Noninvasive assessment of cardiomyopathy development with simultaneous measurement of topical 1H- and 31P-magnetic resonance spectroscopy

Pigs with δ-sarcoglycan deficiency exhibit traits of genetic cardiomyopathy

Genetic cardiomyopathy is a group of intractable cardiovascular disorders involving heterogeneous genetic contribution. This heterogeneity has hindered the development of life-saving therapies for this serious disease. Genetic mutations in dystrophin and its associated glycoproteins cause cardiomuscular dysfunction. Large animal models incorporating these genetic defects are crucial for developing effective medical treatments, such as tissue regeneration and gene therapy. In the present study, we knocked out the δ-sarcoglycan (δ-SG) gene (SGCD) in domestic pig by using a combination of efficient de novo gene editing and somatic cell nuclear transfer. Loss of δ-SG expression in the SGCD knockout pigs caused a concomitant reduction in the levels of α-, β-, and γ-SG in the cardiac and skeletal sarcolemma, resulting in systolic dysfunction, myocardial tissue degeneration, and sudden death. These animals exhibited symptoms resembling human genetic cardiomyopathy and are thus promising for use in preclinical studies of next-generation therapies.

MRS: a noninvasive window into cardiac metabolism

A well-functioning heart requires a constant supply of a balanced mixture of nutrients to be used for the production of adequate amounts of adenosine triphosphate, which is the main energy source for most cellular functions. Defects in cardiac energy metabolism are linked to several myocardial disorders. MRS can be used to study in vivo changes in cardiac metabolism noninvasively. MR techniques allow repeated measurements, so that disease progression and the response to treatment or to a lifestyle intervention can be monitored. It has also been shown that MRS can predict clinical heart failure and death. This article focuses on in vivo MRS to assess cardiac metabolism in humans and experimental animals, as experimental animals are often used to investigate the mechanisms underlying the development of metabolic diseases. Various MR techniques, such as cardiac (31) P-MRS, (1) H-MRS, hyperpolarized (13) C-MRS and Dixon MRI, are described. A short overview of current and emerging applications is given. Cardiac MRS is a promising technique for the investigation of the relationship between cardiac metabolism and cardiac disease. However, further optimization of scan time and signal-to-noise ratio is required before broad clinical application. In this respect, the ongoing development of advanced shimming algorithms, radiofrequency pulses, pulse sequences, (multichannel) detection coils, the use of hyperpolarized nuclei and scanning at higher magnetic field strengths offer future perspective for clinical applications of MRS.

ComparativeIn VitroEffects of Calcineurin Inhibitors on Functional Vascular Relaxations of Both Rat Thoracic and Abdominal Aorta

Background and Aim. Calcineurin inhibitors (CNIs) have shown to develop hypertension in transplant patients. The in vitro incubation effects of cyclosporine (CsA) and tacrolimus (Tac) on vascular relaxations of rat thoracic aorta (TA) and abdominal aorta (AA) need to be investigated. Methods. The optimal concentrations of CsA (1.0 mg/mL) and Tac (0.1 mg/mL) used to compare endothelium-dependent (acetylcholine (ACh)) and endothelium-independent (sodium nitroprusside (SNP)) vascular relaxation against the agonists in phenylephrine (PE-) constricted TA and AA of 13-week-old male Sprague Dawley rats (n = 6). Results. In TA, the maximal vasodilator response elicited by ACh (control: I_max 98%) was significantly (P < 0.01) inhibited by CsA (I_max 10%) but not by Tac (I_max 97%). In AA, (control: IC₅₀ 50 nM; I_max 100%) CsA (IC₅₀ 7 μM; (P < 0.01) showed strong sensitivity to inhibit ACh-dependent vascular relaxation than Tac (IC₅₀ 215 nM (P < 0.05); I_max 98%). CsA and Tac failed to affect the inhibitory responses to SNP in both TA and AA. Conclusion. CsA exerts profound inhibitory effect on endothelium-dependent vasodilatation as compared to Tac in both TA and AA. Aortic rings from the thoracic region are more sensitive to CNIs, since the vasodilator response to ACh is solely mediated by NO while in the AA, ACh likely recruits other endothelial mediators besides NO to maintain vasodilatation.

Gene therapy prevents disruption of dystrophin-related proteins in a model of hereditary dilated cardiomyopathy in hamsters

BACKGROUND

The TO-2 hamster is an animal model of dilated cardiomyopathy (DCM). It has genetic and clinical features in common with humans who carry the gene deletion or mutation of the delta-sarcoglycan (SG) gene, a component in dystrophin-related proteins (DRP). DRP stabilise the sarcolemma during cardiac contraction. We performed in vivo gene therapy of the TO-2 hamster, whose heart is defective in all four SG proteins, to determine its potential as a model for therapy for DCM. In addition to the hereditary origin, heart failure is aggravated by treatment with catecholamines and ameliorated by the administration of some kinds of beta-antagonist both in humans and in TO-2 hamsters.

METHODS

Gene therapy for DCM was achieved by supplementing the delta-SG gene with rAAV vector and intramurally delivering rAAV-delta-SG into the cardiac apex and left ventricle.

RESULTS

This treatment resulted in: (i) a sustained and non-pathogenic expression of both the transcript and transgene of delta-SG and all other SG proteins; (ii) improvement to both morphological and physiological deterioration; and (iii) rescued prognosis compared with untreated TO-2 hamsters, and TO-2 hamsters transfected with reporter gene alone. Another acute heart-failure model was prepared by high-dose isoproterenol treatment in Wistar rats, which resulted in: (i) translocation of dystrophin, but not delta-SG, from the cardiac sarcolemma to the myoplasm; and (ii) fragmentation of dystrophin, probably due to the activation of endogenous protease(s) or proteasome(s) that contributed to muscular dystrophy-like degeneration occurring specifically in cardiomyocytes.

CONCLUSIONS

Both the TO-2 hamster and the isoproterenol-treated Wistar rat models commonly experience disruption of dystrophin or DRP. Targeting the responsible gene with the use of a potent vector may provide a novel strategy for the treatment of advanced heart failure.

A novel paradigm for therapeutic basis of advanced heart failure--assessment by gene therapy

The precise mechanism(s) of the progression of advanced heart failure (HF) should be determined to establish strategies for its treatment or prevention. Based on pathological, molecular, and physiological findings in 3 animal models and human cases, we propose a novel scheme that a vicious cycle formed by increased sarcolemma (SL) permeability, preferential activation of calpain over calpastatin, and translocation and cleavage of dystrophin (Dys) commonly lead to advanced HF. The aim of this article was to assess our recent paradigm that disruption of myocardial Dys is a final common pathway to advanced HF, irrespective of its hereditary or acquired origin, but not intended to provide a comprehensive overview of the various factors that may be involved in the course of HF in different clinical settings. In addition, each component of Dys-associated proteins (DAP) was heterogeneously degraded in vivo and in vitro, i.e. Dys and alpha-sarcoglycan (SG) were markedly destroyed using isolated calpain 2, while delta-SG was not degraded at all. The up-regulation of calpain 2 was confirmed through previously published data that remain insufficient for precise evaluation, supporting our new scheme that the activation of calpain(s) is involved in the steady process of Dys cleavage. In addition, somatic gene therapy is discussed as a potential option to ameliorate the physiological/metabolic indices and to improve the prognosis.

A novel scheme of dystrophin disruption for the progression of advanced heart failure

The precise mechanism of the progression of advanced heart failure is unknown. We assessed a new scheme in two heart failure models: (I) congenital dilated cardiomyopathy (DCM) in TO-2 strain hamsters lacking delta-sarcoglycan (SG) gene and (II) administration of a high-dose of isoproterenol, as an acute heart failure in normal rats. In TO-2 hamsters, we followed the time course of the histological, physiological and metabolic the progressions of heart failure to the end stage. Dystrophin localization detected by immunostaining age-dependently to the myoplasm and the in situ sarcolemma fragility evaluated by Evans blue entry was increased in the same cardiomyocytes. Western blotting revealed a limited cleavage of the dystrophin protein at the rod domain, strongly suggesting a contribution of endogenous protease(s). We found a remarkable up-regulation of the amount of calpain-1 and -2, and no change of their counterpart, calpastatin. After supplementing TO-2 hearts with the normal delta-SG gene in vivo, these pathological alterations and the animals' survival improved. Furthermore, dystrophin but not delta-SG was disrupted by a high dose of isoproterenol, translocated from the sarcolemma to the myoplasm and fragmented. These results of heart failure, irrespective of the hereditary or acquired origin, indicate a vicious cycle formed by the increased sarcolemma permeability, preferential activation of calpain over calpastatin, and translocation and cleavage of dystrophin would commonly lead to advanced heart failure.

Translocation and cleavage of myocardial dystrophin as a common pathway to advanced heart failure: a scheme for the progression of cardiac dysfunction

Advanced heart failure (HF) is the leading cause of death in developed countries. The mechanism underlying the progression of cardiac dysfunction needs to be clarified to establish approaches to prevention or treatment. Here, using TO-2 hamsters with hereditary dilated cardiomyopathy, we show age-dependent cleavage and translocation of myocardial dystrophin (Dys) from the sarcolemma (SL) to the myoplasm, increased SL permeability in situ, and a close relationship between the loss of Dys and hemodynamic indices. In addition, we observed a surprising correlation between the amount of Dys and the survival rate. Dys disruption is not an epiphenomenon but directly precedes progression to advanced HF, because long-lasting transfer of the missing delta-SG gene to degrading cardiomyocytes in vivo with biologically nontoxic recombinant adenoassociated virus (rAAV) vector ameliorated all of the pathological features and changed the disease prognosis. Furthermore, acute HF after isoproterenol toxicity and chronic HF after coronary ligation in rats both time-dependently cause Dys disruption in the degrading myocardium. Dys cleavage was also detected in human hearts from patients with dilated cardiomyopathy of unidentified etiology, supporting a scheme consisting of SL instability, Dys cleavage, and translocation of Dys from the SL to the myoplasm, irrespective of an acute or chronic disease course and a hereditary or acquired origin. Hereditary HF may be curable with gene therapy, once the responsible gene is identified and precisely corrected.

Usefulness of 1H MR spectroscopy in the evaluation of myocardial metabolism in patients with dilated idiopathic cardiomyopathy: pilot study

RATIONALE AND OBJECTIVES

Primary dilated cardiomyopathy is a disease of unknown etiology, and it leads to severe heart failure. Abnormalities of the cardiac metabolism can play an important role in prognosis and influence the symptomatology in this group. The aim of this study was to assess cardiac metabolism using proton spectroscopy magnetic resonance (1H MRS) and to examine whether there is any correlation between cardiac metabolites and functional New York Heart Association (NYHA) class and left ventricular function parameters obtained in echocardiography.

MATERIALS AND METHODS

Fifteen patients with documented idiopathic dilated cardiomyopathy and 12 healthy volunteers were examined. The study protocol included clinical examination, 12-lead electrocardiogram, two-dimensional echocardiogram, and 1H MRS with voxel localized at interventricular septum area. The contents of total creatine (CR) ie, creatine + phosphocreatine, lipids (LIP), lactates (LAC) and their ratios (CR1A, CR2A, CR1/H20, CR2/H20, CR2/CR1, LIPA, LIP/H20, LIP/CR1, LACA, LAC/H20, LAC/CR1) were examined.

RESULTS

Patients with dilated cardiomyopathy had significantly lower levels of creatine CRIA (5.04 +/- 0.88 vs 5.94 +/- 1.15, P < .02) and ratios LIP/H20 (4.34 +/- 2.3 vs 15.46 +/- 20.39, P < .04) and LIP/CR1 (24.49 +/- 21.26 vs 34.08 +/- 13.36, P < .05) compared with healthy volunteers. Significant correlations between NYHA functional class and the ratios CR2/CR1, CR2/H20 (r = 0.59, P < .038, r = 0.59, P < .02, respectively) and between %LVEF and LIP/CR1 (r = 0.64, P < .036), as well as between the duration of the disease (TCH) and LIP/CR1 (r = 0.67, P < .046) were found.

CONCLUSION

A pilot study with proton spectroscopy magnetic resonance showed impairment of the cardiac metabolism in patients with idiopathic dilated cardiomyopathy. A trend to lower values of creatine and lipids, and to lower ratios of some of these metabolites was observed in the dilated cardiomyopathy group compared with healthy subjects. The results require further study.

[A new paradigm for the progression of advanced heart failure]

To clarify the precise mechanism for the progression of advanced heart failure (AdHF), we assessed the scheme in two HF models, using (I) TO-2 strain hamsters sharing common genetic and clinical features to human families with the delta-sarcoglycan (SG) gene mutation and (II) administration of a high-dose (HD) of isoproterenol (Isp) to normal rats. Delta-SG is a component in dystrophin (Dys)-related proteins that stabilize the sarcolemma (SL) during repeated heart beats. In TO-2, we followed time course of hemodynamics, immunostaining and Western blotting of Dys and in situ SL permeability by Evans blue uptake with or without the gene therapy. Dys was age-dependently translocated from the SL to myoplasm (MP) where the SL instability accompanied the fragmentation of Dys. By gene therapy to supplement the normal delta-SG gene in hearts in vivo, we found that Dys translocation was selectively improved in cardiomyocytes expressing the delta-SG transgene, where the SL fragility was ameliorated. Most importantly, the survival period of the animals was prolonged. Furthermore, Dys but not delta-SG was also time-dependently shifted with a HD of Isp from the SL to MP and fragmented, while delta-SG was preserved intact. We present a novel paradigm that disruption of Dys, but not delta-SG per se, leads to AdHF irrespective of hereditary or acquired origin.

Rescue of hereditary form of dilated cardiomyopathy by rAAV-mediated somatic gene therapy: amelioration of morphological findings, sarcolemmal permeability, cardiac performances, and the prognosis of TO-2 hamsters

The hereditary form comprises approximately 1/5 of patients with dilated cardiomyopathy (DCM) and is a major cause of advanced heart failure. Medical and socioeconomic settings require novel treatments other than cardiac transplantation. TO-2 strain hamsters with congenital DCM show similar clinical and genetic backgrounds to human cases that have defects in the delta-sarcoglycan (delta-SG) gene. To examine the long-term in vivo supplement of normal delta-SG gene driven by cytomegalovirus promoter, we analyzed the pathophysiologic effects of the transgene expression in TO-2 hearts by using recombinant adeno-associated virus vector. The transgene preserved sarcolemmal permeability detected in situ by mutual exclusivity between cardiomyocytes taking up intravenously administered Evans blue dye and expressing the delta-SG transgene throughout life. The persistent amelioration of sarcolemmal integrity improved wall thickness and the calcification score postmortem. Furthermore, in vivo myocardial contractility and hemodynamics, measured by echocardiography and cardiac catheterization, respectively, were normalized, especially in the diastolic performance. Most importantly, the survival period of the TO-2 hamsters was prolonged after the delta-SG gene transduction, and the animals remained active, exceeding the life expectancy of animals without transduction of the responsible gene. These results provide the first evidence that somatic gene therapy is promising for human DCM treatment, if the rAAV vector can be justified for clinical use.

Morphological and physiological restorations of hereditary form of dilated cardiomyopathy by somatic gene therapy

TO-2 strain hamsters with dilated cardiomyopathy, gene deletion of delta-sarcoglycan (SG) and no expression of alpha-, beta-, gamma-, and delta-SG proteins are useful for developing the potential gene therapy of intractable heart failure. We prepared recombinant adeno-associated virus vector including normal delta-SG gene driven by CMV promoter and intramurally administered in vivo. The transfected myocardium induced robust expression of both transcript and transgene for 2/3 period of the animal's life expectancy. Immunostaining demonstrated reexpression of not only delta-SG but also other three SGs in 40% cells in the transfected region and normalization of the diameter of transduced cardiomyocytes. Hemodynamic study revealed preferential amelioration of the diastolic indices (LVEDP, the dP/dt(min) and CVP). These results provide the first evidence that supplementation of a specific gene with efficient and sustained transfection capability restores the genetic, morphological, and functional deteriorations.

Strain- and age-dependent loss of sarcoglycan complex in cardiomyopathic hamster hearts and its re-expression by delta-sarcoglycan gene transfer in vivo

The delta-sarcoglycan (SG) gene is deleted in hamsters with hereditary cardiomyopathies. Immunological analyses of heart before, but not after, the progression of cardiomyopathy (CM) revealed that the BIO 14.6 strain, a model of hypertrophic CM, heterogeneously preserved alpha- and gamma-SG with loss of beta- and delta-SG. In contrast, the TO-2 strain, a model of dilated CM, did not show either SG. Furthermore, in vivo transfer of the full length delta-SG gene to TO-2 hearts expressed all four SGs. Thus, this age- and strain-dependent features suggest a more feasible setting for TO-2 than BIO 14.6 to verify both CM progression and the efficacy of gene therapy.

Molecular aspects of magnetic resonance imaging and spectroscopy

Magnetic resonance imaging (MRI) is a well known diagnostic tool in radiology that produces unsurpassed images of the human body, in particular of soft tissue. However, the medical community is often not aware that MRI is an important yet limited segment of magnetic resonance (MR) or nuclear magnetic resonance (NMR) as this method is called in basic science. The tremendous morphological information of MR images sometimes conceal the fact that MR signals in general contain much more information, especially on processes on the molecular level. NMR is successfully used in physics, chemistry, and biology to explore and characterize chemical reactions, molecular conformations, biochemical pathways, solid state material, and many other applications that elucidate invisible characteristics of matter and tissue. In medical applications, knowledge of the molecular background of MRI and in particular MR spectroscopy (MRS) is an inevitable basis to understand molecular phenomenon leading to macroscopic effects visible in diagnostic images or spectra. This review shall provide the necessary background to comprehend molecular aspects of magnetic resonance applications in medicine. An introduction into the physical basics aims at an understanding of some of the molecular mechanisms without extended mathematical treatment. The MR typical terminology is explained such that reading of original MR publications could be facilitated for non-MR experts. Applications in MRI and MRS are intended to illustrate the consequences of molecular effects on images and spectra.

Trimetazidine: potential mechanisms of action in hypertrophic cardiomyopathy

In this review we consider available information on the cardio- and cytoprotective properties and mechanism of action of trimetazidine, an antianginal drug. Two points in particular are addressed: the advantages of trimetazidine over classic drugs and its possible use for the long-term treatment of hypertrophic cardiomyopathy, described as an ischemic disorder.

Both hypertrophic and dilated cardiomyopathies are caused by mutation of the same gene, delta-sarcoglycan, in hamster: an animal model of disrupted dystrophin-associated glycoprotein complex

Cardiomyopathy (CM) is a primary degenerative disease of myocardium and is traditionally categorized into hypertrophic and dilated CMs (HCM and DCM) according to its gross appearance. Cardiomyopathic hamster (CM hamster), a representative model of human hereditary CM, has HCM and DCM inbred sublines, both of which descend from the same ancestor. Herein we show that both HCM and DCM hamsters share a common defect in a gene for delta-sarcoglycan (delta-SG), the functional role of which is yet to be characterized. A breakpoint causing genomic deletion was found to be located at 6.1 kb 5' upstream of the second exon of delta-SG gene, and its 5' upstream region of more than 27.4 kb, including the authentic first exon of delta-SG gene, was deleted. This deletion included the major transcription initiation site, resulting in a deficiency of delta-SG transcripts with the consequent loss of delta-SG protein in all the CM hamsters, despite the fact that the protein coding region of delta-SG starting from the second exon was conserved in all the CM hamsters. We elucidated the molecular interaction of dystrophin-associated glycoproteins including delta-SG, by using an in vitro pull-down study and ligand overlay assay, which indicates the functional role of delta-SG in stabilizing sarcolemma. The present study not only identifies CM hamster as a valuable animal model for studying the function of delta-SG in vivo but also provides a genetic target for diagnosis and treatment of human CM.

Chronic treatment with cyclosporine A in New Zealand rabbit: aortic and erectile tissue alterations

Transplanted patients frequently present erectile impotence. In order to test any interference by cyclosporine A (CsA), which is commonly used in the post-transplantation management, we investigated the in vitro contractile and relaxant responses of corpus cavernosum and aorta from rabbits chronically treated with CsA. Male New Zealand White rabbits 6 months of age were treated with CsA (25 mg/kg per day s.c.) or solvent (corn oil) for 3 weeks. Descending thoracic aorta and erectile tissue were studied in vitro at the end of treatment. Isometric tension was recorded. In thoracic aorta, noradrenaline (0.1-30 mM) induced a concentration-dependent contraction with no difference between the two groups. Acetylcholine (30 nM-3 mM) produced relaxation (52 +/- 4% at 1 mM) that was significantly reduced in comparison to controls (67 +/- 4%, P < 0.05). ATP (3-10 mM) relaxation was not significantly different (maximal 78 +/- 10% and 62 +/- 12% in CsA-treated and controls). The relaxation produced by sodium nitrite was reduced in CsA-treated rabbits (at 10 mM and 0.1 mM concentrations). In erectile tissue, no significant variation in the response of isolated erectile tissue to the above drugs was observed between CsA-treated and control animals. These data indicate that chronic treatment with CsA in rabbits, despite alteration of the in vitro response of thoracic aorta, does not directly influence the function of penile tissue with relaxants.