Allele-Specific Silencing Ameliorates Restrictive Cardiomyopathy Attributable to a Human Myosin Regulatory Light Chain Mutation.

BACKGROUND: Restrictive cardiomyopathy is a rare heart disease associated with mutations in sarcomeric genes and with phenotypic overlap with hypertrophic cardiomyopathy. There is no approved therapy directed at the underlying cause. Here, we explore the potential of an interfering RNA (RNAi) therapeutic for a human sarcomeric mutation in MYL2 causative of restrictive cardiomyopathy in a mouse model. METHODS: A short hairpin RNA (M7.8L) was selected from a pool for specificity and efficacy. Two groups of myosin regulatory light chain N47K transgenic mice were injected with M7.8L packaged in adeno-associated virus 9 at 3 days of age and 60 days of age. Mice were subjected to treadmill exercise and echocardiography after treatment to determine maximal oxygen uptake and left ventricular mass. At the end of treatment, heart, lung, liver, and kidney tissue was harvested to determine viral tropism and for transcriptomic and proteomic analysis. Cardiomyocytes were isolated for single-cell studies. RESULTS: A one-time injection of AAV9-M7.8L RNAi in 3-day-old humanized regulatory light chain mutant transgenic mice silenced the mutated allele (RLC-47K) with minimal effects on the normal allele (RLC-47N) assayed at 16 weeks postinjection. AAV9-M7.8L RNAi suppressed the expression of hypertrophic biomarkers, reduced heart weight, and attenuated a pathological increase in left ventricular mass. Single adult cardiac myocytes from mice treated with AAV9-M7.8L showed partial restoration of contraction, relaxation, and calcium kinetics. In addition, cardiac stress protein biomarkers, such as calmodulin-dependent protein kinase II and the transcription activator Brg1 were reduced, suggesting recovery toward a healthy myocardium. Transcriptome analyses further revealed no significant changes of argonaute (AGO1, AGO2) and endoribonuclease dicer (DICER1) transcripts, and endogenous microRNAs were preserved, suggesting that the RNAi pathway was not saturated. CONCLUSIONS: Our results show the feasibility, efficacy, and safety of RNAi therapeutics directed towards human restrictive cardiomyopathy. This is a promising step toward targeted therapy for a prevalent human disease.

Novel drugs targeting transthyretin amyloidosis.

Transthyretin amyloidosis (ATTR) is either a hereditary disease related to a mutation in the transthyretin gene that leads to neuropathy and/or cardiomyopathy or an acquired disease of the elderly that leads to restrictive cardiomyopathy. The prevalence of this disease is higher than once thought and awareness is likely to increase amongst physicians and in particular cardiologists. Until recently there have been no treatment options for this disease except to treat the heart failure with diuretics and the neuropathy symptomatically. However, there are several emerging pharmacologic therapies designed to slow or stop the progression of ATTR. This article reviews novel therapeutic drugs that work at different points in the pathogenesis of this disease attempting to change its natural history and improve outcomes.

[Gender effect on cardiomyopathy]. / "Effetto donna" nelle cardiomiopatie.

The role of a gender effect (that means differences in clinical manifestations, access to therapies and response to treatments according to gender) in cardiomyopathies remains a matter of debate. Although recent studies have evaluated the differences in the clinical features and prognosis between the two sexes, many issues remain to be elucidated. At present, the only sex-specific condition that affects females is peripartum cardiomyopathy. Recent evidence suggests a pathogenetic role of a prolactin derivative, and ongoing clinical trials are investigating the possibility of targeted therapies using prolactin secretion inhibitors, such as bromocriptine and carbegoline. Although women were considered so far only carriers of X-linked diseases (Anderson-Fabry disease, Danon disease, Hunter syndrome and dystrophinopathies), clinical experience showed a wide spectrum of clinical manifestations in females due to random X chromosome inactivation. Conversely, in mitochondrial diseases (with matrilineal inheritance), cardiomyopathies may occur in the context of clinical multisystemic involvement without significant gender-related differences. Autosomal inherited cardiomyopathies also show different phenotypes and prognostic impact according to gender. The hypothesis of a premenopausal protective role of female hormones towards myocardial involvement has been raised by recent data on transtiretin-related amyloidosis and hypertrophic cardiomyopathy. Preexisting cardiomyopathies may affect pregnancy, labor and delivery in women, since all these conditions are associated with important hemodynamic changes. Women with low-risk hypertrophic cardiomyopathy (asymptomatic and without left ventricular outflow tract gradient) usually can tolerate pregnancy. Conversely, women who are symptomatic before pregnancy or have severe hypertrophy with important outflow tract gradient are at higher risk and should be referred to a tertiary center to be evaluated on a case by case basis. Pregnancy in women with dilated cardiomyopathy and significant left ventricular systolic dysfunction represents a high-risk condition. In addition, information on the clinical course and potential complications in pregnant women with arrhythmogenic right ventricular cardiomyopathy or restrictive cardiomyopathy is limited to individual reports.

[Anesthetic management for mitral valve replacement in a patient with idiopathic hypereosinophilic syndrome].

We have experienced anesthetic management for mitral valve replacement in a 48-year-old female with idiopathic hypereosinophilic syndrome. Preoperative examination showed mild biventricular dysfunction. Anesthesia was induced and maintained with meticulous administration of fentanyl and midazolam in 66% oxygen. Administration of dopamine, dobutamine and prostaglandin E1 contributed to reducing afterload and maintaining cardiac output. The operative and postoperative courses were uneventful. Hypereosinophilic syndrome is one of the identified causes of restrictive cardiomyopathy. Anesthesia for patients with hypereosinophilic syndrome must be carried out carefully, because heart or respiratory failure is the most dangerous complication. In patients with hypereosinophilic syndrome requiring general anesthesia, perioperative steroid cover is advisable. This may reduce or prevent serious lung complications.