Myogenic stem cells in extraocular muscles

描述(申请人提供)：眼外肌(EOMS)是一组高度专业化的骨骼肌，控制眼睛的运动。它们从头部中胚层发育而来，在分子、解剖学和生理学上与其他骨骼肌不同。EOMS具有一种独特的特性，即在与dystrophin-糖蛋白复合体损伤相关的肌营养不良症中幸免于难。在Duchenne肌营养不良症和这种毁灭性的营养不良蛋白缺乏相关疾病的动物模型中，EOMS是幸免的，与对其他肌肉的严重早发或晚发损害相反。EOMS中成肌祖细胞的特异性可能在这些肌肉的优先保留中起作用。令人惊讶的是，人们对成年EOMS中的肌源性干细胞和祖细胞知之甚少。分离EOMS以获取原代细胞的困难导致缺乏适当的细胞培养模型，目的是鉴定支持EOM肌纤维终生维持的细胞的特性。这项申请旨在破译三种细胞类型的细胞和分子特征，这些细胞类型与肢体和横隔肌相比，在EOMS中表现出强劲的生长和更新特性，这一区别可能有助于EOMS免受营养不良和年龄相关性萎缩的影响。这些细胞类型是：a)卫星细胞，传统上被认为是成人骨骼肌成肌祖细胞的主要来源；b)间质成肌祖细胞；c)微血管相关收缩细胞(即周细胞)，可直接与肌纤维融合。本研究的目的是：1)比较EOMS与肢体和横隔肌的卫星细胞和间质细胞表达的肌特异性标志物；2)比较EOMS与肢体和横隔肌的生肌干细胞和前体细胞的生长和更新潜力；3)比较EOMS和肢体和横隔肌的供体卫星细胞和周细胞对在体肌肉修复的贡献。携带不同报告基因(用于追踪不同细胞类型及其后代)的野生型和dystrophin缺失小鼠的细胞将在体内和培养中进行研究。这些研究的预期结果将有助于更好地理解支持成人生活中EOM维持的细胞环境，并将为微血管相关细胞在骨骼肌发生中的作用提供新的见解。进一步鉴定EOM肌源性祖细胞对于制定治疗眼外肌疾病的修复策略是至关重要的。这项拟议的研究还将阐明成肌前体细胞在衰老和肌营养不良的肌肉中的功能状态，为肌肉康复策略提供重要的信息。与公共健康相关：眼外肌(EOMS)是一组高度专业化的骨骼肌，控制着眼睛的运动。EOMS中生肌祖细胞的特异性可能对肌营养不良症中该肌群的优先选择有重要意义，但令人惊讶的是，人们对EOM生肌细胞池知之甚少。这项研究的结果将有助于更好地了解支持成人生活中EOM修复的肌源性干细胞和祖细胞，并将为肌肉康复策略提供重要信息。

DESCRIPTION (provided by applicant): Extraocular muscles (EOMs) are a group of highly specialized skeletal muscles that control eye movements. They develop from the head mesoderm and are molecularly, anatomically and physiologically distinct from other skeletal muscles. EOMs possess a unique quality of being spared in muscular dystrophies associated with impairments in the dystrophin-glycoprotein complex. In Duchenne muscular dystrophy and in animal models of this devastating dystrophin deficiency-associated disease, EOMs are spared, contrary to the severe early- or late-onset damage to other muscles. Specific traits of myogenic progenitors in EOMs may play a role in the preferential sparing of these muscles. Surprisingly, very little is known about the myogenic stem and progenitor cells in adult EOMs. The difficulty in isolating EOMs for harvesting primary cells has resulted in the lack of appropriate cell culture models aimed at identifying the properties of cells that support EOM myofiber maintenance through life. This application proposes to decipher cellular and molecular characteristics of three cell types that display robust growth and renewal properties in EOMs compared to limb and diaphragm muscles, a distinction that may contribute to the sparing of EOMs from dystrophinopathy and age-linked atrophy. These cell types are: a) satellite cells, which are classically recognized as the main source of myogenic progenitors in adult skeletal muscle; b) interstitial myogenic progenitors; c) microvascular-associated contractile cells (i.e., pericytes), which may fuse directly with myofibers. The proposed studies aim to: 1) characterize myogenic-specific marker expression by cells in the satellite cell and interstitium niches of EOMs versus limb and diaphragm muscles; 2) compare growth and renewal potential of myogenic stem and progenitor cells in EOMs versus limb and diaphragm muscles; 3) investigate the potential of donor satellite cells and pericytes from EOMs versus limb and diaphragm muscles to contribute to in vivo muscle repair. Cells from wild type and dystrophin-null mice that carry various reporter genes (for tracing the different cell types and their progeny) will be investigated in vivo and in culture. The expected results of the proposed studies will contribute to a better understanding of the cellular milieu that supports EOM maintenance in adult life and will provide new insights regarding the role of microvasculature-associated cells in skeletal myogenesis. Further characterization of EOM myogenic progenitors is essential for developing repair strategies to treat extraocular muscle disorders. The proposed studies will also shed new light on the functional status of myogenic progenitors in aging and dystrophin-deficient muscles, providing important information for muscle rehabilitation strategies. PUBLIC HEALTH RELEVANCE: Extraocular muscles (EOMs) are a group of highly specialized skeletal muscles that control eye movements. Specific traits of myogenic progenitors in EOMs may have significance as determinants of the preferential sparing of this muscle group in muscular dystrophy, but surprisingly, very little is known about the EOM myogenic cell pool. The results of the proposed studies will contribute to a better understanding of the myogenic stem and progenitor cells that support EOM repair in adult life and will provide important information for muscle rehabilitation strategies.