Myogenic stem cells in extraocular muscles

描述（由申请人提供）：眼外肌（EOMs）是一组高度专业化的骨骼肌，控制眼球运动。它们从头部中胚层发育而来，在分子上、解剖上和生理上都与其他骨骼肌不同。EOMs在与肌营养不良蛋白-糖蛋白复合物损伤相关的肌营养不良中具有独特的特性。在杜氏肌营养不良症和这种毁灭性的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晚发性损伤相反，EOMs没有受到影响。EOMs中肌源性祖细胞的特定特征可能在这些肌肉的优先保留中起作用。令人惊讶的是，我们对成人EOMs中的肌源性干细胞和祖细胞知之甚少。分离EOM以收获原代细胞的困难导致缺乏适当的细胞培养模型，旨在识别支持EOM肌纤维终生维持的细胞特性。与肢体和横膈膜肌肉相比，该应用程序旨在破译三种细胞类型的细胞和分子特征，这些细胞类型在EOMs中显示出强劲的生长和更新特性，这种区别可能有助于EOMs免受营养不良和年龄相关萎缩的影响。这些细胞类型是：a)卫星细胞，通常被认为是成人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)微血管相关的收缩细胞（即周细胞），可直接与肌纤维融合。本研究的目的是：1)研究EOMs与肢体和膈肌的卫星细胞和间质壁龛中细胞对肌生成特异性标志物的表达；2)比较EOMs与肢体和膈肌中肌源性干细胞和祖细胞的生长和更新潜力；3)研究EOMs供体卫星细胞和周细胞对肢体和膈肌的体内肌肉修复的潜力。野生型和无肌营养不良蛋白小鼠的细胞携带多种报告基因（用于追踪不同的细胞类型及其后代），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成人生活中支持EOM维持的细胞环境，并将为微血管相关细胞在骨骼肌形成中的作用提供新的见解。进一步表征EOM肌源性祖细胞对于制定治疗眼外肌疾病的修复策略至关重要。该研究还将揭示肌原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。公共卫生相关性：眼外肌（EOMs）是一组高度专业化的骨骼肌，控制眼球运动。EOM中肌源性祖细胞的特定特征可能是肌营养不良患者优先保留该肌群的决定因素，但令人惊讶的是，我们对EOM的肌源性细胞池知之甚少。这些研究结果将有助于更好地理解成人生活中支持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.