Published online before print March 13, 2008, doi: 10.1161/CIRCRESAHA.108.173153
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© 2008 American Heart Association, Inc.
Integrative Physiology |
Combined Deficiency of Dystrophin and β1 Integrin in the Cardiac Myocyte Causes Myocardial Dysfunction, Fibrosis and Calcification
From the Department of Medicine (L.E., M.S.H., R.Y.L., J.C., M.A.M., A.L.C., R.S.R.), University of California at San Diego School of Medicine, La Jolla; Veterans Administration San Diego Healthcare System (L.E., M.S.H., Y.Y., R.Y.L., J.C., R.S.R.), Calif; Department of Medicine (S.-Y.S.), Tulane University, New Orleans, La; and Department of Cell and Developmental Biology (S.J.K.), University of Illinois, Urbana. Present address for M.S.H.: Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles.
Correspondence to Robert S. Ross, Veterans Administration San Diego Healthcare System, 3350 La Jolla Village Dr, Cardiology Section, 111A, San Diego, CA 92161. E-mail rross{at}ucsd.edu
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The dystrophin–glycoprotein complex is a large complex of membrane-associated proteins linking the cytoskeleton to the extracellular matrix in muscle. Transmembrane heterodimeric (
β) integrins serve also as cellular adhesion molecules and mechanotransducers. In the animal model for Duchenne muscular dystrophy, the mdx mouse, loss of dystrophin causes more severe abnormalities in skeletal than in cardiac muscle. We hypothesized that ablation of cardiac myocyte integrins in the mdx background would lead to a severe cardiomyopathic phenotype. Mdx mice were crossed to ones with cardiac myocyte-specific deletion of β1 integrin (β1KO) to generate β1KOmdx. Unstressed β1KOmdx mice were viable and had normal cardiac function; however, high mortality was seen in peri- and postpartum females by 6 months of age, when severe myocardial necrosis and fibrosis and extensive dystrophic calcification was seen. Decreased ventricular function and blunted adrenergic responsiveness was found in the β1KOmdx mice compared with control (Lox/Lox, no Cre), β1KO, and mdx. Similarly, adult β1KOmdx males were more prone to isoproterenol-induced heart failure and death compared with control groups. Given the extensive calcification, we analyzed transcript levels of genes linked to fibrosis and calcification and found matrix 
-carboxyglutamic acid protein, decorin, periostin, and the osteoblast transcription factor Runx2/Cbfa1 significantly increased in β1KOmdx cardiac muscle. Our data show that combined deficiency of dystrophin and integrins in murine cardiac myocytes results in more severe cardiomyopathic changes in the stressed myocardium than reduction of either dystrophin or integrins alone and predisposes to myocardial calcification.
Key Words: Integrin • muscular dystrophy • dystrophin • heart failure • calcification
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The cardiac myocyte cytoskeleton and contractile apparatus are tethered to the sarcolemma at specialized regions termed costameres, which are aligned with the Z-disk.1 Costameres are important for lateral force transmission from the sarcomere to the extracellular matrix (ECM) and from 1 myocyte to the next.2 Three different cytoskeleton networks comprise the costamere: the dystrophin glycoprotein complex (DGC), the integrins, and the spectrin-based cytoskeleton.
The DGC is composed of several membrane-spanning and associated proteins and is enriched in, but not restricted to, costameric regions.2,3 In muscle, the DGC includes dystrophin, sarcoglycans (, β, , 
, 
, and 
), dystroglycans ( and β), -dystrobrevin, syntrophins (1, β1 and β2), sarcospan, and NO synthase. Dystrophin is a 427-kDa protein that constitutes a core component of the DGC. Mutations in the human dystrophin gene lead to Duchenne muscular dystrophy (DMD), Becker muscular dystrophy, and X-linked dilated cardiomyopathy.4 In mice, an X-linked recessive mutation in the dystrophin gene (mdx) results in loss of dystrophin expression, destabilization of the DGC, and muscular dystrophy. Whereas cardiomyopathy may occur early in the life of patients with muscular dystrophy, dilated cardiomyopathy occurs only in older unstressed mdx animals, eg, 42 weeks of age.5 However, the mdx heart is susceptible to injury when challenged by mechanical or chemical stressors.6 Furthermore, combined loss of dystrophin and utrophin (a dystrophin homolog) results in worsening of the cardiac phenotype.7 Interestingly, the cardiomyopathic features of the dystrophin/utrophin double knockout can, in part, be prevented by transgenic overexpression of dystrophin in cardiomyocytes but not in the vasculature, indicating a direct link between dystrophin deficiency and cardiac myocyte pathology.8
In addition to DGC proteins, the integrins are also enriched in the cardiac myocyte costamere, where they serve important structural and signaling functions.9 Integrins provide for adhesion of cells to the ECM and act as mechanotransducers, converting mechanical stimuli to biochemical ones.10 β1 integrins are the dominant β integrin subunits found in cardiac and skeletal muscle. Muscle integrins, particularly those of the 7β1 heterodimer, together with the DGC, constitute 2 major cellular adhesion systems that provide a physical link between the intracellular cytoskeleton and the ECM.
The DGC and integrin complexes may have overlapping functions, in that: (1) deficiencies of each caused various myopathies; (2) combined deficiency led to an accelerated skeletal muscular dystrophy11; and (3) with loss of dystrophin, integrin expression increased in mouse models and patients.12 The majority of this work has focused on skeletal muscle. Little data are available testing the functional role of both the DGC and integrins specifically in the cardiac myocyte. Therefore, we designed the present study to test the hypothesis that ablation of both systems in cardiac myocytes would lead to more severe cardiomyopathy than in mdx or cardiac-myocyte specific integrin β1 knockout mice, alone.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
An expanded Materials and Methods section is available in an online supplement at http://circres.ahajournals.org.
Animals
Mice with ventricular myocyte specific excision of the β1 integrin gene were generated as previously described.13 To generate mice lacking both β1 integrin expression and dystrophin expression, β1 knockout (β1KO) mice were mated to mdx mice (C57BL/10ScSn-Dmdmdx/J) (The Jackson Laboratory, Bar Harbor, Me). All animal study protocols were approved by the institutional review committee, and all mice were housed in an AALAC–approved facility.
Antibodies
Primary antibodies used were as follows: rabbit polyclonal: anti–β1D integrin13; anti–integrin 7B14; anti–integrin 5 (AB47 provided by Dr Maria Valencik)15; mouse monoclonal: anti-dystrophin (NCL-DYS1, Novocastra Laboratories, Newcastle On Tyne, UK); anti– sarcoglycan (NCL-L--SARC, Novocastra); anti-utrophin (BD Pharmingen, San Diego, Calif); anti-GAPDH (Santa Cruz Biotechnology, Santa Cruz, Calif); anti–-tubulin (Sigma, St Louis, Mo); anti-myomesin (provided by Dr J.-C. Perriard).16
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Expression of Integrin and DGC Proteins in β1KOmdx Mice
We first examined the expression of integrin and DGC proteins in whole heart from 2- to 4-month-old animals. Animals doubly deficient in both dystrophin and β1 integrin (β1KOmdx) were compared with mice singly deficient in either dystrophin or β1 integrin (mdx or β1KO, respectively) or ones with normal expression of proteins in the DGC and integrin complexes (F/F, control). As shown previously,13 cardiac myocyte–specific inactivation of the floxed integrin β1 gene resulted in significant protein reduction by 8 weeks of age (33.8±12% versus control) (Figure 1A and 1D). Concomitant with the reduction in β1D protein expression, the dominant
integrin subunits expressed in the cardiac myocyte, 5 and 7 integrin, were reduced to 
30% of control in β1KO hearts (Figure 1B through 1D). Although the β1KOmdx hearts had comparable reduction in β1D protein (25±11% versus control), expression of 5 and 7 integrins were at, or slightly above, control levels (119±25% and 132±27% of control, respectively; significantly different from β1KO). β1D, 5, and 7 integrin protein expression was either at or slightly above the control level in the mdx mice. 7 integrin was localized in cardiac myocytes (Figure I in the online data supplement). Thus, when the myocyte is deficient in both dystrophin and β1 integrin, 5, and 7 subunit expression is maintained.
|
P<0.05 vs β1KO, 
P<0.05 vs mdx (n=3 to 6).
Cardiac muscle of mdx and β1KOmdx mice did not have detectable levels of dystrophin or -sarcoglycan protein, whereas utrophin was upregulated; β-dystroglycan expression was similar in all 4 groups (Figure 1D and supplemental Figure II).
Significant Myocardial Calcification Is Detected in β1KOmdx Females Despite Only Minimal Changes in Cardiac Function
We next examined the morphometry, histology and function of the hearts from 2-month-old female mice. As is shown in Table I in the online data supplement, morphometry showed that the mdx gene mutation lead to significant reduction in body weight and heart weight (HW), and the normalized HW (HW/tibial length) was significantly lower in the mdx and β1KOmdx groups compared with F/F and β1KO. Cardiac morphology revealed calcified lesions in 3 of 7 β1KOmdx hearts but not in any of the other groups. Histological examination showed focal areas with extensive myocyte replacement, inflammatory infiltrate, and calcium precipitation in only the β1KOmdx hearts (Figure 2A through 2D).
|
Cardiac hemodynamics were examined using invasive catheterization (supplemental Table II). Basally, the β1KOmdx mice showed significant decreases only in cardiac developed pressure and cardiac relaxation (dP/dtmin) (20% and 24%, respectively, compared with F/F control). Cardiac contractility (dP/dtmax) and heart rate were similar in all groups. Like the β1KOmdx mice, the singly deficient β1KO mice had decreased developed pressure and dP/dtmin (21% and 24%, respectively). Mdx mice had a minimal decrease in dP/dtmin only. β-Adrenergic responsiveness was preserved in all groups (Figure 2E through 2H). Thus, the β1KOmdx mice have only minimal alterations of cardiac hemodynamics at 2 months of age despite the presence of focal myocyte replacement and fibrotic calcification.
Pregnancy-Induced Volume Overload Leads to Deterioration in Cardiac Function, Decreased Sensitivity to β-Adrenergic Stimulation, Fibrosis, and Extensive Myocardial Calcification in β1KOmdx Females
Given the basal findings, we evaluated how stress might alter the cardiac function of the doubly deficient mice. Pregnancy is a state in which high volume and low vascular resistance lead to mild hypertrophic growth with an increased cardiac output as a means for compensation.17 When the β1KOmdx females were subjected to the increased hemodynamic load of pregnancy, they were more susceptible to heart failure. The β1KOmdx females often died during gestation and did not survive long following parturition. Following this observation, we performed hemodynamic measurements on peripartum β1KOmdx mice. As is shown in the Table, dP/dtmax and dP/dtmin were reduced by 35% and 43%, respectively, compared with control mice, indicating significantly reduced systolic and diastolic function, respectively. There was a small decrease in dP/dtmin in the β1KO group; a statistically significant difference between this group and the β1KOmdx group was not found. Although diastolic function as assessed by dP/dtmin was affected, relaxation time and the relaxation time constant 
were not changed in the β1KOmdx. As shown in Figure 3, in contrast to F/F, β1KO, and mdx mice, the peripartum β1KOmdx mice had a blunted response to β-adrenergic stimulation.
|
|
=Given our morphometric and histological findings in the baseline state, we examined hearts from the mice in the peripartum period. No significant morphometric hypertrophy was found (supplemental Table III). Histology showed extensive fibrosis and calcification (Figure 4). To determine whether apoptotic cell death was causal in these findings, TUNEL assays were performed but no differences were found between groups (data not shown).
|
Chronic Isoproterenol Treatment Leads to Increased Mortality and Heart Failure in Young β1KOmdx Males
Given the findings with pregnancy, we studied mice subjected to a second type of stress administered by chronic infusion of isoproterenol (Iso). We studied 2- to 3-month males. Baseline echocardiography revealed smaller left ventricular (LV) diastolic dimensions as well as reduced LV mass in mdx and β1KOmdx compared with F/F and β1KO mice, suggesting an overall smaller heart in the presence of the mdx mutation (supplemental Table IV). This observation is consistent with that found in 2-month-old females, in which HW and HW/tibial length were significantly smaller (by 20% and 15%, respectively) in these two groups compared with F/F and β1KO (supplemental Table I). Iso was then administered for 14 days at the rate of 30 mg/kg day via osmotic pumps. Increased mortality in the β1KOmdx and β1KO mice was evident soon after the initiation of the infusion. All surviving mice were followed by echocardiography at days 7 and 14 of treatment. By day 7, echocardiography revealed a significant decrease in fractional shortening in the β1KOmdx, whereas F/F control, β1KO, and mdx groups experienced a slight, insignificant increase in fractional shortening, suggesting a state of compensatory response (Figure 5A and 5B and supplemental Table IV). In addition, by 14 days, LV wall dimensions (intraventricular septum and LV posterior wall thickness) increased significantly over baseline in all groups except for β1KOmdx (Figure 5C and 5D). Morphometry in the surviving mice were in line with these echo findings (supplemental Table V). Enlarged RV chamber size was also evident in 2 of the surviving β1KOmdx mice (Figure 5E) but was not evident in other groups.
|
Survival of the β1KOmdx mice was 50%, and the β1KO group was 86% compared with 100% of the F/F and mdx groups (Figure 6A). Histological examination of Iso-treated mice revealed myocardial damage in all Iso-treated groups regardless of genotype; however, as demonstrated in Figure 6B, Iso-treated β1KOmdx hearts revealed areas of severe fibrosis and extensive myocyte damage.
|
Expression of Regulators of a Calcification Program
Although observed often in skeletal muscle of dystrophic mdx mice,18 ectopic calcification has not been noted in the heart muscle of muscular dystrophy animal models. The calcification process has been most extensively studied in relation to the development of atherosclerotic plaques. In the vessel, it has been proven to be an active and regulated process19 linked to mediators of bone formation, including matrix -carboxyglutamic acid protein (MGP), decorin, periostin, Runx2/Cbfa1, bone morphogenetic protein, and alkaline phosphatase. Given this, we evaluated transcript expression of these mediators in cardiac tissue from our mice using real-time RT-PCR (Figure 7). Levels of MGP were upregulated 10-fold in β1KOmdx hearts compared with other groups (Figure 7A). Decorin mRNA levels were increased 6-fold in β1KOmdx hearts compared with F/F controls, whereas the single KO β1KO hearts and mdx hearts had 3-fold more transcript compared with control (Figure 7B). We observed a trend toward an increase in decorin transcript levels in the β1KO, mdx, and β1KOmdx groups; however, statistically significant differences were not found among these groups (Figure 7B). mRNA levels of periostin and Runx2/Cbfa1 were increased 10-fold in the β1KOmdx hearts compared with F/F controls (Figure 7C and 7D). Expression levels of bone morphogenetic protein-2 (the classic mediator of osteoblast differentiation), alkaline phosphatase, and osteocalcin were not significantly different between any of the groups (data not shown).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Costameric regions of cardiac myocytes consist of protein networks that form physical attachment points between the Z-disks of the cell and the ECM.20 Functionally, the costamere is thought to transmit contractile forces laterally from the sarcomere, across the membrane and the ECM, to neighboring cells.21 Although not specific to the region, both dystrophin and integrins are enriched in costameric regions. Here, we hypothesized that ablation of integrin β1 and dystrophin in cardiac myocytes would result in a severe cardiomyopathy. Our animal model is the first to cause cardiac myocyte specific reduction of the integrin β1 protein in the mdx mice. In doing so, we found that systolic dysfunction occurs following either pregnancy, a state of volume overload, or with chronic β-adrenergic receptor stimulation. Furthermore, we found histological evidence of cardiac calcification. We then examined expression of key regulators of the mineralization process. These transcripts are upregulated during vascular calcification, yet in cardiac tissue from our mice, only a subset of transcripts (MGP, decorin, periostin, and Runx2/Cbfa1) were increased, whereas bone morphogenetic protein, alkaline phosphatase, and osteocalcin were not changed. This implies that the dystrophic calcification process in the myocardium is distinct from but shares some features with the vascular one.
Absence of dystrophin from skeletal muscle leads to an increase in 7 integrin expression.12 In contrast, 7 expression was decreased in laminin 2 chain muscular dystrophy in both man and mouse (dy/dy mice).12 Furthermore, global knockout of murine integrin 7 results in a distinct form of muscular dystrophy characterized by muscle fiber necrosis and degeneration, variable fiber size, and the presence of central nuclei.22 Absence of integrin 7 in mdx mice leads to a more severe skeletal muscle pathology than either integrin 7-null or mdx mice alone.11 Given that integrin- and DGC-mediated ECM–cytoskeleton linkages can functionally overlap, it was hypothesized that upregulation of 7 integrin protein in muscle with dystrophin deficiency occurs as a compensatory process. Supporting this premise were data showing that a 2-fold overexpression of integrin 7 in mice that lack both dystrophin and utrophin (mdx/utr–/–) attenuated skeletal muscle pathology and extended the lifespan of the animal.23
Global knockout of the integrin 7 gene alone or in the mdx background (7/mdx) showed no parallel reduction in integrin β1D expression nor a change in its cellular localization.11,22 In contrast, we found that 7 protein expression was significantly reduced in parallel with β1 integrin reduction in β1KO hearts. However, 7 protein expression was increased above control levels in mdx as well as in the doubly deficient β1KOmdx hearts. Thus, the results from our study and from this previous work suggest that when either integrin or β subunits are reduced, the partner can be properly expressed and localized in the cell. Of importance is that cardiac myocyte β1 integrin can partner with several subunits in addition to 7 integrin. In this regard, we found that both 5 and 7 protein levels were reduced in the single β1KO hearts, whereas both subunits were expressed at or above wild-type levels in the β1KOmdx mice. As mentioned above, the increase in 7 integrin expression in DMD patients and in mdx mice is thought to be regulated transcriptionally, whereas its decrease in our β1KO animals is most probably attributable to protein degradation.
It has been shown that most members of the DGC are absent in dystrophin deficiency. In contrast, utrophin, a 376-kDa dystrophin homolog, is increased and has altered intracellular distribution in muscle of DMD and Becker muscular dystrophy patients as well as in mdx mice.24,25 Deficiency in both dystrophin and utrophin results in more severe cardiac muscle contractile dysfunction than dystrophin deficiency alone26 and expression of a full-length or a truncated form of utrophin markedly improves dystrophic muscle pathology in mdx mice.27 As in other dystrophic models, utrophin was upregulated in hearts of our β1KOmdx animals. Thus, the normal expression of 7 integrin, combined with the compensatory increase in utrophin in the β1KOmdx hearts, may allow for the delayed and conditional onset of the cardiac dysfunction in the absence of integrin β1 and dystrophin in our model.
In heart failure, increased activation of the sympathetic system leads to β-adrenergic receptor downregulation or uncoupling from Gs, along with an increase in Gi.28,29 Furthermore, our prior work has linked β1 integrins to the modulation of β-adrenergic receptor signaling.30 Disruption of β1 integrin signaling in the cardiac myocyte leads to augmentation of Iso-induced stimulation of L-type Ca current (ICa), and overexpression of β1A integrin decreased Iso-induced stimulation of ICa. Thus, the loss of β1 integrin expression and function may enhance β-adrenergic responsiveness to agonists leading to augmentation of ICa. The combination of the integrin-mediated defect, with the dysregulation of Ca+2 homeostasis found in dystrophic muscle, may explain why more severe calcification is found in our doubly deficient β1KOmdx mice than those with loss of β1 integrin or dystrophin alone.
The presence of calcified lesions in the myocardium of β1KOmdx mice is an early event that is independent of abnormal cardiac loading conditions. Although an unusual finding in myocardium of animal models with cardiovascular disease, cardiac calcification is encountered in myocardial freeze–thaw injury model,31 in acute myopericarditis resulting from cytomegalovirus infection,32 and in some genetically manipulated models of cardiomyopathy, such as that with increased L-type Ca2+ channel activity.33 The most striking examples of myocardial calcification are observed with murine global knockout of the intermediate filament desmin in mice with cardiac myosin-binding protein-C gene mutations, as well as in the Syrian hamster model of cardiomyopathy.34–36 The desmin-null mice lack desmin in smooth, skeletal, and cardiac muscle, but damage to cardiac muscle is independent of damage to the vasculature.37 Electron microscopic analysis revealed severe mitochondria swelling/disintegration and disorganization in desmin-null cardiomyocytes.35 Given the extensive damage to mitochondria, it was proposed that the mitochondria might constitute the nidus in which calcified deposits first appear attributable to a disturbance in intracellular Ca+2 homeostasis. Interestingly, mutation of a member of the DGC, -sarcoglycan, is found in the Syrian hamster and is likely causal in the myocardial disease because this mutation may predispose to sarcolemma membrane damage.36
Extensive studies have been performed on calcium homeostasis of dystrophin-deficient skeletal muscle from patients, as well as mdx mice. Some demonstrate increased intracellular Ca+2 concentrations [Ca+2]i in dystrophic muscle, whereas others did not. This discrepancy is likely attributable to the variability in localizing excess Ca+2 in the subsarcolemmal region by different techniques.38 Two studies showed increased resting [Ca+2]i in cardiac muscle cells of mdx mice.39 This change was attributed to several findings: (1) increased expression of the ryanodine receptor; (2) decreased expression of serine-16–phosphorylated phospholamban; (3) increased function of the Na+/Ca2+ exchanger; and possibly (4) increased activity of stretch-activated channels. In addition a drastic decrease in the sarcoplasmic reticulum luminal Ca2+-binding proteins calsequestrin and sarcalumenin were found in cardiac muscle of mdx mice indicating impaired sarcoplasmic reticulum Ca2+-buffering capacity. Although it has not been shown in cardiac muscle, dystrophic skeletal muscle has persistently activated Ca+2 leak channels and these are introduced into the damaged membrane during the natural membrane resealing process. Their function is thought to replete internal Ca+2 stores.40 Thus, it appears that the dystrophic myocyte is prone to calcium loading and myocyte injury resulting in tissue calcification as we found in the present study.
Historically the process of calcification was regarded as a passive and degenerative process; however, recent studies, dominantly in atherosclerotic disease, have shown it to be an active and regulated process.19 The major hypothesis from this work attributes an important role for osteoblast-type cells (arising from a phenotypic change in vascular smooth muscle cells or activation of resident mesenchymal-like or circulating stem cells), which orchestrate a process of bone formation.19 To date, no studies have pursued the basis for the calcification process or the identification of candidate cell types responsible for it in the myocardium.
On examination of our model for potential mediators involved in myocardial calcification, we observed that MGP, decorin, periostin, and Runx2/Cbfa1 transcript levels were significantly increased in hearts of β1KOmdx mice. MGP is a mineral-binding ECM protein produced by vascular smooth muscle cells, as well as chondrocytes, that shows increased expression in human atherosclerotic plaques.41 Its overexpression in our model suggests that its inhibitory function can be overwhelmed as occurs in vascular tissue.19 Periostin is a secreted protein that was initially thought to be bone-specific and required for osteoblast differentiation. However, recent investigations have shown that periostin is expressed in the developing heart and that it has an antiosteogenic effect.42 Increased expression of periostin in patients with heart failure, as well as in animal models of cardiac remodeling, has been reported,43,44 although its specific function is not yet known. The significant increase in Runx2/Cbfa1 transcript, a member of the runt/Cbfa family of transcription factors and a key regulator of osteoblast differentiation, is of particular interest. Runx2/Cbfa1 is a nuclear factor that activates several major osteoblast specific genes such as osteocalcin, bone sialoprotein, osteopontin, and 1-type collagen.45 Moreover, induced expression of Runx2/Cbfa1 in nonosteoblast cells such as fibroblasts activates the expression of osteocalcin and bone sialoprotein, indicating a role for Runx2/Cbfa1 in inducing cells toward osteoblast-like differentiation. Further analysis of the role of Runx2/Cbfa1 in dystrophin/integrin deficiency is necessary.
Our results show that the observed calcification shares some molecular features with mineralized vascular plaques and indicates that this mineralization process is not simply a disordered degenerative event but one involving de novo gene transcription of key mediators and inhibitors of the process. This study is the first presenting a link between combined DGC and integrin complex insufficiency and myocardial calcification.
|
Acknowledgments |
|---|
The authors wish to thank Steve Padilla for excellent technical assistance and Derek Milner for assistance with studies of
7 integrin. Sources of Funding
L.E. was supported by an NIH/NHLBI training grant (HL07444) and a postdoctoral fellowship from American Heart Association–Western States. R.S.R. was supported by NIH grant HL057872 and a Veterans Administration Merit Award. S.J.K. is supported by grants from the NIH and the Muscular Dystrophy Association.
Disclosures
None.
|
Footnotes |
|---|
*Both authors contributed equally to this work.
Original received June 22, 2007; revision received January 31, 2008; accepted March 3, 2008.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
1. Clark KA, McElhinny AS, Beckerle MC, Gregorio CC. Striated muscle cytoarchitecture: an intricate web of form and function. Annu Rev Cell Dev Biol. 2002; 18: 637–706.[CrossRef][Medline] [Order article via Infotrieve]
2. Ervasti JM. Costameres: the Achilles’ heel of Herculean muscle. J Biol Chem. 2003; 278: 13591–13594.
3. Stevenson S, Rothery S, Cullen MJ, Severs NJ. Dystrophin is not a specific component of the cardiac costamere. Circ Res. 1997; 80: 269–280.
4. Lapidos KA, Kakkar R, McNally EM. The dystrophin glycoprotein complex: signaling strength and integrity for the sarcolemma. Circ Res. 2004; 94: 1023–1031.
5. Quinlan JG, Hahn HS, Wong BL, Lorenz JN, Wenisch AS, Levin LS. Evolution of the mdx mouse cardiomyopathy: physiological and morphological findings. Neuromuscul Disord. 2004; 14: 491–496.[CrossRef][Medline] [Order article via Infotrieve]
6. Kamogawa Y, Biro S, Maeda M, Setoguchi M, Hirakawa T, Yoshida H, Tei C. Dystrophin-deficient myocardium is vulnerable to pressure overload in vivo. Cardiovasc Res. 2001; 50: 509–515.
7. Janssen PM, Hiranandani N, Mays TA, Rafael-Fortney JA. Utrophin deficiency worsens cardiac contractile dysfunction present in dystrophin-deficient mdx mice. Am J Physiol Heart Circ Physiol. 2005; 289: H2373–H2378.
8. Hainsey TA, Senapati S, Kuhn DE, Rafael JA. Cardiomyopathic features associated with muscular dystrophy are independent of dystrophin absence in cardiovasculature. Neuromuscul Disord. 2003; 13: 294–302.[CrossRef][Medline] [Order article via Infotrieve]
9. Ross RS, Borg TK. Integrins and the myocardium. Circ Res. 2001; 88: 1112–1119.
10. Ingber D. Integrins as mechanochemical transducers. Curr Opin Cell Biol. 1991; 3: 841–848.[CrossRef][Medline] [Order article via Infotrieve]
11. Rooney JE, Welser JV, Dechert MA, Flintoff-Dye NL, Kaufman SJ, Burkin DJ. Severe muscular dystrophy in mice that lack dystrophin and {alpha}7 integrin. J Cell Sci. 2006; 119 (pt 11): 2185–2195.
12. Hodges BL, Hayashi YK, Nonaka I, Wang W, Arahata K, Kaufman SJ. Altered expression of the alpha7beta1 integrin in human and murine muscular dystrophies. J Cell Sci. 1997; 110 (pt 22): 2873–2881.[Abstract]
13. Shai SY, Harpf AE, Babbitt CJ, Jordan MC, Fishbein MC, Chen J, Omura M, Leil TA, Becker KD, Jiang M, Smith DJ, Cherry SR, Loftus JC, Ross RS. Cardiac myocyte-specific excision of the beta1 integrin gene results in myocardial fibrosis and cardiac failure. Circ Res. 2002; 90: 458–464.
14. Song WK, Wang W, Sato H, Bielser DA, Kaufman SJ. Expression of alpha 7 integrin cytoplasmic domains during skeletal muscle development: alternate forms, conformational change, and homologies with serine/threonine kinases and tyrosine phosphatases. J Cell Sci. 1993; 106: 1139–1152.[Abstract]
15. Valencik ML, McDonald JA. Cardiac expression of a gain-of-function alpha(5)-integrin results in perinatal lethality. Am J Physiol Heart Circ Physiol. 2001; 280: H361–H367.
16. Grove BK, Kurer V, Lehner C, Doetschman TC, Perriard JC, Eppenberger HM. A new 185,000-dalton skeletal muscle protein detected by monoclonal antibodies. J Cell Biol. 1984; 98: 518–524.
17. Abbas AE, Lester SJ, Connolly H. Pregnancy and the cardiovascular system. Int J Cardiol. 2005; 98: 179–189.[CrossRef][Medline] [Order article via Infotrieve]
18. Geissinger HD, Rao PV, Donald-Taylor CK. "mdx" mouse myopathy: histopathological, morphometric and histochemical observations on young mice. J Comp Pathol. 1990; 102: 249–263.[Medline] [Order article via Infotrieve]
19. Abedin M, Tintut Y, Demer LL. Vascular calcification: mechanisms and clinical ramifications. Arterioscler Thromb Vasc Biol. 2004; 24: 1161–1170.
20. Samarel AM. Costameres, focal adhesions, and cardiomyocyte mechanotransduction. Am J Physiol Heart Circ Physiol. 2005; 289: H2291–H2301.
21. Matsumura K, Ervasti JM, Ohlendieck K, Kahl SD, Campbell KP. Association of dystrophin-related protein with dystrophin-associated proteins in mdx mouse muscle. Nature. 1992; 360: 588–591.[CrossRef][Medline] [Order article via Infotrieve]
22. Mayer U, Saher G, Fassler R, Bornemann A, Echtermeyer F, von der MH, Miosge N, Poschl E, von der MK. Absence of integrin alpha 7 causes a novel form of muscular dystrophy. Nat Genet. 1997; 17: 318–323.[Medline] [Order article via Infotrieve]
23. Burkin DJ, Wallace GQ, Nicol KJ, Kaufman DJ, Kaufman SJ. Enhanced expression of the alpha 7 beta 1 integrin reduces muscular dystrophy and restores viability in dystrophic mice. J Cell Biol. 2001; 152: 1207–1218.
24. Karpati G, Carpenter S, Morris GE, Davies KE, Guerin C, Holland P. Localization and quantitation of the chromosome 6-encoded dystrophin-related protein in normal and pathological human muscle. J Neuropathol Exp Neurol. 1993; 52: 119–128.[Medline] [Order article via Infotrieve]
25. Weir AP, Burton EA, Harrod G, Davies KE. A- and B-utrophin have different expression patterns and are differentially up-regulated in mdx muscle. J Biol Chem. 2002; 277: 45285–45290.
26. Grady RM, Teng H, Nichol MC, Cunningham JC, Wilkinson RS, Sanes JR. Skeletal and cardiac myopathies in mice lacking utrophin and dystrophin: a model for Duchenne muscular dystrophy. Cell. 1997; 90: 729–738.[CrossRef][Medline] [Order article via Infotrieve]
27. Tinsley JM, Potter AC, Phelps SR, Fisher R, Trickett JI, Davies KE. Amelioration of the dystrophic phenotype of mdx mice using a truncated utrophin transgene. Nature. 1996; 384: 349–353.[CrossRef][Medline] [Order article via Infotrieve]
28. Bristow MR, Ginsburg R, Minobe W, Cubicciotti RS, Sageman WS, Lurie K, Billingham ME, Harrison DC, Stinson EB. Decreased catecholamine sensitivity and beta-adrenergic-receptor density in failing human hearts. N Engl J Med. 1982; 307: 205–211.[Abstract]
29. Lohse MJ, Engelhardt S, Eschenhagen T. What is the role of beta-adrenergic signaling in heart failure? Circ Res. 2003; 93: 896–906.
30. Cheng Q, Ross RS, Walsh KB. Overexpression of the integrin beta(1A) subunit and the beta(1A) cytoplasmic domain modifies the beta-adrenergic regulation of the cardiac L-type Ca(2+)current. J Mol Cell Cardiol. 2004; 36: 809–819.[CrossRef][Medline] [Order article via Infotrieve]
31. Brunnert SR. Morphologic response of myocardium to freeze-thaw injury in mouse strains with dystrophic cardiac calcification. Lab Anim Sci. 1997; 47: 11–18.[Medline] [Order article via Infotrieve]
32. Gang DL, Barrett LV, Wilson EJ, Rubin RH, Medearis DN. Myopericarditis and enhanced dystrophic cardiac calcification in murine cytomegalovirus infection. Am J Pathol. 1986; 124: 207–215.[Abstract]
33. Nakayama H, Chen X, Baines CP, Klevitsky R, Zhang X, Zhang H, Jaleel N, Chua BH, Hewett TE, Robbins J, Houser SR, Molkentin JD. Ca2+- and mitochondrial-dependent cardiomyocyte necrosis as a primary mediator of heart failure. J Clin Invest. 2007; 117: 2431–2444.[CrossRef][Medline] [Order article via Infotrieve]
34. McConnell BK, Jones KA, Fatkin D, Arroyo LH, Lee RT, Aristizabal O, Turnbull DH, Georgakopoulos D, Kass D, Bond M, Niimura H, Schoen FJ, Conner D, Fischman DA, Seidman CE, Seidman JG. Dilated cardiomyopathy in homozygous myosin-binding protein-C mutant mice. J Clin Invest. 1999; 104: 1235–1244.[Medline] [Order article via Infotrieve]
35. Milner DJ, Weitzer G, Tran D, Bradley A, Capetanaki Y. Disruption of muscle architecture and myocardial degeneration in mice lacking desmin. J Cell Biol. 1996; 134: 1255–1270.
36. Ikeda Y, Martone M, Gu Y, Hoshijima M, Thor A, Oh SS, Peterson KL, Ross J Jr. Altered membrane proteins and permeability correlate with cardiac dysfunction in cardiomyopathic hamsters. Am J Physiol Heart Circ Physiol. 2000; 278: H1362–H1370.
37. Weisleder N, Soumaka E, Abbasi S, Taegtmeyer H, Capetanaki Y. Cardiomyocyte-specific desmin rescue of desmin null cardiomyopathy excludes vascular involvement. J Mol Cell Cardiol. 2004; 36: 121–128.[CrossRef][Medline] [Order article via Infotrieve]
38. Petrof BJ. Molecular pathophysiology of myofiber injury in deficiencies of the dystrophin-glycoprotein complex. Am J Phys Med Rehabil. 2002; 81: S162–S174.[CrossRef][Medline] [Order article via Infotrieve]
39. Alloatti G, Gallo MP, Penna C, Levi RC. Properties of cardiac cells from dystrophic mouse. J Mol Cell Cardiol. 1995; 27: 1775–1779.[CrossRef][Medline] [Order article via Infotrieve]
40. Alderton JM, Steinhardt RA. Calcium influx through calcium leak channels is responsible for the elevated levels of calcium-dependent proteolysis in dystrophic myotubes. J Biol Chem. 2000; 275: 9452–9460.
41. Shanahan CM, Cary NR, Metcalfe JC, Weissberg PL. High expression of genes for calcification-regulating proteins in human atherosclerotic plaques. J Clin Invest. 1994; 93: 2393–2402.[Medline] [Order article via Infotrieve]
42. Norris RA, Kern CB, Wessels A, Moralez EI, Markwald RR, Mjaatvedt CH. Identification and detection of the periostin gene in cardiac development. Anat Rec A Discov Mol Cell Evol Biol. 2004; 281: 1227–1233.[CrossRef][Medline] [Order article via Infotrieve]
43. Katsuragi N, Morishita R, Nakamura N, Ochiai T, Taniyama Y, Hasegawa Y, Kawashima K, Kaneda Y, Ogihara T, Sugimura K. Periostin as a novel factor responsible for ventricular dilation. Circulation. 2004; 110: 1806–1813.
44. Stanton LW, Garrard LJ, Damm D, Garrick BL, Lam A, Kapoun AM, Zheng Q, Protter AA, Schreiner GF, White RT. Altered patterns of gene expression in response to myocardial infarction. Circ Res. 2000; 86: 939–945.
45. Ducy P. Cbfa1: a molecular switch in osteoblast biology. Dev Dyn. 2000; 219: 461–471.[CrossRef][Medline] [Order article via Infotrieve]
This article has been cited by other articles:
 |
|
 |
|
  D. E. Michele, Z. Kabaeva, S. L. Davis, R. M. Weiss, and K. P. Campbell Dystroglycan Matrix Receptor Function in Cardiac Myocytes Is Important for Limiting Activity-Induced Myocardial Damage Circ. Res., November 6, 2009; 105(10): 984 - 993. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Ahmad, M. Bygrave, R. Chhem, L. Hoffman, I. Welch, R. Grange, A. Fenster, D. Hill, and T.-Y. Lee High-Frequency Ultrasound to Grade Disease Progression in Murine Models of Duchenne Muscular Dystrophy J. Ultrasound Med., June 1, 2009; 28(6): 707 - 716. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||