Cellular modeling of neuromuscular disease and development of therapy

Abstract

Currently, exon skipping using antisense oligonucleotides (ASO) is the most promising treatment for Duchenne muscular dystrophy (DMD), an X–linked severe muscle disorder caused by mutations in the DMD gene. In this context, the screening of efficient ASO sequences before clinical trials is laborious. We have recently reported efficient cellular skeletal muscle modeling of DMD by using myogenic differentiation 1 (MYOD1)–transduced urine–derived cells (MYOD1–UDCs) obtained from DMD patients. However, there are several obstacles to applying this model directly for the screening of exon skipping drugs. First, we have no robust evidence that exon skipping efficacy in vitro reflects the efficacy in vivo. Second, dystrophin restoration levels vary in MYOD1–UDCs due to their cellular heterogeneity. To overcome the obstacles, the DMD subjects enrolled in our ongoing exon 44 skipping trial will be evaluated in two ways : one is using myotubes differentiated from patient–derived myoblasts, fibroblasts and UDCs, and the other is using skeletal muscle tissue from the same patients. Furthermore, we have obtained preliminary data using a single cell analysis of RNAseq in normal human UDCs. As a result, we identified some renal stem cell markers expressed on a specific subpopulation of the UDCs. Further study will be needed to confirm whether those markers could be promising targets of MYOD1–induction and subsequent dystrophin expression.

Simultaneously, we also challenge creating neurons from UDCs by introducing several transcription factors. If successful, our study should pave the way for the development of precision medicine to treat various neuromuscular diseases, including amyotrophic lateral sclerosis, spinal and bulbar muscular atrophy.