Myeloid-cell mediated mechanisms driving muscle growth and regeneration

描述（由申请人提供）：我们的研究目标是了解免疫系统和骨骼肌之间的相互作用，这在调节肌肉修复，生长和再生中很重要。通过更好地了解这些关系，可以设计免疫系统或其产品的治疗性操作，以改善急性创伤，废弃或慢性疾病后的肌肉生长和再生。在过去的几年里，这一领域的知识有了长足的进步，表明免疫细胞M2巨噬细胞在肌肉生长和再生中起着重要作用。然而，驱动再生的特定M2巨噬细胞衍生分子的身份仍然未知。我们提出验证M2巨噬细胞产生的蛋白Klotho对损伤后肌肉的正常生长和再生至关重要的新假设。此外，我们将开发一种新的基于细胞的机制，将Klotho“按需”靶向受伤肌肉，以便在肌肉再生的位置和时间特异性地提高治疗蛋白的表达。我们建议在小鼠中使用急性肌肉损伤模型来解决以下目标：目的1：验证基因或药物干预调节Klotho水平影响肌肉再生的假设。我们将通过表达Klotho转基因、切除Klotho基因、移植来自Klotho转基因小鼠的骨髓源性细胞（bmc）和给予Klotho蛋白来控制肌肉损伤小鼠的Klotho水平。小鼠将通过分子、生理和形态学分析来评估改良Klotho水平对肌肉生长和再生的影响。目的2：验证Klotho调节肌肉损伤后炎性细胞从促炎性M1巨噬细胞向促再生M2巨噬细胞转变的假设。我们将测试基因或药理学操作是否会影响肌肉损伤后巨噬细胞的表型或功能。目标3。验证骨髓细胞可以在再生过程中靶向Klotho表达升高的损伤肌肉的假设。我们将产生一种转基因小鼠系，其中Klotho的表达是由炎症背景下髓细胞中高度激活的启动子驱动的，然后检测从这些小鼠中移植bmc是否促进受体受伤肌肉的生长和再生。我们预计这些发现将确立Klotho在促进受伤肌肉生长和再生中的重要性。我们还相信，这项工作可以为一种新的、基于细胞的治疗性分子递送到损伤部位和修复提供基础，这可能具有超越肌肉损伤治疗的意义。

DESCRIPTION (provided by applicant): A goal of our research is to understand interactions between the immune system and skeletal muscle that are important in regulating muscle repair, growth and regeneration. By better understanding these relationships, therapeutic manipulations of the immune system or its products can be designed to improve muscle growth and regeneration following acute trauma, disuse or chronic disease. Over the last several years, knowledge in this area has advanced substantially, showing that immune cells called M2 macrophages play a major role in muscle growth and regeneration. However, the identity of the specific, M2 macrophage-derived molecules that drive regeneration remains unknown. We propose to test the novel hypothesis that the protein Klotho generated by M2 macrophages is essential for normal growth and regeneration of muscle following injury. In addition, we will develop a novel, cell-based mechanism for targeting Klotho to injured muscle "on demand," so that expression of the therapeutic protein is elevated specifically at the location and time of muscle regeneration. We propose to use an acute, muscle-injury model in mice to address the following aims: Aim 1: Test the hypothesis that genetic or pharmacological interventions that modulate Klotho levels affect muscle regeneration. We will manipulate Klotho levels in mice that experience muscle injury by expressing a Klotho transgene, by ablating the Klotho gene, by transplanting bone marrow-derived cells (BMCs) from Klotho transgenic mice and by administering Klotho protein. Mice will be assessed by molecular, physiological and morphological assays to determine the effects of modified Klotho levels on muscle growth and regeneration. Aim 2: Test the hypothesis that Klotho modulates shifts in inflammatory cells from pro-inflammatory M1 macrophages to pro-regenerative M2 macrophages following muscle injury. We will test whether genetic or pharmacological manipulations of Klotho affect macrophage phenotype or function following muscle injury. Aim 3. Test the hypothesis that myeloid cells can be designed to target elevated Klotho expression to injured muscle during regeneration. We will generate a transgenic mouse line in which Klotho expression is driven by a promoter that is most-highly activated in myeloid cells in the context of inflammation and then assay whether transplanting BMCs from those mice promotes growth and regeneration of injured muscle in the recipients. We anticipate that these findings will establish the importance of Klotho in driving growth and regeneration of injured muscle. We also believe that this work can provide a basis for a new, cell-based delivery of therapeutic molecules to sites of injury and repair that may have significance beyond the treatment of muscle injuries.