A NOVEL THERAPEUTIC PROTOCOL TO CORRECT MUSCULAR DYSTROPHIES BY ENGINEREED MESOANGIOBLASTS: FROM CHROMATIN SIGNALS TO MUSCLE REGENERATION

Cell therapy is one promising approach to correct genetic diseases by contributing to tissue regeneration; however, most of the attempts to achieve successful repopulation of diseased organs by cell transplantation in animal models produced disappointing results; this was mainly due to the failure of injected cells to survive in the recipient animals and successfully engraft within their target organs. A considerable number of studies recently attempted to develop alternative strategies to improve the effectiveness of cell-mediated therapy, including protocols aimed at increasing in vitro expansion of the cell population to be transplanted and their homing to target organs upon injection. The recent identification of different types of multi-potent stem cells, some of which can be expanded in vitro, and are therefore suitable for protocols of organ regeneration, has disclosed new perspectives in cell therapy for genetic diseases. A preliminary study indicates that a recently identified population of stem cells - the mesoangioblasts - produce functional improvement upon intra-arterial injection in an animal model of muscular dystrophy. However, the efficiency of mesoangioblasts to “normalize” diseased muscles and restore their function in several animal models of muscular dystrophy remains unexplored and is complicated by the limited knowledge of the signals that regulate stem cell proliferation and differentiation, as well as their survival and muscle homing upon transplantation. Independent lines of research have revealed a critical role of Insulin Growth Factor 1 IGF-1 in enhancing muscle regeneration in normal and dystrophic mice. Other studies attempting to uncover the signals that regulate the expression of muscle-specific genes have identified acetylation of histones and of myogenic regulatory factors as an essential regulatory signal and, based on this evidence a class of compounds - the deacetylase inhibitors - has been shown to enhance muscle differerentiation. Finally, localized production of Nitric Oxide, has been shown to be crucial in order to maintain blood supply to muscle and couple exercise with energy demand. To this aim, both normal and dystrophic mesoangioblasts from two mouse models of Duchenne and Limb-Girdle Muscular Dystrophy will be treated in vitro to optimize their ability to survive and propagate while acquiring a myogenic phenotype, and eventually differentiate into mature muscle cells. Dystrophic mesoangioblasts will also be genetically corrected in vitro by replacement of the diseased with the normal gene. Cells will be intra-arterially delivered to dystrophic muscle that will have been treated with the same agents to favor engraftment of donor cells (TSA, IGF-1, NO). Functional morhological, and biochemical analysis of transplanted muscles will be carried out to test the extent of amelioration of the dystrophic phenotype under the various experimental conditions in order to define the best experimental protocol. The ultimate goal of such a project is to verify the suitability of this protocol for future applications in human patients.