(Circulation. 2001;103:155.)
© 2001 American Heart Association, Inc.
Basic Science Reports |
From the Laboratory of Cardiovascular Pathophysiology, Department of Physiology, University of the Witwatersrand, Johannesburg (A.J.W., O.J.T., S.S., G.R.N.), and the Departments of Anatomical Pathology and Physiology, Medical University of South Africa, Pretoria (O.J.T., E.J.L.), South Africa; and the Department of Medicine, University of Massachusetts, Worcester (T.M., E.S.C., T.E.M.).
| Abstract |
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Methods and ResultsWe studied 2 rat models of LV dilatation: (1) pressure-overload hypertrophy with heart failure (POH-F) induced by suprarenal abdominal aortic banding and (2) LVH induced by 7 months of isoproterenol (ISO, 0.04 mg · kg-1 · d-1) administration. In POH-F rats and in rats receiving ISO, LV dilatation and a reduced systolic chamber performance were noted. Myocardial hydroxyproline concentrations ([HPRO]) were increased in the POH-F rats, whereas in rats receiving ISO, [HPRO] was decreased. In POH-F rats, the ratio of myocardial collagen type I to type III was increased, but in rats receiving ISO, myocardial collagen I/III was unchanged. In contrast to the diverse changes in myocardial collagen concentrations and phenotypes observed in the 2 models of LV dilatation, the ratio of myocardial insoluble to soluble (relationship between cross-linked and noncross-linked) collagen was decreased in both the POH-F and ISO groups. Moreover, administration of captopril (0.22 mmol · kg-1 · d-1), which inhibited the ISO-induced reduction in myocardial insoluble/soluble collagen but not the reduction in [HPRO], prevented the ISO-induced alterations in LV dimensions and performance.
ConclusionsBecause decreases in the ratio of myocardial insoluble to soluble collagen parallel LV dilatation in rats, reductions in myocardial collagen cross-linking may be an important mechanism contributing to LV dilatation in heart disease.
Key Words: collagen systole diastole mechanics remodeling
| Introduction |
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Because all models of LV systolic dysfunction exhibit chamber remodeling, it is conceivable that among the expected diverse alterations in the composition of the myocardial matrix, a common qualitative collagen characteristic would be apparent. To test this supposition, myocardial collagen characteristics were compared in 2 rat models of LV hypertrophy (LVH) that progress to LV dilatation: pressure-overload hypertrophy (POH)1 and isoproterenol (ISO)-induced LVH.3 Moreover, because ACE inhibitors produce beneficial effects in various forms of LV dilatation,12 we reasoned that the same common qualitative collagen characteristic would be a target of captopril (CAP) therapy in the rat model with reduced collagen concentrations (ISO model).
| Methods |
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ISO-Induced LVH
Initially, a dose-titration study was performed to
establish the highest dose of ISO that could be administered for
prolonged periods without producing sudden cardiac death. Subsequently,
50 male 4-month-old Sprague-Dawley (SD, outsourced from OLAC, UK) rats
weighing 250 to 300 g were randomly assigned to 5 groups. ISO
(Imuprel, Adcock Ingram) was administered at a dosage of 0.04
mg · kg-1 · d-1
SC (
0.1 mL) for 7 months to 2 groups of animals. Another 2 groups
received daily subcutaneous injections of the vehicle of ISO for 7
months. To determine the effect of CAP on ISO-mediated cardiac changes,
rats from 1 of the ISO-treated and 1 of the vehicle-treated groups also
received CAP (Fluka BioChemika) at 0.22
mmol · kg-1 · d-1
in the drinking water for 7 months. Rats in the fifth group, which
received no therapy, were euthanized after 1 month of administration of
the vehicle of ISO to evaluate the effects of age (5 versus 11 months)
on myocardial collagen concentrations.
Pressure-Overload Hypertrophy
Harlan Sprague Dawley (Hsd:SD, Charles River,
Wilmington, Mass) rats weighing 150 to 200 g underwent either
aortic banding or sham surgery as previously
described.13 All surviving
rats were studied 20 weeks after surgery. Pulmonary congestion in this
model of POH has been shown to be associated with LV
dilatation.13 Because the
purpose of the present study was to determine whether changes in
collagen cross-linking parallel LV dilatation in POH, we grouped POH
rats according to the presence or absence of pulmonary congestion. Of
the 57 banded rats that survived 20 weeks, 25 rats had a lung
weight/body weight ratio >2 SD above the mean for the control group.
These rats were classified as having decompensated POH with evidence of
heart failure (POH-F). The remaining banded rats (n=32) were called POH
without failure (POH-NF).
Echocardiographic Studies
Echocardiography was performed as previously
described13 on all
ISO-treated rats and their controls at the end of the experimental
period (72 hours after the last dose of ISO) and in POH rats and their
controls 20 weeks after surgery. Fractional endocardial shortening was
calculated from [end-diastolic diameter (EDD)-end-systolic diameter
(ESD)]/(EDDx100).
Isolated Perfused Heart Preparation
Rats were anesthetized and hearts were excised and
immediately rinsed in an ice-cold physiological saline solution as
previously described.13
Hearts were perfused retrogradely at a constant flow with 37°C
physiological saline solution. The coronary flow rate was determined
volumetrically and adjusted to achieve a flow of 12
mL · min-1 · g-1
heart wt in ISO and control rats according to the estimated weight of
the heart measured immediately after excision, with large vessels and
pericardium still attached. In rats with POH and in their controls,
hearts were perfused at coronary perfusion pressures of 100 mm Hg and
80 mm Hg, respectively, to achieve a flow of
12
mL · min-1 · g-1
heart wt. The coronary perfusion pressure was monitored from a side arm
of the aortic perfusion cannula with a Statham P23 transducer. The
hearts were paced at 300 bpm with the voltage 10% above threshold via
platinum wire electrodes attached to the left atrium and the apex of
the heart.
LV developed pressure and LV diastolic pressure were determined by use of a water-filled balloon-tipped cannula coupled to either a Gould P50 (ISO study) or a Statham P23 (POH study) pressure transducer inserted via the left atrium into the LV cavity. A thin-walled latex balloon with a zero pressure filling volume beyond maximum LV lumen capacities was selected for this study to avoid the stiffness of the balloon wall contributing to LV pressure at higher filling volumes. The volume of the balloon wall was assessed with a water-displacement technique, and the same balloon was used throughout each of the studies. LV and coronary perfusion pressures were recorded with either a Hellige (ISO study) or a Gould model RS 3400 (POH study) polygraph. A micromanipulator was used to gradually increase LV volumes to values that resulted in no further change in LV developed pressure. LV pressures were determined at as many multiple small increments in volume as were practically possible to improve the accuracy of curve fitting during later analysis.
LV systolic chamber performance was determined from the slopes of LV developed pressure-volume (P-V) relations (systolic elastance, E).14 LV diastolic remodeling was assessed from the relationship between LV diastolic pressure and LV volume.3 Statistical comparisons of LV diastolic P-V relations were made from the slopes of the linearized relations (LV chamber k) and the volume intercepts (V0) of these relations (see Statistical Analysis section).
Myocardial Collagen
Samples of LV tissue from all rats were weighed and
stored at -70°C for tissue analysis. Myocardial hydroxyproline
concentration ([HPRO]) was determined by the method of Stegemann and
Stalder after acid (HCl)
hydrolysis.15 Myocardial
collagen was extracted and digested with cyanogen bromide (CNBr)
according to the procedure described by Mukherjee and
Sen.16 Using a portion of
the CNBr-digested collagen sample, polyacrylamide gel electrophoresis
was performed on vertical gels with stacking and separating gel
concentrations of 3% and 12.5%, respectively, as previously
described.16 17
The type I/III collagen ratio was determined after gel
scanning.17 The amount of
type I collagen in the myocardium was determined from the product of
(area scanned on the gel corresponding to type I collagen/area for type
I and type III) and myocardial [HPRO]. The type III collagen
concentration was determined similarly. The remaining portion of the
CNBr-digested collagen sample was subjected to acid hydrolysis and
[HPRO] determination. The amounts of noncross-linked (soluble) and
cross-linked (insoluble) collagen in the myocardium were determined
from the product of the percentage of collagen soluble to CNBr
digestion and the total myocardial collagen concentration and the
difference between the total collagen concentration and soluble
collagen concentration, respectively. The relationship between
insoluble and soluble collagen was used as an index of the degree of
collagen
cross-linking.17 18
Histology
Before cardiac tissues obtained from rats receiving
ISO and their controls were stored for biochemical assessment, a
longitudinal slice of the LV from the apex to the base through both the
anterior and posterior LV walls was stored in formalin for subsequent
histology. LV tissue was processed routinely for light microscopy, and
50-µm-thick sections of the long-axis circumference were cut through
the full thickness of the LV wall. Ten slices were obtained at 1-mm
intervals and stained with Massons trichrome from which hematoxylin
was omitted. A pathological grade (modified from Teerlink et
al3 ) was assigned to each
slice as follows: 0, no damage; and 1, patchy fibrosis in 1 to 5 areas
(<20% of the field). In rats receiving ISO, there was no evidence of
either patchy fibrosis in
20% of the field or diffuse, contiguous
subendocardial, or transmural fibrosis. The grades for individual
slices were summed and then divided by the number of slices to produce
a single average pathological score. Scoring was done on coded samples
by an independent observer blinded to the identity of the rat from
which the sample was obtained.
Analysis
Regression analysis was used to determine the lines
of best fit for the cardiac function relations. The systolic LV P-V
relations were found to best fit a linear function. The LV diastolic
P-V relations were found to best fit the exponential function: LV
diastolic
pressure=b · e(m · LV
diastolic volume), which was linearized: ln LV diastolic
pressure=ln b + m(LV diastolic volume) for statistical analysis.
Differences in LV geometry, hemodynamics, pathological score, and
myocardial collagen biochemical analysis between POH-F, POH-NF, and
control groups and between ISO, Control, ISO+CAP, and CAP groups were
assessed by 1-factor ANOVA followed by Tukey post hoc tests. All values
in the text are represented as mean±SEM.
| Results |
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LV Systolic Chamber Performance
Aortic banding produced a decrease in fractional
endocardial shortening
(Table 2
), a right shift in the LV systolic P-V relation
(Figure 1
), and a decrease in the slope of this relation (LV
E,
Table 2
) when there was evidence of pulmonary congestion
(POH-F) but not in the POH-NF group. Chronic ISO administration
produced an effect on indexes of LV systolic chamber function similar
to the changes noted in POH-F rats
(Table 2
,
Figure 1
). CAP therapy of a group of rats receiving ISO
prevented the ISO-mediated decrease in endocardial shortening
(Table 2
), the right shift in the systolic P-V relation
(Figure 1
), and the decrease in the slope of this relation
(LV E,
Table 2
). Administration of CAP to control rats failed to
influence systolic chamber function (LV E, 735±40 mm Hg/mL). Similar
coronary flow rates were obtained in POH-NF and POH-F compared with
control rats (coronary flow rate in
mL · min-1 · g-1:
POH-F, 12.6±1.0; POH-NF, 12.8±0.9; control,
12.2±1.7).
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LV Remodeling
In POH-F but not in POH-NF rats, LV end-diastolic and
end-systolic internal dimensions were increased
(Table 2
), and a marked right shift
(Figure 2
), decreased slope
(Table 2
), and increase in volume intercept
(Table 2
) of LV diastolic P-V relations occurred. ISO
produced an effect on indexes of LV remodeling similar to the changes
noted in POH-F rats
(Table 2
,
Figure 2
). CAP prevented the increase in LV internal
dimensions
(Table 2
) and the right shift, decreased slope, and
increased volume intercept of the diastolic P-V relation
(Figure 2
, Table 2
) produced by ISO.
|
Myocardial Collagen and Fibrosis
The POH-F group had an increased myocardial [HPRO]
(Figure 3
), and rats receiving ISO had a markedly decreased
myocardial [HPRO], compared with their respective control groups
(Figure 4
). CAP therapy failed to influence the ISO-induced
decrease in [HPRO]
(Figure 4
). Administration of CAP to control rats did not
modify myocardial [HPRO] ([HPRO] in µg/mg LV dry wt, 6.26±0.35).
The greater [HPRO] values in the control rats used for the ISO study
(Figure 4
) compared with those used for the POH study
(Figure 3
) may reflect a change in [HPRO] related to both
the age and the strain of the rat (SD for the ISO study and Hsd:SD for
the POH study). Control SD rats euthanized at 5 months of age had
decreased [HPRO] compared with control SD rats 6 months older
([HPRO] in 5-month-old SD rats in µg/mg LV dry wt, 3.14±0.15,
P<0.01 versus [HPRO] in
11-month-old SD rats). In a separate study, we were able to show that
at an equivalent age of 11 months, myocardial [HPRO] varies according
to the strain of rat studied ([HPRO] in µg/mg LV dry wt:
Sprague-Dawley, 6.39±0.28; Long-Evans, 4.19±0.22; Wistar-Kyoto,
3.17±0.09; P<0.01 between all
3 rat strains).
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Seven months of ISO administration resulted in minor and insignificant histological evidence of discrete (patchy) myocardial fibrosis (pathological score: Control, 0.20±0.13; ISO, 0.55±0.21; not significantly different from controls). Six rats receiving ISO had patchy fibrosis in <20% of the field, in contrast to evidence of patchy fibrosis in <20% of the field in 2 control rats. Three rats receiving both CAP and ISO had evidence of patchy fibrosis (pathological score, 0.27±0.14).
The POH-F group of rats exhibited a marked increase in type
I collagen content but no change in type III collagen
(Table 3
), resulting in an increase in the ratio of type
I/III collagen
(Figure 3
). However, ISO administration produced no changes
in collagen phenotypic ratios
(Figure 4
), because both type I and type III myocardial
collagen concentrations were decreased to a similar extent
(Table 3
). CAP failed to modify type I/III collagen ratio in
either the ISO
(Figure 4
) or the control (I/III for control CAP, 3.5±0.26)
group.
|
In contrast to the lack of consistent change in
myocardial [HPRO] or collagen phenotypes in rats receiving ISO
compared with POH-F rats, both the ISO and the POH-F groups had a
decreased collagen cross-linking, as evidenced by a reduction in
insoluble/soluble collagen
(Figures 3
and 4
).
Furthermore, in rats receiving ISO, the decreased collagen
cross-linking was prevented by CAP administration
(Figure 4
).
| Discussion |
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Collagen Concentrations and Phenotypic
Ratios
Myocardial collagen concentrations changed in opposite
directions in the 2 models of LV systolic dysfunction examined in this
study. Collagen concentrations increased in the POH-F group, whereas in
the ISO group, myocardial collagen content decreased. Our results
demonstrating increased myocardial collagen concentrations in POH are
consistent with previous
reports.9 17 19
However, a ß-adrenoceptor agonistinduced decrease in myocardial
HPRO concentrations is in apparent contrast to previous studies on
interstitial effects of ß-adrenoceptor
agonists.20 Our data are
likely to differ from those of authors reporting on increases in
myocardial collagen concentrations after administration of
ISO,20 because we used far
lower doses of ISO.
In the POH-F group, the ratio of collagen type I/III was increased, as previously reported,16 17 whereas ISO administration produced no effect. Hence, it is unlikely that myocardial collagen phenotypic ratios contribute to LV dilatation and dysfunction in rodent models.
Collagen Cross-Linking Versus Content
Our results showing a decrease in myocardial collagen
cross-linking associated with detrimental cardiac chamber remodeling
and subsequent systolic dysfunction in 2 animal models of LV dilatation
are supported by similar findings in tachycardia-induced heart
failure11 and idiopathic
dilated cardiomyopathy.10
Gunja-Smith and colleagues10
demonstrated a marked reduction in the concentration of mature
cross-linked collagen despite increased myocardial collagen
concentrations in patients with idiopathic dilated cardiomyopathy.
Similarly, Spinale and
coworkers11 showed a
reduction in collagen cross-linking in tachycardia-induced heart
failure, although myocardial collagen concentrations were decreased.
The results obtained in idiopathic dilated
cardiomyopathy,10
tachycardia-induced heart
failure,11 POH (this study),
and ISO-induced LV dysfunction (this study), when taken together,
suggest that alterations in myocardial collagen cross-linking may be
responsible for the effects of matrix remodeling (loss of structural
integrity) and LV dilatation.
The relationship between myocardial collagen concentrations and changes in LV function in POH is well established.9 14 19 However, no mechanism(s) by which enhanced myocardial collagen concentrations (which should improve myocyte support) in POH could lead to LV dilatation has been proposed. The results obtained in the present study suggest 1 possible mechanism. An enhanced collagen synthesis may lead to an altered relationship between cross-linked and noncross-linked collagen in favor of a reduction in cross-linked collagen. This, in turn, may impair extracellular matrix integrity.21 22 The structural support provided by the fibrillar collagen matrix is an important determinant of myocyte shape and alignment and the transduction of myocyte shortening into overall myocardial ejection.23 Hence, a loss of collagen support due to increased degradation of mature collagen with replacement by newly synthesized collagen with decreased cross-linking may contribute directly to LV dilatation and systolic dysfunction.
The present study demonstrates that CAP prevented the decrease in collagen cross-linking as well as the LV remodeling and systolic dysfunction induced by administration of ISO. Previous studies in various models of heart failure have reported beneficial effects of ACE inhibition on myocardial collagen structure and composition.24 25 Thus, it is possible that the maintenance of collagen cross-linking by CAP in rats receiving ISO would conserve the structural integrity of the myocardial matrix, thereby preventing LV dilatation and dysfunction.21 22
No mechanism(s) that explains the decrease in myocardial collagen cross-linking in either idiopathic dilated cardiomyopathy,10 tachycardia-induced heart failure,11 POH-F (this study), or ISO-induced ventricular remodeling (this study) has been elucidated. One possibility is that the activity of lysyl oxidase may be decreased, which would result in a reduction in collagen cross-linking. Alternatively, an increased turnover of collagen could reduce the time available for newly synthesized collagen to form stable cross-links and hence structurally adequate fibrils. An increased collagen turnover could result from the enhanced activity of MMPs reported in idiopathic dilated cardiomyopathy,10 tachycardia-induced heart failure,7 11 and POH.8 Indeed, elevations in serum markers of collagen turnover have been reported in patients with idiopathic dilated cardiomyopathy.26
In conclusion, we have shown that irrespective of changes in myocardial collagen concentrations, a decrease in collagen cross-linking parallels LV dilatation in 2 rat models of LV dysfunction. These results suggest that a decrease in myocardial cross-linked collagen relative to noncross-linked collagen contributes to matrix disorganization and LV dilatation.
| Acknowledgments |
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| Footnotes |
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Received May 11, 2000; revision received July 18, 2000; accepted July 20, 2000.
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K. Chen, J. L. Mehta, D. Li, L. Joseph, and J. Joseph Transforming Growth Factor {beta} Receptor Endoglin Is Expressed in Cardiac Fibroblasts and Modulates Profibrogenic Actions of Angiotensin II Circ. Res., December 10, 2004; 95(12): 1167 - 1173. [Abstract] [Full Text] [PDF] |
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M. Gibbs, D. G. A. Veliotes, C. Anamourlis, D. Badenhorst, O. Osadchii, G. R. Norton, and A. J. Woodiwiss Chronic {beta}-adrenoreceptor activation increases cardiac cavity size through chamber remodeling and not via modifications in myocardial material properties Am J Physiol Heart Circ Physiol, December 1, 2004; 287(6): H2762 - H2767. [Abstract] [Full Text] [PDF] |
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K. Sliwa, G. R. Norton, N. Kone, G. Candy, J. Kachope, A. J. Woodiwiss, C. Libhaber, P. Sareli, and R. Essop Impact of initiating carvedilol before angiotensin-converting enzyme inhibitor therapy on cardiac function in newly diagnosed heart failure J. Am. Coll. Cardiol., November 2, 2004; 44(9): 1825 - 1830. [Abstract] [Full Text] [PDF] |
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L. H. Opie Cellular Basis for Therapeutic Choices in Heart Failure Circulation, October 26, 2004; 110(17): 2559 - 2561. [Full Text] [PDF] |
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O. H. Cingolani, X.-P. Yang, Y.-H. Liu, M. Villanueva, N.-E. Rhaleb, and O. A. Carretero Reduction of Cardiac Fibrosis Decreases Systolic Performance Without Affecting Diastolic Function in Hypertensive Rats Hypertension, May 1, 2004; 43(5): 1067 - 1073. [Abstract] [Full Text] [PDF] |
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B. Murtuza, K. Suzuki, G. Bou-Gharios, J. R. Beauchamp, R. T. Smolenski, T. A. Partridge, and M. H. Yacoub Transplantation of skeletal myoblasts secreting an IL-1 inhibitor modulates adverse remodeling in infarcted murine myocardium PNAS, March 23, 2004; 101(12): 4216 - 4221. [Abstract] [Full Text] [PDF] |
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S. M. Emani, A. S. Shah, M. K. Bowman, D. C. White, S. Emani, D. D. Glower, and W. J. Koch Right ventricular targeted gene transfer of a {beta}-adrenergic receptor kinase inhibitor improves ventricular performance after pulmonary artery banding J. Thorac. Cardiovasc. Surg., March 1, 2004; 127(3): 787 - 793. [Abstract] [Full Text] [PDF] |
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A. Cittadini, J.o. Isgaard, M. G. Monti, C. Casaburi, A. Di Gianni, R. Serpico, G. Iaccarino, and L. Sacca Growth hormone prolongs survival in experimental postinfarction heart failure J. Am. Coll. Cardiol., June 18, 2003; 41(12): 2154 - 2163. [Abstract] [Full Text] [PDF] |
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I. L. Ennis, E. M. Escudero, G. M. Console, G. Camihort, C. G. Dumm, R. W. Seidler, M. C. Camilion de Hurtado, and H. E. Cingolani Regression of Isoproterenol-Induced Cardiac Hypertrophy by Na+/H+ Exchanger Inhibition Hypertension, June 1, 2003; 41(6): 1324 - 1329. [Abstract] [Full Text] [PDF] |
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D. Badenhorst, M. Maseko, O. J Tsotetsi, A. Naidoo, R. Brooksbank, G. R Norton, and A. J Woodiwiss Cross-linking influences the impact of quantitative changes in myocardial collagen on cardiac stiffness and remodelling in hypertension in rats Cardiovasc Res, March 1, 2003; 57(3): 632 - 641. [Abstract] [Full Text] [PDF] |
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D. Badenhorst, D. Veliotes, M. Maseko, O. J. Tsotetsi, R. Brooksbank, A. Naidoo, A. J. Woodiwiss, and G. R. Norton {beta}-Adrenergic Activation Initiates Chamber Dilatation in Concentric Hypertrophy Hypertension, March 1, 2003; 41(3): 499 - 504. [Abstract] [Full Text] [PDF] |
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P. W. M. Fedak, S. M. Altamentova, R. D. Weisel, N. Nili, N. Ohno, S. Verma, T.-Y. J. Lee, C. Kiani, D. A. G. Mickle, B. H. Strauss, et al. Matrix remodeling in experimental and human heart failure: a possible regulatory role for TIMP-3 Am J Physiol Heart Circ Physiol, February 1, 2003; 284(2): H626 - H634. [Abstract] [Full Text] [PDF] |
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C. F. Baicu, J. D. Stroud, V. A. Livesay, E. Hapke, J. Holder, F. G. Spinale, and M. R. Zile Changes in extracellular collagen matrix alter myocardial systolic performance Am J Physiol Heart Circ Physiol, January 1, 2003; 284(1): H122 - H132. [Abstract] [Full Text] [PDF] |
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J. Li, P. Lothar Schwimmbeck, C. Tschope, S. Leschka, L. Husmann, S. Rutschow, F. Reichenbach, M. Noutsias, U. Kobalz, W. Poller, et al. Collagen degradation in a murine myocarditis model: relevance of matrix metalloproteinase in association with inflammatory induction Cardiovasc Res, November 1, 2002; 56(2): 235 - 247. [Abstract] [Full Text] [PDF] |
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H. E. Cingolani and M. C. Camilion de Hurtado Na+-H+ Exchanger Inhibition: A New Antihypertrophic Tool Circ. Res., April 19, 2002; 90(7): 751 - 753. [Full Text] [PDF] |
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F. G. Spinale Matrix Metalloproteinases: Regulation and Dysregulation in the Failing Heart Circ. Res., March 22, 2002; 90(5): 520 - 530. [Abstract] [Full Text] [PDF] |
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Y. Y. Li, T. Kadokami, P. Wang, C. F. McTiernan, and A. M. Feldman MMP inhibition modulates TNF-alpha transgenic mouse phenotype early in the development of heart failure Am J Physiol Heart Circ Physiol, March 1, 2002; 282(3): H983 - H989. [Abstract] [Full Text] [PDF] |
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O. J. Tsotetsi, A. J. Woodiwiss, M. Netjhardt, D. Qubu, R. Brooksbank, and G. R. Norton Attenuation of Cardiac Failure, Dilatation, Damage, and Detrimental Interstitial Remodeling Without Regression of Hypertrophy in Hypertensive Rats Hypertension, October 1, 2001; 38(4): 846 - 851. [Abstract] [Full Text] [PDF] |
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D. L. Mann and H. Taegtmeyer Dynamic Regulation of the Extracellular Matrix After Mechanical Unloading of the Failing Human Heart: Recovering the Missing Link in Left Ventricular Remodeling Circulation, September 4, 2001; 104(10): 1089 - 1091. [Full Text] [PDF] |
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Y. Y. Li, Y. Feng, C. F. McTiernan, W. Pei, C. S. Moravec, P. Wang, W. Rosenblum, R. L. Kormos, and A. M. Feldman Downregulation of Matrix Metalloproteinases and Reduction in Collagen Damage in the Failing Human Heart After Support With Left Ventricular Assist Devices Circulation, September 4, 2001; 104(10): 1147 - 1152. [Abstract] [Full Text] [PDF] |
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