affect day‐to‐day activities and quality of life because of a restricted range of motion in affected joints. The precise pathogenic mechanism underlying joint contractures is not fully understood. Lumican belongs to the class II small leucine‐rich repeat proteoglycan superfamily, which makes up collagen fibrils in the extracellular matrix. Lumican is ubiquitously expressed in the skin, liver, heart, uterus and articular cartilage and has reported roles in cell migration, proliferation, angiogenesis and Toll‐like receptor 4 signaling. Previous research has suggested that lumican is involved in the pathogenesis of several fibrotic diseases. Because joint contracture resembles a fibrotic disease, we aimed to investigate the role of lumican in the development of joint contracture in vitro. Here, we showed that protein levels were up‐regulated in the fibrotic joint capsule versus control. We observed that lumican significantly enhanced the proliferation, migration and fibroblast–myofibroblast transition of synovial fibroblasts. Moreover, lumican led to increased transcription of alpha‐smooth muscle actin, matrix metallopeptidase 9, Collagen I, plasminogen activator inhibitor 1 and transforming growth factor‐β in vitro. Lumican treatment promoted collagen lattice contraction in a dose‐dependent manner as early as 24 h after treatment. Thus, our studies reveal that lumican could promote fibroblast–myofibroblast transition and joint contracture.

Composition of the whole transcriptome in the human plasma: Cellular source and modification by aging

Plasma contains several bioactive molecules (RNA, DNA, proteins, lipids, and metabolites), which are well preserved in extracellular vesicles, that are involved in many types of cell-to-cell interactions, and are capable of modifying biological processes in recipient cells. To obtain information about the source of mRNA molecules present in the plasma, we analyzed the plasma extracellular RNA (exRNA) of healthy individuals using RNA-sequencing and compared it to that of the peripheral blood mononuclear cell (PBMCs) of the same individual. The resultant data indicates that large proportion of the transcripts in plasma are derived from cell types other than PBMCs. To assess aging-associated changes in the plasma exRNA composition, gene ontology enrichment analysis was performed, revealing a functional decline in biological processes as a result of aging. Additionally, plasma RNA levels were analyzed with differential expression analysis, revealing 10 transcripts with significant aging-associated changes. Thus, it seems that the plasma exRNA is not fully derived from the PBMCs. Instead, other cell types supply RNAs to constitute the plasma exRNA compartment. This was true in both the young and elderly individuals that were tested. Furthermore, the RNA content of the plasma showed significant changes due to aging, affecting important biological processes.

Lack of sexual dimorphism in a mouse model of isoproterenol-induced cardiac dysfunction

Sex-related differences in cardiovascular diseases are highly complex in humans and model-dependent in experimental laboratory animals. The objective of this work was to comprehensively investigate key sex differences in the response to acute and prolonged adrenergic stimulation in C57Bl/6NCrl mice. Cardiac function was assessed by trans-thoracic echocardiography before and after acute adrenergic stimulation (a single sub-cutaneous dose of isoproterenol 10 mg/kg) in 15 weeks old male and female C57Bl/6NCrl mice. Thereafter, prolonged adrenergic stimulation was achieved by sub-cutaneous injections of isoproterenol 10 mg/kg/day for 14 days in male and female mice. Cardiac function and morphometry were assessed by trans-thoracic echocardiography on the 15th day. Thereafter, the mice were euthanized, and the hearts were collected. Histopathological analysis of myocardial tissue was performed after staining with hematoxylin & eosin, Masson's trichrome and MAC-2 antibody. Gene expression of remodeling and fibrotic markers was assessed by real-time PCR. Cardiac function and morphometry were also measured before and after isoproterenol 10 mg/kg/day for 14 days in groups of gonadectomized male and female mice and sham-operated controls. In the current work, there were no statistically significant differences in the positive inotropic and chronotropic effects of isoproterenol between male and female C57Bl/6NCrl. After prolonged adrenergic stimulation, there was similar degree of cardiac dysfunction, cardiac hypertrophy, and myocardial fibrosis in male and female mice. Similarly, prolonged isoproterenol administration induced hypertrophic and fibrotic genes in hearts of male and female mice to the same extent. Intriguingly, gonadectomy of male and female mice did not have a significant impact on isoproterenol-induced cardiac dysfunction as compared to sham-operated animals. The current work demonstrated lack of significant sex-related differences in isoproterenol-induced cardiac hypertrophy, dysfunction, and fibrosis in C57Bl/6NCrl mice. This study suggests that female sex may not be sufficient to protect the heart in this model of isoproterenol-induced cardiac dysfunction and underscores the notion that sexual dimorphism in cardiovascular diseases is highly model-dependent.

Secretome Analysis of Cardiomyocytes Identifies PCSK6 (Proprotein Convertase Subtilisin/Kexin Type 6) as a Novel Player in Cardiac Remodeling After Myocardial Infarction

BACKGROUND

Acute occlusion of a coronary artery results in swift tissue necrosis. Bordering areas of the infarcted myocardium can also experience impaired blood supply and reduced oxygen delivery, leading to altered metabolic and mechanical processes. Although transcriptional changes in hypoxic cardiomyocytes are well studied, little is known about the proteins that are actively secreted from these cells.

METHODS

We established a novel secretome analysis of cardiomyocytes by combining stable isotope labeling and click chemistry with subsequent mass spectrometry analysis. Further functional validation experiments included ELISA measurement of human samples, murine left anterior descending coronary artery ligation, and adeno-associated virus 9-mediated in vivo overexpression in mice.

RESULTS

The presented approach is feasible for analysis of the secretome of primary cardiomyocytes without serum starvation. A total of 1026 proteins were identified to be secreted within 24 hours, indicating a 5-fold increase in detection compared with former approaches. Among them, a variety of proteins have not yet been explored in the context of cardiovascular pathologies. One of the secreted factors most strongly upregulated upon hypoxia was PCSK6 (proprotein convertase subtilisin/kexin type 6). Validation experiments revealed an increase of PCSK6 on mRNA and protein level in hypoxic cardiomyocytes. PCSK6 expression was elevated in hearts of mice after 3 days of ligation of the left anterior descending artery, a finding confirmed by immunohistochemistry. ELISA measurements in human serum also indicate distinct kinetics for PCSK6 in patients with acute myocardial infarction, with a peak on postinfarction day 3. Transfer of PCSK6-depleted cardiomyocyte secretome resulted in decreased expression of collagen I and III in fibroblasts compared with control treated cells, and small interfering RNA-mediated knockdown of PCSK6 in cardiomyocytes impacted transforming growth factor-β activation and SMAD3 (mothers against decapentaplegic homolog 3) translocation in fibroblasts. An adeno-associated virus 9-mediated, cardiomyocyte-specific overexpression of PCSK6 in mice resulted in increased collagen expression and cardiac fibrosis, as well as decreased left ventricular function, after myocardial infarction.

CONCLUSIONS

A novel mass spectrometry-based approach allows investigation of the secretome of primary cardiomyocytes. Analysis of hypoxia-induced secretion led to the identification of PCSK6 as being crucially involved in cardiac remodeling after acute myocardial infarction.

Myocardial potency of Caesalpinia bonducella Linn. on doxorubicin induced myocardial infarction in albino rats

Objective

Caesalpinia bonducella L. is well known and extremely valuable herb in ayurvedic system of medicine. The present study is aimed to design the evaluation of aqueous extract of Caesalpinia bonducella L. on doxorubicin induced myocardial infarction in wistar strains of albino rats of both sex.

Materials and methods

The experimental animals are divided in to 5 groups of 6 animals each. Group I (Normal Control), Group II (Negative Control, 2.5 mg/kgbw of Doxorubicin i.p.), Group III (2.5 mg/kgbw of Doxorubicin i.p.) + AECB (150 mg/kgbw), Group IV (2.5 mg/kgbw of Doxorubicin i.p.) + AECB (300 mg/kgbw), Group V (2.5 mg/kgbw of Doxorubicin i.p.) + standard drug (Propranolol 5 mg/kgbw). Doxorubicin induced myocardial infarction was confirmed by disturbances in levels of cardiac markers (Lactate Dehydrogenase, Troponin-T, Creatine Kinase-MB Isoenzyme, Creatine Phosphokinase), nucleic acid contents (DNA and RNA), Challenged levels of Membrane bound enzymes such as Na+/K + ATPase, Ca2 + ATPase and Mg2 + ATPase, Decreased tissue protein and altered lipid profile markers.

Results

Doxorubicin induced rats significantly showed increase in the activities of LDH, CK-MB, CPK, Troponin-T, nucleic acids, membrane bound enzymes, lipid profiles and decrease in the serum HDL. Treatment with AECB simultaneously at two different doses such as 150 mg/kg bw, 300 mg/kg bw prevented the leakage of myocardium markers and altered the levels of Protein, DNA, RNA and membrane bound enzymes. The AECB prevented the altered variations in Cholesterol, Triacylglycerols, Phospholipids and Free Fatty Acids. This extract also brought back the levels of Lipoproteins like HDL, LDL and VLDL which were varied in disease control animals.

Conclusion

The present study concludes that AECB is effective in controlling the cardiac markers and lipid levels which could be due to its ability to maintain the membrane stability and repair the myocardial damage.

The extracellular matrix proteoglycan lumican improves survival and counteracts cardiac dilatation and failure in mice subjected to pressure overload

Left ventricular (LV) dilatation is a key step in transition to heart failure (HF) in response to pressure overload. Cardiac extracellular matrix (ECM) contains fibrillar collagens and proteoglycans, important for maintaining tissue integrity. Alterations in collagen production and cross-linking are associated with cardiac LV dilatation and HF. Lumican (LUM) is a collagen binding proteoglycan with increased expression in hearts of patients and mice with HF, however, its role in cardiac function remains poorly understood. To examine the role of LUM in pressure overload induced cardiac remodeling, we subjected LUM knock-out (LUMKO) mice to aortic banding (AB) and treated cultured cardiac fibroblasts (CFB) with LUM. LUMKO mice exhibited increased mortality 1-14 days post-AB. Echocardiography revealed increased LV dilatation, altered hypertrophic remodeling and exacerbated contractile dysfunction in surviving LUMKO 1-10w post-AB. LUMKO hearts showed reduced collagen expression and cross-linking post-AB. Transcriptional profiling of LUMKO hearts by RNA sequencing revealed 714 differentially expressed transcripts, with enrichment of cardiotoxicity, ECM and inflammatory pathways. CFB treated with LUM showed increased mRNAs for markers of myofibroblast differentiation, proliferation and expression of ECM molecules important for fibrosis, including collagens and collagen cross-linking enzyme lysyl oxidase. In conclusion, we report the novel finding that lack of LUM attenuates collagen cross-linking in the pressure-overloaded heart, leading to increased mortality, dilatation and contractile dysfunction in mice.

The Extracellular Matrix in Ischemic and Nonischemic Heart Failure

The ECM (extracellular matrix) network plays a crucial role in cardiac homeostasis, not only by providing structural support, but also by facilitating force transmission, and by transducing key signals to cardiomyocytes, vascular cells, and interstitial cells. Changes in the profile and biochemistry of the ECM may be critically implicated in the pathogenesis of both heart failure with reduced ejection fraction and heart failure with preserved ejection fraction. The patterns of molecular and biochemical ECM alterations in failing hearts are dependent on the type of underlying injury. Pressure overload triggers early activation of a matrix-synthetic program in cardiac fibroblasts, inducing myofibroblast conversion, and stimulating synthesis of both structural and matricellular ECM proteins. Expansion of the cardiac ECM may increase myocardial stiffness promoting diastolic dysfunction. Cardiomyocytes, vascular cells and immune cells, activated through mechanosensitive pathways or neurohumoral mediators may play a critical role in fibroblast activation through secretion of cytokines and growth factors. Sustained pressure overload leads to dilative remodeling and systolic dysfunction that may be mediated by changes in the interstitial protease/antiprotease balance. On the other hand, ischemic injury causes dynamic changes in the cardiac ECM that contribute to regulation of inflammation and repair and may mediate adverse cardiac remodeling. In other pathophysiologic conditions, such as volume overload, diabetes mellitus, and obesity, the cell biological effectors mediating ECM remodeling are poorly understood and the molecular links between the primary insult and the changes in the matrix environment are unknown. This review article discusses the role of ECM macromolecules in heart failure, focusing on both structural ECM proteins (such as fibrillar and nonfibrillar collagens), and specialized injury-associated matrix macromolecules (such as fibronectin and matricellular proteins). Understanding the role of the ECM in heart failure may identify therapeutic targets to reduce geometric remodeling, to attenuate cardiomyocyte dysfunction, and even to promote myocardial regeneration.

AAV9-TAZ Gene Replacement Ameliorates Cardiac TMT Proteomic Profiles in a Mouse Model of Barth Syndrome

Barth syndrome (BTHS) is a rare mitochondrial disease that causes severe cardiomyopathy and has no disease-modifying therapy. It is caused by recessive mutations in the gene tafazzin (TAZ), which encodes tafazzin-an acyltransferase that remodels the inner mitochondrial membrane lipid cardiolipin. To identify novel mechanistic pathways involved in BTHS and evaluate the effects of gene therapy on proteomic profiles, we performed a multiplex tandem mass tagging (TMT) quantitative proteomics analysis to compare protein expression profiles from heart lysates isolated from BTHS, healthy wild-type (WT), and BTHS treated with adeno-associated virus serotype 9 (AAV9)-TAZ gene replacement as neonates or adults. 197 proteins with ≥2 unique peptides were identified. Of these, 91 proteins were significantly differentially expressed in BTHS compared to WT controls. Cause-effect relationships between tafazzin deficiency and altered protein profiles were confirmed through demonstrated significant improvements in expression levels following administration of AAV9-TAZ. The importance of TMEM65 in Cx43 localization to cardiac intercalated discs was revealed as a novel consequence of tafazzin deficiency that was improved following gene therapy. This study identifies novel mechanistic pathways involved in the pathophysiology of BTHS, demonstrates the ability of gene delivery to improve protein expression profiles, and provides support for clinical translation of AAV9-TAZ gene therapy.

Emerging roles of proteoglycans in cardiac remodeling

Cardiac remodeling is the response of the heart to a range of pathological stimuli. Cardiac remodeling is initially adaptive; however, if sustained, it ultimately causes adverse clinical outcomes. Cardiomyocyte loss or hypertrophy, inflammation and fibrosis are hallmarks of cardiac remodeling. Proteoglycans, which are composed of glycosaminoglycans and a core protein, are a non-structural component of the extracellular matrix. The lack of proteoglycans results in cardiovascular defects during development. Moreover, emerging evidence has indicated that proteoglycans act as significant modifiers in ischemia and pressure overload-related cardiac remodeling. Proteoglycans may also provide novel therapeutic strategies for further improvement in the prognosis of cardiovascular diseases.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.