Stem cell-targeted CRISPR gene editing restores dystrophin levels in DMD micePublished: September 20, 2019
Researchers at the University of Missouri School of Medicine uses CRISPR/Cas9-mediated genome editing in muscle stem cells to restore dystrophin levels in Duchenne Muscular Dystrophy (DMD) mice models. Clinical translation of the approach would provide the means for continuous dystrophin expression in regenerated muscle cells.
DMD, the most commonly inherited neuromuscular disease, is a progressive, X-linked degenerative disorder caused by the absence of dystrophin. There is no curative treatment for DMD and there has been significant progress in developing gene replacement therapies over the last decade.
CRISPR/Cas9-mediated genome editing has emerged lately as a promising approach to treat human diseases. In this approach, Cas9 endonuclease is directed to the intended location by guide RNA (gRNA) to create a double-strand break followed by DNA repair at target site.
Delivery of CRISPR genome-editing tools by AAV has been previously tested and has provided encouraging results in restoring dystrophin expression in DMD patient cells in vitro and in mouse models in vivo. However, achieving persistent and long-term expression has been a problem.
In the present study published in Molecular Therapy, Dr Dongsheng Duan and team at the University of Missouri School of Medicine tested whether they could perform CRISPR-mediated gene editing on muscle stem cells (MuSCs), which they hypothesized could not only correct inherent dystrophin deficiency in these cells but also produce dystrophin-positive progeny myofibers. Myofiber degeneration leading to muscle wasting is a hallmark of DMD and myofibers are regenerated from MuSCs.
To test if MuSCs could be edited, they edited the dystrophin gene in MuSCs and transplanted the treated muscle into immune-deficient mice. The transplanted muscle died first, but then regenerated from its stem cells and abundant edited cells were observed in the regenerated muscle.
They then tested if muscle stem cells in a mouse model of DMD could be edited with CRISPR. Similar to what they observed in normal muscle, the stem cells in the diseased muscle were also edited. Cells regenerated from these edited cells successfully produced dystrophin.
Findings from the study provide evidence that muscle stem cells could be successfully edited to restore dystrophin and provide long-term persistence of the protein. With further optimization of the approach, the team is hopeful that this AAV-based MuSC editing may one day be used to treat human DMD patients.
Dr Duan commented: “This finding suggests that CRISPR gene editing may provide a method for lifelong correction of the genetic mutation in DMD and potentially other muscle diseases. Our research shows that CRISPR can be used to effectively edit the stem cells responsible for muscle regeneration. The ability to treat the stem cells that are responsible for maintaining muscle growth may pave the way for a one-time treatment that can provide a source of gene-edited cells throughout a patient’s life.”