Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder characterized by progressive muscular weakness due to the loss of dystrophin. Extracellular Ca2+ flows into the cytoplasm through membrane tears in dystrophin-deficient myofibers, which leads to muscle contracture and necrosis. Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) takes up cytosolic Ca2+ into the sarcoplasmic reticulum (SR), but its activity is decreased in dystrophic muscle. Here, we show that an allosteric SERCA activator, CDN1163, ameliorates dystrophic phenotypes in dystrophin-deficient mdx mice. Administration of CDN1163 prevented exercise-induced muscular damage and restored mitochondrial function. In addition, treatment with CDN1163 for seven weeks enhanced muscular strength and reduced muscular degeneration and fibrosis in mdx mice. Our findings provide preclinical proof-of-concept evidence that pharmacological activation of SERCA could be a promising therapeutic strategy for DMD. Moreover, CDN1163 improved muscular strength surprisingly in wild-type mice, which may pave the new way for the treatment of muscular dysfunction.

Understanding the signaling pathways that regulate proliferation and differentiation of muscle progenitors is essential for successful cell transplantation for treatment of Duchenne muscular dystrophy. Here, we report that a γ-secretase inhibitor, DAPT (N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine tertial butyl ester), which inhibits the release of NICD (Notch intercellular domain), promotes the fusion of human muscle progenitors in vitro and improves their engraftment in the tibialis anterior muscle of immune-deficient mice. Gene expression analysis revealed that DAPT severely down-regulates PTGER2, which encodes prostaglandin (PG) E2 receptor 2 (EP2), in human muscle progenitors in the differentiation condition. Functional analysis suggested that Notch signaling inhibits differentiation and promotes self-renewal of human muscle progenitors via PGE2/EP2 signaling in a cAMP/ PKA-independent manner.

Mesenchymal stem cells (MSCs) are multipotent stem cells that can be isolated from both foetal and adult tissues. Several groups demonstrated that transplantation of MSCs promoted the regeneration of skeletal muscle and ameliorated muscular dystrophy in animal models. Mesenchymal stem cells in skeletal muscle, also known as fibro-adipogenic progenitors (FAPs), are essential for the maintenance of skeletal muscle. Importantly, they contribute to fibrosis and fat accumulation in dystrophic muscle. Therefore, MSCs in muscle are a pharmacological target for the treatment of muscular dystrophies. In this chapter, we briefly update the knowledge on mesenchymal stem/progenitor cells and discuss their therapeutic potential as a regenerative medicine treatment of Duchenne muscular dystrophy.