Deficiency in TIMP-3 increases cardiac rupture and mortality post-myocardial infarction via EGFR signaling: beneficial effects of cetuximab

TIMP3 induces gene expression partly through PI3K and their association with vascularization and heart rate

Background

Tissue inhibitor of metalloproteinase 3 (TIMP3) was recently demonstrated capable to regulate some gene expression in a myocardial infarction model. Here we aim to explore the gene expression profile in TIMP3-treated cardiomyocytes and related potential cardiovascular functions.

Methods

Total RNA extracted from cultured neonatal rat ventricular myocytes (NRVMs) were used for RNA sequencing analysis and real-time PCR. KEGG pathway enrichment assay and Ingenuity Pathway Analysis (IPA) were performed to study the signaling pathways and downstream effects. Western blot was used to detect phosphorylation of protein kinase B (Akt). A Cell Counting Kit-8 assay was employed to evaluate the proliferation of human umbilical vein endothelial cells (HUVECs). Contraction rate of NRVMs was measured with microscopy.

Results

RNA sequencing data showed that expression of 2,526 genes were significantly modulated by recombinant TIMP3 (rTIMP3, 100 ng/ml) in NRVMs. Some differentially expressed genes (DEGs) were validated with real-time PCR. Several KEGG pathways including the phosphoinositide-3-kinase (PI3K)-Akt pathway were significantly regulated by rTIMP3. Phosphorylation of Akt was increased by rTIMP3 and a PI3K inhibitor LY294002 suppressed rTIMP3-induced up-regulation of some genes. Some DEGs were predicted by IPA to increase vascularization, and some to decrease heart rate. RTIMP3 could reduce the contraction rate of NRVMs and its conditioned media increased the proliferation of HUVECs.

Conclusion

TIMP3 can regulate expression of multiple genes partly through PI3K. Some DEGs were associated with activation of vascularization and some with heart rate reduction. This study suggests that TIMP3 can potentially modulate cardiovascular functions via DEGs.

In vitro bioreactor for mechanical control and characterization of tissue constructs

Cardiac fibrosis is a key contributor to the onset and progression of heart failure and occurs from extracellular matrix accumulation via activated cardiac fibroblasts. Cardiac fibroblasts activate in response to mechanical stress and have been studied in the past by applying forces and deformations to three-dimensional, cell-seeded gels and tissue constructs in vitro. Unfortunately, previous stretching platforms have traditionally not enabled mechanical property assessment to be performed with an efficient throughput, thereby limiting the full potential of in vitro mechanobiology studies. We have developed a novel in vitro platform to study cell-populated tissue constructs under dynamic mechanical stimulation while also performing repeatable, non-destructive stress-strain tests in living constructs. Additionally, this platform can perform these tests across all constructs in a multi-well plate simultaneously, providing exciting potential for direct, functional readouts in future screening applications. In our pilot application, we showed that cyclically stretching cell-populated tissue constructs composed of murine cardiac fibroblasts within a 3D fibrin matrix leads to collagen accumulation and increased tissue stiffness over a three-day time course. Results of this study validate our platform's ability to apply mechanical loads to tissues while performing live mechanical analyses to observe cell-mediated tissue remodeling.

Fibroblast mechanotransduction network predicts targets for mechano-adaptive infarct therapies

Regional control of fibrosis after myocardial infarction is critical for maintaining structural integrity in the infarct while preventing collagen accumulation in non-infarcted areas. Cardiac fibroblasts modulate matrix turnover in response to biochemical and biomechanical cues, but the complex interactions between signaling pathways confound efforts to develop therapies for regional scar formation. We employed a logic-based ordinary differential equation model of fibroblast mechano-chemo signal transduction to predict matrix protein expression in response to canonical biochemical stimuli and mechanical tension. Functional analysis of mechano-chemo interactions showed extensive pathway crosstalk with tension amplifying, dampening, or reversing responses to biochemical stimuli. Comprehensive drug target screens identified 13 mechano-adaptive therapies that promote matrix accumulation in regions where it is needed and reduce matrix levels in regions where it is not needed. Our predictions suggest that mechano-chemo interactions likely mediate cell behavior across many tissues and demonstrate the utility of multi-pathway signaling networks in discovering therapies for context-specific disease states.

Modulation of Cardiac Fibrosis in and Beyond Cells

The extracellular matrix (ECM) plays important roles in maintaining physiological structure and functions of various tissues and organs. Cardiac fibrosis is the excess deposition of ECM, including both fibrillar (collagens I and III) and non-fibrillar proteins. Characteristics of fibrosis can vary depending on the pathology, with focal fibrosis occurring following myocardial infarction (MI), and diffuse interstitial and perivascular fibrosis mainly in non-ischemic heart diseases. Compliance of the fibrotic tissue is significantly lower than the normal myocardium, and this can compromise the diastolic, as well as systolic dysfunction. Therefore, strategies to combat cardiac fibrosis have been investigated. Upon injury or inflammation, activated cardiac fibroblasts (myofibroblasts) produce more ECM proteins and cause fibrosis. The activation could be inhibited or the myofibroblasts could be ablated by targeting their specific expressed proteins. Modulation of tissue inhibitors of metalloproteinases (TIMPs) and moderate exercise can also suppress cardiac fibrosis. More recently, sex differences in cardiac fibrosis have come to light with differential fibrotic response in heart diseases as well as in fibroblast functions in vitro. This mini-review discusses recent progress in cardiac fibroblasts, TIMPs, sex differences and exercise in modulation of cardiac fibrosis.

Does the Heart Want What It Wants? A Case for Self-Adapting, Mechano-Sensitive Therapies After Infarction

There is a critical need for interventions to control the development and remodeling of scar tissue after myocardial infarction. A significant hurdle to fibrosis-related therapy is presented by the complex spatial needs of the infarcted ventricle, namely that collagenous buildup is beneficial in the ischemic zone but detrimental in the border and remote zones. As a new, alternative approach, we present a case to develop self-adapting, mechano-sensitive drug targets in order to leverage local, microenvironmental mechanics to modulate a therapy's pharmacologic effect. Such approaches could provide self-tuning control to either promote fibrosis or reduce fibrosis only when and where it is beneficial to do so.

Combined genetic and chemical screens indicate protective potential for EGFR inhibition to cardiomyocytes under hypoxia

The return of blood flow to ischemic heart after myocardial infarction causes ischemia-reperfusion injury. There is a clinical need for novel therapeutic targets to treat myocardial ischemia-reperfusion injury. Here we screened for targets for the treatment of ischemia-reperfusion injury using a combination of shRNA and drug library analyses in HL-1 mouse cardiomyocytes subjected to hypoxia and reoxygenation. The shRNA library included lentiviral constructs targeting 4625 genes and the drug library 689 chemical compounds approved by the Food and Drug Administration (FDA). Data were analyzed using protein-protein interaction and pathway analyses. EGFR inhibition was identified as a cardioprotective mechanism in both approaches. Inhibition of EGFR kinase activity with gefitinib improved cardiomyocyte viability in vitro. In addition, gefitinib preserved cardiac contractility in zebrafish embryos exposed to hypoxia-reoxygenation in vivo. These findings indicate that the EGFR inhibitor gefitinib is a potential candidate for further studies of repurposing the drug for the treatment of myocardial infarction.

Targeted Injection of a Truncated Form of Tissue Inhibitor of Metalloproteinase 3 Alters Post-Myocardial Infarction Remodeling

Infarct expansion can occur after myocardial infarction (MI), which leads to adverse left ventricular (LV) remodeling and failure. An imbalance between matrix metalloproteinase (MMP) induction and tissue inhibitors of MMPs (TIMPs) can accelerate this process. Past studies have shown different biologic effects of TIMP-3, which may depend upon specific domains within the TIMP-3 molecule. This study tested the hypothesis that differential effects of direct myocardial injections of either a full-length recombinant TIMP-3 (F-TIMP-3) or a truncated form encompassing the N-terminal region (N-TIMP-3) could be identified post-MI. MI was induced in pigs that were randomized for MI injections (30 mg) and received targeted injections within the MI region of F-TIMP-3 (n = 8), N-TIMP-3 (n = 9), or saline injection (MI-only, n = 11). At 14 days post-MI, LV ejection fraction fell post-MI but remained higher in both TIMP-3 groups. Tumor necrosis factor and interleukin-10 mRNA increased by over 10-fold in the MI-only and N-TIMP-3 groups but were reduced with F-TIMP-3 at this post-MI time point. Direct MI injection of either a full-length or truncated form of TIMP-3 is sufficient to favorably alter the course of post-MI remodeling. The functional and differential relevance of TIMP-3 domains has been established in vivo since the TIMP-3 constructs demonstrated different MMP/cytokine expression profiles. These translational studies identify a unique and more specific therapeutic strategy to alter the course of LV remodeling and dysfunction after MI. SIGNIFICANCE STATEMENT: Using different formulations of tissue inhibitor of matrix metalloproteinase-3 (TIMP-3), when injected into the myocardial infarction (MI) region, slowed the progression of indices of left ventricular (LV) failure, suggesting that the N terminus of TIMP-3 is sufficient to attenuate early adverse functional events post-MI. Injections of full-length recombinant TIMP-3, but not of the N-terminal region of TIMP-3, reduced relative indices of inflammation at the mRNA level, suggesting that the C-terminal region affects other biological pathways. These unique proof-of-concept studies demonstrate the feasibility of using recombinant small molecules to selectively interrupt adverse LV remodeling post-MI.

Validation of diagnostic criteria and histopathological characterization of cardiac rupture in the mouse model of nonreperfused myocardial infarction

In patients with myocardial infarction (MI), cardiac rupture is an uncommon but catastrophic complication. In the mouse model of nonreperfused MI, reported rupture rates are highly variable and depend not only on the genetic background and sex of animals but also on the method used for documentation of rupture. In most studies, diagnosis of cardiac rupture is based on visual inspection during autopsy; however, criteria are poorly defined. We performed systematic histopathological analysis of whole hearts from C57BL/6J mice dying after nonreperfused MI and evaluated the reliability of autopsy-based criteria in identification of rupture. Moreover, we compared the cell biological environment of the infarct between rupture-related and rupture-independent deaths. Histopathological analysis documented rupture in 50% of mice dying during the first week post-MI. Identification of a gross rupture site was highly specific but had low sensitivity; in contrast, hemothorax had high sensitivity but low specificity. Mice with rupture had lower myofibroblast infiltration, accentuated macrophage influx, and a trend toward reduced collagen content in the infarct. Male mice had increased mortality and higher incidence of rupture. However, infarct myeloid cells harvested from male and female mice at the peak of the incidence of rupture had comparable inflammatory gene expression. In conclusion, the reliability of autopsy in documentation of rupture in infarcted mice is dependent on the specific criteria used. Macrophage-driven inflammation and reduced activation of collagen-secreting reparative myofibroblasts may be involved in the pathogenesis of post-MI cardiac rupture.NEW & NOTEWORTHY We show that cardiac rupture accounts for 50% of deaths in C57BL/6J mice undergoing nonreperfused myocardial infarction protocols. Overestimation of rupture events in published studies likely reflects the low specificity of hemothorax as a criterion for documentation of rupture. In contrast, identification of a gross rupture site has high specificity and low sensitivity. We also show that mice dying of rupture have increased macrophage influx and attenuated myofibroblast infiltration in the infarct. These findings are consistent with a role for perturbations in the balance between inflammatory and reparative responses in the pathogenesis of postinfarction cardiac rupture. We also report that the male predilection for rupture in infarcted mice is not associated with increased inflammatory activation of myeloid cells.

Delivery of a matrix metalloproteinase-responsive hydrogel releasing TIMP-3 after myocardial infarction: effects on left ventricular remodeling

Although improvements in timing and approach for early reperfusion with acute coronary syndromes have occurred, myocardial injury culminating in a myocardial infarction (MI) remains a common event. Although a multifactorial process, an imbalance between the induction of proteolytic pathways, such as matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of metalloproteinase (TIMPs), has been shown to contribute to this process. In the present study, a full-length TIMP-3 recombinant protein (rTIMP-3) was encapsulated in a specifically formulated hyaluronic acid (HA)-based hydrogel that contained MMP-cleavable peptide cross-links, which influenced the rate of rTIMP-3 release from the HA gel. The effects of localized delivery of this MMP-sensitive HA gel (HAMMPS) alone and containing rTIMP-3 (HAMMPS/rTIMP-3) were examined in terms of the natural history of post-MI remodeling. Pigs were randomized to one of the following three different groups: MI and saline injection (MI/saline group, 100-μl injection at nine injection sites, n = 7), MI and HAMMPS injection (MI/HAMMPS group; 100-μl injection at nine injection sites, n = 7), and MI and HAMMPS/rTIMP-3 injection (MI/HAMMPS/rTIMP-3 group; 20-μg/100-μl injection at nine injection sites, n = 7). Left ventricular (LV) echocardiography was serially performed up to 28 days post-MI. LV dilation, as measured by end-diastolic volume, and the degree of MI wall thinning were reduced by ~50% in the HAMMPS/rTIMP-3 group ( P < 0.05). Furthermore, indexes of heart failure progression post-MI, such as LV filling pressures and left atrial size, were also attenuated to the greatest degree in the HAMMPS/rTIMP-3 group. At 28 days post-MI, HAMMPS/rTIMP-3 caused a relative reduction in the transcriptional profile for myofibroblasts as well as profibrotic pathways, which was confirmed by subsequent histochemistry. In conclusion, these findings suggest that localized delivery of a MMP-sensitive biomaterial that releases a recombinant TIMP holds promise as a means to interrupt adverse post-MI remodeling. NEW & NOTEWORTHY The present study targeted a myocardial matrix proteolytic system, matrix metalloproteinases (MMPs), through the use of a recombinant tissue inhibitor of MMPs incorporated into a MMP-sensitive hydrogel, which was regionally injected using a large animal model of myocardial infarction. Left ventricular geometry and function and indexes of myocardial remodeling were improved with this approach and support the advancement of localized therapeutic strategies that specifically target the myocardial matrix.

Myocardial infarction remodeling that progresses to heart failure: a signaling misunderstanding

After myocardial infarction, remodeling of the left ventricle involves a wound-healing orchestra involving a variety of cell types. In order for wound healing to be optimal, appropriate communication must occur; these cells all need to come in at the right time, be activated at the right time in the right amount, and know when to exit at the right time. When this occurs, a new homeostasis is obtained within the infarct, such that infarct scar size and quality are sufficient to maintain left ventricular size and shape. The ideal scenario does not always occur in reality. Often, miscommunication can occur between infarct and remote spaces, across the temporal wound-healing spectrum, and across organs. When miscommunication occurs, adverse remodeling can progress to heart failure. This review discusses current knowledge gaps and recent development of the roles of inflammation and the extracellular matrix in myocardial infarction remodeling. In particular, the macrophage is one cell type that provides direct and indirect regulation of both the inflammatory and scar-forming responses. We summarize current research efforts focused on identifying biomarker indicators that reflect the status of each component of the wound-healing process to better predict outcomes.

Essential role for EGFR tyrosine kinase and ER stress in myocardial infarction in type 2 diabetes

We previously reported that EGFR tyrosine kinase (EGFRtk) activity and endoplasmic reticulum (ER) stress are enhanced in type 2 diabetic (T2D) mice and cause vascular dysfunction. In the present study, we determined the in vivo contribution of EGFRtk and ER stress in acute myocardial infarction induced by acute ischemia (40 min)-reperfusion (24 h) (I/R) injury in T2D (db^-/db^-) mice. We treated db^-/db^- mice with EGFRtk inhibitor (AG1478, 10 mg/kg/day) for 2 weeks. Mice were then subjected to myocardial I/R injury. The db^-/db^- mice developed a significant infarct after I/R injury. The inhibition of EGFRtk significantly reduced the infarct size and ER stress induction. We also determined that the inhibition of ER stress (tauroursodeoxycholic acid, TUDCA, 150 mg/kg per day) in db^-/db^- significantly decrease the infarct size indicating that ER stress is a downstream mechanism to EGFRtk. Moreover, AG1478 and TUDCA reduced myocardium p38 and ERK1/2 MAP-kinases activity, and increased the activity of the pro-survival signaling cascade Akt. Additionally, the inhibition of EGFRtk and ER stress reduced cell apoptosis and the inflammation as indicated by the reduction in macrophages and neutrophil infiltration. We determined for the first time that the inhibition of EGFRtk protects T2D heart against I/R injury through ER stress-dependent mechanism. The cardioprotective effect of EGFRtk and ER stress inhibition involves the activation of survival pathway, and inhibition of apoptosis, and inflammation. Thus, targeting EGFRtk and ER stress has the potential for therapy to overcome myocardial infarction in T2D.

Altered Bone Mechanics, Architecture and Composition in the Skeleton of TIMP-3-Deficient Mice

Tissue inhibitor of metalloproteinases-3 (TIMP-3) maintains a healthy extracellular matrix by regulating matrix metalloproteinases (MMP), disintegrin-metalloproteinases (ADAM), and disintegrin-metalloproteinases with ThromboSpondin-like motifs (ADAMTS) activity. Currently, there is a need for a comprehensive understanding of the effects of TIMP-3 on the bone quality and integrity. In this study, we examined the mechanical, morphological, and compositional properties of TIMP-3 knock out (Timp-3 ^-/-) mouse bone. We hypothesize that the lack of TIMP-3 plays an important role in maintaining the overall bone integrity. Mechanical properties of humeri, lumbar vertebrae, and femurs from Timp-3 ^-/- mice were determined using 3-point bending, compression, and notched 3-point bending, respectively. Morphological properties of the humeral cortical and trabecular bone and the caudal vertebrae cortical bone were evaluated using micro-computed tomography, while the composition of the femoral cortical and trabecular bone was examined using Fourier transform infrared spectroscopic imaging. Our results revealed that the integrity of the Timp-3 ^-/- bone is compromised due to changes in its composition, structure, and mechanics. Reductions in the yield and ultimate load and stress capacity, and loss in bone fracture toughness were attributed to reduced density and thickness, and increased porosity of cortical bone. Thin trabeculae were dense, highly connected, and closely packed in Timp-3 ^-/- bone. Furthermore, altered cortical and trabecular bone mineralization and increased compositional heterogeneity were found in Timp-3 ^-/- bone, all being indicative of high bone remodeling. In conclusion, this study suggests that the lack of TIMP-3 is detrimental to bone development and maintenance.

A single injection of protein-loaded coacervate-gel significantly improves cardiac function post infarction

After myocardial infarction (MI), the heart undergoes fibrotic pathological remodeling instead of repair and regeneration. With multiple pathologies developing after MI, treatment using several proteins is expected to address this range of pathologies more effectively than a single-agent therapy. A factorial design of experiments study guided us to combine three complementary factors in one injection: tissue inhibitor of metalloproteinases-3 (TIMP-3) was embedded in a fibrin gel for signaling in the initial phase of the treatment, while basic fibroblast growth factor (FGF-2) and stromal cell-derived factor 1-alpha (SDF-1α) were embedded in heparin-based coacervates for sustained release and distributed within the same fibrin gel to exert their effects over a longer period. The gel was then tested in a rat model of myocardial infarction. Contractility of rat hearts treated with the protein coacervate-gel composite stabilized and slightly improved after the first week while contractility continued to decrease in rats treated with free proteins or saline over the 8 week study period. Hearts receiving the protein coacervate-gel composite treatment also exhibited reduced ventricular dilation, inflammation, fibrosis, and extracellular matrix (ECM) degradation. Revascularization, cardiomyocyte preservation, stem cell homing, and increased myocardial strain likely all contributed to the repair. This study demonstrates the potential of a multifactorial therapeutic approach in MI, using three complementary proteins delivered sequentially for comprehensive healing. The study also shows the necessity of controlled delivery for growth factors and cytokines to be an effective treatment.

Epidermal Growth Factor Receptor Transactivation: Mechanisms, Pathophysiology, and Potential Therapies in the Cardiovascular System

Epidermal growth factor receptor (EGFR) activation impacts the physiology and pathophysiology of the cardiovascular system, and inhibition of EGFR activity is emerging as a potential therapeutic strategy to treat diseases including hypertension, cardiac hypertrophy, renal fibrosis, and abdominal aortic aneurysm. The capacity of G protein-coupled receptor (GPCR) agonists, such as angiotensin II (AngII), to promote EGFR signaling is called transactivation and is well described, yet delineating the molecular processes and functional relevance of this crosstalk has been challenging. Moreover, these critical findings are dispersed among many different fields. The aim of our review is to highlight recent advancements in defining the signaling cascades and downstream consequences of EGFR transactivation in the cardiovascular renal system. We also focus on studies that link EGFR transactivation to animal models of the disease, and we discuss potential therapeutic applications.

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.

Myofibroblasts and the extracellular matrix network in post-myocardial infarction cardiac remodeling

The cardiac extracellular matrix (ECM) fills the space between cells, supports tissue organization, and transduces mechanical, chemical, and biological signals to regulate homeostasis of the left ventricle (LV). Following myocardial infarction (MI), a multitude of ECM proteins are synthesized to replace myocyte loss and form a reparative scar. Activated fibroblasts (myofibroblasts) are the primary source of ECM proteins, thus playing a key role in cardiac repair. A balanced turnover of ECM through regulation of synthesis by myofibroblasts and degradation by matrix metalloproteinases (MMPs) is critical for proper scar formation. In this review, we summarize the current literature on the roles of myofibroblasts, MMPs, and ECM proteins in MI-induced LV remodeling. In addition, we discuss future research directions that are needed to further elucidate the molecular mechanisms of ECM actions to optimize cardiac repair.

Translating Koch's postulates to identify matrix metalloproteinase roles in postmyocardial infarction remodeling: cardiac metalloproteinase actions (CarMA) postulates

The first matrix metalloproteinase (MMP) was described in 1962; and since the 1990s, cardiovascular research has focused on understanding how MMPs regulate many aspects of cardiovascular pathology from atherosclerosis formation to myocardial infarction and stroke. Although much information has been gleaned by these past reports, to a large degree MMP cardiovascular biology remains observational, with few studies homing in on cause and effect relationships. Koch's postulates were first developed in the 19th century as a way to establish microorganism function and were modified in the 20th century to include methods to establish molecular causality. In this review, we outline the concept for establishing a similar approach to determine causality in terms of MMP functions. We use left ventricular remodeling postmyocardial infarction as an example, but this approach will have broad applicability across both the cardiovascular and the MMP fields.

Expression of the tissue inhibitor of metalloproteinase-3 by transplanted VSMCs modifies heart structure and function after myocardial infarction

OBJECTIVES

Extracellular matrix (ECM) remodelling is a critical aspect of cardiac remodelling following myocardial infarction. Tissue inhibitors of metalloproteinases (TIMPs) are physiological inhibitors of matrix metalloproteinases (MMPs) that degrade the ECM proteins. TIMP-3 is highly expressed in the heart and is markedly downregulated in patients with ischaemic cardiomyopathy. Cell-based gene therapy can enhance the effects of cell transplantation by temporally and spatially regulating the release of the gene product. The purpose of this study was to investigate the role of TIMP-3 gene-transfected vascular smooth muscle cells (VSMCs) in modifying heart structure and function in rats when transplanted 3days after myocardial infarction (MI).

METHODS

Anesthetised rats were subjected to coronary artery ligation followed 3days later by thoracotomy and transplantation of TIMP-3 gene-transfected VSMCs, untransfected VSMCs or medium injected directly into the ischaemic myocardium. We assessed left ventricular structure and function by echocardiography and morphometry, and measured the levels of myocardial matrix metalloproteinase-2 and -9 (MMP-2, MMP-9), TIMP-3 and tumour necrosis factor-α (TNF-α) at 4weeks post-myocardial infarction.

RESULTS

Transplantation of TIMP-3 gene-transfected VSMCs and untransfected VSMCs significantly decreased scar expansion and ventricular dilatation 25days post-transplantation (4weeks after MI). MMPs and TNF-α levels were reduced in the transplantation groups when compared to the group that was given an injection of medium only. Transplantation of TIMP-3 gene-transfected VSMCs was more effective in preventing progressive cardiac dysfunction, ventricular dilatation and in reducing MMP-2, MMP-9 and TNF-α levels when compared to the transplantation of untransfected VSMCs.

CONCLUSIONS

TIMP-3 gene transfection was associated with attenuated left ventricular dilation and recovery of systolic function after MI compared with the control. TIMP-3 transfection enhanced the effects of transplanted VSMCs in rats by inhibiting matrix degradation and inflammatory cytokine expression, leading to improved myocardial remodelling.

Integrative computational and experimental approaches to establish a post-myocardial infarction knowledge map

Vast research efforts have been devoted to providing clinical diagnostic markers of myocardial infarction (MI), leading to over one million abstracts associated with “MI” and “Cardiovascular Diseases” in PubMed. Accumulation of the research results imposed a challenge to integrate and interpret these results. To address this problem and better understand how the left ventricle (LV) remodels post-MI at both the molecular and cellular levels, we propose here an integrative framework that couples computational methods and experimental data. We selected an initial set of MI-related proteins from published human studies and constructed an MI-specific protein-protein-interaction network (MIPIN). Structural and functional analysis of the MIPIN showed that the post-MI LV exhibited increased representation of proteins involved in transcriptional activity, inflammatory response, and extracellular matrix (ECM) remodeling. Known plasma or serum expression changes of the MIPIN proteins in patients with MI were acquired by data mining of the PubMed and UniProt knowledgebase, and served as a training set to predict unlabeled MIPIN protein changes post-MI. The predictions were validated with published results in PubMed, suggesting prognosticative capability of the MIPIN. Further, we established the first knowledge map related to the post-MI response, providing a major step towards enhancing our understanding of molecular interactions specific to MI and linking the molecular interaction, cellular responses, and biological processes to quantify LV remodeling.

Heart attack, known medically as myocardial infarction, often occurs as a result of partial shortage of blood supply to a portion of the heart, leading to the death of heart muscle cells. Following myocardial infarction, complications might arise, including arrhythmia, myocardial rupture, left ventricular dysfunction, and heart failure. Although myocardial infarction can be quickly diagnosed using a various number of tests, including blood tests and electrocardiography, there have been no available prognostic tests to predict the long-term outcome in response to myocardial infarction. Here, we present a framework to analyze how the left ventricle responds to myocardial infarction by combining protein interactome and experimental results retrieved from published human studies. The framework organized current understanding of molecular interactions specific to myocardial infarction, cellular responses, and biological processes to quantify left ventricular remodeling process. Specifically, our knowledge map showed that transcriptional activity, inflammatory response, and extracellular matrix remodeling are the main functional themes post myocardial infarction. In addition, text analytics of relevant abstracts revealed differentiated protein expressions in plasma or serum expressions from patients with myocardial infarction. Using this data, we predicted expression levels of other proteins following myocardial infarction.

5-Lipoxygenase facilitates healing after myocardial infarction

Early healing after myocardial infarction (MI) is characterized by a strong inflammatory reaction. Most leukotrienes are pro-inflammatory and are therefore potential mediators of healing and remodeling after myocardial ischemia. The enzyme 5-lipoxygenase (5-LOX) has a key role in the transformation of arachidonic acid in leukotrienes. Thus, we tested the effect of 5-LOX on healing after MI. After chronic coronary artery ligation, early mortality was significantly increased in 5-LOX^−/− when compared to matching wildtype (WT) mice due to left ventricular rupture. This effect could be reproduced in mice treated with the 5-LOX inhibitor Zileuton. A perfusion mismatch due to the vasoactive potential of leukotrienes is not responsible for left ventricular rupture since local blood flow assessed by magnetic resonance perfusion measurements was not different. However, after MI, there was an accentuation of the inflammatory reaction with an increase of pro-inflammatory macrophages. Yet, mortality was not changed in chimeric mice (WT vs. 5-LOX^−/− bone marrow in 5-LOX^−/− animals), indicating that an altered function of 5-LOX^−/− inflammatory cells is not responsible for the phenotype. Collagen production and accumulation of fibroblasts were significantly reduced in 5-LOX^−/− mice in vivo after MI. This might be due to an impaired migration of 5-LOX^−/− fibroblasts, as shown in vitro to serum. In conclusion, a lack or inhibition of 5-LOX increases mortality after MI because of healing defects. This is not mediated by a change in local blood flow, but through an altered inflammation and/or fibroblast function.

Assessment of cardiac inflammation and remodeling during the development of streptozotocin-induced diabetic cardiomyopathy in vivo: a time course analysis

In this study, we examined cardiac inflammation, fibrosis and left ventricular (LV) function during the development of streptozotocin (STZ)-induced diabetic cardiomyopathy using an animal model of diabetes mellitus (DM). Diabetes was induced in 22 Sprague‑Dawley rats by an intraperitoneal single injection of STZ (70 mg/kg). Non-diabetic animals served as the controls (n=6). LV function was documented using the conductance catheter technique 2 and 6 weeks after the induction of diabetes. Cardiac tissue was analyzed for cardiac immune cell infiltration, oxidative stress and remodeling in rats with STZ-induced diabetes at 2 different time points by immunohistochemistry. Cardiac function was significantly impaired in the diabetic animals. After 2 weeks, the induction of diabetes resulted in impaired cardiac function indexed by a decrease in systolic and diastolic LV function. This impairment of LV performance continued for up to 6 weeks after the STZ injection. This was associated with an increase in cardiac CD3+ and CD8a+ immune cell invasion and fibrosis, indexed by an increase in collagen content (p<0.05). Furthermore, oxidative stress response and matrix remodeling were increased after 2 weeks and this continued for up to 6 weeks after the induction of diabetes. In conclusion, cardiac dysfunction is associated with cardiac inflammation and adverse remodeling in experimental diabetic cardiomyopathy. Our results suggest that the model of STZ-induced diabetic cardiomyopathy is a robust model for investigating cardiac immune response and LV remodeling processes under diabetic conditions.

Left ventricular remodeling in swine after myocardial infarction: a transcriptional genomics approach

Despite the apparent appropriateness of left ventricular (LV) remodeling following myocardial infarction (MI), it poses an independent risk factor for development of heart failure. There is a paucity of studies into the molecular mechanisms of LV remodeling in large animal species. We took an unbiased molecular approach to identify candidate transcription factors (TFs) mediating the genetic reprogramming involved in post-MI LV remodeling in swine. Left ventricular tissue was collected from remote, non-infarcted myocardium, 3 weeks after MI-induction or sham-surgery. Microarray analysis identified 285 upregulated and 278 downregulated genes (FDR < 0.05). Of these differentially expressed genes, the promoter regions of the human homologs were searched for common TF binding sites (TFBS). Eighteen TFBS were overrepresented >two-fold (p < 0.01) in upregulated and 13 in downregulated genes. Left ventricular nuclear protein extracts were assayed for DNA-binding activity by protein/DNA array. Out of 345 DNA probes, 30 showed signal intensity changes >two-fold. Five TFs were identified in both TFBS and protein/DNA array analyses, which showed matching changes for COUP-TFII and glucocorticoid receptor (GR) only. Treatment of swine with the GR antagonist mifepristone after MI reduced the post-MI increase in LV mass, but LV dilation remained unaffected. Thus, using an unbiased approach to study post-MI LV remodeling in a physiologically relevant large animal model, we identified COUP-TFII and GR as potential key mediators of post-MI remodeling.

Cyclic nucleotide phosphodiesterase 1A: a key regulator of cardiac fibroblast activation and extracellular matrix remodeling in the heart

Cardiac fibroblasts become activated and differentiate to smooth muscle-like myofibroblasts in response to hypertension and myocardial infarction (MI), resulting in extracellular matrix (ECM) remodeling, scar formation and impaired cardiac function. cAMP and cGMP-dependent signaling have been implicated in cardiac fibroblast activation and ECM synthesis. Dysregulation of cyclic nucleotide phosphodiesterase (PDE) activity/expression is also associated with various diseases and several PDE inhibitors are currently available or in development for treating these pathological conditions. The objective of this study is to define and characterize the specific PDE isoform that is altered during cardiac fibroblast activation and functionally important for regulating myofibroblast activation and ECM synthesis. We have found that Ca(2+)/calmodulin-stimulated PDE1A isoform is specifically induced in activated cardiac myofibroblasts stimulated by Ang II and TGF-β in vitro as well as in vivo within fibrotic regions of mouse, rat, and human diseased hearts. Inhibition of PDE1A function via PDE1-selective inhibitor or PDE1A shRNA significantly reduced Ang II or TGF-β-induced myofibroblast activation, ECM synthesis, and pro-fibrotic gene expression in rat cardiac fibroblasts. Moreover, the PDE1 inhibitor attenuated isoproterenol-induced interstitial fibrosis in mice. Mechanistic studies revealed that PDE1A modulates unique pools of cAMP and cGMP, predominantly in perinuclear and nuclear regions of cardiac fibroblasts. Further, both cAMP-Epac-Rap1 and cGMP-PKG signaling was involved in PDE1A-mediated regulation of collagen synthesis. These results suggest that induction of PDE1A plays a critical role in cardiac fibroblast activation and cardiac fibrosis, and targeting PDE1A may lead to regression of the adverse cardiac remodeling associated with various cardiac diseases.

Absence of thrombospondin-2 increases cardiomyocyte damage and matrix disruption in doxorubicin-induced cardiomyopathy

Clinical use of the antineoplastic agent doxorubicin (DOX) is limited by its cardiomyocyte toxicity. Attempts to decrease cardiomyocyte injury showed promising results in vitro, but failed to reduce the adverse effects of DOX in vivo, suggesting that other mechanisms contribute to its cardiotoxicity as well. Evidence that DOX also induces cardiac injury by compromising extracellular matrix integrity is lacking. The matricellular protein thrombospondin-2 (TSP-2) is known for its matrix-preserving function, and for modulating cellular function. Here, we investigated whether TSP-2 modulates the process of doxorubicin-induced cardiomyopathy (DOX-CMP). TSP-2-knockout (TSP-2-KO) and wild-type (WT) mice were treated with DOX (2 mg/kg/week) for 12 weeks to induce DOX-CMP. Mortality was significantly increased in TSP-2-KO compared to WT mice. Surviving DOX-treated TSP-2-KO mice had depressed cardiac function compared to WT animals, accompanied by increased cardiomyocyte apoptosis and matrix damage. Enhanced myocyte damage in the absence of TSP-2 was associated with impaired activation of the Akt signaling pathway in TSP-2-KO compared to WT. The absence of TSP-2, in vivo and in vitro, reduced Akt activation both under non-treated conditions and after DOX. Importantly, inhibition of Akt phosphorylation in cardiomyocytes significantly reduced TSP-2 expression, unveiling a unique feedback loop between Akt and TSP-2. Finally, enhanced matrix disruption in DOX-treated TSP-2-KO hearts went along with increased matrix metalloproteinase-2 levels. Taken together, this study is the first to provide evidence for the implication of the matrix element TSP-2 in protecting against DOX-induced cardiac injury and dysfunction.

North American ginseng protects the heart from ischemia and reperfusion injury via upregulation of endothelial nitric oxide synthase

Emerging evidence suggests ginseng has therapeutic potential in cardiovascular disease. The aim of this study was to investigate the role of endothelial nitric oxide synthase (eNOS) in the cardioprotective effects of ginseng during myocardial ischemia and reperfusion (I/R). Treatment with ginseng extract significantly increased Akt phosphorylation and eNOS protein levels in cultured neonatal cardiomyocytes. Upregulation of eNOS was blocked by LY294002, a PI3-kinase inhibitor, suggesting a PI3-kinase/Akt-dependent mechanism. To simulate I/R, cultured neonatal cardiomyocytes from eNOS(-/-) and wild-type (WT) mice were subjected to anoxia and reoxygenation (A/R). Ginseng treatment inhibited A/R-induced apoptosis in WT, but not in either eNOS(-/-) cardiomyocytes or WT cardiomyocytes treated with LY294002. To further study the cardioprotective effects of ginseng in vivo, WT and eNOS(-/-) mice were pretreated with ginseng extract (50mg/kg/day, oral gavage) for 7 days before they were subjected to myocardial I/R. Treatment with ginseng significantly increased Akt phosphorylation and eNOS protein levels in the myocardium. Furthermore, ginseng-induced myocardial eNOS expression was inhibited by LY294002. Strikingly, ginseng treatment significantly decreased infarct size and myocardial apoptosis following I/R in WT mice, but not in either eNOS(-/-) mice or WT mice treated with LY294002. We conclude that ginseng treatment protects the heart from I/R injury via upregulation of eNOS expression. Our study suggests that ginseng may serve as a potential therapeutic agent to limit myocardial I/R injury.