Nerve Repair through Muscle Progenitor Cell Transplantation

描述（由申请人提供）：从骨骼肌中分离的肌肉祖细胞（MPC）已被证明是多能的，并且对于修复肌肉骨骼系统的各种组织（包括骨骼肌和心肌、骨和关节软骨）具有显著的治疗价值，但尚未充分研究它们进行神经源性分化的能力。我们最近观察到小鼠和人的MPC能够在体外和体内经历神经原性和胶质细胞分化，并诱导小鼠坐骨神经缺损的功能愈合。通过组织学和免疫组织化学分析确定的修复过程也通过功能测定（坐骨神经功能指数）进行了验证。虽然我们已经报道了鼠MPCs（mMPCs）和人MPCs（hMPCs）通过分化成神经胶质细胞促进轴突向内生长，但很可能， 使用支架将注射的细胞固定在损伤部位可以进一步促进神经修复。由于我们最近表明，使用细胞片作为干细胞递送载体，将细胞固定在损伤部位，进一步改善了干细胞对损伤心脏和韧带组织的有益作用，因此我们建议表征是否可以通过使用由MPC组成的细胞片来增强神经修复过程（目标#1）。 由于我们已经观察到MPC在各种组织中的再生潜力与细胞诱导血管生成的能力相关，我们认为类似的机制可以解释MPC在神经修复中赋予的有益作用。事实上，已经观察到VEGF施用可以通过血管生成过程支持再生神经纤维的生长;此外，骨髓移植对神经修复的有益作用似乎是通过分泌促进轴突血管生成的各种营养因子而发生的。我们建议通过使用表达VEGF和sFlt-1的MPC的功能获得和丧失实验来确定血管生成在神经愈合过程中发挥的影响（目标#2）。这些目标的成功完成不仅将为MPC移植改善神经愈合的功效的定量证据提供令人兴奋的结果，而且还可以阐明祖细胞与神经损伤部位的微环境（特别是通过血管生成）相互作用的作用机制。

DESCRIPTION (provided by applicant): Muscle Progenitor Cells (MPCs) isolated from skeletal muscle have been shown to be both multipotent and of significant therapeutic value for the repair of various tissues of the musculoskeletal system, including skeletal and cardiac muscles, bone and articular cartilage, yet their ability to undergo neurogenic differentiation has not been fully investigated. We have recently observed that mice and human MPCs are capable of undergoing in vitro and in vivo neurogenic and glial cell differentiation, and inducing functionl healing of sciatic nerve defects in mice. The repair process, determined by histological and immunohistochemical analyses, were also validated by a functional assay (sciatic functional index). Although we have reported that both murine MPCs (mMPCs) and human MPCs (hMPCs) promoted axonal in-growth through their differentiation into glial cells, it is likely that the use of a scaffold to immobilize the injected cells at the injury site could further promote nerve repair. Since we have recently shown that the use of cell sheets as a stem cell delivery vehicle, which immobilizes the cells at the site of injury, further improved the beneficial effect imparted by the stem cells on the injured cardiac and ligamentous tissues, we are proposing to characterize whether the nerve repair process could be enhanced, through the use of a cell sheet comprised of MPCs (Aim #1). Since we have observed that the regenerative potential of MPCs in various tissues correlates with the ability of the cells to induce angiogenesis, we posit that a similar mechanism may explain the beneficial effect imparted by the MPCs in nerve repair. Indeed, it has been observed that VEGF administration can support the growth of regenerating nerve fibers through the process of angiogenesis; moreover, the beneficial effect imparted by bone marrow transplantation on nerve repair appears to occur through the secretion of various trophic factors that promote axon angiogenesis. We are proposing to determine the influence that angiogenesis plays in the nerve healing process (Aim #2) through gain and loss of function experiments using VEGF and sFlt-1 expressing MPCs. Successful completion of these aims will not only provide exciting results for quantitative evidence of the efficacy of MPC transplantation to improve nerve healing, but could also shed light on the mechanism(s) of action by which progenitor cells interact with the microenvironment (especially via angiogenesis) at the site of nerve injury.