マウスの破骨細胞の細胞外微小胞におけるマイクロRNAの発現

破骨細胞の馴化培地中に存在する細胞外微小胞におけるマイクロRNA(miRNA)の発現について検討した。著者らの先行研究において破骨細胞形成に重要と思われたlet-7e、miR-21、miR-33、miR-155、miR-210、miR-223、miR-378、miR-1224の発現を、RT-PCR法を用いて調べた。その結果、破骨細胞の細胞外微小胞にはmiR-378、miR-210、miR-21が極めて高レベルに発現していたが、miR-33やmiR-1224の有意な発現は認めなかった。以上より、破骨細胞は細胞内miRNAのうちの特定のmiRNAを含む微小胞を細胞外に分泌することが示唆された。
Bone is one of the most important oral tissues. Osteoclasts play important roles in bone tissue engineering. Previously, we profiled microRNA (miRNA) expression during osteoclastogenesis using microarrays. miRNAs are small, noncoding RNAs that are involved in various biological processes, including cellular differentiation, proliferation, apoptosis, and organ development. Recently, the presence of miRNAs in extracellular microvesicles was reported. It is not known whether osteoclasts secrete extracellular microvesicles containing miRNAs. We investigated miRNA expression in extracellular microvesicles in conditioned medium of cultured osteoclasts using RT-PCR. Specifically, we investigated eight miRNAs deemed important for osteoclastogenesis in our previous study: let-7e, miR-21, miR-33, miR-155, miR-210, miR-223, miR-378, and miR-1224. Of these, the expression levels of miR-378, miR-210, and miR-21 were very high, while no significant miR-33 or miR-1224 expression was detected. These results suggest that osteoclasts secrete extracellular microvesicles containing specific miRNAs, but that they do not contain the entire set of intracellular miRNAs.