Rat Rotator Cuff Tear RNASeq

Myosteatosis is the pathological accumulation of lipid that occurs in conjunction with atrophy and fibrosis following skeletal muscle injury or disease. Little is known about the mechanisms by which lipid accumulates in myosteatosis, but many studies have demonstrated the degree of lipid infiltration negatively correlates with muscle function and regeneration. Our goal was to identify biochemical pathways that lead to muscle dysfunction and lipid accumulation in injured rotator cuff muscles, a model that demonstrates severe myosteatosis. Adult rats were subjected to a massive tear to the rotator cuff musculature. After a period of either 0 (healthy control), 10, 30, or 60 days, muscles were prepared for RNA sequencing, shotgun lipidomics, metabolomics, biochemical measures, electron microscopy, and muscle fiber contractility. Following rotator cuff injury, there was a decrease in muscle fiber specific force production that was lowest at 30d. There was a dramatic time dependent increase in triacylglyceride content. Interestingly, genes related to not only triacylglyceride synthesis, but also lipid oxidation were largely downregulated over time. Using bioinformatics techniques, we identified that biochemical pathways related to mitochondrial dysfunction and reactive oxygen species were considerably increased in muscles with myosteatosis. Long chain acyl-carnitines and L-carnitine, precursors to beta-oxidation, were depleted following rotator cuff tear. Electron micrographs showed injured muscles displayed large lipid droplets within mitochondria at early time points, and an accumulation of peripheral segment mitochondria at all time points. Several markers of oxidative stress were elevated following rotator cuff tear. The results from this study suggest that the accumulation of lipid in myosteatosis is not a result of canonical lipid synthesis, but occurs due to decreased lipid oxidation in mitochondria. A failure in lipid utilization by mitochondria would ultimately cause an accumulation of lipid even in the absence of increased synthesis. Further study will identify whether this process is required for the onset of myosteatosis.

肌脂沉积（Myosteatosis）是指伴随骨骼肌损伤或疾病后出现的肌萎缩与纤维化共同发生的病理性脂质蓄积。目前学界对肌脂沉积时脂质蓄积的分子机制尚知之甚少，但多项研究已证实脂质浸润程度与肌肉功能及再生能力呈显著负相关。本研究旨在明确损伤肩袖肌肉（该模型可出现严重肌脂沉积）中导致肌肉功能障碍与脂质蓄积的生化通路。实验选用成年大鼠，对其肩袖肌肉群造成大规模撕裂。分别在术后0天（健康对照组）、10天、30天及60天采集肌肉样本，开展RNA测序（RNA Sequencing）、鸟枪法脂质组学（shotgun lipidomics）、代谢组学、生化检测、电子显微镜（electron microscopy）及肌纤维收缩力分析。肩袖损伤后，肌纤维比肌力出现下降，并于30天时降至最低水平；甘油三酯（triacylglyceride）含量随时间推移出现显著升高。值得注意的是，随时间进程，不仅甘油三酯合成相关基因，脂质氧化相关基因也出现了明显下调。通过生物信息学分析手段，本研究发现肌脂沉积肌肉中与线粒体功能障碍及活性氧（reactive oxygen species）相关的生化通路显著激活。作为β氧化（β-oxidation）前体的长链酰基肉碱与左旋肉碱（L-carnitine）在肩袖撕裂后出现耗竭。电子显微镜图像显示，损伤肌肉在早期即可观察到线粒体内出现大型脂滴，且各时间点均可见外周节段线粒体蓄积。肩袖撕裂后，多项氧化应激（oxidative stress）标志物水平均出现升高。本研究结果提示，肌脂沉积中的脂质蓄积并非经典脂质合成通路激活所致，而是源于线粒体脂质氧化能力下降。即便脂质合成未增加，线粒体脂质利用障碍最终也会引发脂质蓄积。后续研究将明确该过程是否为肌脂沉积发病的必要条件。

搜集汇总

背景与挑战

背景概述

该数据集是一个关于大鼠肩袖撕裂后肌肉脂肪变性的RNA测序研究，包含16个样本，使用褐家鼠的冈上肌组织进行RNA-Seq分析。研究重点在于揭示脂质积累与线粒体功能障碍之间的关联，发现肌肉损伤后脂质氧化减少是导致脂肪变性的关键因素，而非传统的脂质合成途径。