Research Assistant The University of Hong Kong, Hong Kong
Abstract: Dystrophinopathy, caused by DMD gene mutations, include Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). DMD presents with severe progressive skeletal muscle weakness, while BMD is milder. Both conditions can lead to early-onset cardiomyopathy and severe heart failure. Increase histone deacetylase (HDAC) activity in dystrophinopathy causes epigenetic changes that inhibit muscle regeneration and promote chronic inflammation, fibrosis and adipogenesis. The HDAC inhibitor Givinostat, has shown promise as a treatment, with preclinical and clinical studies demonstrating its positive impact on DMD skeletal muscle pathology. A phase 3 clinical trial in ambulatory DMD boys aged 6 years and older showed that Givinostat significantly delayed motor deterioration. It has been approved by the US FDA for treating DMD patients aged 6 years and older. However, data on the cardiac effects of Givinostat are limited. In this study, we established integration-free induced pluripotent stem cell (iPSC) lines from 2 patients with BMD and 2 healthy subjects. Both patients have mild skeletal muscle weakness but experienced early-onset of severe cardiomyopathy and heart failure, necessitating heart transplantation. We differentiated the patient-derived iPSC into cardiomyocytes (iPSC-CM) for pathological and functional characterization, and drug screening with Givinostat. Our patient-derived iPSC-CMs showed reduced dystrophin expression, increase cell membrane fragility with significantly elevated ATP and creatine kinase release after hypotonic challenge, and impaired calcium handling properties. Givinostat treatment restored intracellular calcium transient properties in the patient-derived iPSC-CMs, shortening calcium transient duration and accelerated time to peak and time of decay in a dose-dependent manner. However, higher doses were associated with irregular heartbeats. In summary, we found that the HDAC inhibitor Givinostat, had a potential positive functional impact on cardiac pathology of dystrophinopathy using our patient-derived iPSC-CM model. We will continue to investigate the epigenetic mechanisms using single-cell ATAC-seq and paired single-cell RNA-seq to explore Givinostat's genetic regulation of its cardiac effect in dystrophinopathy.
Funding Source: GRF grant (Ref: 17123122) Dystrophinopathy patient-derived iPSC disease model for novel epigenetic mechanisms evaluation and advancing small molecules therapies development (2022-ongoing)
