Immunohistochemical detection of differentially localized up-regulation of lysyl oxidase and down-regulation of matrix metalloproteinase-1 in rhesus monkey model of chronic myocardial infarction

Implantation of Adipose-Derived Mesenchymal Stromal Cells (ADSCs)-Lining Prosthetic Graft Promotes Vascular Regeneration in Monkeys and Pigs

BACKGROUND

Current replacement procedures for stenosis or occluded arteries using prosthetic grafts have serious limitations in clinical applications, particularly, endothelialization of the luminal surface is a long-standing unresolved problem.

METHOD

We produced a cell-based hybrid vascular graft using a bioink engulfing adipose-derived mesenchymal stromal cells (ADSCs) and a 3D bioprinting process lining the ADSCs on the luminal surface of GORE-Tex grafts. The hybrid graft was implanted as an interposition conduit to replace a 3-cm-long segment of the infrarenal abdominal aorta in Rhesus monkeys.

RESULTS

Complete endothelium layer and smooth muscle layer were fully developed within 21 days post-implantation, along with normalized collagen deposition and crosslinking in the regenerated vasculature in all monkeys. The regenerated blood vessels showed normal functionality for the longest observation of more than 1650 days. The same procedure was also conducted in miniature pigs for the interposition replacement of a 10-cm-long right iliac artery and showed the same long-term effective and safe outcome.

CONCLUSION

This cell-based vascular graft is ready to undergo clinical trials for human patients.

Integrin αV mediated activation of myofibroblast via mechanoparacrine of transforming growth factor β1 in promoting fibrous scar formation after myocardial infarction

BACKGROUND

Myocardial infarction (MI) dramatically changes the mechanical stress, which is intensified by the fibrotic remodeling. Integrins, especially the αV subunit, mediate mechanical signal and mechanoparacrine of transforming growth factor β1 (TGF-β1) in various organ fibrosis by activating CFs into myofibroblasts (MFBs). We investigated a possible role of integrin αV mediated mechanoparacrine of TGF-β1 in MFBs activation for fibrous reparation in mice with MI.

METHODS

Heart samples from MI, sham, or MI plus cilengitide (14 mg/kg, specific integrin αV inhibitor) treated mice, underwent functional and morphological assessments by echocardiography, and histochemistry on 7, 14 and 28 days post-surgery. The mechanical and ultrastructural changes of the fibrous scar were further evaluated by atomic mechanics microscope (AFM), immunofluorescence, second harmonic generation (SHG) imaging, polarized light and scanning electron microscope, respectively. Hydroxyproline assay was used for total collagen content, and western blot for protein expression profile examination. Fibroblast bioactivities, including cell shape, number, Smad2/3 signal and expression of extracellular matrix (ECM) related proteins, were further evaluated by microscopic observation and immunofluorescence in polyacrylamide (PA) hydrogel with adjustable stiffness, which was re-explored in fibroblast cultured on stiff matrix after silencing of integrin αV. The content of total and free TGF-β1 was tested by enzyme-linked immunosorbent assay (ELISA) in both infarcted tissue and cell samples.

RESULT

Increased stiffness with heterogeneity synchronized with integrin αV and alpha smooth muscle actin (α-SMA) positive MFBs accumulation in those less mature fibrous areas. Cilengitide abruptly reduced collagen content and disrupted collagen alignment, which also decreased TGF-β1 bioavailability, Smad2/3 phosphorylation, and α-SMA expression in the fibrous area. Accordingly, fibroblast on stiff but not soft matrix exhibited obvious MFB phenotype, as evidenced by enlarged cell, hyperproliferation, well-developed α-SMA fibers, and elevated ECM related proteins, while silencing of integrin αV almost abolished this switch via attenuating paracrine of TGF-β1 and nuclear translocation of Smad2/3.

CONCLUSION

This study illustrated that increased tissue stiffness activates CFs into MFBs by integrin αV mediated mechanoparacrine of TGF-β1, especially in immature scar area, which ultimately promotes fibrous scar maturation.

Platelets modulate cardiac remodeling via the collagen receptor GPVI after acute myocardial infarction

Introduction

Platelets play an important role in cardiovascular diseases. After acute myocardial infarction, platelets display enhanced activation and migrate into the infarct zone. Furthermore, platelets trigger acute inflammation and cardiac remodeling leading to alterations in scar formation and cardiac function as observed in thrombocytopenic mice. GPVI is the major collagen receptor in platelets and important for platelet activation and thrombus formation and stability. Antibody induced deletion of GPVI at the platelet surface or treatment of mice with recombinant GPVI-Fc results in reduced inflammation and decreased infarct size in a mouse model of AMI. However, the role of GPVI has not been fully clarified to date.

Methods/Results

In this study, we found that GPVI is not involved in the inflammatory response in experimental AMI using GPVI deficient mice that were analyzed in a closed-chest model. However, reduced platelet activation in response to GPVI and PAR4 receptor stimulation resulted in reduced pro-coagulant activity leading to improved cardiac remodeling. In detail, GPVI deficiency in mice led to reduced TGF-β plasma levels and decreased expression of genes involved in cardiac remodeling such as Col1a1, Col3a1, periostin and Cthrc1 7 days post AMI. Consequently, collagen quality of the scar shifted to more tight and less fine collagen leading to improved scar formation and cardiac function in GPVI deficient mice at 21d post AMI.

Conclusion

Taken together, this study identifies GPVI as a major regulator of platelet-induced cardiac remodeling and supports the potential relevance of GPVI as therapeutic target to reduce ischemia reperfusion injury and to improve cardiac healing.

Alteration of endothelial permeability ensures cardiomyocyte survival from ischemic insult in the subendocardium of the heart

Previous studies have shown that cardiomyocytes in the subendocardial region of myocardium survive from ischemic insult. This study was undertaken to explore possible mechanisms for the survival of these cardiomyocytes, focusing on changes in endothelial cells (ECs) and blood supply. C57/B6 mice were subjected to permanent ligation of left anterior descending (LAD) coronary artery to induce myocardial ischemia (MI). The hearts were harvested at 1, 4, and 7 days post MI and examined for histological changes. It was found that the survival of cardiomyocytes was associated with a preservation of ECs in the subendocardial region, as revealed by EC-specific tdTomato expression transgenic mice (Tie2tdTomato). However, the EC selective proteins, PECAM1 and VEGFR2, were significantly depressed in these ECs. Consequently, the ratio of PECAM1/tdTomato was significantly decreased, indicating a transformation from PECAM1+ ECs to PECAM1- ECs. Furthermore, EC junction protein, VE-cadherin, was not only depressed but also disassociated from PECAM1 in the same region. These changes led to an increase in EC permeability, as evidenced by increased blood infiltration in the subendocardial region. Thus, the increase in the permeability of ECs due to their transformation in the subendocardial region allows blood infiltration, creating a unique microenvironment and ensuring the survival of cardiomyocytes under ischemic conditions.

Copper promotes cardiac functional recovery via suppressing the transformation of fibroblasts to myofibroblasts in ischemia-infarcted monkey hearts

Myocardial ischemia leads to cardiac fibrosis along with copper (Cu) loss. Cu repletion diminishes myocardial fibrosis and improves cardiac function. The transformation of fibroblasts to myofibroblasts is highly responsible for the pathogenesis of cardiac fibrosis. This study was undertaken to test the hypothesis that Cu inhibition of cardiac fibrosis results from suppression of myofibroblasts. Rhesus monkeys 4-5 years old were subjected to coronary artery ligation to induce myocardial infarction (MI). At the end of the fourth week after the surgery, an ultrasound-directed Cu-albumin microbubble organ-specific Cu delivery technique was used to treat the ischemia-infarcted monkey hearts twice a week for 4 weeks. This treatment increased Cu concentrations in the infarct area, loosened the collagen cross-linking network, restored blood vessel density, and improved cardiac contractility. Total fibroblasts labeled with vimentin were increased in the infarct area, and Cu repletion did not alter this increase. Myofibroblasts, dually labeled with vimentin and α-smooth muscle actin (α-SMA), were also significantly increased in the infarct area but were significantly reduced by Cu repletion. Correspondingly, the products of myofibroblasts, type I and III collagens and inhibitors of collagenases were significantly reduced. In contrast, metalloproteinase-1 (MMP-1) and MMP-1 producing fibroblasts (vimentin⁺ and MMP-1⁺ cells) were significantly increased. These results suggest that Cu inhibits the transformation of fibroblasts to myofibroblasts, leading to a pro-fibrinolytic switch and an improvement in cardiac function.

Only Acute but Not Chronic Thrombocytopenia Protects Mice against Left Ventricular Dysfunction after Acute Myocardial Infarction

BACKGROUND

Platelets are major players of thrombosis and inflammation after acute myocardial infarction (AMI). The impact of thrombocytopenia on platelet-induced cellular processes post AMI is not well defined.

METHODS

The left anterior descending artery was ligated in C57/Bl6 mice and in two thrombocytopenic mouse models to induce AMI.

RESULTS

Platelets from STEMI patients and from C57/Bl6 mice displayed enhanced platelet activation after AMI. This allows platelets to migrate into the infarct but not into the remote zone of the left ventricle. Acute thrombocytopenia by antibody-induced platelet depletion resulted in reduced infarct size and improved cardiac function 24 h and 21 days post AMI. This was due to reduced platelet-mediated inflammation after 24 h and reduced scar formation after 21 days post AMI. The collagen composition and interstitial collagen content in the left ventricle were altered due to platelet interaction with cardiac fibroblasts. Acute inflammation was also significantly reduced in Mpl-/- mice with chronic thrombocytopenia, but cardiac remodeling was unaltered. Consequently, left ventricular function, infarct size and scar formation in Mpl-/- mice were comparable to controls.

CONCLUSION

This study discovers a novel role for platelets in cardiac remodeling and reveals that acute but not chronic thrombocytopenia protects left ventricular function post AMI.

An Improved Monkey Model of Myocardial Ischemic Infarction for Cardiovascular Drug Development

Non-human primate monkey model of myocardial ischemic infarction is precious for translational medicine research. Ligation of the left anterior descending (LAD) artery is a common procedure to induce myocardial ischemic infarction. However, the consistency of the myocardial infarction thus generated remains problematic. The present study was undertaken to critically evaluate the monkey model of myocardial ischemic infarction to develop a procedure for a consistent cross-study comparison. Forty male Rhesus monkeys were divided into 4 groups and subjected to LAD artery ligation at different levels along the artery. In addition, the major diagonal branch was selectively ligated parallel to the ligation site of the LAD artery according to the diagonal branch distribution. Analyses of MRI, echocardiography, cardiac hemodynamics, electrocardiography, histopathology, and cardiac injury biomarkers were undertaken to characterize the monkeys with myocardial infarction. Ligation at 40% of the total length of the artery, measured from the apex end, produced variable infarct areas with inconsistent functional alterations. Ligation at 60% or above coupled with selective ligation of diagonal branches produced a consistent myocardial infarction with uniform dysfunction. However, ligation at 70% caused a lethal threat. After a thorough analysis, it is concluded that ligation at 60% of the total length coupled with selective ligation of diagonal branches, enables standardization of the location of occlusion and the subsequent ischemic area, as well as avoids the influence of the diagonal branches, are ideal to produce a consistent monkey model of myocardial ischemic infarction.

Extracellular matrix remodeling is associated with the survival of cardiomyocytes in the subendocardial region of the ischemic myocardium

A significant amount of cardiomyocytes in subendocardial region survive from ischemic insults. In order to understand the mechanism by which these cardiomyocytes survive, the present study was undertaken to examine changes in these surviving cardiomyocytes and their extracellular matrix. Male C57BL/6 mice aged 8-12 weeks old were subjected to a permanent left anterior descending coronary artery ligation to induce ischemic injury. The hearts were collected at 1, 4, 7, or 28 days after the surgery and examined by histology. At day 1 after left anterior descending ligation, there was a significant loss of cardiomyocytes through apoptosis, but a proportion of cardiomyocytes were surviving in the subendocardial region. The surviving cardiomyocytes were gradually changed from rod-shaped to round-shaped, and appeared disconnected. Connexin 43, an important gap junction protein, was significantly decreased, and collagen I and III deposition was significantly increased in the extracellular matrix. Furthermore, lysyl oxidase, a copper-dependent amine oxidase catalyzing the cross-linking of collagens, was significantly increased in the extracellular matrix, paralleled with the surviving cardiomyocytes. Inhibition of lysyl oxidase activity reduced the number of surviving cardiomyocytes. Thus, the extracellular matrix remodeling is correlated with the deformation of cardiomyocytes, and the electrical disconnection between the surviving cardiomyocytes due to connexin 43 depletion and the increase in lysyl oxidase would help these deformed cardiomyocytes survive under ischemic conditions.

Role of the lysyl oxidase enzyme family in cardiac function and disease

Heart diseases are a major cause of morbidity and mortality world-wide. Lysyl oxidase (LOX) and related LOX-like (LOXL) isoforms play a vital role in remodelling the extracellular matrix (ECM). The LOX family controls ECM formation by cross-linking collagen and elastin chains. LOX/LOXL proteins are copper-dependent amine oxidases that catalyse the oxidation of lysine, causing cross-linking between the lysine moieties of lysine-rich proteins. Dynamic changes in LOX and LOXL protein-expression occur in a variety of cardiac pathologies; these changes are believed to be central to the associated tissue-fibrosis. An awareness of the potential pathophysiological importance of LOX has led to the evaluation of interventions that target LOX/LOXL proteins for heart-disease therapy. The purposes of this review article are: (i) to summarize the basic biochemistry and enzyme function of LOX and LOXL proteins; (ii) to consider their tissue and species distribution; and (iii) to review the results of experimental studies of the roles of LOX and LOXL proteins in heart disease, addressing involvement in the mechanisms, pathophysiology and therapeutic responses based on observations in patient samples and relevant animal models. Therapeutic targeting of LOX family enzymes has shown promising results in animal models, but small-molecule approaches have been limited by non-specificity and off-target effects. Biological approaches show potential promise but are in their infancy. While there is strong evidence for LOX-family protein participation in heart failure, myocardial infarction, cardiac hypertrophy, dilated cardiomyopathy, atrial fibrillation and hypertension, as well as potential interest as therapeutic targets, the precise involvement of LOX-family proteins in heart disease requires further investigation.

Fibroblast growth factor 2-induced human amniotic mesenchymal stem cells combined with autologous platelet rich plasma augmented tendon-to-bone healing

Objective

The purpose of this study was to explore the effect of fibroblast growth factor 2 (FGF-2) on collagenous fibre formation and the osteogenic differentiation of human amniotic mesenchymal stem cells (hAMSCs) in vitro, as well as the effect of FGF-2–induced hAMSCs combined with autologous platelet-rich plasma (PRP) on tendon-to-bone healing in vivo.

Methods

In vitro, hAMSCs were induced by various concentrations of FGF-2 (0, 10, 20, and 40 ​ng/ml) for 14 days, and the outcomes of ligamentous differentiation and osteogenic differentiation were detected by quantitative real-time reverse transcription PCR, Western blot, immunofluorescence, and picrosirius red staining. In addition, a lentivirus carrying the FGF-2 gene was used to transfect hAMSCs, and transfection efficiency was detected by quantitative real time reverse transcription PCR (qRT-PCR) and Western blot. In vivo, the effect of hAMSCs transfected with the FGF-2 gene combined with autologous PRP on tendon-to-bone healing was detected via histological examination, as well as biomechanical analysis and radiographic analysis.

Results

In vitro, different concentrations of FGF-2 (10, 20, and 40 ​ng/ml) all promoted the ligamentous differentiation and osteogenic differentiation of hAMSCs, and the low concentration of FGF-2 (10 ​ng/ml) had a good effect on differentiation. In addition, the lentivirus carrying the FGF-2 gene was successfully transfected into hAMSCs with an optimal multiplicity of infection (MOI) (50), and autologous PRP was prepared successfully. In vivo, the hAMSCs transfected with the FGF-2 gene combined with autologous PRP had a better effect on tendon-to-bone healing than the other groups (p ​< ​0.05), as evidenced by histological examination, biomechanical analysis, and radiographic analysis.

Conclusion

hAMSCs transfected with the FGF-2 gene combined with autologous PRP could augment tendon-to-bone healing in a rabbit extra-articular model.

The translational potential of this article

hAMSCs transfected with the FGF-2 gene combined with autologous PRP may be a good clinical treatment for tendon-to-bone healing, especially for acute sports-related tendon–ligament injuries.

The Role of Lysyl Oxidase Enzymes in Cardiac Function and Remodeling

Lysyl oxidase (LOX) proteins comprise a family of five copper-dependent enzymes (LOX and four LOX-like isoenzymes (LOXL1-4)) critical for extracellular matrix (ECM) homeostasis and remodeling. The primary role of LOX enzymes is to oxidize lysyl and hydroxylysyl residues from collagen and elastin chains into highly reactive aldehydes, which spontaneously react with surrounding amino groups and other aldehydes to form inter- and intra-catenary covalent cross-linkages. Therefore, they are essential for the synthesis of a mature ECM and assure matrix integrity. ECM modulates cellular phenotype and function, and strikingly influences the mechanical properties of tissues. This explains the critical role of these enzymes in tissue homeostasis, and in tissue repair and remodeling. Cardiac ECM is mainly composed of fibrillar collagens which form a complex network that provides structural and biochemical support to cardiac cells and regulates cell signaling pathways. It is now becoming apparent that cardiac performance is affected by the structure and composition of the ECM and that any disturbance of the ECM contributes to cardiac disease progression. This review article compiles the major findings on the contribution of the LOX family to the development and progression of myocardial disorders.

The Association Between Myocardial Fibrosis and Depressed Capillary Density in Rat Model of Left Ventricular Hypertrophy

Myocardial fibrogenesis is initiated once the coordination between oxygen supply and demand is disrupted in pressure overload-induced cardiac hypertrophy. Clinical observations showed that myocardial fibrosis did not evenly occur in the hypertrophic myocardium. The present study was undertaken to specifically address differential vulnerabilities to fibrogenesis of different regions in the myocardium subjected to pressure overload-induced hypertrophy. SD rats were divided into two groups, sham-operated control and ascending artery constriction-induced cardiac hypotrophy. Thirty-four weeks after surgery, rats were sacrificed and hearts were harvested. Myocardial tissues were processed and sequentially sectioned for detection of collagen deposition, myocyte hypertrophy and vascular density analysis. Redundant collagen stained with Sirius red and anti-collagen I antibody was found in the extracellular matrix, but high volume of collagen fraction was largely localized more in posterior and lateral walls than in anterior wall and interventricular septum, which is in accordance with the accumulation of fibroblasts. In association with the differential regional collagen accumulation, the cardiomyocytes were more hypertrophic in the posterior and lateral wall than the other left ventricle. However, the capillary density in the lateral and posterior walls was significantly decreased. The results indicated that the posterior and lateral walls were more vulnerable to fibrogenesis post-pressure overload-induced cardiac hypertrophy, which was associated with the depressed angiogenesis in these two regions.

Dual-layer aligned-random nanofibrous scaffolds for improving gradient microstructure of tendon-to-bone healing in a rabbit extra-articular model

BACKGROUND

Tendon/ligament injuries are common sports injuries. Clinically, the repair of a ruptured tendon or ligament to its bony insertion is needed, but the enthesis structure is not well reestablished following surgical repair. Herein, we fabricated dual-layer aligned-random scaffold (ARS) by electrospinning and aimed to investigate the effect of the scaffold on tendon-to-bone healing in vivo.

MATERIALS AND METHODS

The random and dual-layer aligned-random silk fbroin poly(L-lactic acid-co-e-caprolactone) (P(LLA-CL)) nanofibrous scaffolds were successfully fabricated by electrospinning methods. Ninety New Zealand white rabbits were randomly divided into three groups (random scaffold [RS], ARS, and control groups), and they were subjected to surgery to establish an extra-articular tendon-to-bone healing model with autologous Achilles tendon.

RESULTS

Histological assessment showed that the ARS significantly increased the area of metachromasia, decreased the interface width, and improved collagen maturation and organization at the tendon-bone interface compared with the RS and control groups. Microcomputed tomography analysis showed that the bone tunnel area of RS and ARS groups was significantly smaller than those of the control group. Real-time polymerase chain reaction showed that BMP-2 and osteopontin expression levels of the tissue at the interface between the bone and graft in the RS and ARS groups were higher than those of the control group at 6 weeks. Collagen I expression level of the ARS group was significantly higher than those of the RS and control groups at 6 and 12 weeks. Moreover, the ARS groups had a better ultimate load-to-failure and stiffness than the RS and control groups.

CONCLUSION

ARS could effectively augment the tendon-to-bone integration and improve gradient microstructure in a rabbit extra-articular model by inducing the new bone formation, increasing the area of fibrocartilage, and improving collagen organization and maturation. The dual-layer aligned-random silk fibroin/P(LLA-CL) nanofibrous scaffold is proved to be a promising biomaterial for tendon-to-bone healing.

Identification of Potential Molecular Mechanisms and Candidate Genes Involved in The Acute Phase of Myocardial Infarction

Objective

This study used bioinformatics to determine genetic factors involved in progression of acute myocardial infarction (MI).

Materials and Methods

In this prospective study, gene expression profile GSE59867 was downloaded from the Gene Expression Omnibus database, which contained 46 normal samples obtained from stable coronary artery disease patients (n=46) who were without history of MI (control) and 390 samples from patients (n=111) who had evolving ST-segment elevation myocardial infarction (STEMI) as the MI group. These samples were divided into 4 groups based on time points. After identification of differentially expressed genes (DEGs), we conducted hierarchical clustering and functional enrichment analysis. Protein interaction and transcriptional regulation among DEGs were analysed.

Results

We observed 8 clusters of DEGs that had a peak or a minimum at the t=1 time point according to gene expression levels. Upregulated DEGs showed significant enrichment in the biological process, single-organism cellular process, response to stimulus and stress, and osteoclast differentiation and lysosome. Downregulated DEGs enriched in the T-cell receptor signalling pathway and natural killer cell mediated cytotoxicity. We identified multiple genes, including signal transducer and activator of transcription 3 (STAT3); LCK proto-oncogene, Src family tyrosine kinase (LCK); and FYN proto-oncogene, Src family tyrosine kinase (FYN) from the protein-protein interaction (PPI) network and/or the transcriptional regulatory network.

Conclusion

Cytokine-mediated inflammation, lysosome and osteoclast differentiation, and metabolism processes, as well as STAT3 may be involved in the acute phase of MI.

Copper-induced reduction in myocardial fibrosis is associated with increased matrix metalloproteins in a rat model of cardiac hypertrophy

AAC induces Cu loss from the heart and depressed MMP-2 in combination with increased TIMPs, leading to increased collagen deposition. TETA replenishes Cu in the heart, increases MMP-2, and decreases TIMP-1 and -2, collectively resulting in reduction in cardiac fibrosis.

The association of depressed angiogenic factors with reduced capillary density in the Rhesus monkey model of myocardial ischemia

Depressed capillary density is associated with myocardial ischemic infarction, in which hypoxia-inducible factor 1α (HIF-1α) is increased. The present study was undertaken to examine changes in the angiogenic factors whose expression is regulated by HIF-1 and their relation to the depressed capillary density in the Rhesus monkey model of myocardial ischemic infarction. Male Rhesus monkeys 2-3 years old were subjected to myocardial ischemia by permanent ligation of left anterior descending (LAD) artery leading to the development of myocardial infarction. Eight weeks after LAD ligation, copper concentrations, myocardial histological changes and capillary density were examined, along with Western blot and immunohistochemical analysis of angiogenic factors and detection of HIF-1 activity. Capillary density was significantly decreased but the concentrations of HIF-1α and HIF-1β were significantly increased in the infarct area. However, the levels of mRNA and protein for VEGF and VEGFR1 were significantly decreased. Other HIF-1 regulated angiogenic factors, including Tie-2, Ang-1 and FGF-1, were also significantly depressed, but vascular destabilizing factor Ang-2 was significantly increased. Copper concentrations were depressed in the infarct area. Copper-independent HIF-1 activity was increased shown by the elevated mRNA level of IGF-2, a HIF-1 target gene. Removal of copper by a copper chelator, tetraethylenepentamine, from primary cultures of neonatal rat cardiomyocytes also suppressed the expression of HIF-1 regulated VEGF and BNIP3, but not IGF-2. The data suggest that under ischemic conditions, copper loss suppressed the expression of critical angiogenic genes regulated by HIF-1, but did not affect copper-independent HIF-1 activation of gene expression. This copper-dependent dysregulation of angiogenic gene expression would contribute to the pathogenesis of myocardial ischemic infarction.

MicroRNA-214 exerts a Cardio-protective effect by inhibition of fibrosis

The miRNAs play important roles in regulating myocardial fibrosis. The purpose of this study was to determine the potential roles of microRNA-214 (miR-214) in cardiac fibrosis in vitro and in vivo. In vitro experiment, Ang II-induced cardiac fibroblasts (CFBs) are transfected with pre-miR-214, anti-miR-214 and their oligo controls. Gene expression was checked by Quantitative realtime-PCR (qRT-PCR) and western blotting. In the present experiment, compared with controls, expressions of collagen type I (COL I), collagen type III (COL III), transforming growth factor (TGF)-β1, and tissue inhibitors of metalloproteinase (TIMP)-1 were all increased, but matrix metalloproteinase (MMP)-1 was reduced in CFB by Ang II treatment at both mRNA and protein levels, and these alterations were found reversed by miR-214 transfection. In vivo, an anterior transmural acute myocardial infarction (AMI) was created by occlusion of the left anterior descending coronary artery after Ad-pre-miR-214, Ad-anti-miR-214 or Ad-GFP was delivered separately. Four weeks after AMI, protein contents of COL I, COL III and TGF-β1 in tissue from border area were found increased after AMI, but impaired by overexpression of miR-214. While the expression of MMP-1 was increased by miR-214 stimulation but decreased by miR-214 inhibition. These results suggested that miR-214 exerts cardio-protective effects by inhibition of fibrosis and the inhibitory effect involves TGF-β1 suppression and MMP-1/TIMP-1 regulation. Anat Rec, 299:1348-1357, 2016. © 2016 Wiley Periodicals, Inc.

Decreased copper concentrations but increased lysyl oxidase activity in ischemic hearts of rhesus monkeys

Myocardial ischemia leads to a decrease in copper (Cu) concentrations, along with collagen deposition in which Cu-dependent lysyl oxidase (LOX) catalyzes the cross-linking of collagens leading to tissue stiffness. The present study was undertaken to determine the relationship between decreased Cu concentrations and LOX activities in ischemic hearts of monkeys. Rhesus monkeys were subjected to coronary artery ligation, leading to ischemic infarction. At 8 weeks after the surgery, Cu concentrations and Cu-dependent cytochrome c oxidase (CCO) activities in the infarct area were significantly decreased. Unexpectedly, the Cu-dependent LOX activities in the same area were significantly increased. LOX proteins were accumulated in the cytosol of myofibroblasts, endothelial cells, and residual cardiomyocytes in the infarct area. In contrast, LOX was only found in fibroblasts and myocardial intercalated discs between cardiomyocytes in sham-operated controls. The LOX mRNA level was also increased in the infarct area compared to the sham operated control. This upregulation of LOX was associated with significant increases in collagen deposition; protein levels of type I and III collagens were significantly increased along with increases in their mRNA levels in the infarct area. This finding indicates that under myocardial infarction, Cu-dependent CCO activities were depressed but LOX activities were increased most likely through Cu redistribution although Cu concentrations were significantly depressed.

Pathophysiology of Myocardial Infarction

Myocardial infarction is defined as sudden ischemic death of myocardial tissue. In the clinical context, myocardial infarction is usually due to thrombotic occlusion of a coronary vessel caused by rupture of a vulnerable plaque. Ischemia induces profound metabolic and ionic perturbations in the affected myocardium and causes rapid depression of systolic function. Prolonged myocardial ischemia activates a "wavefront" of cardiomyocyte death that extends from the subendocardium to the subepicardium. Mitochondrial alterations are prominently involved in apoptosis and necrosis of cardiomyocytes in the infarcted heart. The adult mammalian heart has negligible regenerative capacity, thus the infarcted myocardium heals through formation of a scar. Infarct healing is dependent on an inflammatory cascade, triggered by alarmins released by dying cells. Clearance of dead cells and matrix debris by infiltrating phagocytes activates anti-inflammatory pathways leading to suppression of cytokine and chemokine signaling. Activation of the renin-angiotensin-aldosterone system and release of transforming growth factor-β induce conversion of fibroblasts into myofibroblasts, promoting deposition of extracellular matrix proteins. Infarct healing is intertwined with geometric remodeling of the chamber, characterized by dilation, hypertrophy of viable segments, and progressive dysfunction. This review manuscript describes the molecular signals and cellular effectors implicated in injury, repair, and remodeling of the infarcted heart, the mechanistic basis of the most common complications associated with myocardial infarction, and the pathophysiologic effects of established treatment strategies. Moreover, we discuss the implications of pathophysiological insights in design and implementation of new promising therapeutic approaches for patients with myocardial infarction.

Matrix cross-linking lysyl oxidases are induced in response to myocardial infarction and promote cardiac dysfunction

AIMS

After myocardial infarction (MI), extensive remodelling of the extracellular matrix contributes to scar formation. While aiming to preserve tissue integrity, this fibrotic response is also associated with adverse events, including a markedly increased risk of heart failure, ventricular arrhythmias, and sudden cardiac death. Cardiac fibrosis is characterized by extensive deposition of collagen and also by increased stiffness as a consequence of enhanced collagen cross-linking. Members of the lysyl oxidase (LOX) family of enzymes are responsible for the formation of collagen cross-links. This study investigates the contribution of LOX family members to the heart response to MI.

METHODS AND RESULTS

Experimental MI was induced in C57BL/6 mice by permanent ligation of the left anterior descending coronary artery. The expression of LOX isoforms (LOX and LOXL1-4) was strongly increased upon MI, and this response was accompanied by a significant accumulation of mature collagen fibres in the infarcted area. LOX expression was observed in areas of extensive remodelling, partially overlapping with α-smooth muscle actin-expressing myofibroblasts. Tumour growth factor-β as well as hypoxia-activated pathways contributed to the induction of LOX expression in cardiac fibroblasts. Finally, in vivo post-infarction treatment with the broadband LOX inhibitor β-aminopropionitrile or, selectively, with a neutralizing antibody against the canonical LOX isoform attenuated collagen accumulation and maturation and also resulted in reduced ventricular dilatation and improved cardiac function.

CONCLUSION

LOX family members contribute significantly to the detrimental effects of cardiac remodelling, highlighting LOX inhibition as a potential therapeutic strategy for post-infarction recovery.

Systems analysis of gene ontology and biological pathways involved in post-myocardial infarction responses

Background

Pathway analysis has been widely used to gain insight into essential mechanisms of the response to myocardial infarction (MI). Currently, there exist multiple pathway databases that organize molecular datasets and manually curate pathway maps for biological interpretation at varying forms of organization. However, inconsistencies among different databases in pathway descriptions, frequently due to conflicting results in the literature, can generate incorrect interpretations. Furthermore, although pathway analysis software provides detailed images of interactions among molecules, it does not exhibit how pathways interact with one another or with other biological processes under specific conditions.

Methods

We propose a novel method to standardize descriptions of enriched pathways for a set of genes/proteins using Gene Ontology terms. We used this method to examine the relationships among pathways and biological processes for a set of condition-specific genes/proteins, represented as a functional biological pathway-process network. We applied this algorithm to a set of 613 MI-specific proteins we previously identified.

Results

A total of 96 pathways from Biocarta, KEGG, and Reactome, and 448 Gene Ontology Biological Processes were enriched with these 613 proteins. The pathways were represented as Boolean functions of biological processes, delivering an interactive scheme to organize enriched information with an emphasis on involvement of biological processes in pathways. We extracted a network focusing on MI to demonstrate that tyrosine phosphorylation of Signal Transducer and Activator of Transcription (STAT) protein, positive regulation of collagen metabolic process, coagulation, and positive/negative regulation of blood coagulation have immediate impacts on the MI response.

Conclusions

Our method organized biological processes and pathways in an unbiased approach to provide an intuitive way to identify biological properties of pathways under specific conditions. Pathways from different databases have similar descriptions yet diverse biological processes, indicating variation in their ability to share similar functional characteristics. The coverages of pathways can be expanded with the incorporation of more biological processes, predicting involvement of protein members in pathways. Further, detailed analyses of the functional biological pathway-process network will allow researchers and scientists to explore critical routes in biological systems in the progression of disease.

Decreases in electrocardiographic R-wave amplitude and QT interval predict myocardial ischemic infarction in Rhesus monkeys with left anterior descending artery ligation

Clinical studies have demonstrated the predictive values of changes in electrocardiographic (ECG) parameters for the preexisting myocardial ischemic infarction. However, a simple and early predictor for the subsequent development of myocardial infarction during the ischemic phase is of significant value for the identification of ischemic patients at high risk. The present study was undertaken by using non-human primate model of myocardial ischemic infarction to fulfill this gap. Twenty male Rhesus monkeys at age of 2–3 years old were subjected to left anterior descending artery ligation. This ligation was performed at varying position along the artery so that it produced varying sizes of myocardial infarction at the late stage. The ECG recording was undertaken before the surgical procedure, at 2 h after the ligation, and 8 weeks after the surgery for each animal. The correlation of the changes in the ECG waves in the early or the late stage with the myocardial infarction size was analyzed. The R wave depression and the QT shortening in the early ischemic stage were found to have an inverse correlation with the myocardial infarction size. At the late stage, the R wave depression, the QT prolongation, the QRS score, and the ST segment elevation were all closely correlated with the developed infarction size. The poor R wave progression was identified at both the early ischemic and the late infarction stages. Therefore, the present study using non-human primate model of myocardial ischemic infarction identified the decreases in the R wave and the QT interval as early predictors of myocardial infarction. Validation of these parameters in clinical studies would greatly help identifying patients with myocardial ischemia at high risk for the subsequent development of myocardial infarction.

CXC-type chemokines promote myofibroblast phenoconversion and prostatic fibrosis

Recent studies from our group suggest that extracellular matrix (ECM) deposition and fibrosis characterize the peri-urethral prostate tissues of some men suffering from Lower Urinary Tract Symptoms (LUTS) and that fibrosis may be a contributing factor to the etiology of LUTS. Fibrosis can generally be regarded as an errant wound-healing process in response to chronic inflammation, and several studies have shown that the aging prostate tissue microenvironment is rich with inflammatory cells and proteins. However, it is unclear whether these same inflammatory proteins, particularly CXC-type chemokines, can mediate myofibroblast phenoconversion and the ECM deposition necessary for the development of prostatic tissue fibrosis. To examine this, immortalized and primary prostate stromal fibroblasts treated with TGF-β1, CXCL5, CXCL8, or CXCL12 were evaluated morphologically by microscopy, by immunofluorescence and qRT-PCR for αSMA, collagen 1, vimentin, calponin, and tenascin protein and transcript expression, and by gel contraction assays for functional myofibroblast phenoconversion. The results of these studies showed that that immortalized and primary prostate stromal fibroblasts are induced to express collagen 1 and 3 and αSMA gene transcripts and proteins and to undergo complete and functional myofibroblast phenoconversion in response to CXC-type chemokines, even in the absence of exogenous TGF-β1. Moreover, CXCL12-mediated myofibroblast phenoconversion can be completely abrogated by inhibition of the CXCL12 receptor, CXCR4. These findings suggest that CXC-type chemokines, which comprise inflammatory proteins known to be highly expressed in the aging prostate, can efficiently and completely mediate myofibroblast phenoconversion and may thereby promote fibrotic changes in prostate tissue architecture associated with the development and progression of male lower urinary tract dysfunction.