Satellite Cells in Muscular Dystrophy – Lost in Polarity

Recent findings employing the mdx mouse model for Duchenne muscular dystrophy (DMD) have revealed that muscle satellite stem cells play a direct role in contributing to disease etiology and progression of DMD, the most common and severe form of muscular dystrophy. Lack of dystrophin expression in DMD has critical consequences in satellite cells including an inability to establish cell polarity, abrogation of asymmetric satellite stem-cell divisions, and failure to enter the myogenic program. Thus, muscle wasting in dystrophic mice is not only caused by myofiber fragility but is exacerbated by intrinsic satellite cell dysfunction leading to impaired regeneration. Despite intense research and clinical efforts, there is still no effective cure for DMD. In this review we highlight recent research advances in DMD and discuss the current state of treatment and, importantly, how we can incorporate satellite cell-targeted therapeutic strategies to correct satellite cell dysfunction in DMD.

TrendsDystrophic muscle stem cells (satellite cells) are intrinsically impaired and directly contribute to DMD progression in mdx mice, demonstrating that DMD is also a stem cell disease.Satellite cells express high levels of dystrophin, which is expressed during cell division to mediate cell polarity. In mdx satellite cells, establishment of polarity is impaired, resulting in the abrogation of asymmetric cell divisions, mitotic abnormalities, and inefficient generation of myogenic progenitors.Recent advances in genome editing, myogenic cell reprogramming, and myogenic progenitor expansion protocols have important implications for genetic and muscle stem cell transplantation therapies.Combinatorial approaches to restore endogenous satellite cell function with therapies that relieve fibrosis and inflammation associated with muscle degeneration may offer a potential cure for DMD.