Expansion Of Muscle-Derived Stem Cells:Implications of Cell Therapy For Muscle Regeneration

Key to advancing stem cell utilization in regenerative medicine and cell-based therapies is the development of systems to expand cells to clinically relevant numbers while maintaining the desired stem cell phenotype. Mathematical growth models play an important role in developing standardized systems, as they are both predictive tools for expansion potential and tools to describe current kinetic parameters of a stem cell population. One disease that may benefit from cell therapy is Duchenne Muscular Dystrophy (DMD), a muscle disease characterized by the lack of dystrophin expression at the sarcolemma of muscle fibers resulting in muscle fiber necrosis and muscle weakness. While transplantation of normal myoblasts into dystrophin-deficient muscle can restore dystrophin, the use of muscle-derived stem cells (MDSC) has enhanced the success of cell transplantation. For these reasons, muscle stem cell isolation and the development of transplantation techniques have garnered increased attention recently. One limitation of MDSC use is the few numbers of cells available from a muscle biopsy, thus presenting the requirement for in vitro expansion. The overall goal of this study was to provide a thorough quantitative examination of the expansion of MDSC populations. In this project, an imaging system was established to analyze stem cell expansion. The applicability of this system was demonstrated in MDSC expansion with cytokine stimulation. It was found that accounting for the proliferative heterogeneity that exists in stem cell populations would allow for more accurate estimations of kinetic parameters. Next, a more sophisticated imaging system was used to further develop an automated system for analysis of MDSC proliferation and behavioral characterization. Finally, an understanding of the limits of expansion was explored. The role of long-term expansion on stem cell phenotype and regeneration capacity was examined to consider the issue of quantity vs. quality of muscle-derived stem cells. This study provided a systematic method for assessing expansion and an in-depth investigation into the natural progression of stem cell expansion. It is expected that these findings will provide a biological understanding of the limits of expansion and a foundation for more standardized methods of expansion of MDSC as MDSC are advanced to a clinical setting