Inhibiting EZH2 complements steroid effects in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a devastating X-linked disorder caused by mutations in the dystrophin gene. Despite recent advances in understanding the disease etiology and applying emerging treatment methodologies, glucocorticoid derivatives remain the only general therapeutic option that can slow disease development. However, the precise molecular mechanism of glucocorticoid action remains unclear, and there is still need for additional remedies to complement the treatment. Here, using single-nucleus RNA-sequencing and spatial transcriptome analyses of human and mouse muscles, we investigated pathogenic features in DMD patients and palliative effects of glucocorticoids. Our approach further illuminated the importance of proliferating satellite cells, and revealed increased activity of a signal transduction pathway involving EZH2 in the patient cells. Subsequent administration of EZH2 inhibitors to Dmd mutant mice resulted in improved muscle phenotype through maintaining the immune-suppressing effect but overriding the muscle weakness and fibrogenic effects exerted by glucocorticoids. Our analysis reveals pathogenic mechanisms that can be readily targeted by extant therapeutic options for DMD. Muscle biopsies from patients were performed in accordance with informed written consent from Seoul National Hospital Children’s Hospital institutional review board (IRB)-approved protocols (#1009-030-331). The patients did not take any medication at the time of the biopsy. Muscle samples were taken from the quadriceps femoris and frozen with isopentane cooled in liquid nitrogen. Healthy muscle samples were acquired from the quadriceps or abdomen of subjects undergoing surgery for non-muscular symptoms. snRNA-seq was performed on fresh frozen quadriceps femoris obtained from three male individuals with DMD, three male individuals with BMD, and five healthy control subjects. Among the control samples, three were derived from abdominal muscle tissue undergoing surgery for non-muscular symptoms. All participants were under the age of 17, and each group was composed of individuals of similar ages.