21 | Transcriptional and metabolic analyses of cardiac mononucleated cells in dystrophic mdx mice upon treatment with a specific monoamino oxidase B inhibitor

Francesca Fontana^1|2, F.C. Venegas^3|4, E. Baldisseri^3|4, R. Sánchez-Rodríguez^3|4, A. Reggio⁵, A. Palma⁶, M. Canton^3|4, L. Vitiello¹ | ¹Department of Biology, University of Padova, Italy; ²Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Italy; ³Fondazione Istituto di Ricerca Pediatrica Città della Speranza, IRP, Italy; ⁴Department of Biomedical Sciences, University of Padova, Italy; ⁵Saint Camillus International University of Health Sciences, Italy; ⁶Department of Biology and Biotechnologies "Charles Darwin", Sapienza University of Rome, Italy.

Cardiomyopathy is an important cause of morbidity and mortality in Duchenne muscular dystrophy (DMD) patients. Present treatments can alleviate DMD cardiomyopathy, but there are no drugs capable of preventing cardiac tissue remodelling. Oxidative stress and inflammation are crucial players in DMD pathogenesis. The mitochondrial enzyme Monoamine Oxidase B (MAOB) is a key source of ROS, as it catalyzes the oxidative deamination of several amines yielding H₂O₂. In pathological conditions, its activity can overcome the cellular antioxidant defenses, altering the redox homeostasis and eliciting deleterious effects. We recently reported that targeting MAOB with specific inhibitors (iMAOB) can significantly improve skeletal muscle function and decrease inflammation and fibrosis in mdx mice. More recently, we have started to explore the therapeutic potential of iMAOB in relation to DMD cardiomyopathy, treating mdx mice at an age when cardiac disfunction is not yet clinically evident. To this purpose, three-month-old mdx mice were orally treated with iMAOB or vehicle for one month. Myeloid, endothelial and fibro-adipogenic precursor FAP cells were initially analysed via RT-PCR and we found that multiple proinflammatory and pro-fibrotic genes were downregulated by the treatment. We have now expanded our analyses by performing single-cell RNA sequencing onto mononucleated cardiac cells in treated and untreated mdx mice, as well as in wild type animals. Moreover, cardiac mononucleated cells from the same experimental conditions were also sorted by FACS into myeloid, endothelial and FAP/fibroblast sub-populations and these latter were then cultured in vitro and used to assess mitochondrial functionality via Seahorse analysis. Initial results indicate that, as expected, both approaches evidenced clear differences between wild type and mdx hearts, and suggest that the treatment with iMAOB could exert a therapeutic effect both at the transcriptional and at the metabolic level.