Limb contractures are a debilitating and progressive consequence of a wide range of upper motor neuron injuries that affect skeletal muscle function. One type of perinatal brain injury causes cerebral palsy (CP), which affects a child's ability to move and is often painful. While several rehabilitation therapies are used to treat contractures, their long-term effectiveness is marginal since such therapies do not change muscle biological properties. Therefore, new therapies based on a biological understanding of contracture development are needed. Here, we show that myoblast progenitors from contractured muscle in children with CP are hyperproliferative. This phenotype is associated with DNA hypermethylation and specific gene expression patterns that favor cell proliferation over quiescence. Treatment of CP myoblasts with 5-azacytidine, a DNA hypomethylating agent, reduced this epigenetic imprint to TD levels, promoting exit from mitosis and molecular mechanisms of cellular quiescence. Together with previous studies demonstrating reduction in myoblast differentiation, this suggests a mechanism of contracture formation that is due to epigenetic modifications that alter the myogenic program of muscle-generating stem cells. We suggest that normalization of DNA methylation levels could rescue myogenesis and promote regulated muscle growth in muscle contracture and thus may represent a new nonsurgical approach to treating this devastating neuromuscular condition.

中文翻译：

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差异 DNA 甲基化和转录特征表征脑损伤后小儿人类肌肉挛缩中肌肉干细胞的损伤

肢体挛缩是影响骨骼肌功能的各种上运动神经元损伤的衰弱和渐进性后果。一种类型的围产期脑损伤会导致脑瘫 (CP)，这会影响孩子的移动能力，并且通常会很痛苦。虽然有几种康复疗法用于治疗挛缩，但它们的长期有效性是微不足道的，因为这些疗法不会改变肌肉的生物学特性。因此，需要基于对挛缩发展的生物学理解的新疗法。在这里，我们表明来自 CP 儿童收缩肌肉的成肌细胞祖细胞是过度增殖的。这种表型与 DNA 高甲基化和有利于细胞增殖而不是静止的特定基因表达模式有关。用 5-氮杂胞苷处理 CP 成肌细胞，一种 DNA 低甲基化剂，将这种表观遗传印记降低到 TD 水平，促进有丝分裂和细胞静止的分子机制的退出。与先前证明成肌细胞分化减少的研究一起，这表明挛缩形成的机制是由于表观遗传修饰改变了肌肉生成干细胞的生肌程序。我们建议 DNA 甲基化水平的正常化可以挽救肌生成并促进肌肉挛缩中受调节的肌肉生长，因此可能代表一种新的非手术方法来治疗这种破坏性的神经肌肉疾病。与先前证明成肌细胞分化减少的研究一起，这表明挛缩形成的机制是由于表观遗传修饰改变了肌肉生成干细胞的生肌程序。我们建议 DNA 甲基化水平的正常化可以挽救肌生成并促进肌肉挛缩中受调节的肌肉生长，因此可能代表一种新的非手术方法来治疗这种破坏性的神经肌肉疾病。与先前证明成肌细胞分化减少的研究一起，这表明挛缩形成的机制是由于表观遗传修饰改变了肌肉生成干细胞的生肌程序。我们建议 DNA 甲基化水平的正常化可以挽救肌生成并促进肌肉挛缩中受调节的肌肉生长，因此可能代表一种新的非手术方法来治疗这种破坏性的神经肌肉疾病。