Thrombospondins in the heart: potential functions in cardiac remodeling

Serum levels of matrix metalloproteinase 2 and its inhibitor after tonic-clonic seizures

Damage to the blood-brain barrier (BBB) may result from on-going neuroinflammation, which can lead to leakage of blood components, such as leukocytes and serum proteins, into the brain, resulting in disturbed brain homeostasis. The aim of the project was to examine the involvement of modulatory proteins in the processes of BBB integration after epileptic seizures. We investigated serum changes in the levels of MMP-2 and MMP-7 and its inhibitors after seizures in epilepsy patients. Concentrations of these proteins were measured by ELISA in 50 patients at 1-3, 24, and 72 h after generalized tonic-clonic seizures and once in participants of the control group. The level of MMP-2 in serum was slightly higher after seizures (at 1-3 h time point), but the difference was not statistically significant. The levels of trombospondine (TSP) - 1 and - 2 were decreased at 1-3 h after seizures. The expression of TIMP-2 was increased 1 and 24 h after seizures. There were no significant changes in the level of α2-macroglobulin and MMP-7. Changes in the expression of both specific and non-specific inhibitors indicate the initiation of repair processes of the blood-brain barrier and improvement of its integrity. Since we performed serum analysis, further studies are necessary to investigate the correlation with the expression of the investigated markers in the brain. Perhaps this will allow for the identification of new biomarkers associated with epileptic seizures.

Data Mining Identifies CCN2 and THBS1 as Biomarker Candidates for Cardiac Hypertrophy

Cardiac hypertrophy is a condition that may contribute to the development of heart failure. In this study, we compare the gene-expression patterns of our in vitro stem-cell-based cardiac hypertrophy model with the gene expression of biopsies collected from hypertrophic human hearts. Twenty-five differentially expressed genes (DEGs) from both groups were identified and the expression of selected corresponding secreted proteins were validated using ELISA and Western blot. Several biomarkers, including CCN2, THBS1, NPPA, and NPPB, were identified, which showed significant overexpressions in the hypertrophic samples in both the cardiac biopsies and in the endothelin-1-treated cells, both at gene and protein levels. The protein-interaction network analysis revealed CCN2 as a central node among the 25 overlapping DEGs, suggesting that this gene might play an important role in the development of cardiac hypertrophy. GO-enrichment analysis of the 25 DEGs revealed many biological processes associated with cardiac function and the development of cardiac hypertrophy. In conclusion, we identified important similarities between ET-1-stimulated human-stem-cell-derived cardiomyocytes and human hypertrophic cardiac tissue. Novel putative cardiac hypertrophy biomarkers were identified and validated on the protein level, lending support for further investigations to assess their potential for future clinical applications.

The Identification of Key Genes and Biological Pathways in Heart Failure by Integrated Bioinformatics Analysis

Purpose

Heart failure (HF) is a clinical syndrome caused by ventricular insufficiency. In order to further explore the biomarkers related to HF, we apply the high-throughput database.

Materials and Methods

The GSE21610 was applied for the differentially expressed gene (DEG) analysis. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was performed to assess Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The Gene Set Enrichment Analysis (GSEA) was used for gene expression profile GSE21610. The Protein-Protein Interaction (PPI) network and modules were also constructed for research. These hub gene function pathways were estimated in HF progression.

Result

We have identified 434 DEGs in total, including 304 downregulated DEGs and 130 upregulated DEGs. GO and KEGG illustrated that DEGs in HF were significantly enriched in G protein-coupled receptor binding, peroxisome, and cAMP signaling pathway. GSEA results showed gene set GSE21610 was gathered in lipid digestion, defense response to fungus, and intestinal lipid absorption. Finally, through analyzing the PPI network, we screened hub genes CDH1, TFRC, CCL2, BUB1B, and CD19 by the Cytoscape software.

Conclusion

This study uses a series of bioinformatics technologies to obtain hug genes and key pathways related to HF. These analysis results provide us with new ideas for finding biomarkers and treatment methods for HF.

Extracellular matrix remodeling in animal models of anthracycline-induced cardiomyopathy: a meta-analysis

As in other cardiomyopathies, extracellular matrix (ECM) remodeling plays an important role in anthracycline-induced cardiomyopathy. To understand the pattern and timing of ECM remodeling pathways, we conducted a systematic review in which we describe protein and mRNA markers for ECM remodeling that are differentially expressed in the hearts of animals with anthracycline-induced cardiomyopathy. We included 68 studies in mice, rats, rabbits, and pigs with follow-up of 0.1-8.2 human equivalent years after anthracycline administration. Using meta-analysis, we found 29 proteins and 11 mRNAs that were differentially expressed in anthracycline-induced cardiomyopathy compared to controls. Collagens, matrix metalloproteinases (MMPs), inflammation markers, transforming growth factor ß signaling markers, and markers for cardiac hypertrophy were upregulated, whereas the protein kinase B (AKT) pro-survival pathway was downregulated. Their expression patterns over time from single time point studies were studied with meta-regression using human equivalent years as the time scale. Connective tissue growth factor showed an early peak in expression but remained upregulated at all studied time points. Brain natriuretic peptide (BNP) and MMP9 protein levels increased in studies with longer follow-up. Significant associations were found for higher atrial natriuretic peptide with interstitial fibrosis and for higher BNP and MMP2 protein levels with left ventricular systolic function.

Basic Biology of Extracellular Matrix in the Cardiovascular System, Part 1/4: JACC Focus Seminar

The extracellular matrix (ECM) is the noncellular component of tissues in the cardiovascular system and other organs throughout the body. It is formed of filamentous proteins, proteoglycans, and glycosaminoglycans, which extensively interact and whose structure and dynamics are modified by cross-linking, bridging proteins, and cleavage by matrix degrading enzymes. The ECM serves important structural and regulatory roles in establishing tissue architecture and cellular function. The ECM of the developing heart has unique properties created by its emerging contractile nature; similarly, ECM lining blood vessels is highly elastic in order to sustain the basal and pulsatile forces imposed on their walls throughout life. In this part 1 of a 4-part JACC Focus Seminar, we focus on the role, function, and basic biology of the ECM in both heart development and in the adult.

Preconditioning Effect of High-Intensity Interval Training (HIIT) and Berberine Supplementation on the Gene Expression of Angiogenesis Regulators and Caspase-3 Protein in the Rats with Myocardial Ischemia-Reperfusion (IR) Injury

Objective

It has been shown that angiogenesis is a desirable treatment for patients with ischemic heart disease. We set out to investigate the impact of high-intensity interval training (HIIT) and berberine supplementation on the gene expression of angiogenesis-related factors and caspase-3 protein in rats suffering from myocardial ischemic-reperfusion injury.

Methods

Fifty rats were divided into the following groups: (1) trained, (2) berberine supplemented, (3) combined, and (4) IR. Each cohort underwent five sessions of HIIT per week for a duration of 8 weeks followed by induction of ischemia. Seven days after completion of reperfusion, changes in the gene expression of angiogenesis-related factors and caspase-3 protein were evaluated in the heart tissue.

Results

We observed a significant difference between four groups in the transcript levels of vascular endothelial cell growth factor (VEGF), fibroblast growth factor-2 (FGF2), and thrombospondin-1(TSP-1) (p ≤ 0.05). However, the difference in endostatin (ENDO) levels was not significant among the groups despite a discernible reduction (p ≥ 0.05). Moreover, caspase-3 protein and infarct size were significantly reduced in the intervention groups (p ≤ 0.05), and cardiac function increased in response to these interventions.

Conclusion

The treatments exert their effect, likely, by reducing caspase-3 protein and increasing the expression of angiogenesis-promoting factors, concomitant with a reduction in inhibitors of the process.

Guanxinshutong capsule ameliorates cardiac function and architecture following myocardial injury by modulating ventricular remodeling in rats

Guanxinshutong capsule (GXST), which consists of five traditional Chinese medicines, has been used for a long time in China for the treatment of cardiovascular diseases, such as coronary artery disease and myocardial infarction. However, the effects on GXST on myocardial injury (MI) have not been studied in detail. In these experiments, we found that GXST administration decreased MI-associated ventricular remodeling (VR) with a reduction in interventricular septal thickness in diastole (IVSd), left ventricular posterior wall diameter in systole (LVPWs), and left ventricular posterior wall diameter in diastole (LVPWd) to ameliorate cardiac function and architecture, as measured by echocardiography. Furthermore, histological analysis showed that GXST could ameliorate pathological alterations in the myocardium. And Sirius red staining, wheat germ agglutinin staining and inflammation-related immunohistochemistry results showed that GXST ameliorated the fibrosis areas, cardiac hypertrophy and inflammation (IL-6 and TNF-α). In addition, GXST upregulated intercellular junction proteins (N-cad and Cx-43) and downregulated the angiogenesis-related proteins (PDGF and VEGFA), myocardial fibrosis-related proteins (TGF-β1), and matrix metalloproteinase (MMP-2 and MMP-9). We also found that GXST medium-dose group (1 g/kg/d) dosage was the most efficacious. In conclusion, GXST protected cardiac tissues against MI by reducing VR, thus indicating the potential application of GXST in the treatment of MI.

Aptamer-Based Proteomic Platform Identifies Novel Protein Predictors of Incident Heart Failure and Echocardiographic Traits

BACKGROUND

We used a large-scale, high-throughput DNA aptamer-based discovery proteomic platform to identify circulating biomarkers of cardiac remodeling and incident heart failure (HF) in community-dwelling individuals.

METHODS

We evaluated 1895 FHS (Framingham Heart Study) participants (age 55±10 years, 54% women) who underwent proteomic profiling and echocardiography. Plasma levels of 1305 proteins were related to echocardiographic traits and to incident HF using multivariable regression. Statistically significant protein-HF associations were replicated in the HUNT (Nord-Trøndelag Health) study (n=2497, age 63±10 years, 43% women), and results were meta-analyzed. Genetic variants associated with circulating protein levels (pQTLs) were related to echocardiographic traits in the EchoGen (n=30 201) and to incident HF in the CHARGE (n=20 926) consortia.

RESULTS

Seventeen proteins associated with echocardiographic traits in cross-sectional analyses (false discovery rate <0.10), and 8 of these proteins had pQTLs associated with echocardiographic traits in EchoGen (P<0.0007). In Cox models adjusted for clinical risk factors, 29 proteins demonstrated associations with incident HF in FHS (174 HF events, mean follow-up 19 [limits, 0.2-23.7] years). In meta-analyses of FHS and HUNT, 6 of these proteins were associated with incident HF (P<3.8×10-5; 3 with higher risk: NT-proBNP [N-terminal proB-type natriuretic peptide], TSP2 [thrombospondin-2], MBL [mannose-binding lectin]; and 3 with lower risk: ErbB1 [epidermal growth factor receptor], GDF-11/8 [growth differentiation factor-11/8], and RGMC [hemojuvelin]). For 5 of the 6 proteins, pQTLs were associated with echocardiographic traits (P<0.0006) in EchoGen, and for RGMC, a protein quantitative trait loci was associated with incident HF (P=0.001).

CONCLUSIONS

A large-scale proteomics approach identified new predictors of cardiac remodeling and incident HF. Future studies are warranted to elucidate how biological pathways represented by these proteins may mediate cardiac remodeling and HF risk and to assess if these proteins can improve HF risk prediction.

Hypoxia-inducible factor 1-alpha (HIF-1α) as a factor mediating the relationship between obesity and heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF), a common condition with an increased mortality, is strongly associated with obesity and the metabolic syndrome. The latter two conditions are associated with increased epicardial fat that can extend into the heart. This review advances the proposition that hypoxia-inhibitory factor-1α (HIF-1α) maybe a key factor producing HFpEF. HIF-1α, a highly conserved transcription factor that plays a key role in tissue response to hypoxia, is increased in adipose tissue in obesity. Increased HIF-1α expression leads to expression of a potent profibrotic transcriptional programme involving collagen I, III, IV, TIMP, and lysyl oxidase. The net effect is the formation of collagen fibres leading to fibrosis. HIF-1α is also responsible for recruiting M1 macrophages that mediate obesity-associated inflammation, releasing IL-6, MCP-1, TNF-α, and IL-1β with increased expression of thrombospondin, pro α2 (I) collagen, transforming growth factor β, NADPH oxidase, and connective tissue growth factor. These factors can accelerate cardiac fibrosis and impair cardiac diastolic function. Inhibition of HIF-1α expression in adipose tissue of mice fed a high-fat diet suppressed fibrosis and reduces inflammation in adipose tissue. Delineation of the role played by HIF-1α in obesity-associated HFpEF may lead to new potential therapies.

Thrombospondin-1 Production Regulates the Inflammatory Cytokine Secretion in THP-1 Cells Through NF-κB Signaling Pathway

Thrombospondin-1 (TSP-1) is upregulated in several inflammatory diseases. Recent data have shown that macrophages from TSP-1-deficient mice have a reduced inflammatory phenotype, suggesting that TSP-1 plays a part in macrophage activation. DNA microarray approach revealed that Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS) may induce the enhanced TSP-1 expression in human monocytes, suggesting a role of TSP-1-mediated pathogenesis in periodontitis. Until recently, the function of TSP-1 has been a matter of debate. In this study, we explored the role of TSP-1 in inflammatory cytokine secretions and its putative mechanism in pathogenesis of periodontitis. We demonstrated that TSP-1 expression was significantly upregulated in gingival tissues with periodontitis and in P. gingivalis LPS-stimulated THP-1 cells. Deficiency of TSP-1 by transfecting siRNAs decreased IL-6, IL-1β, and TNF-α secretions in THP-1 cells, whereas overexpression of TSP-1 resulted in an upregulation of IL-6, IL-1β, and TNF-α productions. Additional experiments showed that Pyrrolidine dithiocarbamate (PDTC) inhibited IL-6, IL-1β, and TNF-α expression induced by overexpression of TSP-1, accompanying with downregulation of phosphorylated p65 and IκBα protein levels in response to P. gingivalis LPS. These results indicated that TSP-1 played a significant role in P. gingivalis LPS-initiated inflammatory cytokines (IL-6, IL-1β, and TNF-α) secretions of THP-1 cells, and the NF-κB signaling is involved in its induction of expression. Thus, TSP-1 effectively elevated P. gingivalis LPS-induced inflammation mediated by the NF-κB pathway and may be critical for pathology of periodontitis.

Thrombospondins: A Role in Cardiovascular Disease

Thrombospondins (TSPs) represent extracellular matrix (ECM) proteins belonging to the TSP family that comprises five members. All TSPs have a complex multidomain structure that permits the interaction with various partners including other ECM proteins, cytokines, receptors, growth factors, etc. Among TSPs, TSP1, TSP2, and TSP4 are the most studied and functionally tested. TSP1 possesses anti-angiogenic activity and is able to activate transforming growth factor (TGF)-β, a potent profibrotic and anti-inflammatory factor. Both TSP2 and TSP4 are implicated in the control of ECM composition in hypertrophic hearts. TSP1, TSP2, and TSP4 also influence cardiac remodeling by affecting collagen production, activity of matrix metalloproteinases and TGF-β signaling, myofibroblast differentiation, cardiomyocyte apoptosis, and stretch-mediated enhancement of myocardial contraction. The development and evaluation of TSP-deficient animal models provided an option to assess the contribution of TSPs to cardiovascular pathology such as (myocardial infarction) MI, cardiac hypertrophy, heart failure, atherosclerosis, and aortic valve stenosis. Targeting of TSPs has a significant therapeutic value for treatment of cardiovascular disease. The activation of cardiac TSP signaling in stress and pressure overload may be therefore beneficial.

High serum thrombospondin-1 concentration is associated with slower abdominal aortic aneurysm growth and deficiency of thrombospondin-1 promotes angiotensin II induced aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is a common age-related vascular disease characterized by progressive weakening and dilatation of the aortic wall. Thrombospondin-1 (TSP-1; gene Thbs1) is a member of the matricellular protein family important in the control of extracellular matrix (ECM) remodelling. In the present study, the association of serum TSP-1 concentration with AAA progression was assessed in 276 men that underwent repeated ultrasound for a median 5.5 years. AAA growth was negatively correlated with serum TSP-1 concentration (Spearman's rho -0.129, P=0.033). Men with TSP-1 in the highest quartile had a reduced likelihood of AAA growth greater than median during follow-up (OR: 0.40; 95% confidence interval (CI): 0.19-0.84, P=0.016, adjusted for other risk factors). Immunohistochemical staining for TSP-1 was reduced in AAA body tissues compared with the relatively normal AAA neck. To further assess the role of TSP-1 in AAA initiation and progression, combined TSP-1 and apolipoprotein deficient (Thbs1-/-ApoE-/-, n=20) and control mice (ApoE-/-, n=20) were infused subcutaneously with angiotensin II (AngII) for 28 days. Following AngII infusion, Thbs1-/- ApoE-/- mice had larger AAAs by ultrasound (P=0.024) and ex vivo morphometry measurement (P=0.006). The Thbs1-/-ApoE-/- mice also showed increased elastin filament degradation along with elevated systemic levels and aortic expression of matrix metalloproteinase (MMP)-9. Suprarenal aortic segments and vascular smooth muscle cells (VSMCs) isolated from Thbs1-/-ApoE-/- mice showed reduced collagen 3A1 gene expression. Furthermore, Thbs1-/-ApoE-/- mice had reduced aortic expression of low-density lipoprotein (LDL) receptor-related protein 1. Collectively, findings from the present study suggest that TSP-1 deficiency promotes maladaptive remodelling of the ECM leading to accelerated AAA progression.

Thrombospondin expression in myofibers stabilizes muscle membranes

Skeletal muscle is highly sensitive to mutations in genes that participate in membrane stability and cellular attachment, which often leads to muscular dystrophy. Here we show that Thrombospondin-4 (Thbs4) regulates skeletal muscle integrity and its susceptibility to muscular dystrophy through organization of membrane attachment complexes. Loss of the Thbs4 gene causes spontaneous dystrophic changes with aging and accelerates disease in 2 mouse models of muscular dystrophy, while overexpression of mouse Thbs4 is protective and mitigates dystrophic disease. In the myofiber, Thbs4 selectively enhances vesicular trafficking of dystrophin-glycoprotein and integrin attachment complexes to stabilize the sarcolemma. In agreement, muscle-specific overexpression of Drosophila Tsp or mouse Thbs4 rescues a Drosophila model of muscular dystrophy with augmented membrane residence of βPS integrin. This functional conservation emphasizes the fundamental importance of Thbs' as regulators of cellular attachment and membrane stability and identifies Thbs4 as a potential therapeutic target for muscular dystrophy.

Extracellular matrix-mediated cellular communication in the heart

The extracellular matrix (ECM) is a complex and dynamic scaffold that maintains tissue structure and dynamics. However, the view of the ECM as an inert architectural support has been increasingly challenged. The ECM is a vibrant meshwork, a crucial organizer of cellular microenvironments. It plays a direct role in cellular interactions regulating cell growth, survival, spreading, proliferation, differentiation and migration through the intricate relationship among cellular and acellular tissue components. This complex interrelationship preserves cardiac function during homeostasis; however it is also responsible for pathologic remodeling following myocardial injury. Therefore, enhancing our understanding of this cross-talk may provide mechanistic insights into the pathogenesis of heart failure and suggest new approaches to novel, targeted pharmacologic therapies. This review explores the implications of ECM-cell interactions in myocardial cell behavior and cardiac function at baseline and following myocardial injury.

Adenosine stimulates angiogenesis by up-regulating production of thrombospondin-1 by macrophages

Increase of blood capillary density at the interface between normal and ischemic tissue after acute MI reduces infarct size and improves cardiac function. Cardiac injury triggers the production of the matricellular component TSP-1, but its role in angiogenesis is not clear, as both anti- and proangiogenic properties have been reported. It is unknown whether TSP-1 is modulated by other factors released during cardiac injury. Among these, Ado is a well-known promoter of angiogenesis. This study determined whether Ado modulates TSP-1 expression and the implication on angiogenesis. Ado dose dependently increased the production of TSP-1 by human macrophages. With the use of agonists and antagonists of AdoRs, coupled to RNA interference, we observed that this effect is mediated via A2AR and A2BR. The Ado effect was reproduced by cholera toxin (Gs protein activator) and forskolin (adenylate cyclase activator) and blocked by the PKA inhibitor H89. Conditioned medium from Ado-treated macrophages stimulated microvessel outgrowth from aortic ring explants by 400%, and induced vessel formation in matrigel plugs. Microvessel outgrowth and vessel formation were blocked completely by addition of anti-TSP-1 antibodies to conditioned medium. Chronic administration of Ado to rats after MI maintained long-term expression of TSP-1 in the infarct border zone, and this was associated with enhanced border-zone vascularization. Ado up-regulates TSP-1 production by macrophages, resulting in stimulation of angiogenesis. The mechanism involves A2AR and A2BR and is mediated through the cAMP/PKA pathway. This information may be important when designing Ado-based therapies of angiogenesis.

Matrix as an interstitial transport system

The extracellular matrix (ECM) is best known for its function as a structural scaffold for the tissue and more recently as a microenvironment to sequester growth factors and cytokines allowing for rapid and localized changes in their activity in the absence of new protein synthesis. In this review, we explore this and additional new aspects of ECM function in mediating cell-to-cell communications. Fibrillar and nonfibrillar components of ECM can limit and facilitate the transport of molecules through the extracellular space while also regulating interstitial hydrostatic pressure. In turn, transmembrane communications via molecules, such as ECM metalloproteinase inducer, thrombospondins, and integrins, can further mediate cell response to extracellular cues and affect ECM composition and tissue remodeling. Other means of cell-to-cell communication include extracellular microRNA transport and its contribution to gene expression in target cells and the nanotube formation between distant cells, which has recently emerged as a novel conduit for intercellular organelle sharing thereby influencing cell survival and function. The information summarized and discussed here are not limited to the cardiovascular ECM but encompass ECM in general with specific references to the cardiovascular system.

Thrombospondins: old players, new games

PURPOSE OF REVIEW

Thrombospondins (TSPs) are secreted extracellular matrix (ECM) proteins from TSP family, which consists of five homologous members. They share a complex domain structure and have numerous binding partners in ECM and multiple cell surface receptors. Information that has emerged over the past decade identifies TSPs as important mediators of cellular homeostasis, assigning new important roles in cardiovascular pathology to these proteins.

RECENT FINDINGS

Recent studies of the functions of TSP in the cardiovascular system, diabetes and aging, which placed several TSPs in a position of critical regulators, demonstrated the involvement of these proteins in practically every aspect of cardiovascular pathophysiology related to atherosclerosis: inflammation, immunity, leukocyte recruitment and function, function of vascular cells, angiogenesis, and responses to hypoxia, ischemia and hyperglycemia. TSPs are also critically important in the development and ultimate outcome of the complications associated with atherosclerosis--myocardial infarction, and heart hypertrophy and failure. Their expression and significance increase with age and with the progression of diabetes, two major contributors to the development of atherosclerosis and its complications.

SUMMARY

This overview of recent literature examines the latest information on the newfound functions of TSPs that emphasize the importance of ECM in cardiovascular homeostasis and pathology. The functions of TSPs in myocardium, vasculature, vascular complications of diabetes, aging and immunity are discussed.

Identification and comparative analyses of myocardial miRNAs involved in the fetal response to maternal obesity

Human and animal studies show that suboptimal intrauterine environments lead to fetal programming, predisposing offspring to disease in later life. Maternal obesity has been shown to program offspring for cardiovascular disease (CVD), diabetes, and obesity. MicroRNAs (miRNAs) are small, noncoding RNA molecules that act as key regulators of numerous cellular processes. Compelling evidence links miRNAs to the control of cardiac development and etiology of cardiac pathology; however, little is known about their role in the fetal cardiac response to maternal obesity. Our aim was to sequence and profile the cardiac miRNAs that are dysregulated in the hearts of baboon fetuses born to high fat/high fructose-diet (HFD) fed mothers for comparison with fetal hearts from mothers eating a regular diet. Eighty miRNAs were differentially expressed. Of those, 55 miRNAs were upregulated and 25 downregulated with HFD. Twenty-two miRNAs were mapped to human; 14 of these miRNAs were previously reported to be dysregulated in experimental or human CVD. We used an Ingenuity Pathway Analysis to integrate miRNA profiling and bioinformatics predictions to determine miRNA-regulated processes and genes potentially involved in fetal programming. We found a correlation between miRNA expression and putative gene targets involved in developmental disorders and CVD. Cellular death, growth, and proliferation were the most affected cellular functions in response to maternal obesity. Thus, the current study reveals significant alterations in cardiac miRNA expression in the fetus of obese baboons. The epigenetic modifications caused by adverse prenatal environment may represent one of the mechanisms underlying fetal programming of CVD.

Using proteomics to uncover extracellular matrix interactions during cardiac remodeling

The left ventricle (LV) responds to a myocardial infarction with an orchestrated sequence of events that result in fundamental changes to both the structure and function of the myocardium. This collection of responses is termed as LV remodeling. Myocardial ischemia resulting in necrosis is the initiating event that culminates in the formation of an extracellular matrix (ECM) rich infarct scar that replaces necrotic myocytes. While the cardiomyocyte is the major cell type that responds to ischemia, infiltrating leukocytes and cardiac fibroblasts coordinate the subsequent wound healing response. The matrix metalloproteinase family of enzymes regulates the inflammatory and ECM responses that modulate scar formation. Matridomics is the proteomic evaluation focused on ECM, while degradomics is the proteomic evaluation of proteases as well as their inhibitors and substrates. This review will summarize the use of proteomics to better understand matrix metalloproteinase roles in post myocardial infarction LV remodeling.

Microarray analysis of active cardiac remodeling genes in a familial hypertrophic cardiomyopathy mouse model rescued by a phospholamban knockout

Familial hypertrophic cardiomyopathy (FHC) is a disease characterized by ventricular hypertrophy, fibrosis, and aberrant systolic and/or diastolic function. Our laboratories have previously developed two mouse models that affect cardiac performance. One mouse model encodes an FHC-associated mutation in α-tropomyosin: Glu → Gly at amino acid 180, designated as Tm180. These mice display a phenotype that is characteristic of FHC, including severe cardiac hypertrophy with fibrosis and impaired physiological performance. The other model was a gene knockout of phospholamban (PLN KO), a regulator of calcium uptake in the sarcoplasmic reticulum of cardiomyocytes; these hearts exhibit hypercontractility with no pathological abnormalities. Previous work in our laboratories shows that when mice were genetically crossed between the PLN KO and Tm180, the progeny (PLN KO/Tm180) display a rescued hypertrophic phenotype with improved morphology and cardiac function. To understand the changes in gene expression that occur in these models undergoing cardiac remodeling (Tm180, PLN KO, PLN KO/Tm180, and nontransgenic control mice), we conducted microarray analyses of left ventricular tissue at 4 and 12 mo of age. Expression profiling reveals that 1,187 genes changed expression in direct response to the three genetic models. With these 1,187 genes, 11 clusters emerged showing normalization of transcript expression in the PLN KO/Tm180 hearts. In addition, 62 transcripts are highly involved in suppression of the hypertrophic phenotype. Confirmation of the microarray analysis was conducted by quantitative RT-PCR. These results provide insight into genes that alter expression during cardiac remodeling and are active during modulation of the cardiomyopathic phenotype.

SPARC regulates microgliosis and functional recovery following cortical ischemia

Secreted protein acidic rich in cysteine (SPARC) is a matricellular protein that modulates the activity of growth factors, cytokines, and extracellular matrix to play multiple roles in tissue development and repair, such as cellular adhesion, migration, and proliferation. Throughout the CNS, SPARC is highly localized in mature ramified microglia, but its role in microglia--in development or during response to disease or injury--is not understood. In the postnatal brain, immature amoeboid myeloid precursors only induce SPARC expression after they cease proliferation and migration, and transform into mature, ramified resting microglia. SPARC null/CX3CR1-GFP reporter mice reveal that SPARC regulates the distribution and branching of mature microglia, with significant differences between cortical gray and white matter in both controls and SPARC nulls. Following ischemic and excitotoxic lesion, reactive, hypertrophic microglia rapidly downregulate and release SPARC at the lesion, concomitant with reactive, hypertrophic perilesion astrocytes upregulating SPARC. After photothrombotic stroke in the forelimb sensorimotor cortex, SPARC nulls demonstrate enhanced microgliosis in and around the lesion site, which accompanies significantly enhanced functional recovery by 32 d after lesion. Microglia from SPARC nulls also intrinsically proliferate at a greater rate in vitro--an enhanced effect that can be rescued by the addition of exogenous SPARC. SPARC is thus a novel regulator of microglial proliferation and structure, and, in addition to regulating glioma progression, may play an important role in differently regulating the gray and white matter microglial responses to CNS lesion--and modulating behavioral recovery--after injury.

Thrombospondin-4, tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14: novel extracellular matrix modulating factors in cardiac remodelling

Cardiac remodelling is defined as changes in the size, shape, and function of the heart, which are most commonly caused by hypertension-induced left ventricular hypertrophy and myocardial infarction. Both neurohumoral and inflammatory factors have critical roles in the regulation of cardiac remodelling. A characteristic feature of cardiac remodelling is modification of the extracellular matrix (ECM), often manifested by fibrosis, a process that has vital consequences for the structure and function of the myocardium. In addition to established modulators of the ECM, the matricellular protein thrombospondin-4 (TSP-4) as well as the tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 has been recently shown to modulate cardiac ECM. TSP-4 null mice develop pronounced cardiac hypertrophy and fibrosis with defects in collagen maturation in response to pressure overload. TWEAK and Fn14 belong to the tumour necrosis factor superfamily of proinflammatory cytokines. Recently it was shown that elevated levels of circulating TWEAK via Fn14 critically affect the cardiac ECM, characterized by increasing fibrosis and cardiomyocyte hypertrophy in mice. Here we review the literature concerning the role of matricellular proteins and inflammation in cardiac ECM remodelling, with a special focus on TSP-4, TWEAK, and its receptor Fn14.

Global microRNA profiling of the mouse ventricles during development of severe hypertrophic cardiomyopathy and heart failure

MicroRNAs (miRNAs) regulate post-transcriptional gene expression during development and disease. We have determined the miRNA expression levels of early- and end-stage hypertrophic cardiomyopathy (HCM) in a severe, transgenic mouse model of the disease. Five miRNAs were differentially expressed at an early stage of HCM development. Time-course analysis revealed that decreased expression of miR-1 and miR-133a commences at a pre-disease stage, and precedes upregulation of target genes causal of cardiac hypertrophy and extracellular matrix remodelling, suggesting a role for miR-1 and miR-133a in early disease development. At end-stage HCM, 16 miRNA are dysregulated to form an expression profile resembling that of other forms of cardiac hypertrophy, suggesting common responses. Analysis of the mRNA transcriptome revealed that miRNAs potentially target 15.7% upregulated and 4.8% downregulated mRNAs at end-stage HCM, and regulate mRNAs associated with cardiac hypertrophy and electrophysiology, calcium signalling, fibrosis, and the TGF-β signalling pathway. Collectively, these results define the miRNA expression signatures during development and progression of severe HCM and highlight critical miRNA regulated gene networks that are involved in disease pathogenesis.

A thrombospondin-dependent pathway for a protective ER stress response

Thrombospondin (Thbs) proteins are induced in sites of tissue damage or active remodeling. The endoplasmic reticulum (ER) stress response is also prominently induced with disease where it regulates protein production and resolution of misfolded proteins. Here we describe a function for Thbs as ER-resident effectors of an adaptive ER stress response. Thbs4 cardiac-specific transgenic mice were protected from myocardial injury, whereas Thbs4(-/-) mice were sensitized to cardiac maladaptation. Thbs induction produced a unique profile of adaptive ER stress response factors and expansion of the ER and downstream vesicles. Thbs bind the ER lumenal domain of activating transcription factor 6α (Atf6α) to promote its nuclear shuttling. Thbs4(-/-) mice showed blunted activation of Atf6α and other ER stress-response factors with injury, and Thbs4-mediated protection was lost upon Atf6α deletion. Hence, Thbs can function inside the cell during disease remodeling to augment ER function and protect through a mechanism involving regulation of Atf6α.

Matricellular proteins in cardiac adaptation and disease

The term matricellular proteins describes a family of structurally unrelated extracellular macromolecules that, unlike structural matrix proteins, do not play a primary role in tissue architecture, but are induced following injury and modulate cell-cell and cell-matrix interactions. When released to the matrix, matricellular proteins associate with growth factors, cytokines, and other bioactive effectors and bind to cell surface receptors transducing signaling cascades. Matricellular proteins are upregulated in the injured and remodeling heart and play an important role in regulation of inflammatory, reparative, fibrotic and angiogenic pathways. Thrombospondin (TSP)-1, -2, and -4 as well as tenascin-C and -X secreted protein acidic and rich in cysteine (SPARC), osteopontin, periostin, and members of the CCN family (including CCN1 and CCN2/connective tissue growth factor) are involved in a variety of cardiac pathophysiological conditions, including myocardial infarction, cardiac hypertrophy and fibrosis, aging-associated myocardial remodeling, myocarditis, diabetic cardiomyopathy, and valvular disease. This review discusses the properties and characteristics of the matricellular proteins and presents our current knowledge on their role in cardiac adaptation and disease. Understanding the role of matricellular proteins in myocardial pathophysiology and identification of the functional domains responsible for their actions may lead to design of peptides with therapeutic potential for patients with heart disease.

The matricellular protein thrombospondin-1 globally regulates cardiovascular function and responses to stress via CD47

Matricellular proteins play diverse roles in modulating cell behavior by engaging specific cell surface receptors and interacting with extracellular matrix proteins, secreted enzymes, and growth factors. Studies of such interactions involving thrombospondin-1 have revealed several physiological functions and roles in the pathogenesis of injury responses and cancer, but the relatively mild phenotypes of mice lacking thrombospondin-1 suggested that thrombospondin-1 would not be a central player that could be exploited therapeutically. Recent research focusing on signaling through its receptor CD47, however, has uncovered more critical roles for thrombospondin-1 in acute regulation of cardiovascular dynamics, hemostasis, immunity, and mitochondrial homeostasis. Several of these functions are mediated by potent and redundant inhibition of the canonical nitric oxide pathway. Conversely, elevated tissue thrombospondin-1 levels in major chronic diseases of aging may account for the deficient nitric oxide signaling that characterizes these diseases, and experimental therapeutics targeting CD47 show promise for treating such chronic diseases as well as acute stress conditions that are associated with elevated thrombospondin-1 expression.

Proteomics Analysis of Cardiac Extracellular Matrix Remodeling in a Porcine Model of Ischemia/Reperfusion Injury

Background—

After myocardial ischemia, extracellular matrix (ECM) deposition occurs at the site of the focal injury and at the border region.

Methods and Results—

We have applied a novel proteomic method for the analysis of ECM in cardiovascular tissues to a porcine model of ischemia/reperfusion injury. ECM proteins were sequentially extracted and identified by liquid chromatography tandem mass spectrometry. For the first time, ECM proteins such as cartilage intermediate layer protein 1, matrilin-4, extracellular adipocyte enhancer binding protein 1, collagen α-1(XIV), and several members of the small leucine-rich proteoglycan family, including asporin and prolargin, were shown to contribute to cardiac remodeling. A comparison in 2 distinct cardiac regions (the focal injury in the left ventricle and the border region close to the occluded coronary artery) revealed a discordant regulation of protein and mRNA levels; although gene expression for selected ECM proteins was similar in both regions, the corresponding protein levels were much higher in the focal lesion. Further analysis based on >100 ECM proteins delineated a signature of early- and late-stage cardiac remodeling with transforming growth factor-β1 signaling at the center of the interaction network. Finally, novel cardiac ECM proteins identified by proteomics were validated in human left ventricular tissue acquired from ischemic cardiomyopathy patients at cardiac transplantation.

Conclusion—

Our findings reveal a biosignature of early- and late-stage ECM remodeling after myocardial ischemia/reperfusion injury, which may have clinical utility as a prognostic marker and modifiable target for drug discovery.

Thrombospondins as key regulators of synaptogenesis in the central nervous system

Thrombospondins (TSPs) are a family of large, oligomeric multidomain glycoproteins that participate in a variety of biological functions as part of the extracellular matrix (ECM). Through their associations with a number of binding partners, TSPs mediate complex cell-cell and cell-matrix interactions in such diverse processes as angiogenesis, inflammation, osteogenesis, cell proliferation, and apoptosis. It was recently shown in the developing central nervous system (CNS) that TSPs promote the formation of new synapses, which are the unique cell-cell adhesions between neurons in the brain. This increase in synaptogenesis is mediated by the interaction between astrocyte-secreted TSPs and their neuronal receptor, calcium channel subunit α2δ-1. The cellular and molecular mechanisms that underlie induction of synaptogenesis via this interaction are yet to be fully elucidated. This review will focus on what is known about TSP and synapse formation during development, possible roles for TSP following brain injury, and what the previously established actions of TSP in other biological tissues may tell us about the mechanisms underlying TSP's functions in CNS synaptogenesis.

Therapies using anti-angiogenic peptide mimetics of thrombospondin-1

INTRODUCTION

The role of hrombospondin-1 (TSP1) as a major endogenous angiogenesis inhibitor has been confirmed by numerous studies and subsequent mechanistic discoveries. It has yielded a new class of potential drugs against cancer and other angiogenesis-driven diseases.

AREAS COVERED

An overview of TSP1 functions and molecular mechanisms, including regulation and signaling. Functions in endothelial and non-endothelial cells, with emphasis on the role of TSP1 in the regulation of angiogenesis and inflammation. The utility of duplicating these activities for drug discovery. Past and current literature on endogenous TSP1 and its role in the progression of cancer and non-cancerous pathological conditions is summarized, as well as the research undertaken to identify and optimize short bioactive peptides derived from the two TSP1 anti-angiogenic domains, which bind CD47 and CD36 cell surface receptors. Lastly, there is an overview of the efficacy of some of these peptides in pre-clinical and clinical models of angiogenesis-dependent disease.

EXPERT OPINION

It is concluded that TSP1-derived peptides and peptide mimetics hold great promise as future agents for the treatment of cancer and other diseases driven by excessive angiogenesis. They may fulfill unmet medical needs including neovascular ocular disease and the diseases of the female reproductive tract including ovarian cancer.

Matricellular proteins: new molecular targets to prevent heart failure

Matricellular proteins are highly expressed in reparative responses to pressure and volume overload, ischemia, oxidative stress after myocardial injury, and modulate the inflammatory and fibrotic process in ventricular remodeling, which leads to cardiac dysfunction and eventually overt heart failure. Generally, matricellular proteins loosen strong adhesion of cardiomyocytes to extracellular matrix, which would help cells to move for rearrangement and allow inflammatory cells and capillary vessels to spread during tissue remodeling. Among matricellular proteins, osteopontin (OPN) and tenascin-C (TN-C) are de-adhesion proteins and upregulate the expression and activity of matrix metalloproteinases. These matricellular proteins could be key molecules to diagnose cardiac remodeling and also might be targets for the prevention of adverse ventricular remodeling. This review provides an overview of the role of matricellular proteins such as OPN and TN-C in cardiac function and remodeling, as determined by both in basic and in clinical studies.

Metabolic characterization of volume overload heart failure due to aorto-caval fistula in rats

Metabolic interactions between adipose tissue and the heart may play an active role in progression of heart failure (HF). The aim of the study was to examine changes in myocardial and adipose tissue metabolism and gene expression in a rat HF model induced by chronic volume overload. HF was induced by volume overload from aorto-caval fistula (ACF) in 3-month-old male Wistar rats and animals were studied in the phase of decompensated HF (22nd week). HF rats showed marked eccentric cardiac hypertrophy, pulmonary congestion, increased LV end-diastolic pressure, and intraabdominal fat depletion. HF rats had preserved glucose tolerance, but increased circulating free fatty acids (FFA) and attenuated insulin response during oral glucose challenge. Isolated organ studies showed preserved responsiveness of adipose tissue lipolysis and lipogenesis to epinephrine and insulin in ACF. The heart of HF animals had markedly reduced triglyceride content (almost to half of controls), attenuated anti-oxidative reserve (GSH/GSSG), upregulated HF markers (ANP, periostin, thrombospondin-4), specific signaling pathways (Wnt, TGF-β), and downregulated enzymes of mitochondrial fatty acid oxidation, citric acid cycle, and respiratory chain. Adipose tissue transcription profiling showed upregulated receptor for gastric inhibitory polypeptide. In conclusion, ACF-induced HF model displays several deregulations of systemic metabolism. Despite elevation of systemic FFAs, myocardial triglycerides are low and insulin levels are attenuated, arguing against a role of lipotoxicity or insulin resistance in this model. Attenuated postprandial insulin response and relative lack of its antilipolytic effects may facilitate intraabdominal fat depletion observed in ACF-HF animals.

Transforming growth factor (TGF)-β signaling in cardiac remodeling

Myocardial TGF-β expression is upregulated in experimental models of myocardial infarction and cardiac hypertrophy, and in patients with dilated or hypertrophic cardiomyopathy. Through its effects on cardiomyocytes, mesenchymal and immune cells, TGF-β plays an important role in the pathogenesis of cardiac remodeling and fibrosis. TGF-β overexpression in the mouse heart is associated with fibrosis and hypertrophy. Endogenous TGF-β plays an important role in the pathogenesis of cardiac fibrotic and hypertrophic remodeling, and modulates matrix metabolism in the pressure-overloaded heart. In the infarcted heart, TGF-β deactivates inflammatory macrophages, while promoting myofibroblast transdifferentiation and matrix synthesis through Smad3-dependent pathways. Thus, TGF-β may serve as the "master switchThis article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure". for the transition of the infarct from the inflammatory phase to formation of the scar. Because of its crucial role in cardiac remodeling, the TGF-β system may be a promising therapeutic target for patients with heart failure. However, efforts to translate these concepts into therapeutic strategies, in order to prevent cardiac hypertrophy and fibrosis, are hampered by the complex, pleiotropic and diverse effects of TGF-β signaling, by concerns regarding deleterious actions of TGF-β inhibition and by the possibility of limited benefit in patients receiving optimal treatment with ACE inhibitors and β-adrenergic blockers. Dissection of the pathways responsible for specific TGF-β-mediated actions and understanding of cell-specific actions of TGF-β are needed to design optimal therapeutic strategies. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".

Role of matricellular proteins in cardiac tissue remodeling after myocardial infarction

After onset of myocardial infarction (MI), the left ventricle (LV) undergoes a continuum of molecular, cellular, and extracellular responses that result in LV wall thinning, dilatation, and dysfunction. These dynamic changes in LV shape, size, and function are termed cardiac remodeling. If the cardiac healing after MI does not proceed properly, it could lead to cardiac rupture or maladaptive cardiac remodeling, such as further LV dilatation and dysfunction, and ultimately death. Although the precise molecular mechanisms in this cardiac healing process have not been fully elucidated, this process is strictly coordinated by the interaction of cells with their surrounding extracellular matrix (ECM) proteins. The components of ECM include basic structural proteins such as collagen, elastin and specialized proteins such as fibronectin, proteoglycans and matricellular proteins. Matricellular proteins are a class of non-structural and secreted proteins that probably exert regulatory functions through direct binding to cell surface receptors, other matrix proteins, and soluble extracellular factors such as growth factors and cytokines. This small group of proteins, which includes osteopontin, thrombospondin-1/2, tenascin, periostin, and secreted protein, acidic and rich in cysteine, shows a low level of expression in normal adult tissue, but is markedly upregulated during wound healing and tissue remodeling, including MI. In this review, we focus on the regulatory functions of matricellular proteins during cardiac tissue healing and remodeling after MI.