Muscle Biology Research Unit, Division of Animal Products Research, National Institute of Livestock and Grassland Science, NARO, Tsukuba, Japan.
Ion Channel Laboratory, Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Japan.
FEBS Open Bio. 2021 Mar;11(3):768-781. doi: 10.1002/2211-5463.13100. Epub 2021 Feb 16.
Exosomes are released from a variety of cells to communicate with recipient cells. Exosomes contain microRNAs (miRNAs), which are noncoding RNAs that suppress target genes. Our previous proteomic study (FEBS Open Bio 2016, 6, 816-826) demonstrated that 3T3-L1 adipocytes secrete exosome components as well as growth factors, inspiring us to investigate what type of miRNA is involved in adipocyte-secreted exosomes and what functions they carry out in recipient cells. Here, we profiled miRNAs in 3T3-L1 adipocyte-secreted exosomes and revealed suppression of muscle differentiation by adipocyte-derived exosomes. Through our microarray analysis, we detected over 300 exosomal miRNAs during adipocyte differentiation. Exosomal miRNAs present during adipocyte differentiation included not only pro-adipogenic miRNAs but also miRNAs associated with muscular dystrophy. Gene ontology analysis predicted that the target genes of miRNAs are associated primarily with transcriptional regulation. To further investigate whether adipocyte-secreted exosomes regulate the expression levels of genes involved in muscle differentiation, we treated cultured myoblasts with adipocyte-derived exosome fractions. Intriguingly, the expression levels of myogenic regulatory factors, Myog and Myf6, and other muscle differentiation markers, myosin heavy-chain 3 and insulin-like growth factor 2, were significantly downregulated in myoblasts treated with adipocyte-derived exosomes. Immature adipocyte-derived exosomes exhibited a stronger suppressive effect than mature adipocyte-derived exosomes. Our results suggest that adipocytes suppress the expression levels of muscle differentiation-associated genes in myoblasts via adipocyte-secreted exosomes containing miRNAs.
外泌体从各种细胞释放出来以与受体细胞进行通讯。外泌体包含 microRNAs（miRNAs），这是非编码 RNA，可以抑制靶基因。我们之前的蛋白质组学研究（FEBS Open Bio 2016，6，816-826）表明 3T3-L1 脂肪细胞分泌外泌体成分以及生长因子，这启发我们研究脂肪细胞分泌的外泌体中涉及哪种类型的 miRNA，以及它们在受体细胞中执行什么功能。在这里，我们对 3T3-L1 脂肪细胞分泌的外泌体中的 miRNA 进行了分析，并揭示了脂肪细胞衍生的外泌体对肌肉分化的抑制作用。通过我们的微阵列分析，我们在脂肪细胞分化过程中检测到了 300 多种外泌体 miRNA。在脂肪细胞分化过程中存在的外泌体 miRNA 不仅包括促脂肪生成的 miRNA，还包括与肌肉营养不良相关的 miRNA。GO 分析预测，miRNA 的靶基因主要与转录调控相关。为了进一步研究脂肪细胞分泌的外泌体是否调节肌肉分化相关基因的表达水平，我们用脂肪细胞衍生的外泌体部分处理培养的成肌细胞。有趣的是，用脂肪细胞衍生的外泌体处理的成肌细胞中肌生成调节因子 Myog 和 Myf6 以及其他肌肉分化标志物肌球蛋白重链 3 和胰岛素样生长因子 2 的表达水平显著下调。未成熟脂肪细胞衍生的外泌体比成熟脂肪细胞衍生的外泌体具有更强的抑制作用。我们的结果表明，脂肪细胞通过含有 miRNA 的脂肪细胞分泌的外泌体抑制成肌细胞中肌肉分化相关基因的表达水平。
