Cardiomyopathies: from genetics to the prospect of treatment

Targeting ferroptosis as a promising therapeutic strategy to treat cardiomyopathy

Cardiomyopathies are a clinically heterogeneous group of cardiac diseases characterized by heart muscle damage, resulting in myocardium disorders, diminished cardiac function, heart failure, and even sudden cardiac death. The molecular mechanisms underlying the damage to cardiomyocytes remain unclear. Emerging studies have demonstrated that ferroptosis, an iron-dependent non-apoptotic regulated form of cell death characterized by iron dyshomeostasis and lipid peroxidation, contributes to the development of ischemic cardiomyopathy, diabetic cardiomyopathy, doxorubicin-induced cardiomyopathy, and septic cardiomyopathy. Numerous compounds have exerted potential therapeutic effects on cardiomyopathies by inhibiting ferroptosis. In this review, we summarize the core mechanism by which ferroptosis leads to the development of these cardiomyopathies. We emphasize the emerging types of therapeutic compounds that can inhibit ferroptosis and delineate their beneficial effects in treating cardiomyopathies. This review suggests that inhibiting ferroptosis pharmacologically may be a potential therapeutic strategy for cardiomyopathy treatment.

The interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases: Implications for therapy

Microtubules, a highly dynamic cytoskeleton, participate in many cellular activities including mechanical support, organelles interactions, and intracellular trafficking. Microtubule organization can be regulated by modification of tubulin subunits, microtubule-associated proteins (MAPs) or agents modulating microtubule assembly. Increasing studies demonstrate that microtubule disorganization correlates with various cardiocerebrovascular diseases including heart failure and ischemic stroke. Microtubules also mediate intracellular transport as well as intercellular transfer of mitochondria, a power house in cells which produce ATP for various physiological activities such as cardiac mechanical function. It is known to all that both microtubules and mitochondria participate in the progression of cancer and Parkinson's disease. However, the interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases remain unclear. In this paper, we will focus on the roles of microtubules in cardiocerebrovascular diseases, and discuss the interplay of mitochondria and microtubules in disease development and treatment. Elucidation of these issues might provide significant diagnostic value as well as potential targets for cardiocerebrovascular diseases.

Cardiovascular magnetic resonance detects microvascular dysfunction in a mouse model of hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) related myocardial vascular remodelling may lead to the reduction of myocardial blood supply and a subsequent progressive loss of cardiac function. This process has been difficult to observe and thus their connection remains unclear. Here we used non-invasive myocardial blood flow sensitive CMR to show an impairment of resting myocardial perfusion in a mouse model of naturally occurring HCM.

METHODS

We used a mouse model (DBA/2 J; D2 mouse strain) that spontaneously carries variants in the two most susceptible HCM genes-Mybpc3 and Myh7 and bears the key features of human HCM. The C57BL/6 J (B6) was used as a reference strain. Mice with either B6 or D2 backgrounds (male: n = 4, female: n = 4) underwent cine-CMR for functional assessment at 9.4 T. Left ventricular (LV) wall thickness was measured in end diastolic phase by cine-CMR. Quantitative myocardial perfusion maps (male: n = 5, female: n = 5 in each group) were acquired from arterial spin labelling (cine ASL-CMR) at rest. Myocardial perfusion values were measured by delineating different regions of interest based on the LV segmentation model in the mid ventricle of the LV myocardium. Directly after the CMR, the mouse hearts were removed for histological assessments to confirm the incidence of myocardial interstitial fibrosis (n = 8 in each group) and small vessel remodelling such as vessel density (n = 6 in each group) and perivascular fibrosis (n = 8 in each group).

RESULTS

LV hypertrophy was more pronounced in D2 than in B6 mice (male: D2 LV wall thickness = 1.3 ± 0.1 mm vs B6 LV wall thickness = 1.0 ± 0.0 mm, p < 0.001; female: D2 LV wall thickness = 1.0 ± 0.1 mm vs B6 LV wall thickness = 0.8 ± 0.1 mm, p < 0.01). The resting global myocardial perfusion (myocardial blood flow; MBF) was lower in D2 than in B6 mice (end-diastole: D2 MBFglobal = 7.5 ± 0.6 vs B6 MBFglobal = 9.3 ± 1.6 ml/g/min, p < 0.05; end-systole: D2 MBFglobal = 6.6 ± 0.8 vs B6 MBFglobal = 8.2 ± 2.6 ml/g/min, p < 0.01). This myocardial microvascular dysfunction was observed and associated with a reduction in regional MBF, mainly in the interventricular septal and inferior areas of the myocardium. Immunofluorescence revealed a lower number of vessel densities in D2 than in B6 (D2 capillary = 31.0 ± 3.8% vs B6 capillary = 40.7 ± 4.6%, p < 0.05). Myocardial collagen volume fraction (CVF) was significantly higher in D2 LV versus B6 LV mice (D2 CVF = 3.7 ± 1.4% vs B6 CVF = 1.7 ± 0.7%, p < 0.01). Furthermore, a higher ratio of perivascular fibrosis (PFR) was found in D2 than in B6 mice (D2 PFR = 2.3 ± 1.0%, B6 PFR = 0.8 ± 0.4%, p < 0.01).

CONCLUSIONS

Our work describes an imaging marker using cine ASL-CMR with a potential to monitor vascular and myocardial remodelling in HCM.

Cardiac Organoids to Model and Heal Heart Failure and Cardiomyopathies

Cardiac tissue engineering aims at creating contractile structures that can optimally reproduce the features of human cardiac tissue. These constructs are becoming valuable tools to model some of the cardiac functions, to set preclinical platforms for drug testing, or to alternatively be used as therapies for cardiac repair approaches. Most of the recent developments in cardiac tissue engineering have been made possible by important advances regarding the efficient generation of cardiac cells from pluripotent stem cells and the use of novel biomaterials and microfabrication methods. Different combinations of cells, biomaterials, scaffolds, and geometries are however possible, which results in different types of structures with gradual complexities and abilities to mimic the native cardiac tissue. Here, we intend to cover key aspects of tissue engineering applied to cardiology and the consequent development of cardiac organoids. This review presents various facets of the construction of human cardiac 3D constructs, from the choice of the components to their patterning, the final geometry of generated tissues, and the subsequent readouts and applications to model and treat cardiac diseases.

DBA/1 mice display equivalent cardiac function to C57BL/6J mice

NEW FINDINGS

What is the central question of this study? Do normal adult DBA/1 mice have cardiac function and performance equal to those of C57BL/6J mice? What is the main finding and its importance? Male adult DBA/1 mice show equivalent cardiac function to C57BL/6J mice up to 8 months old. Therefore, cardiac dysfunction could be investigated in an autoimmune diseases model established with DBA/1 mice.

ABSTRACT

Cardiovascular mortality has been increasing, and in particular, cardiovascular damage caused by some chronic autoimmune diseases accounts for a large proportion of this. C57BL/6J mice have been used mostly in studies of cardiovascular diseases. However, for purposes of modelling, this strain of mouse has a very low incidence of some chronic immune diseases such as rheumatoid arthritis, to which instead DBA/1 mice are more susceptible. Basic cardiac function differs between mice with different genetic backgrounds. Therefore, we monitored cardiac function and structure of normal male C57BL/6J and DBA/1 mice for six consecutive months. Echocardiography was used to monitor cardiac functions once a month and cardiac systolic function was measured upon isoproterenol challenge at the end of observation. The Excitation-contraction coupling-related proteins were measured by western blotting. Heart tissue sections were subject to haematoxylin-eosin, TUNEL and Alizarin red staining. The results demonstrated that systolic and diastolic function did not vary significantly and both strains were indistinguishable in appearance and structure of hearts. DBA/1 mice showed a good cardiac β-adrenergic response comparable to C57BL/6J mice with isoproterenol treatment. The phosphorylation of phospholamban at either its protein kinase A or its Ca²⁺ /calmodulin-dependent protein kinase II site, as well as the activation of troponin I showed no significant difference between strains. These findings suggested that there was no obvious difference in the heart structure and function of normal male DBA/1 mice compared with C57BL/6J mice. The DBA/1 mouse is a strain applicable to investigating autoimmune disease-induced heart dysfunction and exploring potential interventions.

Thromboembolism in Patients with Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac disease, which has a marked heterogeneity in clinical expression, natural history, and prognosis. HCM is associated with a high prevalence of thromboembolic events (stroke and systemic embolic events), even if taking no account of atrial fibrillation (AF), leading to unexpected disability and death in patients of all ages. Several risk factors of thromboembolism such as AF, greater age, left atrial diameter, heart failure and others have been confirmed in patients with HCM. Conventional thromboembolic predictive models were estimated by several trials in HCM population but it turned out to be unsatisfactory. Based on those previous explorations, researchers tried to modify or develop novel models suitable for HCM population in thromboembolism prediction. In consideration of catastrophic advent events of thromboembolism, current guidelines have recommended life-long anticoagulant therapy after a single short AF. Therefore, early identification of risk factors for thromboembolism, accurate risk stratification, timely preventive measures and aggressive management may help to avoid serious adverse thromboembolic events in HCM population.

Identification of Novel TTN Mutations in Three Chinese Familial Dilated Cardiomyopathy Pedigrees by Whole Exome Sequencing

Familial dilated cardiomyopathy (DCM) is associated with numerous genes, especially those of the sarcomere family. The titin gene (TTN) consists of 365 exons and encodes the largest sarcomere protein (titin) in our bodies. Titin is associated with many diseases, such as hypertrophic cardiomyopathy and DCM. Here we screened three Chinese families affected by DCM, and found that each harbors a stop-gain or splice site mutation in TTN (c.G20137T,c. G52522T,c.44610-2A>C). Assessment of the probands by electrocardiogram, B-mode echocardiography, and cardiac magnetic resonance imaging revealed impaired cardiac function, arrhythmia, or abnormal cardiac structure. In conclusion, using whole exome sequencing, we found three unreported TTN mutations associated with DCM. This has expanded the TTN mutation spectrum of Chinese DCM patients, especially in Henan, the most populous province. These data provide new genetic targets for the diagnosis and treatment of DCM, and will increase our understanding of the relationship between TTN mutation and DCM clinical symptoms.

Non-compaction of ventricular myocardium with polycystic kidney disease with cardiogenic cerebral embolism

Non-compaction of ventricular myocardium is a rare cardiomyopathy involving an early arrest of normal compaction of myocardium during fetal ontogenesis. Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary nephropathy characterised by multiple renal cysts replacing the renal parenchyma and extrarenal manifestations. Here, we report a case of 65-year-old man, chronic smoker, presented with sudden onset right brachial monoparesis, exertional dyspnoea, orthopnoea, bipedal swelling and diagnosed as a case of ADPKD with left ventricular non-compaction cardiomyopathy with acute left ventricular failure and cardiogenic cerebral embolism (no evidence of atrial fibrillation); based on characteristic appearance on two-dimensional echocardiography and cardiac magnetic resonance. The patient was managed with guideline-directed pharmacotherapy for heart failure and anticoagulation as a secondary stroke prevention measure. Through this case report, we try to discuss the association between two rare entities and individualisation of treatment options available as a case-based approach, as no standard treatment guidelines are available.

Mechanical Circulatory Support Device Utilization and Heart Transplant Waitlist Outcomes in Patients With Restrictive and Hypertrophic Cardiomyopathy

BACKGROUND

Patients with restrictive cardiomyopathy (RCM) and hypertrophic cardiomyopathy (HCM) generally are considered poor candidates for mechanical circulatory support devices (MCSDs) and often not able to be bridged mechanically to heart transplantation. This study characterized MCSD utilization and transplant waitlist outcomes in patients with RCM/HCM under the current allocation system and discusses changes in the era of the new donor allocation system.

METHODS AND RESULTS

Patients waitlisted from 2006 to 2016 in the United Network for Organ Sharing registry were stratified by RCM/HCM versus other diagnoses. MCSD utilization and waitlist duration were analyzed by propensity score models. Waitlist outcomes were assessed by cumulative incidence functions with competing events. Predictors of waitlist mortality or delisting for worsening status in patients with RCM/HCM were identified by proportional hazards model. Of 30 608 patients on the waitlist, 5.1% had RCM/HCM. Patients with RCM/HCM had 31 fewer waitlist days (P<0.01) and were ≈26% less likely to receive MCSD (P<0.01). Cumulative incidence of waitlist mortality was similar between cohorts; however, patients with RCM/HCM had higher incidence of heart transplantation. Predictors of waitlist mortality or delisting for worsening status in patients with RCM/HCM without MCSD support included estimated glomerular filtration rate <60 mL/min per 1.73 m², pulmonary capillary wedge pressure >20 mm Hg, inotrope use, and subjective frailty.

CONCLUSIONS

Patients with RCM/HCM are less likely to receive MCSD but have similar waitlist mortality and slightly higher incidence of transplantation compared with other patients. The United Network for Organ Sharing RCM/HCM risk model can help identify patients who are at high risk for clinical deterioration and in need of expedited heart transplantation.

A case of desmoplakin mutation and delayed arrhythmogenic right ventricular cardiomyopathy/dysplasia after atrial septal defect closure

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a slow-developing cardiomyopathy characterized by ventricular arrhythmias and fibrofatty replacement of the right ventricular (RV) myocardium. Its clinical diagnosis is challenging because of its variable clinical presentation and low genetic penetrance. We describe the case of a 67-year-old man who was diagnosed as having ARVC/D with a desmoplakin mutation that appeared after occlusion of an atrial septal defect (ASD). He underwent patch closure surgery for ASD at the age of 54 years. Four years later, he underwent catheter ablation for multifocal atrial tachycardias. Because of pre-syncope and inducible sustained monomorphic ventricular tachycardia, an implantable cardioverter defibrillator was implanted. When he was admitted for worsening heart failure at the age of 61 years, the desmoplakin mutation was detected with progressive left ventricular (LV) dysfunction. Subsequently, he was diagnosed as having ARVC/D with RV dysfunction. At cardiac autopsy, characteristics of ARVC/D, including dilatation, fibrofatty changes in the right ventricle, and diffuse fibrosis in the left ventricle were detected. Along with the effect of RV dysfunction caused by ASD, the progression of LV dysfunction after ASD closure was also possibly caused by the disease progression of ARVC/D. Physicians should carefully assess the various states of ARVC/D. <Learning objective: Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a cardiomyopathy characterized by arrhythmias, fibrofatty replacement of the right ventricular (RV) myocardium, and slow progression to more diffuse ventricular dysfunction. This case involved an atrial septal defect (ASD) that promoted the RV failure and was complicated with delayed progression of ARVC/D after ASD closure. The present case suggests that physicians need to carefully assess the various states of ARVC/D.>.

The pathogenic gene screening in a Chinese familial dilated cardiomyopathy pedigree from Hubei

Dilated cardiomyopathy arises from mutations in many genes. TTN, the gene encoding the sarcomere protein titin, has been insufficiently analyzed for cardiomyopathy mutations because of its enormous size. In this study, we report a Chinese family with two members affected by TTN. Blood samples were collected from all family members. Genomic DNA was isolated from blood, and all coding exons and adjacent intronic sequences of the TTN gene were examined for mutation analysis using polymerase chain reaction (PCR)-based sequencing. The proband (III3) and his sister (III2) carry a TTN c.100126A>G (p.Thr33376Ala) missense mutation. The proband currently exhibits decreased cardiac function accompanied by malignant arrhythmia, and his sister has no obvious clinical symptoms and no abnormal ultrasound findings. The study found that there is a missense mutation in the TTN gene, c.100126A>G (p.Thr33376Ala), in a family whose members suffer from familial dilated cardiomyopathy in Hubei province. TTN is closely related to dilated cardiomyopathy and is an important causative gene of familial dilated cardiomyopathy.

TranslatiOnal Registry for CardiomyopatHies (TORCH) - rationale and first results

AIMS

Non-ischemic cardiomyopathies (CMPs) comprise heart muscle disorders of different causes with high variability in disease phenotypes and clinical progression. The lack of national structures for the efficient recruitment, clinical and molecular classification, and follow-up of patients with non-ischemic CMPs limit the thorough analysis of disease mechanisms and the evaluation of novel diagnostic and therapeutic strategies. This paper describes a national, prospective, multicenter registry for patients with non-ischemic CMPs. The main objective of this registry is to create a central hub for clinical outcome studies, a joint resource for diagnostic and therapeutic trials, a common biomaterial bank, and a resource for detailed molecular analyses utilizing patients' biomaterials.

METHODS AND RESULTS

A comprehensive characterization of the register population and patients' subgroups is planned. First analyses will include descriptive methods evaluating the distribution of outcome variables and possible risk factors followed by test statistics in a cross-sectional design. The aim of the current study is to recruit 2300 patients all over Germany. Eligible participants are patients with primary non-ischemic cardiomyopathies, including hereditary and inflammatory dilated CMP (DCM), left-ventricular noncompaction CMP (LVNC), hypertrophic CMP (HCM), arrhythmogenic right-ventricular CMP (ARVC), myocarditis, and amyloidosis. Of already recruited patients 70% are male and 30% female. With 56% of patients included, DCM is most common.

CONCLUSION/OUTCOME

The primary outcome is all-cause death. Key secondary endpoints are cardiovascular death, adequate ICD shock, survived sudden cardiac death, syncope, documented potentially life-threatening arrhythmia, cardiac transplantation, hospitalization due to worsening of heart failure (HF), and any non-elective cardiovascular hospitalization.

Cardiomyopathies and anaesthesia

Cardiomyopathy is considered as a heart muscle disease of multiple aetiologies, unlike other cardiac diseases related to a definitive pathophysiology. With more and more research and with the advent of genetic analysis pin pointing the disease causing mutations, causative factors have been defined and classifications and definitions have changed over time. Patients with these conditions present to anaesthesiologists in elective and emergency situations, placement of automated internal cardioverter defibrillator (AICD) devices or biventricular pacing but may also be diagnosed at anaesthetic pre-assessment. We describe cardiomyopathies such as dilated cardiomyopathy, hypertrophic cardiomyopathy, post-partum cardiomyopathy and Takotsubo cardiomyopathy in brief and their anaesthetic management.

Hearing Profile in Patients with Dilated and Hypertrophic Cardiomyopathies

INTRODUCTION

Cardiomyopathy may cause disruptions in the micro-vascular system of the stria vascularis in the cochlea, and, subsequently, may result in cochlear degeneration. Degeneration in the stria vascularis affects the physical and chemical processes in the organ of Corti, thereby causing a possible hearing impairment. The objective of this study was to assess the hearing profiles of patients with dilated and hypertrophic cardiomyopathies to determine the relationship between the degree of hearing loss and the degree and duration of the disease and to compare the dilated and hypertrophic cardiomyopathies as regards hearing profile.

METHODS

In this case control study, we studied 21 patients (cases/study group/group 1) and 15 healthy individuals (controls/group 2). Six patients (group 1a) had hypertrophic cardiomyopathy (HCM), and 15 patients (group 1b) had dilated cardiomyopathy (DCM). The data were analyzed using the t-test, chi-squared test, Kruskal-Wallis test, and the Multiple Mann-Whitney test.

RESULTS

The results of this study showed that 80% of those patients with DCM (group 1b) had bilateral sensorineural hearing loss (SNHL), and 100% of the patients with HCM (group 1a) had mild to severe bilateral sloping SNHL. Distortion Product Otoacoustic Emissions (DPOAEs) were present in 14% of the study group and in 100 % of the control group. The results of the measurements of auditory brainstem response (ABR) showed that 50% of the study group had abnormal latencies compared to the control group, and there was no correlation between the duration of the disease and the degree of hearing loss or DPOAE. Fifty percent of the patients with HCM and 35% of the patients with DCM had positive family histories of similar conditions, and 35% of those with HCM had a positive family history of sudden death.

CONCLUSION

The results of this study suggested that the link between heart disease and hearing loss and early identification of hearing loss in patients with cardiomyopathy may reduce morbidity since hearing deficits sometimes precede heart disease.

Transcatheter closure of atrial septal defect associated with arrhythmogenic right ventricular cardiomyopathy: a case report and literature review

Arrhythmogenic right ventricular cardiomyopathy is characterised by progressive, fibrofatty replacement of myocardium, and ventricular arrhythmias, and its prognosis is usually poor. Arrhythmogenic right ventricular cardiomyopathy associated with atrial septal defect is very rare, and this combination may make the diagnosis, treatment, and prognosis difficult. We present a case of a patient with this association who underwent interventional treatment with a septal defect occluder. Transcatheter closure of atrial septal defect in a patient with arrhythmogenic right ventricular cardiomyopathy is hitherto unreported. During a 3-year follow-up he remained relatively stable. We also review the cases reported in the medical literature describing this uncommon association between arrhythmogenic right ventricular cardiomyopathy and atrial septal defect or patent foramen ovale.

Effects of GRK5 and ADRB1 polymorphisms influence on systolic heart failure

BACKGROUND

G-protein receptor kinase 5 (GRK5) Gln41 > Leu and β1-adrenergic receptor (ADRB1) Arg389 > Gly polymorphisms presented the different distribution of genotype frequencies between Caucasian American and African American, and produced the difference in β-blocker treatment effect among them with systolic heart failure (SHF).

OBJECTIVE

This study sought to identify the distributed characteristics of these variant genotypes in Chinese population, and influence of GRK5 and ADRB1 polymorphisms on SHF morbidity and β-blocker treatment effect in patients with SHF.

METHODS

This study was based on cross-sectional survey data. 1794 and 1718 subjects' ADRB1 and GRK5 gene sequencing (sanger method) data were achieved respectively. Blood samples collection, clinical laboratory detection, electrocardiogram and echocardiography examinations were performed. Medication usage was confirmed at in-hospital visits or the questionnaire by personal interview.

RESULTS

GRK5 Leu41Leu genotype was not found in our Chinese population. In non-SHF population, allele frequencies of GRK5 Gln41 and Leu41 were 2782 (0.992) and 22 (0.008) (Hardy-Weinberg equilibrium test χ(2) = 0.088, P = 0.767), and allele frequencies of ADRB1 Arg389 and Gly389 were 2127 (0.715) and 849 (0.285) (χ(2) = 0.272, P = 0.602). In SHF patients, allele frequencies of Gln41 and Leu41 were 446 (0.991) and 4 (0.009) (χ(2) = 0.018, P = 0.893), and allele frequencies of Arg389 and Gly389 were 331 (0.726) and 125 (0.274) (χ(2) = 1.892, P = 0.169). Further in logistic regression model, these ADRB1 and GRK5 variants were not significantly independently associated with the risk of SHF morbidity. Those carrying genotype ADRB1 Gly389Gly did not reduce significantly the risk of SHF morbidity after β-blocker therapy.

CONCLUSIONS

GRK5 Leu41Leu genotype was not found in our Chinese population, neither ADRB1 nor GRK5 variants presented independently associated with the risk of SHF morbidity, most ADRB1 and GRK5 polymorphisms did decrease significantly the risk of SHF morbidity after β-blocker therapy except for those carrying genotype ADRB1 Gly389Gly.

Molecular genetics in hypertrophic cardiomyopathy: towards individualized management of the disease

Hypertrophic cardiomyopathy is a relatively common genetic disease, affecting one person per 500 in the general population, and is clinically defined by the presence of unexplained left ventricular hypertrophy. Although recognized as the most common cause of sudden death in the young (especially in athletes), the cardiac expression of the disease is highly variable with respect to age at onset, degree of symptoms and risk of cardiac death. As a consequence, therapeutic strategies are diverse and must be adapted to the specific features of an individual. Recently, the molecular bases of the disease have been unraveled with the identification of a large number of mutations in genes encoding sarcomeric proteins. This review focuses on the impact of the molecular data on the understanding of the disease, and considers the emerging issues regarding the impact of molecular testing on the management of patients (or relatives) in clinical practice.

Dose-dependent diastolic dysfunction and early death in a mouse model with cardiac troponin mutations

Our aim was to explore the dose-dependent diastolic dysfunction and the mechanisms of heart failure and early death in transgenic (TG) mice modeling human restrictive cardiomyopathy (RCM). The first RCM mouse model (cTnI(193His) mice) carrying cardiac troponin I (cTnI) R193H mutation (mouse cTnI R193H equals to human cTnI R192H) was generated several years ago in our laboratory. The RCM mice manifested a phenotype similar to that observed in RCM patients carrying the same cTnI mutation, i.e. enlarged atria and restricted ventricles. However, the causes of heart failure and early death observed in RCM mice remain unclear. In this study, we have produced RCM TG mice (cTnI(193His)-L, cTnI(193His)-M and cTnI(193His)-H) that express various levels of mutant cTnI in the heart. Histological examination and echocardiography were performed on these mice to monitor the time course of the disease development and heart failure. Our data demonstrate that cTnI mutation-caused diastolic dysfunction is dose-dependent. The key mechanism is myofibril hypersensitivity to Ca(2+) resulting in an impaired relaxation in the mutant cardiac myocytes. Prolonged relaxation time and delay of Ca(2+) decay observed in the mutant cardiac myocytes are correlated with the level of the mutant protein in the heart. Markedly enlarged atria due to the elevated end-diastolic pressure and myocardial ischemia are observed in the heart of the transgenic mice. In the mice with the highest level of the mutant protein, restricted ventricles and systolic dysfunction occur followed immediately by heart failure and early death. Diastolic dysfunction caused by R193H troponin I mutation is specific, showing a dose-dependent pattern. These mouse models are useful tools for the study of diastolic dysfunction. Impaired diastole can cause myocardial ischemia and fibrosis formation, resulting in the development of systolic dysfunction and heart failure with early death in the RCM mice with a high level of the mutant protein in the heart.

Cardiomyocyte growth and sarcomerogenesis at the intercalated disc

Cardiomyocytes grow during heart maturation or disease-related cardiac remodeling. We present evidence that the intercalated disc (ID) is integral to both longitudinal and lateral growth: increases in width are accommodated by lateral extension of the plicate tread regions and increases in length by sarcomere insertion within the ID. At the margin between myofibril and the folded membrane of the ID lies a transitional junction through which the thin filaments from the last sarcomere run to the ID membrane and it has been suggested that this junction acts as a proto Z-disc for sarcomere addition. In support of this hypothesis, we have investigated the ultrastructure of the ID in mouse hearts from control and dilated cardiomyopathy (DCM) models, the MLP-null and a cardiac-specific β-catenin mutant, cΔex3, as well as in human left ventricle from normal and DCM samples. We find that the ID amplitude can vary tenfold from 0.2 μm up to a maximum of ~2 μm allowing gradual expansion during heart growth. At the greatest amplitude, equivalent to a sarcomere length, A-bands and thick filaments are found within the ID membrane loops together with a Z-disc, which develops at the transitional junction position. Here, also, the tops of the membrane folds, which are rich in αII spectrin, become enlarged and associated with junctional sarcoplasmic reticulum. Systematically larger ID amplitudes are found in DCM samples. Other morphological differences between mouse DCM and normal hearts suggest that sarcomere inclusion is compromised in the diseased hearts.

TNNT2 gene polymorphisms are associated with susceptibility to idiopathic dilated cardiomyopathy in the Han Chinese population

Background. Idiopathic dilated cardiomyopathy (DCM) is characterized by ventricular chamber enlargement and systolic dysfunction. The pathogenesis of DCM remains uncertain, and the TNNT2 gene is potentially associated with DCM. To assess the role of TNNT2 in DCM, we examined 10 tagging single nucleotide polymorphisms (SNPs) in the patients. Methods. A total of 97 DCM patients and 189 control subjects were included in the study, and all SNPs were genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Results. In the TNNT2 gene, there was a significant association between DCM and genotype for the tagging SNPs rs3729547 (χ² = 6.63, P = 0.036, OR = 0.650, and 95% CI = 0.453–0.934) and rs3729843 (χ² = 9.787, P = 0.008, OR = 1.912, and 95% CI = 1.265–2.890) in the Chinese Han population. Linkage disequilibrium (LD) analysis showed that the SNPs rs7521796, rs2275862, rs3729547, rs10800775, and rs1892028, which are approximately 6 kb apart, were in high LD (D′ > 0.80) in the DCM patients. Conclusion. These results suggest that the TNNT2 polymorphisms might play an important role in susceptibility to DCM in the Chinese Han population.

Insights into restrictive cardiomyopathy from clinical and animal studies

Cardiomyopathies are diseases that primarily affect the myocardium, leading to serious cardiac dysfunction and heart failure. Out of the three major categories of cardiomyopathies (hypertrophic, dilated and restrictive), restrictive cardiomyopathy (RCM) is less common and also the least studied. However, the prognosis for RCM is poor as some patients dying in their childhood. The molecular mechanisms behind the disease development and progression are not very clear and the treatment of RCM is very difficult and often ineffective. In this article, we reviewed the recent progress in RCM research from the clinical studies and the translational studies done on diseased transgenic animal models. This will help for a better understanding of the mechanisms underlying the etiology and development of RCM and for the design of better treatments for the disease.

Mutations with pathogenic potential in proteins located in or at the composite junctions of the intercalated disk connecting mammalian cardiomyocytes: a reference thesaurus for arrhythmogenic cardiomyopathies and for Naxos and Carvajal diseases

In the past decade, an avalanche of findings and reports has correlated arrhythmogenic ventricular cardiomyopathies (ARVC) and Naxos and Carvajal diseases with certain mutations in protein constituents of the special junctions connecting the polar regions (intercalated disks) of mature mammalian cardiomyocytes. These molecules, apparently together with some specific cytoskeletal proteins, are components of (or interact with) composite junctions. Composite junctions contain the amalgamated fusion products of the molecules that, in other cell types and tissues, occur in distinct separate junctions, i.e. desmosomes and adherens junctions. As the pertinent literature is still in an expanding phase and is obviously becoming important for various groups of researchers in basic cell and molecular biology, developmental biology, histology, physiology, cardiology, pathology and genetics, the relevant references so far recognized have been collected and are presented here in the following order: desmocollin-2 (Dsc2, DSC2), desmoglein-2 (Dsg2, DSG2), desmoplakin (DP, DSP), plakoglobin (PG, JUP), plakophilin-2 (Pkp2, PKP2) and some non-desmosomal proteins such as transmembrane protein 43 (TMEM43), ryanodine receptor 2 (RYR2), desmin, lamins A and C, striatin, titin and transforming growth factor-β3 (TGFβ3), followed by a collection of animal models and of reviews, commentaries, collections and comparative studies.

Cardiac-specific deletion of the microtubule-binding protein CENP-F causes dilated cardiomyopathy

CENP-F is a large multifunctional protein with demonstrated regulatory roles in cell proliferation, vesicular transport and cell shape through its association with the microtubule (MT) network. Until now, analysis of CENP-F has been limited to in vitro analysis. Here, using a Cre-loxP system, we report the in vivo disruption of CENP-F gene function in murine cardiomyocytes, a cell type displaying high levels of CENP-F expression. Loss of CENP-F function in developing myocytes leads to decreased cell division, blunting of trabeculation and an initially smaller, thin-walled heart. Still, embryos are born at predicted mendelian ratios on an outbred background. After birth, hearts lacking CENP-F display disruption of their intercalated discs and loss of MT integrity particularly at the costamere; these two structures are essential for cell coupling/electrical conduction and force transduction in the heart. Inhibition of myocyte proliferation and cell coupling as well as loss of MT maintenance is consistent with previous reports of generalized CENP-F function in isolated cells. One hundred percent of these animals develop progressive dilated cardiomyopathy with heart block and scarring, and there is a 20% mortality rate. Importantly, although it has long been postulated that the MT cytoskeleton plays a role in the development of heart disease, this study is the first to reveal a direct genetic link between disruption of this network and cardiomyopathy. Finally, this study has broad implications for development and disease because CENP-F loss of function affects a diverse array of cell-type-specific activities in other organs.

Hypertrophy-associated polymorphisms ascertained in a founder cohort applied to heart failure risk and mortality

A three-stage approach was undertaken using genome-wide, case-control, and case-only association studies to identify genetic variants associated with heart failure mortality. In an Amish founder population (n = 851), cardiac hypertrophy, a trait integral to the adaptive response to failure, was found to be heritable (h² = 0.28, p = 0.0002) and GWAS revealed 21 candidate hypertrophy SNPs. In a case (n = 1,610)-control (n = 463) study in unrelated Caucasians, one of the SNPs associated with hypertrophy (rs2207418, p = 8 × 10⁻⁶), was associated with heart failure, RR = 1.85(1.25-2.73, p = 0.0019). In heart failure cases rs2207418 was associated with increased mortality, HR = 1.51(1.20-1.97, p = 0.0004). There was consistency between studies, with the GG allele being associated with increased ventricular mass (~13 g/m²) in the Amish, heart failure risk, and heart failure mortality. This SNP is in a gene desert of chromosome 20p12. Five genes are within 2.0 mbp of rs2207418 but with low LD between their SNPs and rs2207418. A region near this SNP is highly conserved in multiple vertebrates (lod score = 1,208). This conservation and the internal consistency across studies suggests that this region has biologic importance in heart failure, potentially acting as an enhancer or repressor element. rs2207418 may be useful for predicting a more progressive form of heart failure that may require aggressive therapy.

Endoplasmic-reticulum calcium depletion and disease

The endoplasmic reticulum (ER) as an intracellular Ca(2+) store not only sets up cytosolic Ca(2+) signals, but, among other functions, also assembles and folds newly synthesized proteins. Alterations in ER homeostasis, including severe Ca(2+) depletion, are an upstream event in the pathophysiology of many diseases. On the one hand, insufficient release of activator Ca(2+) may no longer sustain essential cell functions. On the other hand, loss of luminal Ca(2+) causes ER stress and activates an unfolded protein response, which, depending on the duration and severity of the stress, can reestablish normal ER function or lead to cell death. We will review these various diseases by mainly focusing on the mechanisms that cause ER Ca(2+) depletion.

Safety of transesophageal echocardiography

Since its introduction into the operating room in the early 1980s, transesophageal echocardiography (TEE) has gained widespread use during cardiac, major vascular, and transplantation surgery, as well as in emergency and intensive care medicine. Moreover, TEE has become an invaluable diagnostic tool for the management of patients with cardiovascular disease in a nonoperative setting. In comparison with other diagnostic modalities, TEE is relatively safe and noninvasive. However, the insertion and manipulation of the ultrasound probe can cause oropharyngeal, esophageal, or gastric trauma. Here, the authors review the safety profile of TEE by identifying complications and propose a set of relative and absolute contraindications to probe placement. In addition, alternative echocardiographic modalities (e.g., epicardial echocardiography) that may be considered when TEE probe placement is contraindicated or not feasible are discussed.

A myomesin mutation associated with hypertrophic cardiomyopathy deteriorates dimerisation properties

Myomesin plays an important structural and functional role in the M-band of striated muscles. The C-terminal domain 13 of myomesin dimerises and forms antiparallel strands which cross-link neighboring Myosin filaments and titin in the M-line of the sarcomeres. These interactions stabilise the contractile apparatus during striated muscle contraction. Since myomesin is an important component of the M-band we screened the myomesin gene for genetic variants in patients with hypertrophic cardiomyopathy (HCM). We identified the missense mutation V1490I in domain 12 of myomesin in a family with inherited HCM. Analytical ultracentrifugation experiments, circular dichroism spectra, and surface plasmon resonance spectroscopy of myomesin fragments were carried out to investigate the effects of the mutation V1490I on structure and function of myomesin domains 11-13 and 12-13. Both the wild type and mutated myomesin domains My11-13 revealed similar secondary structures and formed stable dimers. Mutated myomesin domains My11-13 and My12-13 dimers revealed a reduced thermal stability and a significantly decreased dimerisation affinity, showing disturbed functional properties of V1490I mutated myomesin. However, monomeric myomesin domains My11-12, i.e. without dimerisation domain 13 showed no difference in thermal stability between wild type and V1490I mutated myomesin. In conclusion, the V1490I mutation associated with HCM lead to myomesin proteins with abnormal functional properties which affect dimerisation properties of myomesin domain 13. These effects may contribute to the pathogenesis of HCM.

Genetic background affects function and intracellular calcium regulation of mouse hearts

AIMS

The genetic background is currently under close scrutiny when determining cardiovascular disease progression and response to therapy. However, this factor is rarely considered in physiological studies, where it could influence the normal behaviour and adaptive responses of the heart. We aim to test the hypothesis that genetic strain variability is associated with differences in excitation-contraction coupling mechanisms, in particular those involved in cytoplasmic Ca(2+) regulation, and that they are concomitant to differences in whole-heart function and cell morphology.

METHODS AND RESULTS

We studied 8- to 10-week-old male C57BL/6, BALB/C, FVB, and SV129 mice. Echocardiography and radiotelemetry were used to assess cardiac function in vivo. FVB mice had increased left ventricular ejection fraction and fractional shortening with significantly faster heart rate (HR) and lack of diurnal variation of HR. Confocal microscopy, sarcomere length tracking, and epifluorescence were used to investigate cell volume, t-tubule density, contractility, and Ca(2+) handling in isolated ventricular myocytes. Sarcomere relaxation and time-to-peak of the Ca(2+) transient were prolonged in BALB/C myocytes, with more frequent Ca(2+) sparks and significantly higher sarcoplasmic reticulum (SR) Ca(2+) leak. There were no strain differences in the contribution of different Ca(2+) extrusion mechanisms. SV129 had reduced SR Ca(2+) leak with elevated SR Ca(2+) content and smaller cell volume and t-tubule density compared with myocytes from other strains.

CONCLUSION

These results demonstrate that a different genetic background is associated with physiological differences in cardiac function in vivo and differences in morphology, contractility, and Ca(2+) handling at the cellular level.

Evolving molecular diagnostics for familial cardiomyopathies: at the heart of it all

Cardiomyopathies are an important and heterogeneous group of common cardiac diseases. An increasing number of cardiomyopathies are now recognized to have familial forms, which result from single-gene mutations that render a Mendelian inheritance pattern, including hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy and left ventricular noncompaction cardiomyopathy. Recently, clinical genetic tests for familial cardiomyopathies have become available for clinicians evaluating and treating patients with these diseases, making it necessary to understand the current progress and challenges in cardiomyopathy genetics and diagnostics. In this review, we summarize the genetic basis of selected cardiomyopathies, describe the clinical utility of genetic testing for cardiomyopathies and outline the current challenges and emerging developments.

Identification of a new lamin A/C mutation in a Chinese family affected with atrioventricular block as the prominent phenotype

Even though mutations in LMNA have been reported in patients with typical dilated cardiomyopathy (DCM) and atrioventricular block (AVB) previously, the purpose of this study was to disclose this novel genetic abnormality in one Chinese family with the atypical phenotype of progressive AVB followed by DCM with normal QRS interval. Genome-wide linkage analysis mapped the AVB gene in this family to a marker at chromosome 1q21.2, where the LMNA gene was located. Direct DNA sequence analysis revealed a heterozygous G to A transition at nucleotide 244 in exon 1 of LMNA, which resulted in an E82K mutation. The E82K mutation co-segregated with all affected individuals in the family, and was not present in 200 normal controls. Further clinical evaluation of mutation carriers showed that 5 of 6 AVB patients exhibited mild DCM with a late onset of age in the fourth and fifth decades. Ejection fractions were documented in 5 patients with DCM, but 4 showed a normal value of > or = 50%. Echocardiography showed that atrial dilatation occurred earlier than ventricular dilatation in the patients. This study suggests that progressive AVB with normal QRS interval and accompanying DCM at later stages may represent a distinct type of DCM. The molecular mechanism by which the E82K mutation causes AVB as the prominent phenotype in DCM may be a focus of future studies.

Mutations in Troponin that cause HCM, DCM AND RCM: what can we learn about thin filament function?

Troponin (Tn) is a critical regulator of muscle contraction in cardiac muscle. Mutations in Tn subunits are associated with hypertrophic, dilated and restrictive cardiomyopathies. Improved diagnosis of cardiomyopathies as well as intensive investigation of new mouse cardiomyopathy models has significantly enhanced this field of research. Recent investigations have showed that the physiological effects of Tn mutations associated with hypertrophic, dilated and restrictive cardiomyopathies are different. Impaired relaxation is a universal finding of most transgenic models of HCM, predicted directly from the significant changes in Ca(2+) sensitivity of force production. Mutations associated with HCM and RCM show increased Ca(2+) sensitivity of force production while mutations associated with DCM demonstrate decreased Ca(2+) sensitivity of force production. This review spotlights recent advances in our understanding on the role of Tn mutations on ATPase activity, maximal force development and heart function as well as the correlation between the locations of these Tn mutations within the thin filament and myofilament function.

Myocardin is required for cardiomyocyte survival and maintenance of heart function

Despite intense investigation over the past century, the molecular mechanisms that regulate maintenance and adaptation of the heart during postnatal development are poorly understood. Myocardin is a remarkably potent transcriptional coactivator expressed exclusively in cardiac myocytes and smooth muscle cells during postnatal development. Here we show that myocardin is required for maintenance of cardiomyocyte structure and sarcomeric organization and that cell-autonomous loss of myocardin in cardiac myocytes triggers programmed cell death. Mice harboring a cardiomyocyte-restricted null mutation in the myocardin gene (Myocd) develop dilated cardiomyopathy and succumb from heart failure within a year. Remarkably, ablation of the Myocd gene in the adult heart leads to the rapid-onset of heart failure, dilated cardiomyopathy, and death within a week. Myocd gene ablation is accompanied by dissolution of sarcomeric organization, disruption of the intercalated disc, and cell-autonomous loss of cardiomyocytes via apoptosis. Expression of myocardin/serum response factor-regulated myofibrillar genes is extinguished, or profoundly attenuated, in myocardin-deficient hearts. Conversely, proapoptotic factors are induced and activated in myocardin-deficient hearts. We conclude that the transcriptional coactivator myocardin is required for maintenance of heart function and ultimately cardiomyocyte survival.

Calcium Pumps in Health and Disease

Ca2+-ATPases (pumps) are key actors in the regulation of Ca2+ in eukaryotic cells and are thus essential to the correct functioning of the cell machinery. They have high affinity for Ca2+ and can efficiently regulate it down to very low concentration levels. Two of the pumps have been known for decades (the SERCA and PMCA pumps); one (the SPCA pump) has only become known recently. Each pump is the product of a multigene family, the number of isoforms being further increased by alternative splicing of the primary transcripts. The three pumps share the basic features of the catalytic mechanism but differ in a number of properties related to tissue distribution, regulation, and role in the cellular homeostasis of Ca2+. The molecular understanding of the function of the pumps has received great impetus from the solution of the three-dimensional structure of one of them, the SERCA pump. These spectacular advances in the structure and molecular mechanism of the pumps have been accompanied by the emergence and rapid expansion of the topic of pump malfunction, which has paralleled the rapid expansion of knowledge in the topic of Ca2+-signaling dysfunction. Most of the pump defects described so far are genetic: when they are very severe, they produce gross and global disturbances of Ca2+ homeostasis that are incompatible with cell life. However, pump defects may also be of a type that produce subtler, often tissue-specific disturbances that affect individual components of the Ca2+-controlling and/or processing machinery. They do not bring cells to immediate death but seriously compromise their normal functioning.

Sudden adult death

In the investigation of sudden death in adults, channelopathies, such as long QT syndrome, have risen to the fore in the minds of forensic pathologists in recent years. Examples of these disorders are touched upon in this review as an absence of abnormal findings at postmortem examination is characteristic and the importance of considering the diagnosis lies in the heritable nature of these conditions. Typically, a diagnosis of a possible channelopathy is evoked as an explanation for a 'negative autopsy' in a case of apparent sudden natural death. However, the one potential adverse effect of this approach is that subtle causes of sudden death may be overlooked. The intention of this article is to review and discuss potential causes of sudden adult death (mostly natural) that should be considered before resorting to a diagnosis of possible channelopathy. Nonetheless, it becomes apparent that many of the potential causes of sudden death can have a genetic basis. Thus, it becomes an important consideration that there may be a genetic basis to sudden death that extends beyond the negative autopsy.

Beneficial Effect on Cardiac Function by Intravenous Immunoglobulin Treatment in Patients with Dilated Cardiomyopathy is not due to Neutralization of Anti-receptor Autoantibody

Anti-beta1-adrenoceptor (beta1AR) autoantibodies have been shown to be pathophysiologically important in idiopathic dilated cardiomyopathy (DCM). Treatment with intravenous immunoglobulin (IVIG) has shown beneficial effects in both DCM and ischemic cardiomyopathy. However, the underlying mechanism has not been clarified. In the present study, we therefore examined whether the improvement of cardiac function was due to neutralization of functional beta1AR autoantibodies by anti-idiotypic antibodies. Autoantibodies against the beta1AR was analysed in sera from patients with DCM and coronary artery disease (CAD) treated with IVIG or placebo before, 6 and 12 months. Six month after treatment, DCM patients showed increase in beta1AR autoantibodies, mostly in IgG1 and IgG2, whereas in CAD patients mostly in IgG2. No changes in beta1AR autoantibodies after 12 months were detected. In summary, our results indicate that improvement of cardiac function by IVIG is not due to neutralization of beta1AR autoantibodies.

Finding disease-specific coordinated functions by multi-function genes: insight into the coordination mechanisms in diseases

We developed an approach using multi-function disease genes to find function pairs whose co-deregulation might induce a disease. Analyzing cancer genes, we found many cancer-specific coordinated function pairs co-deregulated by dysfunction of multi-function genes and other molecular changes in cancer. Studying two subtypes of cardiomyopathy, we found they show certain consistency at the functional coordination level. Our approach can also provide important information for finding novel disease genes as well as their mechanisms in diseases.

Does delta-sarcoglycan-associated autosomal-dominant cardiomyopathy exist?

In this study we clinically and genetically characterize a consanguineous family with a homozygous novel missense mutation in the delta-sarcoglycan gene and a second delta-sarcoglycan mutation that has previously been reported to cause severe autosomal-dominant dilated cardiomyopathy. We identified a novel missense mutation in exon 6 (p.A131P) of the delta-sarcoglycan gene, which in a homozygous state leads to the clinical picture of a limb girdle muscular dystrophy. In four heterozygous carriers for the mutation, aged 3-64 years, a second sequence variant in exon 6 (p.S151A) of the delta-sarcoglycan gene was detected on the other allele. This second missense change had previously been reported to be responsible for fatal autosomal-dominant dilated cardiomyopathy at young age. Comprehensive clinical and cardiac investigation in all of the compound heterozygous family members revealed no signs of cardiomyopathy or limb girdle muscular dystrophy. Our findings demonstrate that, even in the presence of a second disease-causing mutation, the p.S151A mutation in the delta-sarcoglycan gene does not result in cardiomyopathy. This finding questions the pathological relevance of this sequence variant for causing familial autosomal-dominant dilated cardiomyopathy and thereby the role of the delta-sarcoglycan gene in general as a disease-causing gene for autosomal-dominant dilated cardiomyopathy.

Serological evidence for the association of Bartonella henselae infection with arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an important cause of sudden death in young adults. On the basis of histopathological findings its pathogenesis may involve both a genetic origin and an inflammatory process. Bartonella henselae may cause endomyocarditis and was detected in myocardium from a young male who succumbed to sudden cardiac death.

HYPOTHESIS

We hypothesized that chronic infection with Bartonella henselae could contribute to the pathogenesis of ARVC.

METHODS

We investigated sera from 49 patients with ARVC for IgG antibodies to Bartonella henselae. In this study, 58 Swiss blood donors tested by the same method served as controls.

RESULTS

Six patients with ARVC (12%) had positive (>1:256) IgG titres in the immunofluorescence test with Bartonella henselae. In contrast, only 1 elevated titre was found in 58 controls (p < or = 0.05). Interestingly, all patients with increased titres had no familial occurrence of ARVC.

CONCLUSIONS

Further studies in larger patient cohorts seem justified to investigate a possible causal link between chronic Bartonella henselae and ARVC, in particular its sporadic (nonfamilial) form.

HBEGF, SRA1, and IK: Three cosegregating genes as determinants of cardiomyopathy

Human dilated cardiomyopathy (DCM), a disorder of the cardiac muscle, causes considerable morbidity and mortality and is one of the major causes of sudden cardiac death. Genetic factors play a role in the etiology and pathogenesis of DCM. Disease-associated genetic variations identified to date have been identified in single families or single sporadic patients and explain a minority of the etiology of DCM. We show that a 600-kb region of linkage disequilibrium (LD) on 5q31.2-3, harboring multiple genes, is associated with cardiomyopathy in three independent Caucasian populations (combined P-value = 0.00087). Functional assessment in zebrafish demonstrates that at least three genes, orthologous to loci in this LD block, HBEGF, IK, and SRA1, result independently in a phenotype of myocardial contractile dysfunction when their expression is reduced with morpholino antisense reagents. Evolutionary analysis across multiple vertebrate genomes suggests that this heart failure-associated LD block emerged by a series of genomic rearrangements across amphibian, avian, and mammalian genomes and is maintained as a cluster in mammals. Taken together, these observations challenge the simple notion that disease phenotypes can be traced to altered function of a single locus within a haplotype and suggest that a more detailed assessment of causality can be necessary.

Unresolved issues in myocardial reperfusion injury

While the basic pathobiology of myocardial ischemic injury and reperfusion has been determined over the last 50 years, there are important, unresolved, or at least not completely elucidated, issues in the field. These include the relative contributions of different modes of cell injury and death to evolving myocardial infarcts; interactions of phenomena produced by reperfusion, including stunning and preconditioning; and potential new approaches for successfully combining adjuvant therapy with coronary artery opening. A model of myocardial ischemic and reperfusion injury is proposed involving the potential expression of apoptotic and oncotic pathways in the same perturbed cardiomyocytes. Promising new cardioprotective strategies for reducing lethal reperfusion injury are discussed, including ischemic postconditioning, activators of the reperfusion injury salvage kinase (RISK) pathway, inhibitors of protein kinase c-delta, and inhibitors of the mitochondrial membrane permeability transition pore (PTP). Major outstanding clinical challenges are also discussed, including the development of clinical care systems that can routinely deliver very timely coronary opening and reperfusion, perhaps combined with adjuvant therapy, and the development of strategies to retard adverse remodeling and congestive heart failure in patients with significant myocardial infarction and scarring, perhaps by refinements in stem cell therapy.

Genetics of ischaemic stroke; single gene disorders

Examples of single gene disorders have been described for all major subtypes of ischaemic stroke: accelerated atherosclerosis and subsequent thrombo-embolism (e.g. homocysteinuria), weakening of connective tissue resulting in arterial dissections (e.g. Ehler-Danlos type IV), disorders of cerebral small vessels (e.g. cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and the collagen COL4A1 mutation), disorders increasing the thrombogenic potential of the heart through affecting the myocardium or the heart valves or through disturbance of the heart rhythm (e.g. hypertrophic cardiomyopathy), mitochondrial cytopathies increasing cerebral tissue susceptibility to insults (e.g. mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes), and finally disorders of coagulation that can either directly cause stroke or act synergistically with the aforementioned abnormalities (e.g. sickle cell disease). Most of these disorders are rare but they are important to consider particularly in young patients with stroke, those with a family history or those who have other characteristics of a particular syndrome.

Substitution of Brown Norway chromosome 16 preserves cardiac function with aging in a salt-sensitive Dahl consomic rat

Determination of the genetic factors that control the progression of left ventricular hypertrophy (LVH) to heart failure has been difficult despite extensive study in animal models. Here we have characterized a consomic rat model of LVH resulting from the introgression of chromosome 16 from the normotensive Brown Norway (BN) rat onto the genetic background of the Dahl salt-sensitive (SS/Mcwi) rat by marker assisted breeding. The SS-16BN/Mcwi consomic rats are normotensive but display LVH equivalent to the hypertensive SS/Mcwi rats at early ages. In this study we tracked the development of LVH by echocardiography and analyzed changes in cardiac function and morphology with aging in the SS-16BN/Mcwi, SS/Mcwi, and BN to determine if the consomic SS-16BN/Mcwi was a model of hypertrophic cardiomyopathy (HCM). Aging SS-16BN/Mcwi rats showed no evidence of heart failure or impaired cardiac function upon extensive analysis of left ventricle function by echocardiography and pressure-volume relationships, while their parental SS/Mcwi experienced deterioration in function between 18 and 36 wk of age. In addition aging SS-16BN/Mcwi did not exhibit tissue remodeling common to pathological hypertrophy and HCM such as increased fibrosis and reduced capillary density in the myocardium. In fact, SS-16BN/Mcwi were better protected from developing LV fibrosis with age than either the hypertensive SS/Mcwi or normotensive BN parental strains. This suggests that a gene or genes on chromosome 16 may be involved with both blood pressure regulation and preservation of cardiac function with aging.

A human phospholamban promoter polymorphism in dilated cardiomyopathy alters transcriptional regulation by glucocorticoids

Depressed calcium handling by the sarcoplasmic reticulum (SR) Ca-ATPase and its regulator phospholamban (PLN) is a key characteristic of human and experimental heart failure. Accumulating evidence indicates that increases in the relative levels of PLN to Ca-ATPase in failing hearts and resulting inhibition of Ca sequestration during diastole, impairs contractility. Here, we identified a genetic variant in the PLN promoter region, which increases its expression and may serve as a genetic modifier in dilated cardiomyopathy (DCM). The variant AF177763.1:g.203A>C (at position -36 bp relative to the PLN transcriptional start site) was found only in the heterozygous form in 1 out of 296 normal subjects and in 22 out of 381 cardiomyopathy patients (heart failure at age of 18-44 years, ejection fraction=22+/-9%). In vitro analysis, using luciferase as a reporter gene in rat neonatal cardiomyocytes, indicated that the PLN-variant increased activity by 24% compared to the wild type. Furthermore, the g.203A>C substitution altered the specific sequence of the steroid receptor for the glucocorticoid nuclear receptor (GR)/transcription factor in the PLN promoter, resulting in enhanced binding to the mutated DNA site. These findings suggest that the g.203A>C genetic variant in the human PLN promoter may contribute to depressed contractility and accelerate functional deterioration in heart failure.