模拟微重力下秀丽隐杆线虫的力学感知和肌萎缩的发生机制——太空飞行线虫试验地面平行对照研究部分

Mechanisms of Muscular Atrophy and Gravisensing After Simulated Microgravity in Caenorhabditis elegans: Parallel Control to Spaceflight Research in C. elegans

目前,微重力导致肌萎缩的分子机制尚不清楚,重力感知是该事件发生的关键环节.为了回答这一问题,在此之前首先实施了太空线虫试验,这部分结果已经在本刊报道过.而本次研究主要是在地面上建立了模拟微重力环境,观察处理后秀丽隐杆线虫(C.elegans)体壁肌细胞结构和功能的变化,一方面用于验证太空试验,同时比较两种处理结果的异同,以便于评价地面模拟微重力的有效性.经过14天19.5h旋转模拟微重力处理后,对线虫生存率和运动能力进行了观察,并检测了几个重要的肌相关基因表达和蛋白质水平.模拟微重力下线虫生存率没有明显变化,但运动频率显著下降,爬行轨迹也发生了轻微改变,运动幅度降低,提示线虫运动功能出现障碍.从形态学上观察发现:肌球蛋白A(myosinA)免疫荧光染色显示模拟微重力组肌纤维面积缩小,而肌细胞致密体(dense-body)染色可见荧光亮度下降.这些结果直接提示模拟微重力使线虫出现了肌萎缩.随后Western blotting试验结果揭示,模拟微重力组线虫体壁肌的主要结构蛋白——myosinA含量减少,进一步确证了微重力性肌萎缩发生.在基因水平,旋转后抗肌萎缩蛋白基因(dys-1)表达明显上升,而hlh-1,unc-54,myo-3和egl-19的mRNA水平均下调,提示dys-1在骨骼肌感知和传导力学信息方面有重要作用,而hlh-1,unc-54,myo-3和egl-19则分别从结构和功能两个途径促进了微重力性肌萎缩的发生和发展.本次试验所得到的结果同太空飞行试验结果十分相似,一方面强化了太空试验结论,另一方面说明在地面上模拟微重力对生物体进行研究是有效可行的,将有助于提高太空试验的质量.

At present, the molecular mechanism underlying microgravity-induced muscular atrophy is still unknown, and gravisensing is the key point in this process. In order to answer these questions a research project of Caenorhabditis elegans （C. elegans） in spaceflight was carried out, which had been reported in this journal before. An environment of simulated microgravity on ground was established, and its major effects on body-wall muscles of C. elegans in the structures and functions were examined, which further confirmed the results from spaceflight studies, and comparing between these two different treatments was benefit for valuing the validity of simulated microgravity. Firstly, the survival rate and movement ability of C. elegans were observed, and five important muscle-related genes and three proteins were measured after 14 days 19.5 h rotation. The animals displayed reduced rates of movement with a lower ratio （height/width） in crawl trace wave in simulated microgravity, indicating a functional defect. In morphological observation deceased muscle fiber size in myosin immunofluorescence and duller dense-body staining were found in microgravity group, suggesting muscular atrophy had happened in C. elegans. Meantime the result of Western blotting showed the quantity of myosin A decreased significantly in simulated microgravity group, further confirming muscular atrophy. In genes transcription, it was noted that dys-1 increased significantly in body-wall muscles, while hlh-1, unc-54, myo-3 and egl-19 mRNA levels declined after rotation. This study provided evidence that dys-1 are involved in the transduction of mechanical information in skeletal muscle, potentially play a vital role in gravisensing. Genes of hlh-1, unc-54, myo-3 and egl-19 induced the muscular atrophy in simulated microgravity from the structures and functions ways respectively. Data of this study consolidated the results in our spaceflight researches. On the other hand, it is implied that simulated microgravity is an effective ways for improving the quality of space studies.