Differentiation of periodontal ligament (PDL) cells occurs under specific induction; furthermore, NF-kappaB signaling is important for regulation of bone differentiation. MicroRNAs are small non-coding RNAs that repress the translation of target genes and modulate cellular processes. miR-146a has been reported to modulate NF-kappaB signaling. This study hypothesized that miR-146a has a regulatory role in PDL differentiation by affecting NF-kappaB signaling. Immortalized PDL (I-PDL) cell lines were established by exogenous telomerase expression. The genesis of alkaline phosphatase and the up-regulation of miR-146a were induced by ascorbic acid in the I-PDL cells and primary PDL cells. I-PDL cells with exogenous miR-146a expression showed attenuation of NF-kappaB activity and exhibited higher differentiation relative to the controls. Exogenous NF-kappaB expression decreased the expression of differentiation markers, while the inactivation of endogenous NF-kappaB increased alkaline phosphatase in I-PDL cells. This study concludes that miR-146a promotes the differentiation in PDL cells through the down-regulation of NF-kappaB signaling.

Vascular smooth muscle cells (VSMCs) serve a decisive role in intimal hyperplasia, a common pathophysiological process that leads to numerous vascular disorders. The present study aimed to investigate the unknown mechanisms underlying VSMC phenotypic modulation and identified a novel microRNA (miRNA/miR)-17-5p/homeobox B13 (HOXB13) axis involved in the phenotypic switching, proliferation and migration of VSMCs. VSMCs were isolated from the thoracic aorta of Sprague-Dawley rats, cell proliferation was determined by Cell Counting Kit-8 (CCK-8) assay, cell migration was examined by Transwell migration assay and gene expression was detected using reverse transcription-quantitative PCR and western blot analyses. It was firstly found that incubation with platelet-derived growth factor-BB (PDGF-BB) recombinant protein resulted in a significant increase in HOXB13 expression in VSMCs. Using multiple miRNA prediction tools, miR-17-5p was identified as a potential regulator for HOXB13, since it had a 7-base perfect binding site and a 5-base imperfect binding site with the 3'-untranslated region of HOXB13 mRNA, and these sequences were highly conserved across species. The regulatory effect of miR-17-5p on HOXB13 was validated using luciferase reporter assays. The expression level of miR-17-5p was increased in VSMCs under PDGF-BB stimulation, and was negatively correlated with HOXB13 mRNA and protein expression. Moreover, the miR-17-5p mimics significantly inhibited the proliferation and migration of VSMCs, while antagomiR-17-5p showed the opposite effects, which could be abolished by HOXB13 knockdown. The miR-17-5p/HOXB13 axis also regulated the expression levels of the markers of differentiated VSMCs (α-smooth muscle actin, transgelin and smoothelin), proliferating cell nuclear antigen and cell migration proteins, including MMP-2 and -9. In conclusion, the present study demonstrated that miR-17-5p inhibited the phenotypic modulation VSMCs stimulated by PDGF-BB by downregulating HOXB13, indicating that these factors may be potential therapeutic targets for intimal hyperplasia.