Cellular mechanisms of tissue fibrosis. 2. Contributory pathways leading to myocardial fibrosis: moving beyond collagen expression

Small Intestinal Submucosa Hydrogel Loaded With Gastrodin for the Repair of Achilles Tendinopathy

Achilles tendinopathy (AT) is an injury caused by overuse of the Achilles tendon or sudden force on the Achilles tendon, with a considerable inflammatory infiltrate. As Achilles tendinopathy progresses, inflammation and inflammatory factors affect the remodeling of the extracellular matrix (ECM) of the tendon. Gastrodin(Gas), the main active ingredient of Astrodia has anti-inflammatory, antioxidant, and anti-apoptotic properties. The small intestinal submucosa (SIS) is a naturally decellularized extracellular matrix(dECM)material and has a high content of growth factors as well as good biocompatibility. However, the reparative effects of SIS and Gas on Achilles tendinopathy and their underlying mechanisms remain unknown. Here, it is found that SIS hydrogel loaded with gastrodin restored the mechanical strength of the Achilles tendon, facilitated ECM remodeling, and restored ordered collagen arrangement by promoting the translocation of protein synthesis. It also decreases the expression of inflammatory factors and reduces the infiltration of inflammatory cells by inhibiting the NF-κB signaling pathway. It is believed that through further research, Gas + SIS may be used in the future for the treatment of Achilles tendinopathy and other Achilles tendon injury disorders.

A soft robotic sleeve mimicking the haemodynamics and biomechanics of left ventricular pressure overload and aortic stenosis

Preclinical models of aortic stenosis can induce left ventricular pressure overload and coarsely control the severity of aortic constriction. However, they do not recapitulate the haemodynamics and flow patterns associated with the disease. Here we report the development of a customizable soft robotic aortic sleeve that can mimic the haemodynamics and biomechanics of aortic stenosis. By allowing for the adjustment of actuation patterns and blood-flow dynamics, the robotic sleeve recapitulates clinically relevant haemodynamics in a porcine model of aortic stenosis, as we show via in vivo echocardiography and catheterization studies, and a combination of in vitro and computational analyses. Using in vivo and in vitro magnetic resonance imaging, we also quantified the four-dimensional blood-flow velocity profiles associated with the disease and with bicommissural and unicommissural defects re-created by the robotic sleeve. The design of the sleeve, which can be adjusted on the basis of computed tomography data, allows for the design of patient-specific devices that may guide clinical decisions and improve the management and treatment of patients with aortic stenosis.

Implications of enigmatic transglutaminase 2 (TG2) in cardiac diseases and therapeutic developments

Cardiac diseases are the leading cause of mortality and morbidity worldwide. Mounting evidence suggests that transglutaminases (TGs), tissue TG (TG2) in particular, are involved in numerous molecular responses underlying the pathogenesis of cardiac diseases. The TG family has several intra- and extracellular functions in the human body, including collagen cross-linking, angiogenesis, cell growth, differentiation, migration, adhesion as well as survival. TGs are thiol- and calcium-dependent acyl transferases that catalyze the formation of a covalent bond between the γ-carboxamide group of a glutamine residue and an amine group, thus increasing the stability, rigidity, and stiffness of the myocardial extracellular matrix (ECM). Excessive accumulation of cross-linked collagen leads to increase myocardial stiffness and fibrosis. Beyond TG2 extracellular protein cross-linking action, mounting evidence suggests that this pleiotropic TG isozyme may also promote fibrotic diseases through cell survival and profibrotic pathway activation at the signaling, transcriptional and translational levels. Due to its multiple functions and localizations, TG2 fulfils critical yet incompletely understood roles in myocardial fibrosis and associated heart diseases, such as cardiac hypertrophy, heart failure, and age-related myocardial stiffness under several conditions. This review summarizes current knowledge and existing gaps regarding the ECM-dependent and ECM-independent roles of TG2 and highlights the therapeutic prospects of targeting TG2 to treat cardiac diseases.

Inflammation-induced left ventricular fibrosis is partially mediated by tumor necrosis factor-α

OBJECTIVE

To determine the mechanisms of inflammation-induced left ventricular (LV) remodeling and effects of blocking circulating tumor necrosis factor alpha (TNF-α) in a model of systemic inflammation.

METHODS

Seventy Sprague-Dawley rats were divided into three groups: the control group, the collagen-induced arthritis (CIA) group, and the anti-TNF-α group. Inflammation was induced in the CIA and anti-TNF-α groups. Following the onset of arthritis, the anti-TNF-α group received the TNF-α inhibitor, etanercept, for 6 weeks. LV geometry and function were assessed with echocardiography. Circulating inflammatory markers were measured by ELISA and LV gene expression was assessed by comparative TaqMan® polymerase chain reaction.

RESULTS

The LV relative gene expression of pro-fibrotic genes, transforming growth factor β (TGFβ) (p = 0.03), collagen I (Col1) (p < 0.0001), and lysyl oxidase (LOX) (p = 0.002), was increased in the CIA group compared with controls, consistent with increased relative wall thickness (p = 0.0009). Col1 and LOX expression in the anti-TNF-α group were similar to controls (both, p > 0.05) and tended to be lower compared to the CIA group (p = 0.06 and p = 0.08, respectively), and may, in part, contribute to the decreased relative wall thickness in the anti-TNF-α group compared to the CIA group (p = 0.03). In the CIA group, the relative gene expression of matrix metalloproteinase 2 (MMP2) and MMP9 was increased compared to control (p = 0.04) and anti-TNF-α (p < 0.0001) groups, respectively.

CONCLUSION

Chronic systemic inflammation induces fibrosis and dysregulated LV extracellular matrix remodeling by increasing local cardiac pro-fibrotic gene expression, which is partially mediated by TNF-α. Inflammation-induced LV diastolic dysfunction is likely independent of myocardial fibrosis.

Epigenetic Modulation of Radiation-Induced Diacylglycerol Kinase Alpha Expression Prevents Pro-Fibrotic Fibroblast Response

Simple Summary

To reduce long-term fibrosis risk after radiotherapy, we demonstrated with different experimental approaches that modulation of the epigenetic pattern at the DGKA enhancer can attenuate pro-fibrotic reactions in human fibroblasts. We used (epi)genomic editing of the DGKA enhancer and administration of various epigenetic drugs and were able to modulate radiation-induced expression of DGKA and pro-fibrotic collagens. Based on our results, clinical application of bromodomain inhibitors will open promising ways to epigenetically modulate DGKA expression and might provide novel therapeutic options to prevent or even reverse radiotherapy-induced fibrotic reactions.

Abstract

Radiotherapy, a common component in cancer treatment, can induce adverse effects including fibrosis in co-irradiated tissues. We previously showed that differential DNA methylation at an enhancer of diacylglycerol kinase alpha (DGKA) in normal dermal fibroblasts is associated with radiation-induced fibrosis. After irradiation, the transcription factor EGR1 is induced and binds to the hypomethylated enhancer, leading to increased DGKA and pro-fibrotic marker expression. We now modulated this DGKA induction by targeted epigenomic and genomic editing of the DGKA enhancer and administering epigenetic drugs. Targeted DNA demethylation of the DGKA enhancer in HEK293T cells resulted in enrichment of enhancer-related histone activation marks and radiation-induced DGKA expression. Mutations of the EGR1-binding motifs decreased radiation-induced DGKA expression in BJ fibroblasts and caused dysregulation of multiple fibrosis-related pathways. EZH2 inhibitors (GSK126, EPZ6438) did not change radiation-induced DGKA increase. Bromodomain inhibitors (CBP30, JQ1) suppressed radiation-induced DGKA and pro-fibrotic marker expression. Similar drug effects were observed in donor-derived fibroblasts with low DNA methylation. Overall, epigenomic manipulation of DGKA expression may offer novel options for a personalized treatment to prevent or attenuate radiotherapy-induced fibrosis.

Excessive fibroblast growth factor 23 promotes renal fibrosis in mice with type 2 cardiorenal syndrome

Cardiorenal syndrome (CRS) has a high mortality, but its pathogenesis remains elusive. Fibroblast growth factor 23 (FGF23) is increased in both renal dysfunction and cardiac dysfunction, and FGF receptor 4 (FGFR4) has been identified as a receptor for FGF23. Deficiency of FGF23 causes growth retardation and shortens the lifespan, but it is unclear whether excess FGF23 is detrimental in CRS. This study sought to investigate whether FGF23 plays an important role in CRS-induced renal fibrosis. A mouse model of CRS was created by surgical myocardial infarction for 12 weeks. CRS mice showed a significant increase of circulatory and renal FGF23 protein levels, as well as an upregulation of p-GSK, active-β-catenin, TGF-β, collagen I and vimentin, a downregulation of renal Klotho expression and induction of cardiorenal dysfunction and cardiorenal fibrosis. These changes were enhanced by cardiac overexpression of FGF23 and attenuated by FGF receptor blocker PD173074 or β-catenin blocker IGC001. In fibroblasts (NRK-49F), expression of FGFR4 rather than Klotho was detected. Recombinant FGF23 upregulated the expression of p-GSK, active-β-catenin, TGF-β, collagen I and vimentin proteins. These changes were attenuated by FGFR4 blockade with BLU9931 or β-catenin blockade with IGC001. We concluded that FGF23 promotes CRS-induced renal fibrosis mediated by partly activating FGFR4/β-catenin signaling pathway.

Changes in Myocardial Microstructure and Mechanics With Progressive Left Ventricular Pressure Overload

This study assessed the regional changes in myocardial geometry, microstructure, mechanical behavior, and properties that occur in response to progressive left ventricular pressure overload (LVPO) in a large animal model. Using an index of local biomechanical function at early onset of LVPO allowed for prediction of the magnitude of left ventricular chamber stiffness (Kc) and left atrial area at LVPO late timepoints. Our study found that LV myocardial collagen content alone was insufficient to identify mechanisms for LV myocardial stiffness with progression to heart failure with preserved ejection fraction (HFpEF). Serial assessment of regional biomechanical function might hold value in monitoring the natural history and progression of HFpEF, which would allow evaluation of novel therapeutic approaches.

Ski drives an acute increase in MMP-9 gene expression and release in primary cardiac myofibroblasts

Many etiologies of heart disease are characterized by expansion and remodeling of the cardiac extracellular matrix (ECM or matrix) which results in cardiac fibrosis. Cardiac fibrosis is mediated in cardiac fibroblasts by TGF‐β₁/R‐Smad2/3 signaling. Matrix component proteins are synthesized by activated resident cardiac fibroblasts known as myofibroblasts (MFB). These events are causal to heart failure with diastolic dysfunction and reduced cardiac filling. We have shown that exogenous Ski, a TGF‐β₁/Smad repressor, localizes in the cellular nucleus and deactivates cardiac myofibroblasts. This deactivation is associated with reduction of myofibroblast marker protein expression in vitro, including alpha smooth muscle actin (α‐SMA) and extracellular domain‐A (ED‐A) fibronectin. We hypothesize that Ski also acutely regulates MMP expression in cardiac MFB. While acute Ski overexpression in cardiac MFB in vitro was not associated with any change in intracellular MMP‐9 protein expression versus LacZ‐treated controls,exogenous Ski caused elevated MMP‐9 mRNA expression and increased MMP‐9 protein secretion versus controls. Zymographic analysis revealed increased MMP‐9‐specific gelatinase activity in myofibroblasts overexpressing Ski versus controls. Moreover, Ski expression was attended by reduced paxillin and focal adhesion kinase phosphorylation (FAK ‐ Tyr 397) versus controls. As myofibroblasts are hypersecretory and less motile relative to fibroblasts, Ski's reduction of paxillin and FAK expression may reflect the relative deactivation of myofibroblasts. Thus, in addition to its known antifibrotic effects, Ski overexpression elevates expression and extracellular secretion/release of MMP‐9 and thus may facilitate internal cytoskeletal remodeling as well as extracellular ECM components. Further, as acute TGF‐β₁ treatment of primary cardiac MFB is known to cause rapid translocation of Ski to the nucleus, our data support an autoregulatory role for Ski in mediating cardiac ECM accumulation.

Reprint of "The complex dynamics of myocardial interstitial fibrosis in heart failure. Focus on collagen cross-linking"

Myocardial interstitial fibrosis (MIF) is a common finding in heart failure (HF) patients, both with preserved and reduced ejection fraction, as well as in HF animal models. MIF is associated with impaired cardiac function and worse clinical outcome. The impact of MIF is influenced not only by the quantity but also by changes in the quality of collagen fibers and in the extracellular matrix components, such as a shift in collagen types proportion, increased fibronectin polymerization and increased degree of collagen cross-linking (CCL). In particular, CCL, a process that renders collagen fibers stiffer and more resistant to degradation, is increased both in patients and animal models of HF. Importantly, in HF patients increased cardiac CCL is directly associated with increased left ventricular stiffness and a higher risk of hospitalization for HF. The aim of this review is to address the complexity of MIF in HF, focusing on CCL.

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.

The complex dynamics of myocardial interstitial fibrosis in heart failure. Focus on collagen cross-linking

Myocardial interstitial fibrosis (MIF) is a common finding in heart failure (HF) patients, both with preserved and reduced ejection fraction, as well as in HF animal models. MIF is associated with impaired cardiac function and worse clinical outcome. The impact of MIF is influenced not only by the quantity but also by changes in the quality of collagen fibers and in the extracellular matrix components, such as a shift in collagen types proportion, increased fibronectin polymerization and increased degree of collagen cross-linking (CCL). In particular, CCL, a process that renders collagen fibers stiffer and more resistant to degradation, is increased both in patients and animal models of HF. Importantly, in HF patients increased cardiac CCL is directly associated with increased left ventricular stiffness and a higher risk of hospitalization for HF. The aim of this review is to address the complexity of MIF in HF, focusing on CCL.

Local production of tenascin-C acts as a trigger for monocyte/macrophage recruitment that provokes cardiac dysfunction

Aims

Tenascin-C (TNC) is an endogenous danger signal molecule strongly associated with inflammatory diseases and with poor outcome in patients with cardiomyopathies. Its function within pathological cardiac tissue during pressure overload remains poorly understood.

Methods and results

We showed that TNC accumulates after 1 week of transverse aortic constriction (TAC) in the heart of 12-week-old male mice. By cross bone marrow transplantation experiments, we determined that TNC deposition relied on cardiac cells and not on haematopoietic cells. The expression of TNC induced by TAC, or by administration of a recombinant lentivector coding for TNC, triggered a pro-inflammatory cardiac microenvironment, monocyte/macrophage (MO/MΦ) accumulation, and systolic dysfunction. TNC modified macrophage polarization towards the pro-inflammatory phenotype and stimulated RhoA/Rho-associated protein kinase (ROCK) pathways to promote mesenchymal to amoeboid transition that enhanced macrophage migration into fibrillar collagen matrices. The amplification of inflammation and MO/MΦ recruitment by TNC was abrogated by genetic invalidation of TNC in knockout mice. These mice showed less ventricular remodelling and an improved cardiac function after TAC as compared with wild-type mice.

Conclusions

By promoting a pro-inflammatory microenvironment and macrophage migration, TNC appears to be a key factor to enable the MO/MΦ accumulation within fibrotic hearts leading to cardiac dysfunction. As TNC is highly expressed during inflammation and sparsely during the steady state, its inhibition could be a promising therapeutic strategy to control inflammation and immune cell infiltration in heart disease.

Left ventricular remodelling in chronic primary mitral regurgitation: implications for medical therapy

Surgical repair or replacement of the mitral valve is currently the only recommended therapy for severe primary mitral regurgitation. The chronic elevation of wall stress caused by the resulting volume overload leads to structural remodelling of the muscular, vascular and extracellular matrix components of the myocardium. These changes are initially compensatory but in the long term have detrimental effects, which ultimately result in heart failure. Understanding the changes that occur in the myocardium due to volume overload at the molecular and cellular level may lead to medical interventions, which potentially could delay or prevent the adverse left ventricular remodelling associated with primary mitral regurgitation. The pathophysiological changes involved in left ventricular remodelling in response to chronic primary mitral regurgitation and the evidence for potential medical therapy, in particular beta-adrenergic blockers, are the focus of this review.

Protective role of Gentianella acuta on isoprenaline induced myocardial fibrosis in rats via inhibition of NF-κB pathway

Gentianella acuta (Michx.) Hulten (G. acuta) has been widely used in Mongolian medicines for the treatment of cardiovascular diseases in Ewenki and Oroqen, Inner Mongolia autonomous region, China. The aim of this study was to investigate the effects and related mechanism of G. acuta on isoproterenol (ISO)-induced oxidative stress, fibrosis, and myocardial damage in rats. Male Sprague Dawley rats were randomly divided into the normal control group, ISO induced group and ISO+G. acuta treatment group. Rats were administered with ISO subcutaneously (5 mg/kg/day) for 7 days, and were orally administered simultaneously with aqueous extracts of G. acuta for 21 days. This investigation showed G. acuta treatment ameliorated cardiac structural disorder, excessive collagenous fiber accumulation and cardiac malfunction. Compared with the ISO induced model group, G. acuta treatment increased superoxide dismutase (SOD) activities and glutathione (GSH) level, prevented the rise of malondialdehyde (MDA), and decreased hydroxyproline contents in the heart tissues. Moreover, G. acuta reduced the expression of transforming growth factor β1 (TGF-β1) and connective tissue growth factor (CTGF), and inhibited the expression and activation of NF-κB-P65 in myocardial tissues. These results suggested that G. acuta protects against ISO-induced cardiac malfunction probably by preventing oxidative stress, and fibrosis, and the mechanism might be through inhibiting NF-κB pathway.

Modernized Classification of Cardiac Antiarrhythmic Drugs

BACKGROUND

Among his major cardiac electrophysiological contributions, Miles Vaughan Williams (1918-2016) provided a classification of antiarrhythmic drugs that remains central to their clinical use.

METHODS

We survey implications of subsequent discoveries concerning sarcolemmal, sarcoplasmic reticular, and cytosolic biomolecules, developing an expanded but pragmatic classification that encompasses approved and potential antiarrhythmic drugs on this centenary of his birth.

RESULTS

We first consider the range of pharmacological targets, tracking these through to cellular electrophysiological effects. We retain the original Vaughan Williams Classes I through IV but subcategorize these divisions in light of more recent developments, including the existence of Na+ current components (for Class I), advances in autonomic (often G protein-mediated) signaling (for Class II), K+ channel subspecies (for Class III), and novel molecular targets related to Ca2+ homeostasis (for Class IV). We introduce new classes based on additional targets, including channels involved in automaticity, mechanically sensitive ion channels, connexins controlling electrotonic cell coupling, and molecules underlying longer-term signaling processes affecting structural remodeling. Inclusion of this widened range of targets and their physiological sequelae provides a framework for a modernized classification of established antiarrhythmic drugs based on their pharmacological targets. The revised classification allows for the existence of multiple drug targets/actions and for adverse, sometimes actually proarrhythmic, effects. The new scheme also aids classification of novel drugs under investigation.

CONCLUSIONS

We emerge with a modernized classification preserving the simplicity of the original Vaughan Williams framework while aiding our understanding and clinical management of cardiac arrhythmic events and facilitating future developments in this area.

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.

Cardiac fibrosis in regenerative medicine: destroy to rebuild

The major limitations for cardiac regeneration in patients after myocardial infarction (MI) are the wide loss of cardiomyocytes and the adverse structural alterations of extracellular matrix (ECM). Cardiac fibroblast differentiation into myofibroblasts (MFB) leads to a huge deposition of ECM and to the subsequent loss of ventricular structural integrity. All these molecular events depict the fundamental features at the basis of the post-MI fibrosis and deserve in depth cellular and molecular studies to fill the gap in the clinical practice. Indeed, to date, there are no effective therapeutic approaches to limit the post-MI massive fibrosis development. In this review we describe the involvement of integrins and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)/ADAMTS-like (ADAMTSL) proteins in cardiac reparative pro-fibrotic response after MI, proposing some of them as novel potential pharmacological tools.

Abundance, localization, and functional correlates of the advanced glycation end-product carboxymethyl lysine in human myocardium

Advanced glycation end‐products (AGEs) play a role in the pathophysiology of diabetes mellitus (DM) and possibly hypertension (HTN). In experimental DM, AGEs accumulate in myocardium. Little is known about AGEs in human myocardium. We quantified abundance, localization, and functional correlates of the AGE carboxymethyl lysine (CML) in left ventricular (LV) myocardium from patients undergoing coronary bypass grafting (CBG). Immunoelectron microscopy was used to quantify CML in epicardial biopsies from 98 patients (71 M, 27 F) with HTN, HTN + DM or neither (controls), all with normal LV ejection fraction. Myofilament contraction‐relaxation function was measured in demembranated myocardial strips. Echocardiography was used to quantify LV structure and function. We found that CML was abundant within cardiomyocytes, but minimally associated with extracellular collagen. CML counts/μm² were 14.7% higher in mitochondria than the rest of the cytoplasm (P < 0.001). There were no significant sex or diagnostic group differences in CML counts [controls 45.6 ± 3.6/μm² (±SEM), HTN 45.8 ± 3.6/μm², HTN + DM 49.3 ± 6.2/μm²; P = 0.85] and no significant correlations between CML counts and age, HgbA1c or myofilament function indexes. However, left atrial volume was significantly correlated with CML counts (r = 0.41, P = 0.004). We conclude that in CBG patients CML is abundant within cardiomyocytes but minimally associated with collagen, suggesting that AGEs do not directly modify the stiffness of myocardial collagen. Coexistent HTN or HTN + DM do not significantly influence CML abundance. The correlation of CML counts with LAV suggests an influence on diastolic function independent of HTN, DM or sex whose mechanism remains to be determined.

Tissue transglutaminase induction in the pressure-overloaded myocardium regulates matrix remodelling

Aims

Tissue transglutaminase (tTG) is induced in injured and remodelling tissues, and modulates cellular phenotype, while contributing to matrix cross-linking. Our study tested the hypothesis that tTG may be expressed in the pressure-overloaded myocardium, and may regulate cardiac function, myocardial fibrosis and chamber remodelling.

Methods and results

In order to test the hypothesis, wild-type and tTG null mice were subjected to pressure overload induced through transverse aortic constriction. Moreover, we used isolated cardiac fibroblasts and macrophages to dissect the mechanisms of tTG-mediated actions. tTG expression was upregulated in the pressure-overloaded mouse heart and was localized in cardiomyocytes, interstitial cells, and in the extracellular matrix. In contrast, expression of transglutaminases 1, 3, 4, 5, 6, 7 and FXIII was not induced in the remodelling myocardium. In vitro, transforming growth factor (TGF)-β1 stimulated tTG synthesis in cardiac fibroblasts and in macrophages through distinct signalling pathways. tTG null mice had increased mortality and enhanced ventricular dilation following pressure overload, but were protected from diastolic dysfunction. tTG loss was associated with a hypercellular cardiac interstitium, reduced collagen cross-linking, and with accentuated matrix metalloproteinase (MMP)2 activity in the pressure-overloaded myocardium. In vitro, tTG did not modulate TGF-β-mediated responses in cardiac fibroblasts; however, tTG loss was associated with accentuated proliferative activity. Moreover, when bound to the matrix, recombinant tTG induced synthesis of tissue inhibitor of metalloproteinases (TIMP)-1 through transamidase-independent actions.

Conclusions

Following pressure overload, endogenous tTG mediates matrix cross-linking, while protecting the remodelling myocardium from dilation by exerting matrix-preserving actions.

Na/K-ATPase signaling mediates miR-29b-3p regulation and cardiac fibrosis formation in mice with chronic kidney disease

The Na/K-ATPase is an important membrane ion transporter and a signaling receptor that is essential for maintaining normal cell function. The current study examined the role of Na/K-ATPase signaling in regulating miR-29b-3p, an anti-fibrotic microRNA, in a mouse chronic kidney disease (CKD) model (5/6th partial nephrectomy or PNx). The results showed that CKD induced significant reduction of miR-29b-3p expression in the heart tissue by activation of Src and NFκB signaling in these animals. To demonstrate the role of Na/K-ATPase signaling, we also performed the PNx surgery on Na/K-ATPase α1 heterozygous (α1+/-) mice, which expresses ~40% less Na/K-ATPase α1 compared to their wild type littermates (WT) and exhibits deficiency in Na/K-ATPase signaling. We found that CKD did not significantly change the miR-29b-3p expression in heart tissue from the α1+/- animals. We also found that CKD failed to activate Src and NFκB signaling in these animals. Using isolated cardiac fibroblasts from α1+/- mice and their WT littermates, we showed that ouabain, a specific Na/K-ATPase ligand, induces decreased miR-29b-3p expression in fibroblasts isolated from WT mice, but had no effect in cells from α1+/- mice. Inhibition of NFκB by Bay11-7082 prevented ouabain-induced miR-29b-3p reduction in WT fibroblasts. To further confirm the in vivo effect of Na/K-ATPase signaling in regulation of miR-29b-3p and cardiac fibrosis in CKD animals, we used pNaKtide, a Src inhibiting peptide derived from the sequence of Na/K-ATPase, to block the activation of Na/K-ATPase signaling. The result showed that pNaKtide injection significantly increased miR-29b-3p expression and mitigated the CKD-induced cardiac fibrosis in these animals. These results clearly demonstrated that Na/K-ATPase signaling is an important mediator in CKD that regulates miR-29b-3p expression and cardiac fibrosis, which provides a novel target for regulation of miR-29b-3p in CKD. We also demonstrate that antagonizing Na/K-ATPase signaling by pNaKtide can reduce organ fibrosis through the stimulation of tissue miR-29b-3p expression.

MicroRNA-30c suppresses the pro-fibrogenic effects of cardiac fibroblasts induced by TGF-β1 and prevents atrial fibrosis by targeting TGFβRII

Atrial fibrosis serves as an important contributor to atrial fibrillation (AF). Recent data have suggested that microRNA-30c (miR-30c) is involved in fibrotic remodelling and cancer development, but the specific role of miR-30c in atrial fibrosis remains unclear. The purpose of this study was to investigate the role of miR-30c in atrial fibrosis and its underlying mechanisms through in vivo and in vitro experiments. Our results indicate that miR-30c is significantly down-regulated in the rat abdominal aortic constriction (AAC) model and in the cellular model of fibrosis induced by transforming growth factor-β1 (TGF-β1). Overexpression of miR-30c in cardiac fibroblasts (CFs) markedly inhibits CF proliferation, differentiation, migration and collagen production, whereas decrease in miR-30c leads to the opposite results. Moreover, we identified TGFβRII as a target of miR-30c. Finally, transferring adeno-associated virus 9 (AAV9)-miR-30c into the inferior vena cava of rats attenuated fibrosis in the left atrium following AAC. These data indicate that miR-30c attenuates atrial fibrosis via inhibition of CF proliferation, differentiation, migration and collagen production by targeting TGFβRII, suggesting that miR-30c might be a novel potential therapeutic target for preventing atrial fibrosis.

Increased macrophage-derived SPARC precedes collagen deposition in myocardial fibrosis

Myocardial fibrosis and the resultant increases in left ventricular stiffness represent pivotal consequences of chronic pressure overload (PO) that impact both functional capacity and the rates of morbid and mortal events. However, the time course and cellular mechanisms that underlie PO-induced fibrosis have not been completely defined. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that has been shown to be required for insoluble collagen deposition and increased myocardial stiffness in response to PO in mice. As macrophages are associated with increases in fibrillar collagen, the hypothesis that macrophages represent a source of increased SPARC production in the PO myocardium was tested. The time course of changes in the myocardial macrophage population was compared with changes in procollagen type I mRNA, production of SPARC, fibrillar collagen accumulation, and diastolic stiffness. In PO hearts, mRNA encoding collagen type I was increased at 3 days, whereas increases in levels of total collagen protein did not occur until 1 wk and were followed by increases in insoluble collagen at 2 wk. Increases in muscle stiffness were not detected before increases in insoluble collagen content (>1 wk). Significant increases in myocardial macrophages that coincided with increased SPARC were found but did not coincide with increases in mRNA encoding collagen type I. Furthermore, immunohistochemistry and flow cytometry identified macrophages as a cellular source of SPARC. We conclude that myocardial macrophages play an important role in the time-dependent increases in SPARC that enhance postsynthetic collagen processing, insoluble collagen content, and myocardial stiffness and contribute to the development of fibrosis. NEW & NOTEWORTHY Myocardial fibrosis and the resultant increases in left ventricular and myocardial stiffness represent pivotal consequences of chronic pressure overload. In this study a murine model of cardiac fibrosis induced by pressure overload was used to establish a time course of collagen expression, collagen deposition, and cardiac macrophage expansion.

Endostatin Stimulates Proliferation and Migration of Myofibroblasts Isolated from Myocardial Infarction Model Rats

Myofibroblasts contribute to the healing of infarcted areas after myocardial infarction through proliferation, migration, and production of extracellular matrix (ECM). Expression of endostatin, a cleaved fragment of type XVIII collagen, increases in the heart tissue of an experimental myocardial infarction model. In the present study, we examined the effect of endostatin on the function of myofibroblasts derived from an infarcted area. The myocardial infarction model was created by ligating the left anterior descending artery in rats. Two weeks after the operation, α-smooth muscle actin (α-SMA)-positive myofibroblasts were isolated from the infarcted area. Endostatin significantly increased the proliferation and migration of myofibroblasts in vitro. On the other hand, endostatin had no effect on the production of type I collagen, a major ECM protein produced by myofibroblasts. Endostatin activated Akt and extracellular signal-regulated kinase (ERK), and the pharmacological inhibition of these signaling pathways suppressed the endostatin-induced proliferation and migration. A knockdown of the COL18A1 gene in the myocardial infarction model rats using small interference RNA (siRNA) worsened the cardiac function concomitant with wall thinning and decreased the α-SMA-positive myofibroblasts and scar formation compared with that of control siRNA-injected rats. In summary, we demonstrated for the first time that endostatin might be an important factor in the healing process after myocardial infarction through the activation of myofibroblasts.

Roles of SPARC in urothelial carcinogenesis, progression and metastasis

Secreted Protein Acidic and Rich in Cysteine (SPARC) is a matricellular glycoprotein that is implicated in myriad physiological and pathological conditions characterized by extensive remodeling and plasticity. The functions and disease association of SPARC in cancer is being increasingly appreciated as it plays multi-faceted contextual roles depending on the cancer type, cell of origin and the unique cancer milieu at both primary and metastatic sites. Herein we will review our current knowledge of the role of SPARC in the multistep cascades of urinary bladder carcinogenesis, progression and metastasis from preclinical models and clinical data and shine the light on its prognostic and therapeutic potentials.

Pneumonia as a cardiovascular disease

Community-acquired pneumonia (CAP) is an important cause of death around the globe. Up to 30% of patients admitted to hospital for CAP develop cardiovascular complications (i.e. new/worsening heart failure, new/worsening arrhythmias, myocardial infarctions and/or strokes), acutely and up to 10 years thereafter. Cardiac complications result from complex interactions between preexisting conditions, relative ischaemia, upregulation of the sympathetic system, systemic inflammation and direct pathogen-mediated damage to the cardiovascular system. The exact mechanisms underlying the direct host-pathogen interactions are of great interest to identify potential therapeutic and preventative targets for CAP. In this review, we summarize the epidemiological data, risk factors and the pathogen-driven cardiovascular damage affecting patients with CAP.

Severe Pneumococcal Pneumonia Causes Acute Cardiac Toxicity and Subsequent Cardiac Remodeling

RATIONALE

Up to one-third of patients hospitalized with pneumococcal pneumonia experience major adverse cardiac events (MACE) during or after pneumonia. In mice, Streptococcus pneumoniae can invade the myocardium, induce cardiomyocyte death, and disrupt cardiac function following bacteremia, but it is unknown whether the same occurs in humans with severe pneumonia.

OBJECTIVES

We sought to determine whether S. pneumoniae can (1) translocate the heart, (2) induce cardiomyocyte death, (3) cause MACE, and (4) induce cardiac scar formation after antibiotic treatment during severe pneumonia using a nonhuman primate (NHP) model.

METHODS

We examined cardiac tissue from six adult NHPs with severe pneumococcal pneumonia and three uninfected control animals. Three animals were rescued with antibiotics (convalescent animals). Electrocardiographic, echocardiographic, and serum biomarkers of cardiac damage were measured (troponin T, N-terminal pro-brain natriuretic peptide, and heart-type fatty acid binding protein). Histological examination included hematoxylin and eosin staining, immunofluorescence, immunohistochemistry, picrosirius red staining, and transmission electron microscopy. Immunoblots were used to assess the underlying mechanisms.

MEASUREMENTS AND MAIN RESULTS

Nonspecific ischemic alterations were detected by electrocardiography and echocardiography. Serum levels of troponin T and heart-type fatty acid binding protein were increased (P < 0.05) after pneumococcal infection in both acutely ill and convalescent NHPs. S. pneumoniae was detected in the myocardium of all NHPs with acute severe pneumonia. Necroptosis and apoptosis were detected in the myocardium of both acutely ill and convalescent NHPs. Evidence of cardiac scar formation was observed only in convalescent animals by transmission electron microscopy and picrosirius red staining.

CONCLUSIONS

S. pneumoniae invades the myocardium and induces cardiac injury with necroptosis and apoptosis, followed by cardiac scarring after antibiotic therapy, in an NHP model of severe pneumonia.

Humanin inhibits apoptosis in pituitary tumor cells through several signaling pathways including NF-κB activation

Humanin (HN) and Rattin (HNr), its homologous in the rat, are peptides with cytoprotective action in several cell types such as neurons, lymphocytes and testicular germ cells. Previously, we have shown that HNr is expressed in pituitary cells and that HN inhibited the apoptotic effect of TNF-α in both normal and tumor pituitary cells. The aim of the present study was to identify signaling pathways that mediate the antiapoptotic effect of HN in anterior pituitary cells from ovariectomized rats and in GH3 cells, a somatolactotrope cell line. We assessed the role of STAT3, JNK, Akt and MAPKs as well as proteins of the Bcl-2 family, previously implicated in the antiapoptotic effect of HN. We also evaluated the participation of NF-κB in the antiapoptotic action of HN. STAT3 inhibition reversed the inhibitory effect of HN on TNF-α-induced apoptosis in normal and pituitary tumor cells, indicating that STAT3 signaling pathway mediates the antiapoptotic effect of HN on pituitary cells. Inhibition of NF-κB pathway did not affect action of HN on normal anterior pituitary cells but blocked the cytoprotective effect of HN on TNF-α-induced apoptosis of GH3 cells, suggesting that the NF-κB pathway is involved in HN action in tumor pituitary cells. HN also induced NF-κB-p65 nuclear translocation in these cells. In pituitary tumor cells, JNK and MEK inhibitors also impaired HN cytoprotective action. In addition, HN increased Bcl-2 expression and decreased Bax mitochondrial translocation. Since HN expression in GH3 cells is higher than in normal pituitary cells, we may suggest that through multiple pathways HN could be involved in pituitary tumorigenesis.

Liquiritigenin attenuates cardiac injury induced by high fructose-feeding through fibrosis and inflammation suppression

Diabetes combined with cardiomyopathy is considered as an essential complication, showing diastolic persistently and causing cardiac injury, which is linked to fibrosis progression and inflammation response. Fibrosis and inflammation response are two markers for cardiomyopathy. Liquiritigenin is a flavanone, isolated from Radix glycyrrhiza, which exhibits various biological properties, including anti-cancer and anti-inflammatory activities. Here, in our study, the protective effects and anti-inflammatory activity of liquiritigenin were explored in mice and cardiac muscle cells treated by fructose to reveal the possible mechanism by which liquiritigenin attenuates cardiac injury. The mice were separated into five groups. The diabetic model of mouse was established with 30% high fructose feeding. Liquiritigenin dramatically reduced the lipid accumulation induced by high fructose diet. Compared to mice only treated with high fructose, mice in the presence of liquiritigenin after fructose feeding developed less cardiac fibrosis with lower levels of alpha smooth muscle-actin (α-SMA), Collagen type I, Collagen type II, TGF-β1 and Procol1a1. Additionally, liquiritigenin markedly down-regulated inflammatory cytokines secretion and phosphorylated NF-κB via inhibiting IKKα/IκBα signaling pathway. Our results indicate that liquiritigenin has a protective role in high fructose feeding-triggered cardiac injury through fibrosis and inflammation response suppression by inactivating NF-κB signaling pathway. Thus, liquiritigenin may be a potential candidate for diabetes-associated cardiac injury.

Effect of Phosphatase and Tensin Homologue on Chromosome 10 on Angiotensin II-Mediated Proliferation, Collagen Synthesis, and Akt/P27 Signaling in Neonatal Rat Cardiac Fibroblasts

Cardiac fibroblasts (CFs) play a key role in cardiac fibrosis by regulating the balance between extracellular matrix synthesis and breakdown. Although phosphatase and tensin homologue on chromosome 10 (PTEN) has been found to play an important role in cardiovascular disease, it is not clear whether PTEN is involved in functional regulation of CFs. In the present study, PTEN was overexpressed in neonatal rat CFs via recombinant adenovirus-mediated gene transfer. The effects of PTEN overexpression on cell-cycle progression and angiotensin II- (Ang II-) mediated regulation of collagen metabolism, synthesis of matrix metalloproteinases, and Akt/P27 signaling were investigated. Compared with uninfected cells and cells infected with green fluorescent protein-expressing adenovirus (Ad-GFP), cells infected with PTEN-expressing adenovirus (Ad-PTEN) significantly increased PTEN protein and mRNA levels in CFs (P < 0.05). The proportion of CFs in the G1/S cell-cycle phase was significantly higher for PTEN-overexpressing cells. In addition, Ad-PTEN decreased mRNA expression and the protein synthesis rate of collagen types I and III and antagonized Ang II-induced collagen synthesis. Overexpression of PTEN also decreased Ang II-induced matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1) production as well as gelatinase activity. Moreover, Ad-PTEN decreased Akt expression and increased P27 expression independent of Ang II stimulation. These results suggest that PTEN could regulate its functional effects in neonatal rat CFs partially via the Akt/P27 signaling pathway.

Crucial Role of miR-433 in Regulating Cardiac Fibrosis

Dysregulation of microRNAs has been implicated in many cardiovascular diseases including fibrosis. Here we report that miR-433 was consistently elevated in three models of heart disease with prominent cardiac fibrosis, and was enriched in fibroblasts compared to cardiomyocytes. Forced expression of miR-433 in neonatal rat cardiac fibroblasts increased proliferation and their differentiation into myofibroblasts as determined by EdU incorporation, α-SMA staining, and expression levels of fibrosis-associated genes. Conversely, inhibition of miR-433 exhibited opposite results. AZIN1 and JNK1 were identified as two target genes of miR-433. Decreased level of AZIN1 activated TGF-β1 while down-regulation of JNK1 resulted in activation of ERK and p38 kinase leading to Smad3 activation and ultimately cardiac fibrosis. Importantly, systemic neutralization of miR-433 or adeno-associated virus 9 (AAV9)-mediated cardiac transfer of a miR-433 sponge attenuated cardiac fibrosis and ventricular dysfunction following myocardial infarction. Thus, our work suggests that miR-433 is a potential target for amelioration of cardiac fibrosis.

Human relaxin gene expression delivered by bioreducible dendrimer polymer for post-infarct cardiac remodeling in rats

In consensus, myocardial infarction (MI) is defined as irreversible cell death secondary to prolonged ischemia in heart. The aim of our study was to evaluate the therapeutic potential of anti-fibrotic human Relaxin-expressing plasmid DNA with hypoxia response element (HRE) 12 copies (HR1) delivered by a dendrimer type PAM-ABP polymer G0 (HR1/G0) after MI on functional, hemodynamic, geometric, and cardiac extracellular matrix (ECM) remodeling in rats. HR1/G0 demonstrated significantly improved LV systolic function, hemodynamic parameters, and geometry on 1 wk and 4 wks after MI in rats, compared with I/R group. The resolution of regional wall motional abnormalities and the increased blood flow of infarct-related coronary artery supported functional improvements of HR1/G0. Furthermore, HR1/G0 polyplex showed favorable post-infarct cardiac ECM remodeling reflected on the favorable cardiac ECM compositions. Overall, this is the first study, which presented an advanced platform for the gene therapy that reverses adverse cardiac remodeling after MI with a HR1 gene delivered by a bioreducible dendrimer polymer in the cardiac ECM.

Differential impact of mechanical unloading on structural and nonstructural components of the extracellular matrix in advanced human heart failure

Adverse remodeling of the extracellular matrix (ECM) is a significant characteristic of heart failure. Reverse remodeling of the fibrillar ECM secondary to mechanical unloading of the left ventricle (LV) by left ventricular assist device (LVAD) has been subject of intense investigation; however, little is known about the impacts on nonfibrillar ECM and matricellular proteins that also contribute to disease progression. Explanted failing hearts were procured from patients with nonischemic dilated cardiomyopathy (DCM) with or without LVAD support, and compared to nonfailing control hearts. LV free wall specimens were formalin-fixed, flash-frozen or optimum cutting temperature-mount frozen. Histologic and biochemical assessment of fibrillar ECM showed that LVAD support was associated with lower levels of insoluble collagen, collagen type I mRNA, and collagen I/III ratio compared with no-LVAD hearts. A disintegrin and Metalloproteinase with Thrombospondin Motifs-2 (ADAM-TS2), a procollagen endopeptidase, was reduced in no-LVAD but not in LVAD hearts. The rise in ECM proteolytic activities was significantly lower in LVAD hearts. Matrix metalloproteinases (MMP1, MMP2, MMP8, MMP13, and MT1-MMP/MMP14) were comparable between DCM hearts. Tissue inhibitor of metalloproteinase (TIMP)3 and TIMP4 messenger RNA and protein showed the greatest reduction in no-LVAD hearts. Basement membrane proteins exhibited less severe disarray of laminin and fibronectin-1 in LVAD-supported hearts. The rise in matricellular protein, osteopontin, was suppressed in LVAD hearts, whereas secreted protein, acidic, cysteine-rich (SPARC) levels was unaffected by LVAD. Mechanical unloading of the failing DCM hearts can restore the fibrillar ECM and the basement membrane, contributing toward improved clinical outcomes. However, persistent elevation of matricellular proteins such as SPARC could contribute to the relapse of failing hearts on removal of LVAD support.

Aging and the cardiac collagen matrix: Novel mediators of fibrotic remodelling

Cardiovascular disease is a leading cause of death worldwide and there is a pressing need for new therapeutic strategies to treat such conditions. The risk of developing cardiovascular disease increases dramatically with age, yet the majority of experimental research is executed using young animals. The cardiac extracellular matrix (ECM), consisting predominantly of fibrillar collagen, preserves myocardial integrity, provides a means of force transmission and supports myocyte geometry. Disruptions to the finely balanced control of collagen synthesis, post-synthetic deposition, post-translational modification and degradation may have detrimental effects on myocardial functionality. It is now well established that the aged heart is characterized by fibrotic remodelling, but the mechanisms responsible for this are incompletely understood. Furthermore, studies using aged animal models suggest that interstitial remodelling with disease may be age-dependent. Thus with the identification of new therapeutic strategies targeting fibrotic remodelling, it may be necessary to consider age-dependent mechanisms. In this review, we discuss remodelling of the cardiac collagen matrix as a function of age, whilst highlighting potential novel mediators of age-dependent fibrotic pathways.

Enhanced ADAM17 expression is associated with cardiac remodeling in rats with acute myocardial infarction

AIM

This study aimed to investigate the dynamic expression of A-disintegrin-and-metalloproteinase-17 (ADAM17) during cardiac remodeling after acute myocardial infarction (AMI).

MAIN METHODS

Forty male Wistar rats with a permanent ligation of the left anterior descending artery were equally divided into four groups based on predefined sacrifice time: MI1d, MI1w, MI4w and MI12w. As controls, 36 rats only with left thoracotomy were equally divided into four groups. Cardiac remodeling was assessed by echocardiography and hematoxylin and eosin (H&E) staining. ADAM17 mRNA was detected by real-time reverse transcription polymerase chain reaction, and protein expression of ADAM17, tissue inhibitor of metalloproteinases-3 (TIMP-3) and TNF-α was analyzed by western blotting.

KEY FINDINGS

The systolic function was sharply worsened in the MI1w group (versus the Con1w group, P<0.05), but left ventricular weight index was significantly increased after 4weeks post-MI (P<0.05). H&E staining revealed that one week after AMI, myocardial tissue in the epicardial border zone of the infarcted heart was mixed with broken mitochondrial cristae and decreased matrix density. ADAM17 mRNA and protein expression was significantly increased, accompanied by decreased TIMP-3 and upregulated TNF-α expression in the MI1w group (versus the MI1d group, all P<0.05). Moreover, dynamic ADAM17 mRNA expression was positively correlated with enlarged LVEDd and LVESd (P=0.001, P=0.003) and negatively with LVEF (P=0.039) in AMI rats.

SIGNIFICANCE

Enhanced ADAM17 expression, along with decreased TIMP-3 and increased TNF-α expression, especially within one week after AMI, is associated with cardiac remodeling.

Cerebral palsy

Cerebral palsy is the most common cause of childhood-onset, lifelong physical disability in most countries, affecting about 1 in 500 neonates with an estimated prevalence of 17 million people worldwide. Cerebral palsy is not a disease entity in the traditional sense but a clinical description of children who share features of a non-progressive brain injury or lesion acquired during the antenatal, perinatal or early postnatal period. The clinical manifestations of cerebral palsy vary greatly in the type of movement disorder, the degree of functional ability and limitation and the affected parts of the body. There is currently no cure, but progress is being made in both the prevention and the amelioration of the brain injury. For example, administration of magnesium sulfate during premature labour and cooling of high-risk infants can reduce the rate and severity of cerebral palsy. Although the disorder affects individuals throughout their lifetime, most cerebral palsy research efforts and management strategies currently focus on the needs of children. Clinical management of children with cerebral palsy is directed towards maximizing function and participation in activities and minimizing the effects of the factors that can make the condition worse, such as epilepsy, feeding challenges, hip dislocation and scoliosis. These management strategies include enhancing neurological function during early development; managing medical co-morbidities, weakness and hypertonia; using rehabilitation technologies to enhance motor function; and preventing secondary musculoskeletal problems. Meeting the needs of people with cerebral palsy in resource-poor settings is particularly challenging.

Sex differences in porcine left ventricular myocardial remodeling due to right ventricular pacing

Background

Although sex differences in heart failure (HF) prevalence and severity have been recognized, its molecular mechanisms are poorly understood. We used a tachycardia-induced cardiomyopathy model to determine the sex specific remodeling pattern in male and female adult pigs.

Methods

We compared the echocardiographic and molecular measures of myocardial remodeling in 19 male and 12 female pigs with chronic symptomatic systolic HF due to right ventricle (RV) pacing (170 bpm) and 6 male and 5 female sham-operated controls. Males achieved subsequent HF stages earlier than females.

Results

The progression of symptomatic HF was associated with the reduction of the left ventricle (LV) ejection fraction in both sexes (all p < 0.05). A significant LV dilatation occurred only in males (p < 0.001). The HF development was accompanied by an increased pro-hypertrophic factor GATA4 and TGF-β1 messenger RNA (mRNA) expression in the LV only in male pigs (all p < 0.01). The total gelatinolytic activity in LV was higher in males than females (irrespective of HF, p < 0.05), and the HF progression was associated with a reduced total gelatinolytic activity (p < 0.05) in the LV only in males. No differences in LV myocardial collagen content were found between HF groups and sexes. Cardiomyocyte cross-sectional diameter was significantly smaller in male hearts as compared to female (p < 0.05).

Conclusions

Male and female porcine hearts respond differently to RV pacing. Males, most likely due to a higher extracellular matrix turnover, demonstrated a significant LV dilatation, followed by a strong induction of pro-hypertrophic program, and an earlier development of symptomatic HF.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-015-0048-4) contains supplementary material, which is available to authorized users.

Deficiency of ataxia telangiectasia mutated kinase delays inflammatory response in the heart following myocardial infarction

Background

Ataxia‐telangiectasia results from mutations in ataxia telangiectasia mutated kinase (ATM) gene. We recently reported that ATM deficiency attenuates left ventricular (LV) dysfunction and dilatation 7 days after myocardial infarction (MI) with increased apoptosis and fibrosis. Here we investigated the role of ATM in the induction of inflammatory response, and activation of survival signaling molecules in the heart acute post‐MI.

Methods and Results

LV structure, function, inflammatory response, and biochemical parameters were measured in wild‐type (WT) and ATM heterozygous knockout (hKO) mice 1 and 3 days post‐MI. ATM deficiency had no effect on infarct size. MI‐induced decline in heart function, as measured by changes in percent fractional shortening, ejection fraction and LV end systolic and diastolic volumes, was lower in hKO‐MI versus WT‐MI (n=10 to 12). The number of neutrophils and macrophages was significantly lower in the infarct LV region of hKO versus WT 1 day post‐MI. Fibrosis and expression of α‐smooth muscle actin (myofibroblast marker) were higher in hKO‐MI, while active TGF‐β1 levels were higher in the WT‐MI 3 days post‐MI. Myocyte cross‐sectional area was higher in hKO‐sham with no difference between the two MI groups. MMP‐9 protein levels were similarly increased in the infarct LV region of both MI groups. Apoptosis was significantly higher in the infarct LV region of hKO at both time points. Akt activation was lower, while Bax expression was higher in hKO‐MI infarct.

Conclusion

ATM deficiency results in decreased dilative remodeling and delays inflammatory response acute post‐MI. However, it associates with increased fibrosis and apoptosis.

What does procollagen C-endopeptidase enhancer protein 2 have to do with HDL-cholesteryl ester uptake? Or how I learned to stop worrying and love reverse cholesterol transport?

PURPOSE OF REVIEW

The purpose of this study is to provide an update on the role HDL apolipoprotein A-I plays in reducing the risk of cardiovascular disease (CVD) and how it relates to reverse cholesterol transport (RCT).

RECENT FINDINGS

Despite numerous studies showing that plasma HDL cholesterol concentrations are correlated with a reduced risk of CVD, pharmacologic elevation of HDL has not shown any beneficial effects to date. In contrast, studies correlating the measure of an individual's plasma cholesterol efflux capacity show greater promise as a tool for assessing CVD risk. Although ATP-binding cassette transporter 1-mediated lipidation of apoA-I is considered the principal source of plasma HDL, it represents only one side of the RCT pathway. Equally important is the second half of the RCT pathway in which the liver scavenger receptor class B1 selectively removes HDL cholesteryl esters for excretion. The combined action of the two enzyme systems is reflected in the overall steady-state concentration of plasma HDL cholesterol. For example, reduced ATP-binding cassette transporter 1-mediated production of nascent HDL lowers plasma HDL concentration, just as an increase in cholesteryl ester uptake by scavenger receptor class B1 reduces HDL levels. Thus, the complexity of intravascular HDL metabolism suggests that steady-state plasma HDL concentrations do not provide adequate information regarding an individual's HDL quality or function. Herein, we describe a new player, procollagen C-endopeptidase enhancer 2, which shows atheroprotective function and influences both sides of RCT by enhancing production and catabolism of HDL cholesteryl esters.

SUMMARY

The discovery of a new molecule, procollagen C-endopeptidase enhancer 2, implicated in the regulation of HDL cholesteryl ester concentrations suggests that the extracellular matrix and the proteins that regulate its function represent a new and as yet unexplored realm of HDL cholesterol metabolism.

Immunohistochemical Analysis of MMP-2 Expression in the Myocardium During the Postinfarction Period

Immunohistochemical analysis revealed 2.5-fold increased of expression MMP-2 in myocardium samples during the early period (up to 3 days) of postinfarction reparative regeneration. During this period, MMP-2 was detected mainly in monocytes/macrophages circulating in the blood and migrating to the necrotic zone, while expression in the intermuscular and perivascular connective tissue was lower. At later terms, with development of large focal and diffuse cardiosclerosis, MMP-2 expression significantly decreased (to the initial level) and was detected mainly in the foci of intermuscular and perivascular fibrosis, its area in the sections increased by 1.8 times. Evaluation of MMP-2 expression in the blood vessels showed that the immunohistochemical reaction was the most pronounced in the walls of new sinusoidal vessels and the minimum in the intramural arteries of medium diameter. These results attest to an important role of MMP in connective tissue remodeling (proteolytic degradation) during the early period of postinfarction reparative regeneration. The decrease in MMP-2 expression observed at later terms correlated with myocardial fibrosis progression.

Activation of common signaling pathways during remodeling of the heart and the bladder

The heart and the urinary bladder are hollow muscular organs, which can be afflicted by pressure overload injury due to pathological conditions such as hypertension and bladder outlet obstruction. This increased outflow resistance induces hypertrophy, marked by dramatic changes in the organs' phenotype and function. The end result in both the heart and the bladder can be acute organ failure due to advanced fibrosis and the subsequent loss of contractility. There is emerging evidence that microRNAs (miRNAs) play an important role in the pathogenesis of heart failure and bladder dysfunction. MiRNAs are endogenous non-coding single-stranded RNAs, which regulate gene expression and control adaptive and maladaptive organ remodeling processes. This Review summarizes the current knowledge of molecular alterations in the heart and the bladder and highlights common signaling pathways and regulatory events. The miRNA expression analysis and experimental target validation done in the heart provide a valuable source of information for investigators working on the bladder and other organs undergoing the process of fibrotic remodeling. Aberrantly expressed miRNA are amendable to pharmacological manipulation, offering an opportunity for development of new therapies for cardiac and bladder hypertrophy and failure.

Physiological Implications of Myocardial Scar Structure

Once myocardium dies during a heart attack, it is replaced by scar tissue over the course of several weeks. The size, location, composition, structure, and mechanical properties of the healing scar are all critical determinants of the fate of patients who survive the initial infarction. While the central importance of scar structure in determining pump function and remodeling has long been recognized, it has proven remarkably difficult to design therapies that improve heart function or limit remodeling by modifying scar structure. Many exciting new therapies are under development, but predicting their long-term effects requires a detailed understanding of how infarct scar forms, how its properties impact left ventricular function and remodeling, and how changes in scar structure and properties feed back to affect not only heart mechanics but also electrical conduction, reflex hemodynamic compensations, and the ongoing process of scar formation itself. In this article, we outline the scar formation process following a myocardial infarction, discuss interpretation of standard measures of heart function in the setting of a healing infarct, then present implications of infarct scar geometry and structure for both mechanical and electrical function of the heart and summarize experiences to date with therapeutic interventions that aim to modify scar geometry and structure. One important conclusion that emerges from the studies reviewed here is that computational modeling is an essential tool for integrating the wealth of information required to understand this complex system and predict the impact of novel therapies on scar healing, heart function, and remodeling following myocardial infarction.

Nox2 contributes to cardiac fibrosis in diabetic cardiomyopathy in a transforming growth factor-β dependent manner

PURPOSE

This study aimed to investigate the effect of Nox2 on cardiac fibrosis and to elucidate the regulatory mechanism of Nox2 in the development of DCM.

METHODS

We established normal and insulin-resistant cellular model using neonatal rat cardiac fibroblasts. Then Nox2-specific siRNA were transfected into cardiac fibroblasts with Lipofectamine ® 2000 and crambled siRNA sequence was considered as control. Meanwhile, a part of cells were randomly selected to be treated with or without transforming growth factor-β (TGF-β). Moreover, quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were respectively performed to determine the expression level of related molecules, such as Nox2, collagen type I and III (COL I and III) and PI3K/AKT and PKC/Rho signaling pathway-related proteins.

RESULTS

TGF-β stimulation significantly increased the expression level of Nox2 both in mRNA and protein levels. Suppression of the Nox2 markedly decreased the expression of COL I and COL III in normal and insulin-resistant cellular model with TGF-β stimulation. Moreover, suppression of the Nox2 significantly decreased the expression of PI3K/AKT and PKC/Rho signaling pathway-related proteins in insulin-resistant cellular model with TGF-β stimulation. However, suppression of Nox2 had no effects on these proteins without TGF-β stimulation.

CONCLUSIONS

Our finding reveals that Nox2 may promote synthesis of COL I and III via involved in PI3K/AKT and PKC/Rho signaling pathway in a TGF-β dependent manner and consequently promote cardiac fibrosis in the development of DCM.

Procollagen C-endopeptidase Enhancer Protein 2 (PCPE2) Reduces Atherosclerosis in Mice by Enhancing Scavenger Receptor Class B1 (SR-BI)-mediated High-density Lipoprotein (HDL)-Cholesteryl Ester Uptake

Studies in human populations have shown a significant correlation between procollagen C-endopeptidase enhancer protein 2 (PCPE2) single nucleotide polymorphisms and plasma HDL cholesterol concentrations. PCPE2, a 52-kDa glycoprotein located in the extracellular matrix, enhances the cleavage of C-terminal procollagen by bone morphogenetic protein 1 (BMP1). Our studies here focused on investigating the basis for the elevated concentration of enlarged plasma HDL in PCPE2-deficient mice to determine whether they protected against diet-induced atherosclerosis. PCPE2-deficient mice were crossed with LDL receptor-deficient mice to obtain LDLr(-/-), PCPE2(-/-) mice, which had elevated HDL levels compared with LDLr(-/-) mice with similar LDL concentrations. We found that LDLr(-/-), PCPE2(-/-) mice had significantly more neutral lipid and CD68+ infiltration in the aortic root than LDLr(-/-) mice. Surprisingly, in light of their elevated HDL levels, the extent of aortic lipid deposition in LDLr(-/-), PCPE2(-/-) mice was similar to that reported for LDLr(-/-), apoA-I(-/-) mice, which lack any apoA-I/HDL. Furthermore, LDLr(-/-), PCPE2(-/-) mice had reduced HDL apoA-I fractional clearance and macrophage to fecal reverse cholesterol transport rates compared with LDLr(-/-) mice, despite a 2-fold increase in liver SR-BI expression. PCPE2 was shown to enhance SR-BI function by increasing the rate of HDL-associated cholesteryl ester uptake, possibly by optimizing SR-BI localization and/or conformation. We conclude that PCPE2 is atheroprotective and an important component of the reverse cholesterol transport HDL system.

Tetrandrine reverses human cardiac myofibroblast activation and myocardial fibrosis

Tetrandrine (TTD) is a calcium channel blocker with documented antifibrotic actions. In this study, for the first time, we identified that TTD can directly prevent in vitro human cardiac myofibroblast activation and limit in vivo myocardial fibrosis. In vitro, cardiac myofibroblasts from human atrial biopsies (N = 10) were seeded in three-dimensional collagen matrices. Cell-collagen constructs were exposed to transforming growth factor-β1 (10 ng/ml), with or without TTD (1 and 5 μM) for 48 h. Collagen gel contraction, myofibroblast activation (α-smooth muscle actin expression), expression of profibrotic mRNAs, and rate of collagen protein synthesis were compared. TTD decreased collagen gel contraction (79.7 ± 1.3 vs 60.1 ± 8.9%, P < 0.01), α-smooth muscle actin expression (flow cytometry), collagen synthesis ([(3)H]proline incorporation), and collagen mRNA expression. Cell viability was similar between groups (annexin positive cells: 1.7 vs. 1.4%). TTD inhibited collagen gel contraction in the presence of T-type and L-type calcium channel blockers, and the intracellular calcium chelator BAPTA-AM (15 μM), suggesting that the observed effects are not mediated by calcium homeostasis. In vivo, Dahl salt-sensitive hypertensive rats were treated with variable doses of TTD (by intraperitoneal injection over 4 wk) and compared with untreated controls (N = 12). Systemic blood pressure was monitored by tail cuff. Myocardial fibrosis and left ventricular compliance were assessed by histology and passive pressure-volume analysis. Myocardial fibrosis was attenuated compared with untreated controls (%collagen area: 9.4 ± 7.3 vs 2.1 ± 1.0%, P < 0.01). Left ventricular compliance was preserved. In conclusion, TTD reverses human cardiac myofibroblast activation and myocardial fibrosis, independent of calcium channel blockade.

Non-human primate and rat cardiac fibroblasts show similar extracellular matrix-related and cellular adhesion gene responses to substance P

BACKGROUND

The sensory nerve neuropeptide substance P (SP) regulates cardiac fibrosis in rodents under pressure overload conditions. Interestingly, SP induces transient increased expression of specific genes in isolated rat cardiac fibroblasts, without resultant changes in cell function. This suggests that SP 'primes' fibroblasts, but does not directly activate them. We investigated whether these unusual findings are specific to rodent fibroblasts or are translatable to a larger animal model more closely related to humans.

METHODS

We compared the effects of SP on genes associated with extracellular matrix (ECM) regulation, cell-cell adhesion, cell-matrix adhesion and ECM in cardiac fibroblasts isolated from a non-human primate and Sprague-Dawley rats.

RESULTS

We found that rodent and non-human primate cardiac fibroblasts showed similar responses in genes that relate to ECM regulation and cell adhesion in response to SP. There were large discrepancies in ECM component genes, however, this did not result in collagen or laminin synthesis in rat or non-human primate fibroblasts in response to SP.

CONCLUSIONS

This study further supports the notion that SP serves as a 'primer' for fibroblasts rather than initiating direct effects and suggests that rodent fibroblasts are a suitable model for studying gene and functional responses to SP in the absence of human or non-human primate fibroblasts.

Lack of collagen VIII reduces fibrosis and promotes early mortality and cardiac dilatation in pressure overload in mice

AIMS

In pressure overload, left ventricular (LV) dilatation is a key step in transition to heart failure (HF). We recently found that collagen VIII (colVIII), a non-fibrillar collagen and extracellular matrix constituent, was reduced in hearts of mice with HF and correlated to degree of dilatation. A reduction in colVIII might be involved in LV dilatation, and we here examined the role of reduced colVIII in pressure overload-induced remodelling using colVIII knock-out (col8KO) mice.

METHODS AND RESULTS

Col8KO mice exhibited increased mortality 3-9 days after aortic banding (AB) and increased LV dilatation from day one after AB, compared with wild type (WT). LV dilatation remained increased over 56 days. Forty-eight hours after AB, LV expression of main structural collagens (I and III) was three-fold increased in WT mice, but these collagens were unaltered in the LV of col8KO mice together with reduced expression of the pro-fibrotic cytokine TGF-β, SMAD2 signalling, and the myofibroblast markers Pxn, α-SMA, and SM22. Six weeks after AB, LV collagen mRNA expression and protein were increased in col8KO mice, although less pronounced than in WT. In vitro, neonatal cardiac fibroblasts from col8KO mice showed lower expression of TGF-β, Pxn, α-SMA, and SM22 and reduced migratory ability possibly due to increased RhoA activity and reduced MMP2 expression. Stimulation with recombinant colVIIIα1 increased TGF-β expression and fibroblast migration.

CONCLUSION

Lack of colVIII reduces myofibroblast differentiation and fibrosis and promotes early mortality and LV dilatation in response to pressure overload in mice.

The protective effect of microRNA-320 on left ventricular remodeling after myocardial ischemia-reperfusion injury in the rat model

The primary objective of this study investigated the role of microRNA-320 (miR-320) on left ventricular remodeling in the rat model of myocardial ischemia-reperfusion (I/R) injury, and we intended to explore the myocardial mechanism of miR-320-mediated myocardium protection. We collected 120 male Wistar rats (240-280 g) in this study and then randomly divided them into three groups: (1) sham surgery group (sham group: n=40); (2) ischemia-reperfusion model group (I/R group: n=40); and (3) I/R model with antagomir-320 group (I/R+antagomir-320 group: n=40). Value changes of heart function in transesophageal echocardiography were recorded at various time points (day 1, day 3, day 7, day 15 and day 30) after surgery in each group. Myocardial sections were stained with hematoxylin and eosin (H&E) and examined with optical microscope. The degree of myocardial fibrosis was assessed by Sirius Red staining. Terminal dUTP nick end-labeling (TUNEL) and qRT-PCR methods were used to measure the apoptosis rate and to determine the miR-320 expression levels in myocardial tissues. Transesophageal echocardiography showed that the values of left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular systolic pressure (LVSP) and ±dp/dtmax in the I/R group were obviously lower than those in the sham group, while the left ventricular end-diastolic pressure (LVEDP) value was higher than that in the sham group. The values of LVEF, LVFS, LVSP and ±dp/dtmax showed a gradual decrease in the I/R group, while the LVEDP value showed an up tendency along with the extension of reperfusion time. The H&E staining revealed that rat myocardial tissue in the I/R group presented extensive myocardial damage; for the I/R+antagomir-320 group, however, the degree of damage in myocardial cells was obviously better than that of the I/R group. The Sirius Red staining results showed that the degree of myocardial fibrosis in the I/R group was more severe along with the extension of the time of reperfusion. For the I/R+antagomir-320 group, the degree of myocardial fibrosis was less severe than that in the I/R group. Tissues samples in both the sham and I/R+antagomir-320 groups showed a lower apoptosis rate compared to I/R group. The qRT-PCR results indicated that miR-320 expression in the I/R group was significantly higher than that in both the sham and I/R+antagomir-320 groups. The expression level of miR-320 is significantly up-regulated in the rat model of myocardial I/R injury, and it may be implicated in the prevention of myocardial I/R injury-triggered left ventricular remodeling.