THE ROLE OF BCL-2 IN SKELETAL MUSCLE STEM CELLS

成熟骨骼肌的生长或修复依赖于一个小的， 特征不佳的肌源性细胞群，称为卫星细胞 由于它们位于肌纤维周围和肌肉纤维下方 围绕着基膜。受生长因子、压力或 损伤后，这些通常处于静止状态的细胞会增殖、分化和 成为长寿肌肉纤维的稳定组成部分。卫星细胞是 对肌肉动态平衡至关重要，并对肌肉有直接影响 修复、疾病进展和衰老。只有一小部分卫星 细胞具有肌肉干细胞的特征。干细胞产生了 对这两种成肌细胞，它们在有限数量的 分裂，以及更多的自我更新干细胞，保持较高的 核扩散潜力。静止的肌肉干细胞很难 由于数量稀少和缺乏对生化的定义而进行的研究 或分子特征。拟议研究的目标是 确定肌肉干细胞的特征，并利用这些特征 研究干细胞在肌肉生长和修复中的作用，尤其是 关于与肌肉营养不良相关的退行性疾病。近期 研究表明，抑制细胞凋亡的蛋白质，如 BCL-2在多种组织中的自我更新干细胞中均有表达 皮肤、上皮和肠道等组织。我们发现，一个 体外培养的一小部分肌源性细胞表达Bcl-2 与它们作为肌源性干细胞的模式一致。在……里面 此外，我们还发现来自Bcl2基因缺陷动物的卫星细胞 产生的肌肉菌落明显小于它们的 野性的兄弟姐妹。为了扩大这些观察，肌肉细胞将被 在体外和体内进行检测，以确定Bcl-2是否 表达是肌肉干细胞的一个特征。与细胞凋亡相关 基因表达(Bcl2等)也将在MDX小鼠中进行研究， Duchenne肌营养不良症模型的建立 急性退化期，干细胞广泛激活和修复。 将制造出由肌肉驱动的表达Bcl2的转基因小鼠- 特异性MRF4启动子。这些小鼠将与MDX小鼠交配以 确定过表达的Bcl-2是否可以抑制肌肉退变或 影响患病肌肉中干细胞群体的大小。 总而言之，结果应该有助于肌干的鉴定。 细胞，并确定细胞凋亡调节因子在肌肉生长中的作用 和动态平衡。这些信息将大大有助于我们的 对肌肉生物学的了解，并可能导致新的治疗方法 治疗肌肉疾病、肌肉萎缩和更好的策略 基于肌肉的基因治疗方法。

The growth or repair of mature skeletal muscle relies upon a small, poorly characterized population of myogenic cells termed satellite cells due to their location peripheral to muscle fibers and beneath the surrounding basal lamina. Activated by growth factors, stress or injury, these normally quiescent cells proliferate, differentiate, and become a stable part of long-lived muscle fibers. Satellite cells are critical for muscle homeostasis and have a direct impact on muscle repair, disease progression, and aging. Only small subsets of satellite cells have characteristics of muscle stem cells. Stem cells give rise to both myoblasts, which differentiate after a limited number of divisions, as well as more self-renewing stem cells that maintain a high proliferation potential. Quiescent muscle stem cells are difficult to study due to their sparse number and the lack of defining biochemical or molecular features. The objective of the proposed research is to identify characteristic features of muscle stem cells, and use these to study the role of stem cells in muscle growth and repair, particularly with respect to degeneration associated with muscular dystrophy. Recent work suggests that proteins that inhibit apoptotic cell death, such as Bcl-2, are expressed in self-renewing stem cells found in various tissues such as skin epithelium and intestine. We have found that a small subset of myogenic cells grown in vitro expresses Bcl-2 in a pattern consistent with them acting as myogenic stem cells. In addition, we found that satellite cells from Bcl-2-deficient animals give rise to muscle colonies that are significantly smaller than their wild-type siblings. To extend these observations, muscle cells will be examined, both in vitro and in vivo, to determine whether Bcl-2 expression is a characteristic of muscle stem cells. Apoptosis-related gene expression (Bcl-2, and others) will also be studied in mdx mice, a model for Duchenne muscular dystrophy in which muscles undergo an acute phase of degeneration, extensive stem cell activation and repair. Transgenic mice will be made which express Bcl-2 driven by the muscle- specific MRF4 promoter. These mice will be mated with mdx mice to determine if overexpressed Bcl-2 can inhibit muscle degeneration or affect the size of stem cell populations present in diseased muscle. In summary, results should facilitate identification of muscle stem cells and determine the role of apoptosis regulators in muscle growth and homeostasis. Such information will significantly contribute to our understanding of muscle biology, and may lead to new therapeutic strategies for treatment of muscle disorders, muscle atrophy and better methods for muscle-based gene therapy.