miR‑760 regulates skeletal muscle proliferation in rheumatoid arthritis by targeting Myo18b.

MicroRNAs serve an important role in the development of several diseases. Numerous genes regulate the skeletal muscle differentiation of C2C12 myoblasts. The role of miR‑760 in rheumatoid arthritis (RA) has not been reported, to the best of our knowledge. Therefore, the aim of the present study was to examine the role of miR‑760 in regulating skeletal muscle proliferation in RA. Potential genes functionally involved in the tarsal joint of a collagen‑induced RA model were identified using Gene Expression Omnibus. Reverse transcription‑quantitative PCR and western blot analyses were performed to determine the mRNA and protein expression levels. The proliferation, cell cycle progression and migration of C2C12 myoblasts were detected using Cell Counting Kit‑8, flow cytometry and wound‑healing assays, respectively. TargetScan was used to predict the potential target genes of miR‑760, and this was verified using a dual‑luciferase reporter assay. In the present study, myosin‑18b (Myo18b) expression was determined to be downregulated in the RA model. Silencing Myo18b decreased the proliferation, abrogated the cell cycle progression, and reduced the migration and differentiation of C2C12 myoblasts. Expression levels of cyclin‑dependent kinase 2, cyclin D1, matrix metalloproteinase (MMP)‑2, MMP‑9, myogenin and myosin heavy chain 6 were all decreased when Myo18b was silenced. Furthermore, overexpression of Myo18b induced opposing effects on C2C12 myoblasts. It was shown that Myo18b was a target gene of miRNA‑760. Overexpression of miR‑760 decreased proliferation, cell cycle progression, migration and differentiation in C2C12 myoblasts, and decreased the expression of Myo18b. The opposite results were observed when miR‑760 was downregulated. In conclusion, miR‑760 inhibited proliferation and differentiation by targeting Myo18b in C2C12 myoblasts. The results of the present study may contribute to understanding the mechanisms underlying RA skeletal muscle proliferation, and miR‑760/Myo18b may serve as potential targets for treating patients with RA.