MICA: Strategy for heart repair in Duchenne Muscular Dystrophy (DMD) using genetically engineered autologous Mesoangioblasts

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The NHS official website indicates that around 70,000 people have Muscular Dystrophy (MD) or a related condition in the UK. Duchenne Muscular Dystrophy (DMD) is the most common and one of the most severe forms of MD. DMD is an inherited disease due to lack of expression of the dystrophin protein, causing a progressive waste of skeletal muscle which lead to progressive loss of ambulation, muscle weakness and muscle wasting in children. In the most severe cases, also heart muscle cells are affected, and this result in heart failure, the most common cause of premature death in DMD patients. All MDs still lack an effective therapy, even though administration of steroids (although with severe adverse effects), corrective surgery, assisted ventilation and drugs to support cardiac function have improved both the duration and the quality of life for patients.Many approaches based on either stem cells or gene therapy have entered clinical experimentation with the aim of repairing DMD heart, but none has reached significant clinical efficacy. The limited success of these therapies is due both to the difficulties of delivering the treatment to the heart and to the activation of the immune system of the patients towards donor cells or viral vectors. To overcome these limitations, I have developed a cell mediated exon skipping strategy, for skeletal muscle, currently being tested in a clinical trial in Manchester (EudrAct n.2019-001825-28), based upon transplantation of autologous Mesoangioblasts (Mabs), which are vessel-associated myogenic progenitors. Mabs are genetically corrected using a lentivector expressing a small nuclear RNA (snRNA) designed to induce exon-skipping on dystrophin exon 51 and to generate a short but functional version of dystrophin. The novelty of this approach is based on the ability of snRNA to diffuse along the regenerating muscle fibre and then correcting the resident dystrophic neighbouring nuclei inducing exon skipping. However, Mabs can be used only for the treatment of skeletal muscle as they cannot naturally differentiate into cardiac muscle: for this reason, the heart of the MD patients would remain untreated. In this project I will address this problem. It is well known that fibroblasts can be converted to cardiac muscle cells but, in comparison with Mabs, they cannot be delivered systematically, due to their inability to cross the vessel walls. This makes cardiac-converted fibroblasts good candidates to treat only localised lesions like myocardial infarct but not to treat progressive and widespread cardiomyopathies. My preliminary data show that Mabs can be converted to cardiomyocytes by transient over-expression of specific cardiac related genes in around 10-15 days. I therefore hypothesize that this time window will allow to deliver these Mabs-converted cardiomyocytes by cardiac catheterization in the whole heart. This project aims to evaluate the structural and functional amelioration of the heart in a mouse model of DMD after transplantation of Mabs-converted cardiomyocytes. Moreover, I will quantify the extent of the fusion of genetically corrected Mabs-converted cardiomyocytes with resident cardiomyocytes and subsequently the rate of correction, by exon-skipping, in the neighbouring nuclei quantifying the amount of dystrophin produced.The core element of this strategy is already in clinical experimentation for DMD skeletal muscle but not for the heart. This project will test the applicability of the cell mediated exon-skipping strategy to the heart. The succesful outcome of this project, demonstrating the efficacy of this strategy, will lead the way for a future clinical testing of this strategy in the heart of DMD patients and in heart diseases in general.