TIMP-3 deficiency leads to dilated cardiomyopathy

Intracellular targets of matrix metalloproteinase-2 in cardiac disease: rationale and therapeutic approaches

A new paradigm of matrix metalloproteinase-2 (MMP-2) action in the heart undergoing oxidative stress has emerged. Although best known for its role in the proteolysis of extracellular protein targets, MMP-2 is also localized to the sarcomere within the cardiomyocyte. Oxidative stress activates full-length MMP-2 without need for proteolytic processing and inactivates an endogenous inhibitor, tissue inhibitor of metalloproteinase-4. MMP-2 proteolyzes specific targets within the cell to cause acute, reversible contractile dysfunction. Inhibitors of MMPs are discussed and their possible use for the therapy of acute heart injury caused by oxidative stress is examined.

Use of diffusion tensor imaging to predict myocardial viability after warm global ischemia: possible avenue for use of non-beating donor hearts

BACKGROUND

The assessment of myocardial viability after global warm ischemia (WI) but before reperfusion is challenging. We hypothesized that fractional anisotropy (FA), a magnetic resonance imaging (MRI) parameter of water diffusion that characterizes cellular integrity within tissues, provides a rapid and useful method for evaluating the viability of hearts after WI.

METHODS

Dog hearts were exposed to 60 minutes of WI after exanguination, explanted and preserved in a cold, non-beating state for 6 hours, using continuous perfusion (CP) or static cold storage (CS). Toward the end of preservation, a global FA assessment, acquired using MRI, was compared with analyses obtained from myocardial biopsies that included adenosine triphosphate (ATP), endothelin-1 (ET-1) and caspase-3 levels, light microscopy and tetrazolium staining. Functional recovery was analyzed after restoration of blood flow on a non-working Langendorff preparation.

RESULTS

FA measured at the end of CP showed strong correlations with all parameters of functional recovery (developed pressure, R = 0.60; dP/dt, R = 0.96; -dP/dt, R = 0.96). Although FA also correlated with tissue levels of ATP, ET-1 and caspase-3 (R = 0.77, -0.84, -0.64), recovery of myocardial function did not correlate with these markers or any other conventional analyses of myocardial injury (troponin I, changes on light microscopy or tetrazolium staining).

CONCLUSIONS

FA, an MRI-based parameter that indicates cellular integrity, was found to reflect better myocardial ATP stores, less induction of ET-1 and caspase-3 and improved functional recovery of hearts after global WI. As a clinically applicable tool capable of rapidly differentiating reversible from lethal injury, diffusion tensor imaging may prove useful in the eventual adoption of non-beating donor hearts for transplantation.

Tissue Inhibitor of Metalloproteinase-3 Deficiency Inhibits Blood Pressure Elevation and Myocardial Microvascular Remodeling Induced by Chronic Administration of N.OMEGA.-Nitro-L-Arginine Methyl Ester in Mice

Hypertension is a major risk factor for cardiovascular disease. Thus, prevention of hypertension and consequent organ damage is important for reducing its incidence. In the present study, we examined the involvement of tissue inhibitor of metalloproteinase-3 (Timp-3) in N(omega)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension and accompanying vascular remodeling in mice. L-NAME was orally administered to wild-type (WT) and Timp-3 knockout (KO) mice for 6 weeks, blood pressure was monitored, and histological changes in myocardial arteries were examined. After L-NAME administration, blood pressure was lower in Timp-3 KO mice than in WT mice. The coronary arteries of WT and Timp-3 KO mice were similar after L-NAME treatment and showed no differences compared to untreated control mice. However, cardiac microvessels differed histologically between WT and Timp-3 KO mice. Vascular walls were less thickened in Timp-3 KO than in WT mice, and fibrotic changes were significantly reduced in Timp-3 KO mice. Moreover, the L-NAME-induced production of reactive oxygen species in cardiac microvessels was lower in Timp-3 KO than in WT mice. These results indicate that Timp-3 plays an important role in L-NAME-induced hypertension and myocardial vascular remodeling. Our findings suggest that Timp-3 may be a novel therapeutic target for the treatment of hypertension and consequent organ damage.

Heart valve tissue engineering: concepts, approaches, progress, and challenges

Potential applications of tissue engineering in regenerative medicine range from structural tissues to organs with complex function. This review focuses on the engineering of heart valve tissue, a goal which involves a unique combination of biological, engineering, and technological hurdles. We emphasize basic concepts, approaches and methods, progress made, and remaining challenges. To provide a framework for understanding the enabling scientific principles, we first examine the elements and features of normal heart valve functional structure, biomechanics, development, maturation, remodeling, and response to injury. Following a discussion of the fundamental principles of tissue engineering applicable to heart valves, we examine three approaches to achieving the goal of an engineered tissue heart valve: (1) cell seeding of biodegradable synthetic scaffolds, (2) cell seeding of processed tissue scaffolds, and (3) in-vivo repopulation by circulating endogenous cells of implanted substrates without prior in-vitro cell seeding. Lastly, we analyze challenges to the field and suggest future directions for both preclinical and translational (clinical) studies that will be needed to address key regulatory issues for safety and efficacy of the application of tissue engineering and regenerative approaches to heart valves. Although modest progress has been made toward the goal of a clinically useful tissue engineered heart valve, further success and ultimate human benefit will be dependent upon advances in biodegradable polymers and other scaffolds, cellular manipulation, strategies for rebuilding the extracellular matrix, and techniques to characterize and potentially non-invasively assess the speed and quality of tissue healing and remodeling.

Spatial disruption and enhanced degradation of collagen with the transition from compensated ventricular hypertrophy to symptomatic congestive heart failure

The cardiac extracellular matrix (ECM) maintains the structural and mechanical integrity of the myocardium. We determined the alterations in the composition of the ECM coincident with the transition from compensated left ventricular (LV) hypertrophy (LVH) to symptomatic congestive heart failure (CHF) and the mechanisms underlying such changes. Heart failure was induced in ferrets by aortic banding. Myocardial collagen content was assessed by HPLC and histological analysis. Matrix metalloproteinase (MMP) activity and tissue inhibitor of metalloproteinase (TIMP) expression were evaluated using gelatin zymography and Western blotting, respectively. LV free wall thickness increased by 29% in asymptomatic LVH and was associated with a 20% increase in interstitial fibrosis (P < 0.05). CHF was coincident with increased plasma angiotensin II levels (149 +/- 48, 40 +/- 19, and 5.6 +/- 1 pg/ml for CHF, LVH, and sham, respectively; P < 0.01, CHF vs. sham and LVH), ventricular dilatation (LV internal diameter = 15 +/- 0.4 vs. 9 +/- 0.1 mm, P < 0.05), increased active MMP-9 (3.0- and 2.2-fold increase over sham and LVH, respectively, n = 5-10 animals per group, P < 0.01), and reduced myocardial total collagen content (3.5 +/- 0.4, 2.6 +/- 0.3, and 2.2 +/- 0.3% in sham, LVH, and CHF, respectively, P < 0.05). In CHF the distribution of collagen was markedly altered, becoming punctate in nature. No difference in MMP-2 activity, TIMP-1, TIMP-2, TIMP-3, or TIMP-4 expression, or collagen cross-linking was found at any time. The present work demonstrates structural reorganization and loss of collagen from cardiac ECM during the transition to decompensated CHF. The enhanced MMP-9 activity coincident with the transition to CHF provides potential therapeutic opportunities for managing the progression from asymptomatic LVH to symptomatic CHF.

Differential expression of MMPs and TIMPs in moderate and severe heart failure in a transgenic model

BACKGROUND

Altered expression of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) accompanies the development of heart failure (HF). However, changes in MMP and TIMP protein levels or activity during the progression from compensated to decompensated failure remains incompletely examined.

METHODS AND RESULTS

Transgenic mice (Tg) with cardiac-specific overexpression of tumor necrosis factor-alpha (TNF1.6) develop a sex-related, progressive cardiac dilation and HF. Echocardiographic measures were used to categorize HF severity in male (M) and female (F) Tg and wild-type (WT) mice between 4 and 50 weeks of age. Cardiac TIMPs-1, TIMPs-2, and MMP-3 (enzyme-linked immunosorbent assay), and potential (APMA-activated) MMP-9 activity were measured at similar ages. In situ zymography assessed tissue gelatinase activity. Systolic function, ventricular dimensions, and presence of pleural effusions identified severe HF in younger M Tg mice (by 18 weeks) and older F Tg (>34 weeks). Regardless of age, sex, or HF severity, Tg mice expressed significantly more TIMP-1 (Tg 119-193 pg/mg vs. WT 13-24 pg/mg, P < .001) and potential MMP-9 activity (Tg 0.41-0.58 ng/mg vs. WT 0.015-0.028 ng/mg, P < .002). M Tg expressed elevated MMP-3 (4 weeks, 0.16 +/- 0.1 ng/mg protein vs. WT 0.04 +/- 0.01 ng/mg, P < .003), which increased with age and HF severity (18 weeks, 0.51 +/- 0.3 ng/mg P < .01). F Tg showed no increase in MMP-3 at 4 weeks but a progressive increase with age and HF severity (18 weeks 0.09 +/- 0.04 ng/mg, P < .02 vs. Tg M or WT; 34 weeks 0.13 +/- 0.02 ng/mg, P < .001 vs. WT). To test the hypothesis that increased MMP-3 may differentially activate MMP-9 in M Tg, in situ zymography was performed and revealed a significant increase in gelatinase activity in M Tg mice relative to both WT and F Tg.

CONCLUSION

MMP-3 may regulate activation of MMP-9/gelatinase, the progression of cardiac remodeling, and development of decompensated heart failure.

Matrix metalloproteinases in development and disease

Matrix metalloproteinases (MMPs) are key modulators of many biological processes during pathophysiological events, such as skeletal formation, angiogenesis, cellular migration, inflammation, wound healing, coagulation, lung and cardiovascular diseases, arthritis, and cancer. Twenty-four members of the MMP family have been identified in humans, degrading many components of the extracellular matrix, cellular receptors, and cytokines. This review describes the molecular structure, activation and inhibition, and substrate specificity of MMPs, and their biological function in development and disease.

Elastin stabilizes an infarct and preserves ventricular function

BACKGROUND

After a myocardial infarction, the injured region becomes fibrotic and the myocardial scar may expand if the ventricular wall lacks elasticity. Cardiac dilatation may precipitate the vicious cycle of progressive heart failure. The present study evaluated the functional benefits of increasing elastin within a myocardial scar using cell based gene therapy.

METHODS AND RESULTS

A myocardial infarction was generated by ligation of the left anterior descending artery in rats. Six days later, 2 x 10(6) syngeneic rat endothelial cells transfected with the rat elastin gene (elastin group, n=14) or an empty plasmid (control group, n=14) were transplanted into the infarct scar. Cardiac function, left ventricular (LV) volume, and infarct size were monitored over 3 months by echocardiography, Langendorff measurements, and planimetry. Elastin deposition was evaluated in the cells and in the infarct region by Western blot assay and by histological examination. Recombinant elastin was found in the scar in the elastin group but not the control group during the 3 months after cell transplantation. Histological assessment demonstrated organized elastic fibers within the infarct region. LV volume and infarct size were significantly smaller (P<0.05) in the elastin group than in the control group. Cardiac function evaluated by echocardiography and during Langendorff perfusion was significantly better (P<0.05) in the elastin group than in the control group.

CONCLUSIONS

Expressing recombinant elastin within the myocardial scar reduced scar expansion and prevented LV enlargement after a myocardial infarction. Altering matrix remodeling after an infarct preserved the LV function for at least 3 months.

Altered expression of disintegrin metalloproteinases and their inhibitor in human dilated cardiomyopathy

BACKGROUND

Disintegrin metalloproteinases (ADAMs) may contribute to structural cardiac remodeling by altering cell-surface matrix receptors (integrins) and activating potent biomolecules. We compared expression of ADAMs, their endogenous inhibitor tissue inhibitor of metalloproteinases (TIMP)-3, and integrins in human heart tissue with varied patterns of structural remodeling.

METHODS AND RESULTS

Myocardium was obtained from patients with dilated cardiomyopathy (n=20), hypertrophic obstructive cardiomyopathy (n=5), and nonfailing donor hearts (n=7). Paired samples (n=10) were obtained before left ventricular assist device insertion and at transplantation. The expressions of ADAM10, ADAM12, ADAM15, and ADAM17, TIMP-3, and integrin receptors beta1D and beta3 were determined by quantitative immunoblotting. Integrin shedding was assessed by the ratio of integrin cleavage products to intact protein abundance. Confocal microscopy was performed. Dilated cardiomyopathy was characterized by increased ADAM10 and ADAM15 expression and reduced TIMP-3 expression. The integrin beta1D cleavage ratio was elevated, indicating receptor shedding. ADAM10 and ADAM15 expressions correlated with the cleavage ratio. ADAM10 colocalized with integrin beta1D by confocal microscopy. ADAM10 expression correlated with clinical indices of chamber dilatation and systolic dysfunction. Hemodynamic unloading reduced ADAM10 and ADAM12 expressions and increased integrin beta1D expression. ADAM12 and integrin beta1D expressions were increased in HOCM. ADAM17 was increased in both dilated cardiomyopathy and hypertrophic obstructive cardiomyopathy.

CONCLUSIONS

Disintegrin metalloproteinases are differentially expressed in human myocardium, reflecting the underlying pattern of structural remodeling. ADAM10 and ADAM15 may contribute to cardiac dilatation by reducing cell-matrix interactions via integrin shedding. Targeting disintegrin metalloproteinases, perhaps by restoring deficient TIMP-3 levels with gene or cell-based therapies, may prevent progressive chamber dilatation in human dilated cardiomyopathy.

Tissue Inhibitor of Metalloproteinase-3 Plays Important Roles in the Kidney Following Unilateral Ureteral Obstruction

Tissue inhibitor of metalloproteinase-3 (Timp-3), an inhibitor of matrix-degrading enzymes, is an important molecule for maintenance of the extracellular matrix. In this study, we generated Timp-3-deficient mice and used them to examine the effect of Timp-3-deficiency on blood pressure and to investigate the role of Timp-3 in the kidney following unilateral ureteral obstruction. The blood pressure and heart rate of Timp-3-deficient mice were not significantly different from those of wild-type mice. On the other hand, the obstructed kidneys of Timp-3-deficient mice developed more severe hydronephrosis than those of wild-type animals. Matrix metalloproteinase activities assessed by in situ zymography and transforming growth factor-beta expression were elevated in Timp-3-deficient mice. The renal tissues were thinner and the ratio of renal medulla to cortex was significantly lower in the obstructed Timp-3-deficient kidneys. These findings indicate that Timp-3-deficiency does not substantially affect the blood pressure in mice, and that Timp-3 plays an important role in the maintenance of renal macrostructure after unilateral ureteral obstruction.

Cell transplantation preserves matrix homeostasis: A novel paracrine mechanism

OBJECTIVES

Cell transplantation prevents chamber dilatation, but the underlying molecular mechanisms remain undefined. Structural cardiac remodeling involves matrix degradation from an imbalance of matrix metalloproteinases (MMP) relative to endogenous tissue inhibitors of metalloproteinases (TIMP). We aimed to determine the capacity of cell transplantation to alter extracellular matrix in the failing heart and, in so doing, identify novel paracrine molecular mediators underlying the beneficial effects of cell transplantation on chamber dilatation.

METHODS

Smooth muscle cells were transplanted to the dilating left ventricle of cardiomyopathic hamsters (CTX, n = 15) compared with age-matched media-injected cardiomyopathic (CON, n = 15) and normal hamsters (n = 7). After 5 weeks, left ventricular volume was measured by computerized planimetry. Fibrillar collagen was examined by confocal microscopy. Matrix homeostasis was quantified by measuring MMP/TIMP expression/activity relative to myocardial collagen synthesis (14C-proline uptake).

RESULTS

Left ventricular dilatation was attenuated in CTX hearts (P = .02). CTX restored perimysial collagen fiber content and architecture to normal levels. TIMP-2 and TIMP-3 expression were enhanced in CTX (TIMP-2, 195% +/- 42% of CON, P = .02; TIMP-3, 118% +/- 3% of CON, P = .002), and correspondingly, gelatinase MMP-2 activity was reduced (P < .05). The TIMP:MMP ratio was increased in CTX hearts (TIMP-2 to MMP-2, 410% +/- 134% of CON, P = .04, and TIMP-3 to MMP-9, 205% +/- 47% of CON, P = .03), reflecting a reduced capacity for matrix degradation. Collagen synthesis was equivalent (CTX vs CON), suggesting that restored matrix architecture was a function of attenuated matrix degradation.

CONCLUSIONS

These data provide the first evidence that cell transplantation limits ventricular dilatation in the failing heart through a paracrine-mediated mechanism that preserves extracellular matrix homeostasis.

Matrix modulation and heart failure: new concepts question old beliefs

PURPOSE OF REVIEW

Myocardial remodeling is a complex process involving several molecular and cellular factors. Extracellular matrix has been implicated in the remodeling process. Historically, the myocardial extracellular matrix was thought to serve solely as a means to align cells and provide structure to the tissue. Although this is one of its important functions, evidence suggests that the extracellular matrix plays a complex and divergent role in influencing cell behavior. This paper characterizes some of the notable studies on this dynamic entity and on adverse myocardial remodeling that have been published over the past year, which further question the belief that the extracellular matrix is a static structure.

RECENT FINDINGS

Progress has been made in understanding how the extracellular matrix is operative in the three major conditions (myocardial infarction, left ventricular hypertrophy due to overload, and dilated cardiomyopathy) that involve myocardial remodeling. Several studies have examined plasma profiles of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases following myocardial infarction and during left ventricular hypertrophy as surrogate markers of remodeling/remodeled myocardium. It has been demonstrated that bioactive signaling molecules and growth factors, proteases, and structural proteins influence cell-matrix interactions in the context of left ventricular hypertrophy. Finally, studies that either removed or added tissue inhibitor of metalloproteinases species in the myocardium demonstrated the importance of this regulatory protein in the remodeling process.

SUMMARY

Understanding the cellular and molecular triggers that in turn give rise to changes in the extracellular matrix could provide opportunities to modify the remodeling process.

Combination of tumor necrosis factor-alpha ablation and matrix metalloproteinase inhibition prevents heart failure after pressure overload in tissue inhibitor of metalloproteinase-3 knock-out mice

Cytokine and extracellular matrix (ECM) homeostasis are distinct systems that are each dysregulated in heart failure. Here we show that tissue inhibitor of metalloproteinase (TIMP)-3 is a critical regulator of both systems in a mouse model of left ventricular (LV) dilation and dysfunction. Timp-3(-/-) mice develop precipitous LV dilation and dysfunction reminiscent of dilated cardiomyopathy (DCM), culminating in early onset of heart failure by 6 weeks, compared with wild-type aortic-banding (AB). Timp-3 deficiency resulted in increased TNFalpha converting enzyme (TACE) activity within 6 hours after AB leading to enhanced tumor necrosis factor-alpha (TNFalpha) processing. In addition, TNFalpha production increased in timp-3(-/-)-AB myocardium. A significant elevation in gelatinase and collagenase activities was observed 1 week after AB, with localized ECM degradation in timp-3(-/-)-AB myocardium. Timp-3(-/-)/tnfalpha(-/-) mice were generated and subjected to AB for comparative analyses with timp-3(-/-)-AB mice. This revealed the critical role of TNFalpha in the early phase of LV remodeling, de novo expression of Matrix metalloproteinases (MMP)-8 in the absence of TNFalpha, and highlighted the importance of interstitial collagenases (MMP-2, MMP-13, and MT1-MMP) for cardiac ECM degradation. Ablation of TNFalpha, or limiting MMP activity with a synthetic MMP inhibitor (PD166793), each partially attenuated LV dilation and cardiac dysfunction in timp-3(-/-)-AB mice. Notably, combining TNFalpha ablation with MMP inhibition completely rescued heart disease in timp-3(-/-)-AB mice. This study provides a basis for anti-TNFalpha and MMP inhibitor combination therapy in heart disease.

Lack of tissue inhibitor of metalloproteinases-3 results in an enhanced inflammatory response in antigen-induced arthritis

Tissue inhibitor of metalloproteinases-3 (TIMP-3) is known to inhibit matrix metalloproteinases, aggrecanases, and tumor necrosis factor (TNF)-alpha-converting enzyme (TACE, ADAM17). These metalloproteases participate in different aspects of joint destruction in inflammatory arthritis. To determine the relative importance of this inhibitor in joint pathology, wild-type and Timp3-/- mice were immunized with methylated bovine serum albumin followed by arthritis induction by intra-articular injection of the same antigen. Animals were monitored for up to 14 days after challenge, and joint tissues were analyzed by routine and Safranin O staining and for the presence of aggrecan neoepitopes produced by metalloprotease cleavage. Serum TNF-alpha was measured by immunoassay. Compared to wild-type animals, Timp3-/- mice showed a dramatic increase in the initial inflammatory response to intra-articular antigen injection, and serum TNF-alpha levels were greatly elevated in the Timp3-/- animals after immunization. However, these differences in clinical features disappeared by days 7 to 14. No difference in Safranin O staining or aggrecan cleavage site neoepitope abundance was seen. Thus, in inflammatory joint disease TIMP-3 likely dampens the inflammatory response of TNF-alpha by reducing ADAM17 activity.

Cardiac remodeling and failure From molecules to man (Part II)

Once considered an inert physical scaffolding, the extracellular matrix (ECM) is increasingly being appreciated as a central structural support and dynamic signaling system for cells to assemble into functional tissues. The ECM can respond to environmental stimuli and tissue injury by altering its abundance, composition, and spatial organization, with profound consequences on the structure and function of the tissues that it inhabits. ECM remodeling is now recognized as a central process underlying the maladaptive reorganization of cardiac size, shape, and function during the progression of CHF. ECM remodeling is largely determined by the balance of degradative enzymes, the MMPs, with respect to a highly regulated and complex assortment of multifunctional endogenous inhibitors, the TIMPs. Clinical studies over the past decade document increased MMP activities associated with diseased hearts. Animal models of cardiovascular disease, as well as transgenic mouse models, further support a role for MMPs in cardiac remodeling. Similarly, clinical, experimental, and genetic approaches implicate the involvement of TIMPs in heart disease, and TIMP expression is selectively reduced in the failing heart. The four known TIMP species are differentially regulated in the heart, and their specific role during the progression of CHF is not clear. Unique among TIMPs, TIMP-3 is ECM bound, highly expressed in the heart, uniformly reduced in failing hearts, and a potent endogenous inhibitor of MMPs and A Disintegrin and metalloproteinase (ADAMs) implicated in cardiac disease. The control of ECM remodeling in the failing heart may provide a missing link in our currently inadequate armamentarium of treatments for patients with CHF, and a better understanding of the complex role of TIMP proteins in the normal and failing myocardium, particularly the unique role of TIMP-3, may facilitate the development of targeted anti-remodeling strategies.

Reprogramming of the Human Atrial Transcriptome in Permanent Atrial Fibrillation

Atrial fibrillation is associated with increased expression of ventricular myosin isoforms in atrial myocardium, regarded as part of a dedifferentiation process. Whether reexpression of ventricular isoforms in atrial fibrillation is restricted to transcripts encoding for contractile proteins is unknown. Therefore, this study compares atrial mRNA expression in patients with permanent atrial fibrillation to atrial mRNA expression in patients with sinus rhythm and to ventricular gene expression using Affymetrix U133 arrays. In atrial myocardium, we identified 1434 genes deregulated in atrial fibrillation, the majority of which, including key elements of calcium-dependent signaling pathways, displayed downregulation. Functional classification based on Gene Ontology provided the specific gene sets of the interdependent processes of structural, contractile, and electrophysiological remodeling. In addition, we demonstrate for the first time a prominent upregulation of transcripts involved in metabolic activities, suggesting an adaptive response to increased metabolic demand in fibrillating atrial myocardium. Ventricular-predominant genes were 5 times more likely to be upregulated in atrial fibrillation (174 genes upregulated, 35 genes downregulated), whereas atrial-specific transcripts were predominantly downregulated (56 genes upregulated, 564 genes downregulated). Overall, in fibrillating atrial myocardium, functional classes of genes characteristic of ventricular myocardium were found to be upregulated (eg, metabolic processes), whereas functional classes predominantly expressed in atrial myocardium were downregulated (eg, signal transduction and cell communication). Therefore, dedifferentiation with adoption of a ventricular-like signature is a general feature of the fibrillating atrium.

Loss or inhibition of uPA or MMP-9 attenuates LV remodeling and dysfunction after acute pressure overload in mice

Left ventricular (LV) hypertrophy is a natural response of the heart to increased pressure loading, but accompanying fibrosis and dilatation may result in irreversible life-threatening heart failure. Matrix metalloproteinases (MMPs) have been invoked in various cardiac diseases, however, direct genetic evidence for a role of the plasminogen activator (PA) and MMP systems in pressure overload-induced LV hypertrophy and in heart failure is lacking. Therefore, the consequences of transverse aortic banding (TAB) were analyzed in mice lacking tissue-type PA (t-PA(-/-)), urokinase-type PA (u-PA(-/-)), or gelatinase-B (MMP-9(-/-)), and in wild-type (WT) mice after adenoviral gene transfer of the PA-inhibitor PAI-1 or the MMP-inhibitor TIMP-1. TAB elevated LV pressure comparably in all genotypes. In WT and t-PA(-/-) mice, cardiomyocyte hypertrophy was associated with myocardial fibrosis, LV dilatation and dysfunction, and pump failure after 7 weeks. In contrast, in u-PA(-/-) mice or in WT mice after PAI-1- and TIMP-1-gene transfer, cardiomyocyte hypertrophy was moderate and only minimally associated with cardiac fibrosis and LV dilatation, resulting in better preservation of pump function. Deficiency of MMP-9 had an intermediate effect. These findings suggest that the use of u-PA- or MMP-inhibitors might preserve cardiac pump function in LV pressure overloading.