Muscle mass and area usually decrease with age, and this phenomenon is known as sarcopenia. This age-related atrophy correlates with insufficient levels of muscle cells differentiate and proliferate regulated by the TGF-β signaling pathway and the expression of E3s ubiquitin-protein ligase by the aged. Sarcopenia makes a huge impact on the aging society, because it has the characteristic of high incidence, extensive adverse effects and disease aggravation gradually. Guided by a single-guide RNA (sgRNA), Cas9 nuclease has been widely used in genome editing, opening up a new pathway for sarcopenia treatment. Here, we present two rAAV9 systems, pX601-AAV-CMV:SaCas9-U6:sgRNA and pX601-AAV-EF1α:SaCas9-tRNAGLN: sgRNA, which edited myostatin efficiently. By delivering the two rAAV-SaCas9 targets to myostatin via intramuscular injection of aged mice, an increase in body weight and an increase in the number and area of myofibers were observed. Knockout of myostatin led to TGF-β signaling pathway changes, and increased MyoD, Pax7 and MyoG protein levels and increased the number of satellite cells to improve muscle cells differentiation. Moreover, knockout of myostatin prevented the atrophy of muscle cells through reduced Murf1 and MAFbx protein levels. We found that both rAAV-SaCas9 systems had gene editing efficiency, reducing the expression of myostatin by affecting the relevant signaling pathways, thereby altering the physiological status. We showed that myostatin has an important role in activating skeletal muscle proliferation and inhibiting muscular atrophy during aging. Thus, we propose that knockout of myostatin using the rAAV9-SaCas9 system has significant therapeutic potential in sarcopenia.

中文翻译：

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通过 AAV-SaCas9 介导的肌生长抑制素基因编辑改善老年小鼠的肌肉萎缩。

肌肉质量和面积通常随着年龄的增长而减少，这种现象被称为肌肉减少症。这种与年龄相关的萎缩与由 TGF-β 信号通路调节的肌肉细胞分化和增殖水平不足以及老年人对 E3s 泛素蛋白连接酶的表达有关。肌肉减少症具有发病率高、不良反应广泛、病情逐渐加重的特点，对老龄化社会造成巨大影响。Cas9核酸酶在单向导RNA（sgRNA）的指导下，已广泛应用于基因组编辑，为肌肉减少症的治疗开辟了一条新途径。在这里，我们展示了两个 rAAV9 系统，pX601-AAV-CMV:SaCas9-U6:sgRNA 和 pX601-AAV-EF1α:SaCas9-tRNAGLN:sgRNA，它们有效地编辑了肌肉生长抑制素。通过肌内注射老年小鼠，将两个 rAAV-SaCas9 靶标递送至肌生长抑制素，观察到体重增加以及肌纤维数量和面积增加。敲除肌肉生长抑制素导致 TGF-β 信号通路发生变化，并增加 MyoD、Pax7 和 MyoG 蛋白水平并增加卫星细胞数量以改善肌肉细胞分化。此外，肌生长抑制素的敲除通过降低 Murf1 和 MAFbx 蛋白水平来防止肌肉细胞萎缩。我们发现两个 rAAV-SaCas9 系统都具有基因编辑效率，通过影响相关信号通路来降低肌肉生长抑制素的表达，从而改变生理状态。我们发现肌肉生长抑制素在激活骨骼肌增殖和抑制衰老过程中的肌肉萎缩方面具有重要作用。因此，