We study human muscle development, and are actively investigating potential cell-based therapies for the treatment of degenerative muscle diseases, such as muscle dystrophy. This project will define the pathway that muscle stem cells follow as they form new muscle, and identify which muscle stem cells are most useful for therapy. Our approach will be to examine human embryonic stem cells as they become muscle stem cells and mature muscle in culture, to define the stages of normal muscle development. We will then transplant these stem cells at various stages of development into the leg muscles of mice with muscular dystrophy, and study how these cells become new muscle tissue, how this impacts the animals’ ability to exercise, and the strength of the treated muscles. Our goal for this research is to fully understand the normal process of human muscle stem cell development, and to identify specific stem cells that provide therapeutic benefit when transplanted into dystrophic muscle.
Muscular dystrophies are profoundly debilitating disorders that affect more than 1 in 3,500 male births. They comprise a group of genetic diseases that cause progressive weakness and damage to skeletal muscle resulting from abnormal proteins critical to muscle health. These abnormal proteins are thought to predispose muscle to damage from normal activity, leading to premature depletion of normal muscle stem cells that maintain muscle health during normal use. This research will identify human embryonic stem cells that are able to repair damaged muscle, thereby providing a new approach to therapy for patients with muscle disease. The medical treatments developed as a result of these studies will not only benefit the health of Californians with muscular dystrophy and other degenerative muscle diseases, but also should result in significant savings in health care costs. This research will push the field of muscle regenerative medicine forward despite the paucity of federal funds for embryonic stem cell research, and better prepare us to utilize these funds when they become available in the future.
The goal of this proposal is to define the differentiation pathway of human embryonic stem cells (hESCs) into muscle stem cells and then to mature muscle. Specific stages along this pathway will be related to the in vivo functionality and therapeutic efficacy of these cells in a mouse model of muscular dystrophy. There are two Specific Aims: 1) to utilize genetic constructs and cell surface markers to define the cellular phenotypes of hESC-derived muscle stem cells as they differentiate into muscle cells; and 2) to test the functionality of hESC-derived muscle stem cells in vivo in a mouse model of muscular dystrophy.
Significance and Innovation:
- Muscular dystrophies represent a clear clinical need, and there is genuine potential for a stem cell solution.
- If successful, the project could significantly impact the study of skeletal muscle disease and the clinical use of human muscle cells for cell therapy.
- Reviewers viewed the proposal as high risk but with high potential rewards.
Feasibility and Experimental Design:
- Reviewers considered the project as likely to be feasible, although some aspects may require alternative approaches, which are identified in the application.
- The research plan is focused, logically described and based on sound preliminary data.
- A key strength of the proposal is the array of tools for defining the myogenic pathway that have been developed by the applicant.
- Reviewers noted some minor weaknesses in the experimental design including uncertainty about the specificity of the reporter constructs, possible differences among different cell populations, and a lack of consideration of the possibility of transplanted cells differentiating into other cell lineages in the dystrophic muscle environment.
Principal Investigator (PI) and Research Team:
- The PI has a strong track-record in developing molecular methods for studying stem cell differentiation and is well-published in areas essential for the proposal.
- The PI will be appropriately supported by collaborators with significant expertise in muscle physiology as well as familiarity with the in vivo mouse model and transplantation of cells into that model.
- The research institution provides an excellent environment.
Responsiveness to RFA:
- In some important aspects, the proposal is very responsive to the RFA, as it is focused on defining the myogenic differentiation pathway from hESCs. However, some of the work is marginally responsive, since it involves the identification of markers and cell types rather than elucidation of mechanisms of differentiation or cell engraftment.