Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan.
Chiyoda Corporation, Yokohama 220-8765, Japan.
Sci Rep. 2016 Dec 22;6:39545. doi: 10.1038/srep39545.
Bone loss is a serious problem in spaceflight; however, the initial action of microgravity has not been identified. To examine this action, we performed live-imaging of animals during a space mission followed by transcriptome analysis using medaka transgenic lines expressing osteoblast and osteoclast-specific promoter-driven GFP and DsRed. In live-imaging for osteoblasts, the intensity of osterix- or osteocalcin-DsRed fluorescence in pharyngeal bones was significantly enhanced 1 day after launch; and this enhancement continued for 8 or 5 days. In osteoclasts, the signals of TRAP-GFP and MMP9-DsRed were highly increased at days 4 and 6 after launch in flight. HiSeq from pharyngeal bones of juvenile fish at day 2 after launch showed up-regulation of 2 osteoblast- and 3 osteoclast- related genes. Gene ontology analysis for the whole-body showed that transcription of genes in the category "nucleus" was significantly enhanced; particularly, transcription-regulators were more up-regulated at day 2 than at day 6. Lastly, we identified 5 genes, c-fos, jun-B-like, pai-1, ddit4 and tsc22d3, which were up-regulated commonly in the whole-body at days 2 and 6, and in the pharyngeal bone at day 2. Our results suggested that exposure to microgravity immediately induced dynamic alteration of gene expression levels in osteoblasts and osteoclasts.
骨丢失是航天飞行中的一个严重问题；然而，微重力的初始作用尚未确定。为了研究这种作用，我们在航天任务期间对动物进行了实时成像，然后使用表达成骨细胞和破骨细胞特异性启动子驱动 GFP 和 DsRed 的 medaka 转基因系进行转录组分析。在成骨细胞的实时成像中，发射后 1 天，咽骨中osterix 或骨钙素-DsRed 荧光的强度显著增强；这种增强持续了 8 或 5 天。在破骨细胞中，TRAP-GFP 和 MMP9-DsRed 的信号在发射后第 4 天和第 6 天在飞行中高度增加。发射后第 2 天幼鱼咽骨的 HiSeq 显示出 2 个成骨细胞和 3 个破骨细胞相关基因的上调。对整个机体的基因本体分析表明，“核”类别中基因的转录显著增强；特别是，转录调节剂在第 2 天比第 6 天上调更多。最后，我们鉴定了 5 个基因，c-fos、jun-B-like、pai-1、ddit4 和 tsc22d3，它们在第 2 天和第 6 天在整个机体中以及在第 2 天在咽骨中共同上调。我们的结果表明，暴露于微重力会立即引起成骨细胞和破骨细胞中基因表达水平的动态改变。
