BCL-2 AND SKELETAL MUSCLE STEM CELLS

BCL-2 和骨骼肌干细胞

• 批准号: 2794097
• 负责人: Janice A Dominov
• 金额: $ 8.27万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-30 至 2001-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2794097
• 关键词: BCL2 gene /protein; apoptosis; biomarker; cell population study; cell proliferation; embryo /fetus tissue /cell culture; gene expression; genetically modified animals; genotype; immunocytochemistry; laboratory mouse; muscle cells; muscle satellite cell; muscular dystrophy; myoblasts; myogenesis; regeneration; tissue /cell culture

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.

成熟骨骼肌的生长或修复依赖于一个小的、 特征不明的肌源细胞群，称为卫星细胞 由于它们位于肌纤维周围和肌纤维下方 周围基底层。 由生长因子、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 成为长寿肌纤维的稳定部分。 卫星细胞是 对肌肉稳态至关重要，对肌肉有直接影响 修复、疾病进展和衰老。 仅卫星的一小部分 细胞具有肌肉干细胞的特征。 干细胞产生 两种成肌细胞，经过有限数量的分化后 分裂，以及更多的自我更新干细胞，保持高 增殖潜力。 静止的肌肉干细胞很难 由于其数量稀少且缺乏定义的生化指标而进行的研究 或分子特征。 拟议研究的目的是 识别肌肉干细胞的特征，并利用它们 研究干细胞在肌肉生长和修复中的作用，特别是 关于与肌营养不良症相关的退化。 最近的 研究表明，抑制细胞凋亡的蛋白质，例如 Bcl-2，在多种自我更新干细胞中表达 皮肤上皮和肠道等组织。 我们发现一个 体外生长的一小部分肌原细胞在体外表达 Bcl-2 模式与它们作为肌源干细胞的作用一致。 在 此外，我们发现来自 Bcl-2 缺陷动物的卫星细胞 产生的肌肉集落明显小于其 野生型兄弟姐妹。 为了扩展这些观察，肌肉细胞将被 进行体外和体内检查，以确定 Bcl-2 是否 表达是肌肉干细胞的一个特征。细胞凋亡相关 基因表达（Bcl-2 等）也将在 mdx 小鼠中进行研究， 杜氏肌营养不良症模型，其中肌肉经历 退化的急性期，广泛的干细胞激活和修复。 将培育出表达由肌肉驱动的 Bcl-2 的转基因小鼠 特异性 MRF4 启动子。 这些小鼠将与 mdx 小鼠交配 确定过度表达的 Bcl-2 是否可以抑制肌肉变性或 影响患病肌肉中干细胞群的大小。 总之，结果应有助于识别肌肉干 细胞并确定细胞凋亡调节因子在肌肉生长中的作用 和体内平衡。 此类信息将极大地有助于我们 了解肌肉生物学，并可能带来新的治疗方法 治疗肌肉疾病、肌肉萎缩等的策略 基于肌肉的基因治疗方法。