Myogenic stem cells in extraocular muscles

描述（由申请人提供）：眼外肌（EOM）是一组控制眼球运动的高度特化的骨骼肌。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。EOM具有在与肌营养不良蛋白-糖蛋白复合物中的损伤相关的肌营养不良症中幸免的独特品质。在Duchenne肌营养不良症和这种破坏性肌营养不良蛋白缺乏相关疾病的动物模型中，与其他肌肉的严重早发性或迟发性损伤相反，EOM得以幸免。眼外肌中肌源性祖细胞的特定性状可能在这些肌肉的优先保留中发挥作用。令人惊讶的是，很少有人知道成肌干细胞和祖细胞在成年眼外肌。分离用于收获原代细胞的EOM的困难导致缺乏旨在鉴定支持EOM肌纤维维持终生的细胞的性质的适当细胞培养模型。本申请提出破译三种细胞类型的细胞和分子特征，与肢体和膈肌相比，这些细胞类型在EOM中显示出稳健的生长和更新特性，这一区别可能有助于避免EOM患肌营养不良蛋白病和年龄相关性萎缩。这些细胞类型是：a）卫星细胞，其被经典地认为是成年骨骼肌中肌源性祖细胞的主要来源; B）间质性肌源性祖细胞; c）微血管相关收缩细胞（即，周细胞），其可直接与肌纤维融合。拟议的研究旨在：1）表征EOM与肢体和膈肌的卫星细胞和肌原性微环境中细胞的肌原性特异性标志物表达; 2）比较EOM与肢体和膈肌中肌原性干细胞和祖细胞的生长和更新潜力; 3）研究来自EOM与肢体和膈肌的供体卫星细胞和周细胞有助于体内肌肉修复的潜力。将在体内和培养物中研究来自携带各种报告基因（用于追踪不同细胞类型及其后代）的野生型和肌养蛋白缺失小鼠的细胞。拟议的研究的预期结果将有助于更好地了解支持成年人EOM维持的细胞环境，并将提供有关微血管相关细胞在骨骼肌发生中的作用的新见解。眼外肌肌源性祖细胞的进一步表征对于开发治疗眼外肌疾病的修复策略是必不可少的。拟议的研究还将揭示肌源性祖细胞在衰老和肌营养不良蛋白缺乏肌肉中的功能状态，为肌肉康复策略提供重要信息。眼外肌（EOM）是一组高度专业化的骨骼肌，控制眼球运动。眼外肌中肌源性祖细胞的特定性状可能作为肌营养不良症中该肌群的优先保留的决定因素具有重要意义，但令人惊讶的是，对眼外肌源性细胞库知之甚少。拟议的研究结果将有助于更好地了解支持成年人眼外肌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.