myocardial infarction; left ventricular remodeling; extracellular matrix; matrix metalloproteinases
Myocardial infarction (MI) remains a major cause of morbidity and mortality worldwide. Rapid advances in the treatment of acute MI have significantly improved short-term outcomes in patient, due in large part to successes in preventing myocardial cell death and limiting infarct area during the time of ischemia and subsequent reperfusion. Matrix metalloproteases (MMPs) play key roles in post-MI cardiac remodeling and in the development of adverse outcomes. This review highlights the importance of MMPs in the injury and remodeling response of the left ventricle and also discusses their potential as therapeutic targets Additional pre-clinical and clinical research is needed to further investigate and understand the cardioprotective effects of MMPs inhibitors.
myocardial infarction; left ventricle; extracellular matrix; matrix metalloproteinases; left ventricle remodeling
The extracellular matrix (ECM) provides structural support by serving as a scaffold for cells, and as such the ECM maintains normal tissue homeostasis and mediates the repair response following injury. In response to myocardial infarction (MI), ECM expression is generally upregulated in the left ventricle (LV), which regulates LV remodeling by modulating scar formation. The ECM directly affects scar formation by regulating growth factor release and cell adhesion, and indirectly affects scar formation by regulating the inflammatory, angiogenic, and fibroblast responses. This review summarizes the current literature on ECM expression patterns and fibroblast mechanisms in the myocardium, focusing on the ECM response to MI. In addition, we discuss future research areas that are needed to better understand the molecular mechanisms of ECM action, both in general and as a means to optimize infarct healing.
extracellular matrix; myocardial infarction; fibroblasts; cardiac myocytes; cell-ECM communication; proteomics
Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) circulates systemically in over 50% of periodontal disease (PD) patients and is associated with increased matrix metalloproteinase (MMP)-9. We hypothesized that low systemic Pg-LPS would stimulate an inflammatory response in the left ventricle (LV) through MMP-9, leading to a decrease in cardiac function. Wild-type (WT) and MMP-9 null mice (4–7 months old) were exposed for 1 or 28 days to low dose Pg-LPS or saline (n ≥ 6/group). MMP-9 significantly increased in WT mice LV at 1 and 28 days of exposure, compared to control (P < 0.05 for both). Fractional shortening decreased subtly yet significantly in WT mice by day 28 (31 ± 1%) compared to control (35 ± 1%; P < 0.05), and this decrease was attenuated in null (34 ± 1%) mice. Plasma cardiac troponin I levels were elevated in WT mice at day 28. Macrophage-related factors increased over twofold in WT plasma and LV after day 1 (monocyte chemoattractant protein-5, macrophage inflammatory protein (MIP)-1α, MIP-1γ, stem cell factor, Ccl12, Ccl9, Il8rb, Icam1, Itgb2, and Spp1; all P < 0.05), indicating a moderate inflammatory response. Levels returned to baseline by day 28, suggesting tolerance to Pg-LPS. In contrast, macrophage-related factors remained elevated in day 28 null mice, indicating a sustained defense against Pg-LPS stimulation. Consistent with these findings, LV macrophage numbers increased in both groups at day 1 and returned to baseline by day 28 in the WT mice only. Major histocompatibility complex (MCH) II remained elevated in the null group at day 28, confirming Pg-tolerance in the WT. Interestingly Il-1α, a regulator of macrophage immunosuppression, increased in the plasma of WT mice only on day 28, suggesting that Il-1α plays a role in tolerance in a MMP-9-dependent manner. In conclusion, circulating Pg-LPS induced tolerance in WT mice, resulting in significant LV changes and subtle cardiac dysfunction. MMP-9 played a major role in the regulation of chronic systemic inflammation and associated cardiac dysfunction.
Cardiac function; inflammation; matrix metalloproteinase-9; periodontal disease; Porphyromonas gingivalis; proteomics
Survival following myocardial infarction (MI) has improved substantially over the last 40 years; however, the incidence of subsequent congestive heart failure has dramatically increased as a consequence. Discovering plasma markers that signify adverse cardiac remodeling may allow high-risk patients to be recognized earlier and may provide an improved way to assess treatment efficacy. Alterations in extracellular matrix (ECM) regulate cardiac remodeling following MI and potentially provide a large array of candidate indicators.
The field of cardiac proteomics has progressed rapidly over the past 20 years, since publication of the first two-dimensional electrophoretic gels of left ventricle proteins. Proteomic approaches are now routinely utilized to better understand how the left ventricle responds to injury.
In this review, we will discuss how methods have developed to allow comprehensive evaluation of the ECM proteome. We will explain how ECM proteomic data can be used to predict adverse remodeling for an individual patient and highlight future directions. Although this review will focus on the use of ECM proteomics to better understand post-MI remodeling responses, these approaches have applicability to a wide-range of cardiac pathologies, including pressure overload hypertrophy, viral myocarditis, and non-ischemic heart failure.
proteomics; remodeling; myocardial infarction; biomarker; MMP
Adverse cardiac remodeling following myocardial infarction (MI) remains a significant cause of congestive heart failure. Additional and novel strategies that improve our ability to predict, diagnose, or treat remodeling are needed. Numerous groups have explored single and multiple biomarker strategies to identify diagnostic prognosticators of remodeling progression, which will improve our ability to promptly and accurately identify high-risk individuals. The identification of better clinical indicators should further lead to more effective prediction and timely treatment.
Matrix metalloproteinase (MMP-9) is one potential biomarker for cardiac remodeling, as demonstrated by both animal models and clinical studies. In animal MI models, MMP-9 expression significantly increases and is linked with inflammation, diabetic microvascular complications, extracellular matrix degradation and synthesis, and cardiac dysfunction. Clinical studies have also established a relationship between MMP-9 and post-MI remodeling and mortality, making MMP-9 a viable candidate to add to the multiple biomarker list.
By definition, a proximal biomarker shows a close relationship with its target disease, whereas a distal biomarker exhibits non-targeted disease modifying outcomes. In this review, we explore the ability of MMP-9 to serve as a proximal biomarker for cardiac remodeling and a distal biomarker for inflammation. We summarize the current molecular basis and clinical platform that allow us to include MMP-9 as a biomarker in both categories.
biomarker; cardiovascular; congestive heart failure; inflammation; MMP-9; myocardial infarction
Approximately half of heart failure patients have a normal ejection fraction, a condition designated as heart failure with preserved ejection fraction (HFpEF). This heart failure subtype disproportionately affects women and the elderly and is commonly associated with other cardiovascular comorbidities, such as hypertension and diabetes. HFpEF is increasing at a steady rate and is predicted to become the leading cause of heart failure within a decade. HFpEF is characterized by impaired diastolic function, thought to be due to concentric remodeling of the heart along with increased stiffness of both the extracellular matrix and myofilaments. In addition, oxidative stress and inflammation are thought to have a role in HFpEF progression, along with endothelial dysfunction and impaired nitric oxide-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) signaling. Surprisingly a number of clinical studies have failed to demonstrate any benefit of drugs effective in heart failure with systolic dysfunction in HFpEF patients. Thus, HFpEF is one of the largest unmet needs in cardiovascular medicine and there is a substantial need for new therapeutic approaches and strategies that target mechanisms specific for HFpEF. This conclusion is underscored by the recently reported disappointing results of the RELAX trial, which assessed the use of phosphodiesterase-5 inhibitor sildenafil for treating HFpEF. In animal models, endothelial nitric oxide synthase (eNOS) activators and If current inhibitors have shown benefit in improving diastolic function and there is a rationale for assessing matrix metalloproteinase-9 (MMP-9) inhibitors and nitroxyl donors. LCZ696, a combination drug of angiotensin II receptor blocker and neprilysin inhibitor, and the aldosterone receptor antagonist spironolactone are currently in clinical trial for treating HFpEF. Here we present an overview of the etiology and diagnosis of HFpEF that segues into a discussion of new therapeutic approaches emerging from basic research, as well as drugs currently in clinical trial, that primarily target diastolic dysfunction or imbalanced ventricular-arterial coupling.
editorial; hypertension; calcium channel blockers; sympathetic activation; cilnidipine
The extracellular matrix (ECM) is a critical tissue component, providing structural support as well as important regulatory signaling cues to govern cellular growth, metabolism, and differentiation. The study of ECM proteins, however, is hampered by the low solubility of ECM components in common solubilizing reagents. ECM proteins are often not detected during proteomics analyses using unbiased approaches due to solubility issues and relatively low abundance compared to highly abundant cytoplasmic and mitochondrial proteins. Decellularization has become a common technique for ECM protein-enrichment and is frequently used in engineering studies. Solubilizing the ECM after decellularization for further proteomic examination has not been previously explored in depth. In this study, we describe testing of a series of protocols that enabled us to develop a novel optimized strategy for the enrichment and solubilization of ECM components. Following tissue decellularization, we use acid extraction and enzymatic deglycosylation to facilitate resolubilization. The end result is the generation of three fractions for each sample: soluble components, cellular components, and an insoluble ECM fraction. These fractions, developed in mass spectrometry-compatible buffers, are amenable to proteomics analysis. The developed protocol allows identification (by mass spectrometry) and quantification (by mass spectrometry or immunoblotting) of ECM components in tissue samples.
The study of extracellular matrix (ECM) proteins in pathological and non-pathological conditions is often hampered by the low solubility of ECM components in common solubilizing reagents. Additionally, ECM proteins are often not detected during global proteomic analyses due to their relatively low abundance compared to highly abundant cytoplasmic and mitochondrial proteins. In this manuscript we describe testing of a series of protocols that enabled us to develop a final novel optimized strategy for the enrichment and solubilization of ECM components. The end result is the generation of three fractions for each sample: soluble components, cellular components, and an insoluble ECM fraction. By analysis of each independent fraction, differences in protein levels can be detected that in normal conditions would be masked. These fractions are amenable to mass spectrometry analysis to identify and quantify ECM components in tissue samples. The manuscript places a strong emphasis on the immediate practical relevance of the method, particularly when using mass spectrometry approaches; additionally, the optimized method was validated and compared to other methodologies described in the literature.
Extracellular matrix; Enrichment; Decellularization; Heart; Solubility; Matrix metalloproteinases
The cardiac extracellular matrix (ECM) provides a platform for cells to maintain structure and function, which in turn maintains tissue function. In response to injury, the ECM undergoes remodeling that involves synthesis, incorporation, and degradation of matrix proteins, with the net outcome determined by the balance of these processes. The major goals of this review are a) to serve as an initial resource for students and investigators new to the cardiac ECM remodeling field, and b) to highlight a few of the key exciting avenues and methodologies that have recently been explored. While we focus on cardiac injury and responses of the left ventricle (LV), the mechanisms reviewed here have pathways in common with other wound healing models.
extracellular matrix; left ventricular remodeling; matrix metalloproteinases; inflammation; fibrosis; review
MMP-9 deletion has been shown to improve remodeling of the left ventricle (LV) post-myocardial infarction (MI), but the mechanisms to explain this improvement have not been fully elucidated. MMP-9 has a broad range of in vitro substrates, but relevant in vivo substrates are incompletely defined. Accordingly, we evaluated the infarct regions of wild-type (wt) and MMP-9 null (null) mice using a proteomic strategy. Wt and null groups showed similar infarct sizes (48±3 in wt and 45±3% in null), indicating that both groups received an equal injury stimulus. LV infarct tissue was homogenized and analyzed by two-dimensional gel electrophoresis and mass spectrometry. Of 31 spot intensity differences, the intensities of 9 spots were higher and 22 spots were lower in null mice compared to wt (all p<0.05). Several extracellular matrix (ECM) proteins were identified in these spots by mass spectrometry, including fibronectin, tenascin-C, thrombospondin-1, and laminin. Fibronectin was observed on the gels at a lower than expected molecular weight in the wt group, which suggested substrate cleavage, and the lower molecular weight spot was observed at lower intensity in the MMP-9 null group, which suggested cleavage by MMP-9. Immunoblotting confirmed the presence of fibronectin cleavage products in the wt samples and lower levels in the absence of MMP-9. In conclusion, examining infarct tissue from wt and MMP-9 null mice by proteomic analysis provides a powerful and unique method to identify in vivo candidate MMP substrates.
cardiac remodeling; MMP-9; extracellular matrix; mice; proteomics; myocardial infarction
The concept that extracellular matrix (ECM) turnover occurs during cardiac remodeling is a well-accepted paradigm. To date, a multitude of studies document that remodeling is accompanied by increases in the synthesis and deposition of ECM components as well as increases in extracellular proteases, especially matrix metalloproteinases (MMPs), which break down ECM components. Further, soluble ECM fragments generated from enzymatic action serve to stimulate cell behavior and have been proposed as candidate plasma biomarkers of cardiac remodeling. This review briefly summarizes our current knowledge base on cardiac ECM turnover following myocardial infarction (MI), but more importantly extends discussion by defining avenues that remain to be explored to drive the ECM remodeling field forward. Specifically, this review will discuss cause and effect roles for the ECM changes observed following MI and the potential role of the ECM changes that may serve as trigger points to regulate remodeling. While the pattern of remodeling following MI is qualititatively similar but quantitively different from various types of injury, the basic theme in remodeling is repeated. Therefore, while we use the MI model as the prototype injury model, the themes discussed here are also relevant to cardiac remodeling due to other types of injury.
LIM and cysteine-rich domains 1; cardiac hypertrophy; editorial
editorial; isolated systolic hypertension; combined systolic/diastolic hypertension; endothelial dysfunction; MMP; vascular calcification
editorial; diastolic compliance; PKC
hypertrophy; tumor necrosis factor α converting enzyme; matrix metalloproteinase; editorial
Following myocardial infarction (MI), circulating blood monocytes respond to chemotactic factors, migrate into the infarcted myocardium, and differentiate into macrophages. At the injury site, macrophages remove necrotic cardiac myocytes and apoptotic neutrophils; secrete cytokines, chemokines, and growth factors; and modulate phases of the angiogenic response. As such, the macrophage is a primary responder cell type that is involved in the regulation of post-MI wound healing at multiple levels. This review summarizes what is currently known about macrophage functions post-MI and borrows literature from other injury and inflammatory models to speculate on additional roles. Basic science and clinical avenues that remain to be explored are also discussed.
macrophage; myocardial infarction; matrix metalloproteinases; left ventricular remodeling; angiogenesis; fibrosis
hypertrophy; congestive heart failure; 5′-AMP activated protein kinase; editorial
angiotensin converting enzyme inhibitors; matrix metalloproteinase-9; editorial
Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells and tissue and not surprisingly many theories have arisen to link ROS-induced oxidative stress to aging and health. While studies clearly link ROS to a plethora of divergent diseases, their role in aging is still debatable. Genetic knock-down manipulations of antioxidants alter the levels of accrued oxidative damage, however, the resultant effect of increased oxidative stress on lifespan are equivocal. Similarly the impact of elevating antioxidant levels through transgenic manipulations yield inconsistent effects on longevity. Furthermore, comparative data from a wide range of endotherms with disparate longevity remain inconclusive. Many long-living species such as birds, bats and mole-rats exhibit high-levels of oxidative damage, evident already at young ages. Clearly, neither the amount of ROS per se nor the sensitivity in neutralizing ROS are as important as whether or not the accrued oxidative stress leads to oxidative-damage-linked age-associated diseases. In this review we examine the literature on ROS, its relation to disease and the lessons gleaned from a comparative approach based upon species with widely divergent responses. We specifically focus on the longest lived rodent, the naked mole-rat, which maintains good health and provides novel insights into the paradox of maintaining both an extended healthspan and lifespan despite high oxidative stress from a young age.
Comparative biology of aging; mitochondria; naked mole-rat; oxidative stress; proteasome; autophagy; reactive oxygen species
To determine if matrix metalloproteinase (MMP)-28 mediates cardiac aging, wild-type (WT) and MMP-28−/− young (7 ± 1 months, n = 9 each) and old (20 ± 2 months, n = 7 each) female mice were evaluated. MMP-28 expression in the left ventricle (LV) increased 42% in old WT mice compared to young controls (p < 0.05). By Doppler echocardiography, LV function declined at 20 ± 2 months of age for both groups. However, dobutamine stress responses were similar, indicating that cardiac reserve was maintained. Plasma proteomic profiling revealed that macrophage inflammatory protein (MIP)-1 α, MIP-1β and MMP-9 plasma levels did not change in WT old mice but were significantly elevated in MMP-28−/− old mice (all p < 0.05), suggestive of a higher inflammatory status when MMP-28 is deleted. RT2-PCR gene array and immunoblotting analyses demonstrated that MIP-1α and MMP-9 gene and protein levels in the LV were also higher in MMP-28−/− old mice (all p < 0.05). Macrophage numbers in the LV increased similarly in WT and MMP-28−/− old mice, compared to respective young controls (both p < 0.05). Collagen content was not different among the WT and MMP-28−/− young and old mice. In conclusion, LV inflammation increases with age, and MMP-28 deletion further elevates inflammation and extracellular matrix responses, without altering macrophage numbers or collagen content.
MMP-28; cardiac aging; extracellular matrix; inflammation; macrophage; collagen; left ventricle; mice
Myocardial infarction (MI) is a leading cause of death worldwide. Permanent ligation of the left anterior descending coronary artery (LAD) is a commonly used surgical model to study post-MI effects in mice. LAD occlusion induces a robust wound healing response that includes extracellular matrix (ECM) remodeling. This chapter provides a detailed guide on the surgical procedure to permanently ligate the LAD. Additionally, we describe a prototype method to enrich cardiac tissue for ECM, which allows one to focus on ECM remodeling in the left ventricle following surgically induced MI in mice.
Myocardial infarction; Cardiac wound healing; Mice; Extracellular matrix; Matrix metalloproteinases; Inflammation; Decellularization