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(Circulation. 2002;105:753.)
© 2002 American Heart Association, Inc.

Basic Science Reports

Selective Matrix Metalloproteinase Inhibition Reduces Left Ventricular Remodeling but Does Not Inhibit Angiogenesis After Myocardial Infarction

Merry L. Lindsey, PhD; Joseph Gannon; Masanori Aikawa, MD, PhD; Frederick J. Schoen, MD, PhD; Elena Rabkin, MD, PhD; Lori Lopresti-Morrow, BS; Jamie Crawford; Shawn Black, PhD; Peter Libby, MD; Peter G. Mitchell, MD; Richard T. Lee, MD

From the Leducq Center for Cardiovascular Research (M.L.L., J.G., M.A., P.L., R.T.L.), Cardiovascular Division, Department of Medicine, and the Department of Pathology (F.J.S., E.R.), Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass; and Pfizer Central Research (L.L.-M., J.C., S.B., P.G.M.), Groton, Conn.

Correspondence to Richard T. Lee, MD, Cardiovascular Division, Partners Research Facility, Room 279, 65 Landsdowne St, Cambridge, MA 02139. E-mail rlee{at}rics.bwh.harvard.edu

	Abstract

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Background— Broad inhibition of matrix metalloproteinases (MMPs) attenuates left ventricular remodeling after myocardial infarction (MI). However, it is not clear if selective MMP inhibition strategies will be effective or if MMP inhibition will impair angiogenesis after MI.

Methods and Results— We used a selective MMP inhibitor (MMPi) that does not inhibit MMP-1 in rabbits, which, like humans but unlike rodents, express MMP-1 as a major collagenase. On day 1 after MI, rabbits were randomized to receive either inhibitor (n=10) or vehicle (n=8). At 4 weeks after MI, there were no differences in infarct size or collagen fractional area. However, MMPi reduced ventricular dilation. The increase in end-diastolic dimension from day 1 to week 4 was 3.1±0.5 mm for vehicle versus 1.3±0.3 mm for MMPi (P<0.01). The increase in end-systolic dimension was 2.8±0.5 mm for vehicle and 1.3±0.4 mm for MMPi (P<0.05). Furthermore, MMPi reduced infarct wall thinning; the minimal infarct thickness was 0.8±0.1 mm for vehicle and 1.6±0.3 mm for MMPi (P<0.05). Interestingly, the MMPi group had increased numbers of vessels in the subendocardial layer of the infarct; the number of capillaries was increased in the subendocardial layer (46±4 vessels/field versus 17±3 vessels/field for vehicle; P<0.001), and the number of arterioles was also increased (4.0±0.8 vessels/field versus 2.0±0.4 vessels/field for vehicle; P<0.05).

Conclusions— MMP inhibition attenuates left ventricular remodeling even when the dominant collagenase MMP-1 is not inhibited; furthermore, this selective MMP inhibition appears to increase rather than decrease neovascularization in the subendocardium.

Key Words: ventricles • myocardial infarction • metalloproteinases • remodeling

	Introduction

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Left ventricular remodeling after myocardial infarction (MI) is a leading cause of congestive heart failure, and the degree of remodeling predicts morbidity and mortality.^1,2 Because heart failure can occur despite the use of agents such as ACE inhibitors and ß-adrenergic–blocking agents, new strategies to prevent progressive ventricular dilation are needed. One such strategy is matrix metalloproteinase (MMP) inhibition.^3,4 Several lines of evidence implicate MMPs, members of a family of metalloenzymes that can degrade extracellular matrix components, as mediators of remodeling events in the myocardium. First, expression of specific MMPs increases in the myocardium after MI, in the presence or absence of reperfusion,^5,6 and in nonischemic dilated cardiomyopathy.⁷ Second, broad pharmacological inhibition of MMPs blocks postinfarction ventricular dilation in mice and rats^4,8 as well as pacing-induced dilation in pigs.³ Furthermore, deletion or overexpression of MMPs in genetically engineered mice regulates cardiac hypertrophy, function, and postinfarction remodeling.^9–11

The mechanisms by which MMP inhibition regulates ventricular dilation are incompletely described. One theory is that disruption of collagen fibrils during the dilation process is necessary for cardiomyocytes to establish new matrix attachments.¹² This theory is consistent with the ventricular dilation that occurs in mice with transgenic overexpression of human MMP-1, an important interstitial collagenase in humans that is not expressed postnatally in rodents.¹¹ However, inhibition of collagen degradation may not be the sole mechanism of MMP inhibition in ventricular remodeling. For example, mice with targeted deletion of MMP-9, an enzyme that can digest a broad variety of substrates but not fibrillar collagen, have attenuated ventricular remodeling¹⁰ and decreased cardiac rupture after infarction.⁹

Thus, selective MMP inhibition that does not block fibrillar collagen degradation might reduce ventricular remodeling. This hypothesis is highly relevant because many small molecules can inhibit different MMPs, and these compounds will potentially have different pharmacological effects. For example, broad-spectrum MMP inhibition in humans can cause symptomatic tendonitis. In a previous study, a compound that did not inhibit MMP-1 activity reduced left ventricular (LV) dilation early after infarction in mice.⁸ However, because mice do not express MMP-1 postnatally, this selective MMP inhibition strategy is best tested in a species with a complement of myocardial MMPs more representative of human myocardium. This study used rabbits with experimental coronary artery occlusion to evaluate the effects of selective MMP inhibition on infarct expansion. Furthermore, because in some circumstances MMPs appear to promote endothelial migration and angiogenesis,^13–15 we analyzed the impact of selective MMP inhibition on neovascularization.

	Methods

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All animal procedures were conducted in accordance with guidelines published in the Guide for the Care and Use of Laboratory Animals (DHEW publication NIH 85–23, revised 1985, Office of Science and Health Reports, DRR/NIH, Bethesda, Md). All studies were approved by the Animal Research Committee of Harvard Medical School.

Pump Implantation and Coronary Artery Ligation
New Zealand White male rabbits (weight, 1.5 to 2 kg; Millbrook Breeding Labs, Amherst, Mass) were anesthetized with 16.7 mg/kg ketamine and 6.7 mg/kg xylazine (intramuscular), intubated, and mechanically ventilated with a respirator. Anesthesia was maintained with 1% isoflurane. An ear vein was cannulated with a 24-gauge catheter for saline and quinidine administration. A subcutaneous injection of buprenorphine (0.01 to 0.05 mg/kg) was given before surgery and every 12 hours for the next 48 hours and longer as needed. An Esox implantable infusion pump (V08; Access Technologies) was implanted between the scapulae and tied down with 2-0 silk, with ampicillin-saline (10 g/L saline) used as an irrigant. The catheter was placed into the peritoneum for continuous drug infusion. A left thoracotomy was performed, the pericardium was cut, and the large marginal branch of the circumflex coronary artery was permanently occluded with a 4-0 Prolene suture. Ischemia was confirmed by blanching downstream of the ligation and by persistent ST elevation on the ECG. Quinidine (5 mg/kg IV) was given just before ligation and continued for 10 minutes to limit ventricular arrhythmias.^16–20

Drug Administration and Plasma Assay
CP-471,474 (Pfizer Inc, MW 368) is a previously described MMP inhibitor.⁸ CP-471,474 was dissolved in 30% methylcellulose for a final concentration of 30 g/L. The pumps were refilled with freshly prepared drug or vehicle alone every 1 to 2 days. Flow rates were calculated on the basis of the remaining volume in the pumps. The final dosage of MMP inhibitor was 120 mg/d.

At presurgical examination, day 2, week 1, week 2, week 3, and week 4 after MI, blood was collected through the ear vein in heparinized tubes. The tubes were centrifuged for 5 minutes at 12 000g, and plasma was stored at -80C until use. Plasma concentrations were analyzed by liquid chromatographic assay with mass spectroscopy detection monitoring for an ion characteristic of CP-471,474. For this assay, the range of detection was <25 ng/mL to >5 µg/mL.

Echocardiographic Imaging
Echocardiographic acquisition and analysis were performed by an echocardiographer blinded to treatment group. Echocardiographic studies were performed under light anesthesia with spontaneous respiration with intramuscular ketamine and xylazine. The heart rate for a normal conscious rabbit is 200 to 300 bpm; all images were taken at a heart rate >150 bpm to minimize effects of anesthesia. Images were acquired with the use of a Sonos 5500 (Agilent Technologies) and a 12-MHz transducer and were analyzed at the time of acquisition. Measurements were taken from long-axis 2-dimensional views with end-diastolic and systolic short-axis measurements at the center of the ventricle. Echocardiographic studies were performed at baseline (18 to 24 hours after MI) and weekly for 4 weeks. For each measurement, 3 consecutive cardiac cycles were averaged. The average standard deviation for the baseline measurements (n=18) was 2.5% and 3.7% for end-diastolic and systolic measurements, respectively.

Tissue Collection and Infarct Characterization
A lethal dose of ketamine and xylazine was injected through the ear vein, followed by 10 mL of cardioplegic solution to arrest the heart in diastole. The heart was removed from the chest, and the right and left ventricles separated. The left ventricle was sectioned from apex to base, and both ventricles were incubated in 1% triphenyl tetrazolium in warm cardioplegic solution for 20 minutes. These slices were photographed, and infarct size was calculated through the use of image analysis software. Each image was analyzed 5 times and averaged. Wall thickness was determined by measurement of the width of the thinnest part of the infarct and the thickest part of the septum, with the use of custom-written image-analysis software. The thinning ratio is an index of the amount of wall thinning in the infarct normalized to the thickness of the septum and is calculated by dividing the infarct wall thickness with septal wall thickness.²¹ For both infarct size and wall thickness measurements, the observer was blinded to treatment group.

Western Analysis
Frozen tissue from infarcted regions was homogenized in lysis buffer (9.8 mol/L urea, 2% (wt/vol) NP40, and 100 mmol/L DTT) and centrifuged twice at 13 000g for 10 minutes. Equal amounts of protein were loaded onto 10% polyacrylamide gels and transferred onto PVDF membranes. The MMP, tissue inhibitor of metalloproteinase (TIMP), and angiostatin antibodies (Oncogene) were used at 1 µg/mL, and blots were visualized by means of chemiluminescence.

Histology
The midcavity section was fixed in 4% paraformaldehyde, embedded in paraffin, and sectioned at 5 µm. Sections were stained with picrosirius red and Masson’s trichrome stain to evaluate collagen deposition. Immunohistochemistry was performed with the use of Vector kits that use the ABC technique. The DAB chromogen was used to visualize positive staining, and the sections were counterstained with hematoxylin and/or eosin. An antibody that selectively recognizes the C-terminal neoepitope generated by collagenase (MMP 1, MMP 8, MMP 13, or MT1-MMP) cleavage of collagen I, II, or III (9A4 antibody) was used at a concentration of 14 µg/mL.^22–24 Endothelial cells were detected by biotinylated Griffonia (Bandeiraea) Simplicifolia Lectin-I (GSL, Vector Laboratories; 100 µg/mL). For quantitative analysis of immunoreactive cleaved collagen, measurements were performed with the use of Image-Pro software (Media Cybernetics) to calculate the percentage of total area stained positive. GSL staining was quantified manually by counting the number of vessels per field from the infarcted region, scanned at x25 magnification.⁹ For both, quantification was performed in a blinded manner by using a minimum of 5 sections for each animal. All animals were used for the analysis.

Statistical Analysis
Data are presented as mean±SEM. The echocardiographic data were analyzed by repeated-measures ANOVA; comparisons between individual groups were made with the use of a Student’s t test. A 2-tailed value of P<0.05 was considered statistically significant.

	Results

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Drug Levels
Mean drug levels were assayed from plasma samples. The mean plasma concentration ranged from 100 ng/mL (270 nmol/L) to 350 ng/mL (945 nmol/L) for the duration of the study (Figure 1). The IC₅₀ values for CP-471,474 are 1170 nmol/L for MMP-1; 0.7 nmol/L for MMP-2; 16 nmol/L for MMP-3; 13 nmol/L for MMP-9; and 0.9 nmol/L for MMP-13.⁸ CP-471,474 is 90% plasma protein bound in most species. Therefore, although the plasma concentration at the 4-week time point approached the IC₅₀ for MMP-1, it is unlikely that MMP-1 was inhibited at the tissue level. These data indicate that rabbits allocated to the treatment group received therapeutic levels of inhibitor at all time points examined.

View larger version (11K): [in this window] [in a new window]   Figure 1. Therapeutic MMP inhibitor levels in plasma. Plasma levels were collected at day 2 (24 hours after drug infusion was initiated), week 1, week 2, week 3, and week 4 after MI. Dotted lines indicate IC50 for MMP-3 (6 ng/mL) and MMP-1 (433 ng/mL). IC50 for MMPs 2, 9, and 13 are all <6 ng/mL.

Mortality and Infarct Sizes
Of the 23 rabbits that survived MI surgery, 18 survived the entire 4-week protocol. The 5 deaths occurred between 5 and 20 days after MI (total mortality rate, 22%), and there was no difference in mortality rate between the MMP inhibitor (MMPi) and vehicle groups (n=3 and n=2, respectively). There was also no difference in infarct size. The vehicle group had an average infarct size of 26±2% (range, 17% to 31%), whereas the MMPi group had an average infarct size of 30±3% (range, 16% to 44%; P=0.27).

Echocardiographic Measurements
Baseline measurements are listed in Table 1. Infarcted rabbits allocated to MMPi had significantly smaller increases in end-diastolic dimensions (EDD) and end-systolic dimensions (ESD) compared with vehicle (Figure 2). At 3 weeks, the increase in EDD from day 1 after MI was 2.1±0.4 mm for vehicle and 1.6±0.4 mm for MMPi; the increase in vehicle EDD was significantly higher than week-1 values (P<0.01). The increase in ESD at 3 weeks was 2.2±0.4 mm for vehicle and 1.8±0.4 mm for MMPi; the increase in vehicle ESD was significantly higher than week-1 values (P<0.05). At 4 weeks, the change in EDD was 3.1±0.5 mm and 1.3±0.3 mm for vehicle and MMPi, respectively. The increase in vehicle EDD was significantly higher than week-1 values (P<0.01) and MMPi week-4 values (P<0.01). The change in ESD was 2.8±0.5 mm for vehicle and 1.3±0.4 mm for MMPi. The increase in vehicle ESD was significantly higher than week-1 values (P<0.01) and MMPi week-4 values (P<0.05). At 4 weeks, there was no correlation between individual differences in plasma MMPi levels and EDD (r²=0.03; P=0.68) or ESD (r²=0.05; P=0.58), indicating that rabbits with higher plasma MMPi levels did not have additional effects on LV dilation. Although these data demonstrate that LV dilation is reduced in rabbits treated with MMPi despite lack of MMP-1 inhibition, we cannot exclude the possibility that some degree of MMP-1 inhibition caused by higher MMPi plasma levels at week 4 affected remodeling.

View this table: [in this window] [in a new window]   Table 1. Baseline Echocardiographic Measurements of Infarcted Rabbits

View larger version (16K): [in this window] [in a new window]   Figure 2. Changes in EDD (EDD) and ESD (ESD) from day 1 after MI in MMPi and vehicle groups. MMPi attenuated remodeling at 3 and 4 weeks after MI. *P<0.05 and **P<0.01, vehicle at 1 week vs vehicle at 3 weeks or 4 weeks; P<0.05 and P<0.01, vehicle vs MMPi.

Collagen, Wall Thickness, and MMP Levels
To determine if selective MMPi reduced collagen accumulation in the infarct area, a midcavity section was stained with Masson’s trichrome, and the percentage of area occupied by collagen was calculated. The entire section was scanned at low power and used for quantification. The vehicle group had 31±4% collagen fractional area, whereas MMPi had 26±4% collagen fractional area (P=0.37). There were also no differences in infarct total collagen by picrosirius red staining or collagen I, collagen III, MMP-1, MMP-3, MMP-8, and TIMP-1 levels by Western analyses (Table 2). MMP-7 and MMP-13 levels were increased in the infarcted regions of the MMPi group.

View this table: [in this window] [in a new window]   Table 2. Western Analyses

Although MMPi did not change total collagen, it did reduce postinfarct wall thinning (Figure 3). The average wall thickness at the infarct was 0.8±0.1 mm for vehicle and 1.6±0.3 mm for MMPi (P<0.05). There was a trend toward more compensatory hypertrophy in the vehicle group (5.2±0.6 mm for vehicle; 4.2±0.3 mm for MMPi), although this did not reach statistical significance (P=0.056). The average thinning ratio was 0.17±0.03 for vehicle and 0.40±0.08 for MMPi (P<0.05).

View larger version (24K): [in this window] [in a new window]   Figure 3. Selective MMP inhibition reduces infarct thinning. A, Representative hearts stained with hematoxylin and eosin from MMPi and vehicle groups. RV indicates right ventricle; and LV infarct, left ventricle infarct. As shown in B, there was significantly less wall thinning in the group treated with MMPi. C, Thinning ratio was significantly different between the 2 groups. *P<0.05.

MMP Inhibition Selectivity
To verify ongoing collagen cleavage after infarct despite selective MMPi by an independent measure, immunohistochemistry was performed with the use of the 9A4 antibody that recognizes the C-terminal neoepitope generated by collagenase (MMP 1, MMP 8, MMP 13, or MT1-MMP) cleavage of collagen I, II, or III (9A4 antibody).^22–24 For each animal, the area stained was quantified by averaging 10 random high-power fields from the infarct area. There was no difference in the areas of cleaved collagen between vehicle and MMPi-treated groups by image analysis, indicating that fibrillar collagen cleavage was not inhibited by MMPi (Figure 4).

View larger version (120K): [in this window] [in a new window]   Figure 4. Collagen cleavage is not impaired in MMPi group. Sections were immunostained with 9A4 Ab (brown stain), which recognizes collagen that has been cleaved and counterstained with hematoxylin and eosin. Top, Representative images taken at x10 magnification (bar=400 µm); bottom, higher magnification (x40) of same field (bar=100 µm). Quantitative image analysis showed no difference in area of staining, as indicated by graph.

Neovascularization
Experimental evidence indicates that MMPs participate in angiogenesis, and therefore MMP inhibition may potentially impair beneficial neovascularization after MI. However, MMPs may also generate inhibitors of angiogenesis, so that MMP inhibition could potentially promote neovascularization.^25–28 In infarcted rabbits treated with MMPi, there were significant differences in vessel numbers in the infarct region, as demonstrated by staining with biotinylated GSL-I. Control animals had a distinct paucity of vascularization in the subendocardium, with the majority of vessels present in the midmyocardium. In contrast, MMPi had a more uniform distribution of vessels (Figure 5). One potential mediator of this effect is angiostatin, an inhibitor of angiogenesis that is generated by MMPs. To determine if this difference could be due to the generation of angiostatin by MMPs, angiostatin levels were measured in plasma samples by Western analysis. No differences were observed between the 2 groups (Figure 6). Angiostatin levels were also unchanged in myocardial samples (data not shown).

View larger version (55K): [in this window] [in a new window]   Figure 5. Angiogenesis was increased in the selective MMP inhibitor group. A, Qualitative increase in vessels in subendocardial layer of MMPi group compared with vehicle group in B (x20 magnification; bar=200 µm). Subendocardium is on the right side. Number of capillaries and arterioles was quantified by counting number of vessels per high-powered field. Mean±SEM of the number of endothelial-lined vessels per field, scanned at x25 magnification. Number of vessels in subendocardial layer increased in MMPi group compared with vehicle group (C and D). Endo indicates subendocardium; Mid, mid-myocardium; and Epi, epicardium. *P<0.05, **P<0.01, ***P<0.001.

View larger version (26K): [in this window] [in a new window]   Figure 6. No difference in angiostatin levels between the MMPi and vehicle groups. Western blots for angiostatin, demonstrating band at 50 kDa, are shown on top. Below is density (arbitrary units) for the 2 groups, presented as mean±SEM.

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
The primary finding of this study is that selective MMP inhibition attenuated LV remodeling after MI. EDD and ESD progressively increased in rabbits receiving the vehicle, whereas MMPi reduced dilation. At 4 weeks after MI, MMPi did not increase total collagen levels in the infarct area but reduced wall thinning. This suggests that a noncollagenolytic mechanism is critical in regulating ventricular remodeling and highlights the potential importance of noncollagen MMP substrates. At 4 weeks, the chronic healing phase has commenced and is characterized by reactive fibrosis and hypertrophy in the remote myocardium.^29–32 The decrease in infarct wall thickness and thinning ratio in the MMPi group suggest a protective effect in preserving wall thickness in the scar and preventing compensatory hypertrophy in the septum, thus preserving tissue homogeneity. This finding is similar to results shown by Heymans et al,⁹ who demonstrated a reduction in ventricular aneurysms in MMP-9 null mice after MI.

A surprising finding of this study is that angiogenesis was not decreased by MMPi. The lack of vessels in the subendocardium in control animals is a hallmark of ischemic cell death and is related to the transmural gradient of collateral blood flow, which is preferentially shunted to preserve the subepicardial region.³³ That the MMPi group had more vessels in the subendocardial layer raises the hypothesis that MMPs in vivo generate angiostatic factors that may prevent vessel formation in this area of high metabolic demand. This finding again suggests a potential importance for non–matrix MMP substrates. Although MMPs can directly stimulate angiogenesis, MMPs can also generate inhibitors of angiogenesis such as angiostatin.^25,28,34,35 In these experiments, we could not demonstrate a change in angiostatin in either the plasma or myocardium of these animals. However, the compensatory increase in MMPs 7 and 13 suggests a potential role for these MMPs in regulating either neovascularization or remodeling.

In summary, selective MMP inhibition prevented progressive LV dilation in a rabbit model of ventricular remodeling. This reduction in dilation was not due to changes in collagen levels, suggesting that factors other than absolute collagen levels are responsible. One such effect may be increased angiogenesis.

	Acknowledgments

 
This study was supported by grants from the National Institute of Health (HL-65273 and HL-10337).

Received September 18, 2001; revision received November 29, 2001; accepted December 14, 2001.

	References

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				F. B. Engel, P. C. H. Hsieh, R. T. Lee, and M. T. Keating FGF1/p38 MAP kinase inhibitor therapy induces cardiomyocyte mitosis, reduces scarring, and rescues function after myocardial infarction PNAS, October 17, 2006; 103(42): 15546 - 15551. [Abstract] [Full Text] [PDF]

				H. Matsusaka, T. Ide, S. Matsushima, M. Ikeuchi, T. Kubota, K. Sunagawa, S. Kinugawa, and H. Tsutsui Targeted deletion of p53 prevents cardiac rupture after myocardial infarction in mice Cardiovasc Res, June 1, 2006; 70(3): 457 - 465. [Abstract] [Full Text] [PDF]

				Z. He, D. M. Opland, K. J. Way, K. Ueki, N. Bodyak, P. M. Kang, S. Izumo, R. N. Kulkarni, B. Wang, R. Liao, et al. Regulation of Vascular Endothelial Growth Factor Expression and Vascularization in the Myocardium by Insulin Receptor and PI3K/Akt Pathways in Insulin Resistance and Ischemia Arterioscler. Thromb. Vasc. Biol., April 1, 2006; 26(4): 787 - 793. [Abstract] [Full Text] [PDF]

				S. Janssens and H. R. Lijnen What has been learned about the cardiovascular effects of matrix metalloproteinases from mouse models? Cardiovasc Res, February 15, 2006; 69(3): 585 - 594. [Abstract] [Full Text] [PDF]

				D. Vanhoutte, M. Schellings, Y. Pinto, and S. Heymans Relevance of matrix metalloproteinases and their inhibitors after myocardial infarction: A temporal and spatial window Cardiovasc Res, February 15, 2006; 69(3): 604 - 613. [Abstract] [Full Text] [PDF]

				M. L. Lindsey, G. P. Escobar, L. W. Dobrucki, D. K. Goshorn, S. Bouges, J. T. Mingoia, D. M. McClister Jr., H. Su, J. Gannon, C. MacGillivray, et al. Matrix metalloproteinase-9 gene deletion facilitates angiogenesis after myocardial infarction Am J Physiol Heart Circ Physiol, January 1, 2006; 290(1): H232 - H239. [Abstract] [Full Text] [PDF]

				H. Su, F. G. Spinale, L. W. Dobrucki, J. Song, J. Hua, S. Sweterlitsch, D. P. Dione, P. Cavaliere, C. Chow, B. N. Bourke, et al. Noninvasive Targeted Imaging of Matrix Metalloproteinase Activation in a Murine Model of Postinfarction Remodeling Circulation, November 15, 2005; 112(20): 3157 - 3167. [Abstract] [Full Text] [PDF]

				H. Matsusaka, M. Ikeuchi, S. Matsushima, T. Ide, T. Kubota, A. M. Feldman, A. Takeshita, K. Sunagawa, and H. Tsutsui Selective disruption of MMP-2 gene exacerbates myocardial inflammation and dysfunction in mice with cytokine-induced cardiomyopathy Am J Physiol Heart Circ Physiol, November 1, 2005; 289(5): H1858 - H1864. [Abstract] [Full Text] [PDF]

				S. Perlini, G. Palladini, I. Ferrero, R. Tozzi, S. Fallarini, A. Facoetti, R. Nano, F. Clari, G. Busca, R. Fogari, et al. Sympathectomy or Doxazosin, But Not Propranolol, Blunt Myocardial Interstitial Fibrosis in Pressure-Overload Hypertrophy Hypertension, November 1, 2005; 46(5): 1213 - 1218. [Abstract] [Full Text] [PDF]

				V. Fuster, P. R. Moreno, Z. A. Fayad, R. Corti, and J. J. Badimon Atherothrombosis and High-Risk Plaque: Part I: Evolving Concepts J. Am. Coll. Cardiol., September 20, 2005; 46(6): 937 - 954. [Abstract] [Full Text] [PDF]

				M. L. Lindsey, D. K. Goshorn, C. E. Squires, G. P. Escobar, J. W. Hendrick, J. T. Mingoia, S. E. Sweterlitsch, and F. G. Spinale Age-dependent changes in myocardial matrix metalloproteinase/tissue inhibitor of metalloproteinase profiles and fibroblast function Cardiovasc Res, May 1, 2005; 66(2): 410 - 419. [Abstract] [Full Text] [PDF]

				J. Chen, C.-H. Tung, J. R. Allport, S. Chen, R. Weissleder, and P. L. Huang Near-Infrared Fluorescent Imaging of Matrix Metalloproteinase Activity After Myocardial Infarction Circulation, April 12, 2005; 111(14): 1800 - 1805. [Abstract] [Full Text] [PDF]

				A. T. Yan, R. T. Yan, and P. P. Liu Narrative Review: Pharmacotherapy for Chronic Heart Failure: Evidence from Recent Clinical Trials Ann Intern Med, January 18, 2005; 142(2): 132 - 145. [Abstract] [Full Text] [PDF]

				S. Heymans, F. Lupu, S. Terclavers, B. Vanwetswinkel, J.-M. Herbert, A. Baker, D. Collen, P. Carmeliet, and L. Moons Loss or Inhibition of uPA or MMP-9 Attenuates LV Remodeling and Dysfunction after Acute Pressure Overload in Mice Am. J. Pathol., January 1, 2005; 166(1): 15 - 25. [Abstract] [Full Text] [PDF]

				J. S. Ikonomidis, J. W. Hendrick, A. M. Parkhurst, A. R. Herron, P. G. Escobar, K. B. Dowdy, R. E. Stroud, E. Hapke, M. R. Zile, and F. G. Spinale Accelerated LV remodeling after myocardial infarction in TIMP-1-deficient mice: effects of exogenous MMP inhibition Am J Physiol Heart Circ Physiol, January 1, 2005; 288(1): H149 - H158. [Abstract] [Full Text] [PDF]

				J. Sundstrom, J. C. Evans, E. J. Benjamin, D. Levy, M. G. Larson, D. B. Sawyer, D. A. Siwik, W. S. Colucci, P. Sutherland, P. W.F. Wilson, et al. Relations of Plasma Matrix Metalloproteinase-9 to Clinical Cardiovascular Risk Factors and Echocardiographic Left Ventricular Measures: The Framingham Heart Study Circulation, June 15, 2004; 109(23): 2850 - 2856. [Abstract] [Full Text] [PDF]

				L. Barandon, T. Couffinhal, P. Dufourcq, J. Ezan, P. Costet, D. Daret, C. Deville, and C. Duplaa Frizzled A, a novel angiogenic factor: promises for cardiac repair Eur. J. Cardiothorac. Surg., January 1, 2004; 25(1): 76 - 83. [Abstract] [Full Text] [PDF]

				R. E. Chapman and F. G. Spinale Extracellular protease activation and unraveling of the myocardial interstitium: critical steps toward clinical applications Am J Physiol Heart Circ Physiol, January 1, 2004; 286(1): H1 - H10. [Full Text] [PDF]

				L. Barandon, T. Couffinhal, J. Ezan, P. Dufourcq, P. Costet, P. Alzieu, L. Leroux, C. Moreau, D. Dare, and C. Duplaa Reduction of Infarct Size and Prevention of Cardiac Rupture in Transgenic Mice Overexpressing FrzA Circulation, November 4, 2003; 108(18): 2282 - 2289. [Abstract] [Full Text] [PDF]

				W. M. Yarbrough, R. Mukherjee, G. P. Escobar, J. T. Mingoia, J. A. Sample, J. W. Hendrick, K. B. Dowdy, J. E. McLean, A. S. Lowry, T. P. O'Neill, et al. Selective Targeting and Timing of Matrix Metalloproteinase Inhibition in Post-Myocardial Infarction Remodeling Circulation, October 7, 2003; 108(14): 1753 - 1759. [Abstract] [Full Text] [PDF]

				F. J. Villarreal, M. Griffin, J. Omens, W. Dillmann, J. Nguyen, and J. Covell Early Short-Term Treatment With Doxycycline Modulates Postinfarction Left Ventricular Remodeling Circulation, September 23, 2003; 108(12): 1487 - 1492. [Abstract] [Full Text] [PDF]

M. L. Lindsey, J. Yoshioka, C. MacGillivray, S. Muangman, J. Gannon, A. Verghese, M. Aikawa, P. Libby, S. M. Krane, and R. T. Lee Effect of a Cleavage-Resistant Collagen Mutation on Left Ventricular Remodeling Circ. Res., August 8, 2003; 93(3): 238 - 245. [Abstract]