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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - MIRAGE (MicroRNAs as therapeutic targets for ARVC.)

Teaser

Summary

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic cardiac disease mainly characterised by the progressive substitution of the myocardium with fatty or fibro-fatty tissue. Although initially thought to be rare, ARVC is the second most common cause of unexpected sudden death in the young and may account for as many as 22,4% of sudden death among athletes. Clinically, ARVC is characterised by ventricular arrhythmias, often associated with syncope and sudden cardiac death, which can be its first manifestation, and shows wide heterogeneity, with inter- and intra-familial variability, ranging from benign to malignant forms. This wide clinical spectrum complicates the diagnosis of the disease, making the identification of at risk subjects difficult. Moreover, as a cause of sudden death, ARVC has devastating psychosocial and economic consequences as many victims are relatively young adults in their productive years of life. Despite the fact that the disease has been described almost thirty years ago, the pathogenic mechanisms leading to its development have not been elucidated yet. The understanding of the molecular dynamics related to this deadly disease and the improvement of its diagnosis, hence, is crucial. Together with modifier genes, common sequence variants, and environmental as well as endogenous factors (e.g., age, gender), epigenetic mechanisms are hypothesised to account for a large part of the variation between individuals. It is clear that epigenetic modifiers, such as RNA-based mechanisms, are molecular targets for disadvantageous environmental stimuli and may lead to the onset of complex and heterogeneous diseases such as ARVC. MicroRNAs (miRNAs) are a class of short, approximately 22 nucleotides, non-coding RNAs that switch off their target gene under different stimuli. Compelling evidence shows that distinct forms of heart failure are characterised by specific miRNA mechanisms, opening new treatment paradigms aimed at pivotal miRNAs for each heart failure stratum. It has been estimated that the human heart expresses more than 800 miRNAs. For ARVC, no study has reported cardiac tissue miRNA involvement that may provide insights into the specifics of the disease. The overall objective of this study is to provide new insights to study the disease mechanisms underlying the development of ARVC and to identify novel RNA-based targets in mouse models and ARVC patients. To reach this aim, we analysed both the RNA from the heart of a transgenic mouse model for ARVC overexpressing a mutation in DSG2 gene found in a human patient as well as the RNA from ARVC patientsâ€™ plasma. In order to take into account biological gender differences, an equal number of samples (both from transgenic male and female mice and humans) was chosen. We were able to determine the cardiac and circulating miRNA profiling associated with ARVC, thus opening the venue to further investigation on ARVC. The results obtained in this study provide new insights in understanding the pathogenesis of the disease and in the development of novel tailored RNA-based drugs that take into account the diversity of the patients affected with different cardiac diseases. Moreover, our data on circulating miRNAs will be used to define novel non-invasive biomarkers that will improve the complicated diagnosis of the disease.

Work performed

In the context of our project, we provided an inventory of miRNAs that are differentially expressed in hearts from the ARVC transgenic mouse model. These data will be used in other studies not only as starting point to identify genes involved in the pathogenesis of the disease, but also in the pharmaceutical field. Indeed, recent reports showed that the expression of miRNAs can be modulated with inhibitors (antagomirs) or mimics, thus leading to an improvement of the pathogenic condition. Hence, in collaboration with Cristal Therapeutics and Mirabilis Therapeutics BV, both biotech companies in Maastricht, we investigated different cardiac-specific delivery systems of these RNA-based drugs. The progress made within this project will help in the development of novel tailored therapeutic approaches which will take into account the genetic diversity of ARVC patients.
As remarkably stable molecules in body fluids, like the bloodstream, circulating miRNAs have the potential of being used as biomarkers for several pathophysiological conditions, including ARVC. Accordingly, in collaboration with Prof. T. Thum from Hannover, we investigated the value of circulating miRNAs as diagnostic biomarkers in a clinical cohort of ARVC patients. These results will be compared with data obtained from studies in cohorts of patients affected with other cardiovascular diseases and will help in supporting the complex ARVC diagnosis, patient stratification and treatment monitoring.
The obtained results have already been presented at both scientific and non scientific national and international meetings, and will be further disseminated in the very next future with the progression of the study, thus reaching a significant number of users working in different sectors as well as a broader public.

Final results

ARVC is one of the major causes of sudden death in young people, with adverse consequences in the psychosocial field. The knowledge on its pathogenesis is still limited and therefore there is a great need to unravel the events leading to its development. The definition of the miRNA profiling in transgenic ARVC hearts not only revealed new factors involved in the progression of the disease, but also enables novel studies focused on the discernment of the pathogenic mechanisms. Moreover, the provided ARVC microRNA signature will allow identifying RNA-based therapeutic targets. This has a strong impact in the management of the disease, since nowadays the therapy still consists on palliative anti-arrhythmic drugs, such as beta-blockers, sotalol, mexiletine, and amiodarone, or more invasive interventions, such as the implantation of a cardioverter defibrillator or the catheter ablation, which are used also to treat other cardiac diseases. As ultimate benefit, then, our results will help to abandon the one-size-fits-all approach adopted to treat cardiopathic patients and to stratify them by their underlying pathophysiology.
Another aspect regards the diagnosis of ARVC, which is still difficult to perform. Therefore, there is a great need to develop novel diagnostic tools for the stratification and monitoring of ARVC patients. The identification of circulating miRNAs as non-invasive diagnostic biomarkers in clinical cohorts of ARVC has the potential to improve the diagnostic criteria increasing their specificity and sensitivity, especially in detecting early disease or identifying affected relatives of probands, thus reducing the incidence of early mortality. Taken together, our results have the potential to improve life expectancy and quality of life and by achieving an improvement of treatment outcomes and a reduced need for complex interventions (e.g. heart transplantation) will lead to a marked decrease in healthcare costs and improve the healthcare systems sustainability.