MiR-12200-5p Targets Multiple Members of Wnt Signaling Pathway to Inhibit Osteoblast Differentiation and Bone Formation.

BACKGROUND: Osteoporosis is widespread and has become an emerging problem in the elderly. MicroRNAs could affect osteoblast differentiation and further regulate the occurrence of osteoporosis by targeting osteogenic differentiation signaling pathways. Our screening study found that miR-12200-5p simultaneously targeted six important factors within the Wnt signaling pathway (Apc, Tcf4, Tcf7, Wnt3a, Wnt5a, and Lrp6), indicating that miR-12200-5p might function as a strong regulator of this pathway. Since the Wnt pathway exists as one of the most essential pathways for osteogenic differentiation, miR-12200-5p may have an important role in the development of osteoporosis. OBJECTIVE: This study intended to explore the regulatory role and corresponding mechanism of miR-12200-5p in osteoblast differentiation. METHODS: We investigated the differentiation of osteoblast after the treatments of miR-12200-5p mimic and inhibitor. The interactions between miR-12200-5p and its target genes were also detected. Furthermore, the rescue effect of miR-12200-5p inhibitor on osteoporosis was evaluated using an ovariectomized osteoporosis mouse model. RESULTS: MiR-12200-5p significantly inhibited osteoblast differentiation, and bound with the 3'-UTR sequences of its target genes (Apc, Tcf4, Tcf7, Wnt3a, Wnt5a, and Lrp6) to reduce the expressions of these genes. The inhibition of miR-12200-5p would almost fully alleviate postmenopausal osteoporosis. CONCLUSION: MiR-12200-5p could strongly repress osteoblast differentiation and bone formation by targeting multiple members of the Wnt signaling pathway simultaneously. The study supplemented the theoretical and experimental basis for researching the mechanism of osteogenic differentiation and inspired the development of novel therapeutic strategies for osteoporosis.

Transfer RNAs-derived small RNAs and their application potential in multiple diseases.

The role of tRNAs is best known as adapter components of translational machinery. According to the central dogma of molecular biology, DNA is transcribed to RNA and in turn is translated into proteins, in which tRNA outstands by its role of the cellular courier. Recent studies have led to the revision of the canonical function of transfer RNAs (tRNAs), which indicates that tRNAs also serve as a source for short non-coding RNAs called tRNA-derived small RNAs (tsRNAs). tsRNAs play key roles in cellular processes by modulating complicated regulatory networks beyond translation and are widely involved in multiple diseases. Herein, the biogenesis and classification of tsRNAs were firstly clarified. tsRNAs are generated from pre-tRNAs or mature tRNAs and are classified into tRNA-derived fragments (tRFs) and tRNA halves (tiRNA). The tRFs include five types according to the incision loci: tRF-1, tRF-2, tRF-3, tRF-5 and i-tRF which contain 3' tiRNA and 5' tiRNA. The functions of tsRNAs and their regulation mechanisms involved in disease processes are systematically summarized as well. The mechanisms can elaborate on the specific regulation of tsRNAs. In conclusion, the current research suggests that tsRNAs are promising targets for modulating pathological processes, such as breast cancer, ischemic stroke, respiratory syncytial virus, osteoporosis and so on, and maintain vital clinical implications in diagnosis and therapeutics of various diseases.