Theranostics 2019; 9(8):2198-2208. doi:10.7150/thno.30798 This issue Cite
Research Paper
Department of Blood Transfusion, Lab of Radiation biology, The Second Affiliated Hospital, Third Military Medical University, Chongqing, 400037, China.
*These authors contributed equally to this work and should be considered co-first authors.
Irradiation can greatly inhibit osteogenesis of bone marrow mesenchymal stem cells (BM-MSCs). However, the mechanism remains unclear.
Methods: We analyzed the expression profile of long noncoding RNAs (lncRNAs) in BM-MSCs using microarray data. LncRNA TUG1 (Taurine Upregulated Gene 1) was selected and tested in radiated BM-MSCs and non-radiated BM-MSCs. Functional analyses (in vitro) were performed to confirm the role of TUG1 in the osteogenic inhibition induced by irradiation. A RIP (RNA immunoprecipitation) assay was performed to detect the interaction of TUG1 and Smad5. Smad5 and the phosphorylated Smad5 (p-Smad5) were tested by western blot. The nuclear translocation of p-Smad5 were tested by immunofluorescence analysis. Furthermore, a series of Smad5 deletions was constructed to identify the TUG1 binding site of Smad5.
Results: We found that numerous lncRNAs, including TUG1, exhibit significant expression differences after irradiation. After irradiation TUG1 was significantly increased in BM-MSCs and inhibited osteogenesis. Furthermore, TUG1 directly bound to Smad5, an osteogenic enhancer. Although the phosphorylation level of Smad5 was increased following irradiation, osteogenesis of BM-MSCs was decreased. Mechanistically, TUG1 interacting with the 50-90 aa region of Smad5 and blocks the nuclear translocation of p-Smad5, abolishing osteogenic signalling after irradiation.
Conclusion: These results indicate that TUG1 is a negative regulator of Smad5 signalling and suppresses osteogenesis of BM-MSCs after irradiation.
Keywords: TUG1, Osteogenesis, Bone Marrow Mesenchymal Stem Cells, Smad5, Irradiation