Emerging gene editing strategies for Duchenne muscular dystrophy targeting stem cells

Abstract

The progressive loss of muscle mass characteristic of many muscular dystrophies impairs the efficacy of most of the gene and molecular therapies currently being pursued for the treatment of those disorders. It is becoming increasingly evident that a therapeutic application, to be effective, needs to target not only mature myofibers, but also muscle progenitors cells or muscle stem cells able to form new muscle tissue and to restore myofibers lost as the result of the diseases or during normal homeostasis so as to guarantee effective and lost lasting effects. Correction of the genetic defect using oligodeoxynucleotides (ODNs) or engineered nucleases holds great potential for the treatment of many of the musculoskeletal disorders. The encouraging results obtained by studying in vitro systems and model organisms have set the groundwork for what is likely to become an emerging field in the area of molecular and regenerative medicine. Furthermore, the ability to isolate and expand from patients various types of muscle progenitor cells capable of committing to the myogenic lineage provides the opportunity to establish cell lines that can be used for transplantation following ex vivo manipulation and expansion. The purpose of this article is to provide a perspective on approaches aimed at correcting the genetic defect using gene editing strategies and currently under development for the treatment of Duchenne muscular dystrophy (DMD), the most sever of the neuromuscular disorders. Emphasis will be placed on describing the potential of using the patient own stem cell as source of transplantation and the challenges that gene editing technologies face in the field of regenerative biology.

Skeletal muscle satellite cells: Mediators of muscle growth during development and implications for developmental disorders

“…Most interestingly, somewhat similar to the ECM changes in CP, there are marked fibrotic changes in DMD patients' muscles and in transgenic mouse models . Currently, novel therapies targeting muscle stem cell dysfunction are being evaluated as a means to improve muscle function in dystrophies . Recently, focal treatment in mdx mice with Wnt7a was shown to result in structural improvements, such as increased SC number and fiber hypertrophy .…”

“…110,112,113 Currently, novel therapies targeting muscle stem cell dysfunction are being evaluated as a means to improve muscle function in dystrophies. [114][115][116] Recently, focal treatment in mdx mice with Wnt7a was shown to result in structural improvements, such as increased SC number and fiber hypertrophy. 114 In addition, as would be expected, antifibrotic therapies can improve muscle function by reducing fibrosis and improving muscle regeneration capacity.…”

Engraftment potential of dermal fibroblasts following in vivo myogenic conversion in immunocompetent dystrophic skeletal muscle

“… 19 It will additionally be important in all genetic correction strategies to apply recent advances in gene editing and vector technologies that may, for example, allow human autologous cells to carry full-length dystrophin. 4 , 32 …”

“… 3 Many cell types have been explored for their potential to contribute to skeletal muscle in the context of muscle wasting disorders. 4 While engraftment has been demonstrated, efficiency is reduced due to immune clearance, hypoxia, apoptosis, and minimal migration from the site of injection. 5 Cell source also remains an issue; for example, muscle-derived satellite cells are difficult to isolate and expand, and cells from dystrophic tissue may have intrinsic properties, such as low population doubling capacities and precocious differentiation, that limit their therapeutic applications.…”

Prosurvival Factors Improve Functional Engraftment of Myogenically Converted Dermal Cells into Dystrophic Skeletal Muscle

“…A wide variety of cells have been tested for their ability to engraft in skeletal muscle, supply dystrophin, improve contractile properties, and participate in regeneration [4]. Patient-derived, or autologous cells are attractive due to better immunological compatibility than donor-derived cells, but autologous cells must be accessible and of sufficient quantity for feasible creation of a therapeutic cell population.…”