The degree of intramuscular adipose tissue accumulation is one of the factors affecting meat quality. Accumulation of adipocytes is also observed under the pathological condition of skeletal muscle such as muscular dystrophy and sarcopenia. The origin of adipocytes seen in skeletal muscle is mesenchymal progenitor cells that can give rise to both adipocytes and fibroblasts. In the present study, we demonstrated that siRNA-mediated suppression of MyoD expression in rat skeletal muscle progenitor cell culture, which comprises both myogenic satellite cells and mesenchymal progenitor cells, resulted in diminished myotube formation and an unexpected spontaneous appearance of white adipocytes. Suppressing myomaker expression also resulted in complete absence of myotube formation without reducing MyoD expression, but no adipogenesis was seen in this scenario, indicating that decline in MyoD expression rather than decreased myotube formation is necessary to induce adipogenesis. In addition, spontaneous adipogenesis induced by suppressing MyoD expression in culture was inhibited by the conditioned medium from control culture, indicating that anti-adipogenic factor(s) are secreted from MyoD-positive myogenic cells. These results indicate the presence of regulatory mechanism on adipogenesis by myogenic cells.

中文翻译：

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MyoD 的抑制诱导骨骼肌祖细胞培养中的自发脂肪生成

肌肉内脂肪组织堆积的程度是影响肉质的因素之一。在骨骼肌的病理状态下，如肌营养不良和肌肉减少症，也观察到脂肪细胞的堆积。在骨骼肌中看到的脂肪细胞的起源是间充质祖细胞，它可以产生脂肪细胞和成纤维细胞。在本研究中，我们证明了 siRNA 介导的大鼠骨骼肌祖细胞培养物中 MyoD 表达的抑制，包括生肌卫星细胞和间充质祖细胞，导致肌管形成减少和白色脂肪细胞的意外自发出现。抑制 myomaker 表达也导致完全没有肌管形成而不减少 MyoD 表达，但在这种情况下没有观察到脂肪生成，表明 MyoD 表达的下降而不是肌管形成的减少是诱导脂肪生成所必需的。此外，通过抑制培养物中的 MyoD 表达诱导的自发脂肪形成被来自对照培养物的条件培养基抑制，表明抗脂肪形成因子是从 MyoD 阳性生肌细胞分泌的。这些结果表明存在对生肌细胞脂肪生成的调节机制。表明抗脂肪形成因子是由 MyoD 阳性生肌细胞分泌的。这些结果表明存在对生肌细胞脂肪生成的调节机制。表明抗脂肪形成因子是由 MyoD 阳性生肌细胞分泌的。这些结果表明存在对生肌细胞脂肪生成的调节机制。