Alteration of circular RNA expression in rat dental follicle cells during osteogenic differentiation.

Circular RNAs (circRNAs) are novel noncoding RNAs and play crucial roles in various biological processes. However, little is known about the functions of circRNAs in osteogenic differentiation. The current study aimed to investigate the differential expression of circRNAs in rat dental follicle cells (rDFCs) during osteogenic differentiation, identified by RNA high-throughput sequencing and quantitative real-time polymerase chain reaction. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to further explore the biofunctions of circRNA biofunctions. Two hundred sixty-six differentially-expressed circRNAs that are involved in several important signaling pathways, including mitogen-activated protein kinases (MAPK) and transforming growth factor-ß (TGF-ß) signaling pathways were revealed. Among these, circFgfr2 and its predicted downstream targets, miR-133 and BMP6 (bone morphogenetic protein-6), were identified both in vivo and in vitro. For further validation, circFgfr2 was overexpressed in rDFCs, the results showed that the expression of miR-133 was downregulated and the expression of BMP6 was upregulated. Taken together, the results revealed the circRNA expression profiles and indicated the importance of circRNAs of rDFCs. In addition, circFgfr2 might promote osteogenesis by controlling miR-133/BMP6, which is a potential new target for the manipulation of tooth regeneration and bone formation.

LL-37 inhibits LPS-induced inflammation and stimulates the osteogenic differentiation of BMSCs via P2X7 receptor and MAPK signaling pathway.

Oral diseases, such as periapical periodontitis and periodontitis, are characterized by inflammation-induced bone loss. LL-37, a human antimicrobial peptide (AMP), has multiple biological functions and the potential to promote osteogenesis. Therefore, this study aimed to investigate the regulatory effects of LL-37 within normal and inflammatory microenvironments. The roles of P2X7 receptor (P2X7R) and mitogen-activated protein kinase (MAPK) signaling pathway were also demonstrated. The results showed that LL-37 promoted bone marrow stromal cell (BMSC) proliferation, migration and osteogenic differentiation. LL-37 inhibited the expression of the inflammatory cytokines interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and receptor activator of nuclear factor kappa-B ligand (RANKL) at both protein and gene levels, and attenuated the lipopolysaccharide (LPS)-induced inhibition of osteogenesis. Immunofluorescence (IF) confirmed P2X7R expression in BMSCs. BBG, a P2X7R antagonist, significantly attenuated LL-37-promoted osteogenesis. The phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun NH2-terminal kinase (JNK) increased after LL-37 stimulation, which did not affect p38 phosphorylation. The effects of LL-37 on osteogenesis-related gene expression were markedly attenuated by selective inhibitors of ERK1/2 and JNK. Furthermore, a mouse model of LPS-stimulated calvarial osteolysis was established, and results showed that LL-37 markedly inhibited osteoclastic bone resorption. In conclusion, we speculate that LL-37 inhibits inflammation and promotes BMSC osteogenesis via P2X7R and MAPK signaling pathway.

7ND protein exerts inhibitory effects on both osteoclast differentiation in vitro and lipopolysaccharide­induced bone erosion in vivo.

Excessive numbers of osteoclasts are responsible for inflammation­induced osteolysis. Identification of osteoclast­targeting agents may facilitate the development of a novel therapeutic approach for the treatment of pathological bone loss. Seven­amino acid truncated (7ND) protein, a mutant form of monocyte chemoattractant protein­1 (MCP­1), functions as a competitive inhibitor of MCP­1. However, the effects of 7ND protein on osteoclast differentiation remain unknown. Therefore, in the present study, the effects of 7ND protein on osteoclast differentiation induced by tumour necrosis factor superfamily member 11 were investigated. In the present study, 7ND protein inhibited the osteoclast differentiation of peripheral blood mononuclear cells without influencing cell proliferation. Furthermore, to evaluate the effects of 7ND protein in vivo, a lipopolysaccharide (LPS)­induced calvarial bone erosion animal model was established. The 7ND protein remarkably attenuated LPS­induced bone resorption, as assessed by micro­computed tomography and histological analysis. Taken together, the present results suggested the feasibility of local delivery of 7ND protein to mitigate osteoclast differentiation and LPS­induced osteolysis, which may represent a potential approach to treat inflammatory bone destruction.

Effect of obturation technique with immediate and delayed post space preparation on apical voids and bond strength of apical gutta-percha.

OBJECTIVE: The purpose of this study was to evaluate the effect of immediate and delayed post space preparation on the sealing ability of two root canal obturation techniques by using micro-computed tomography imaging and a push-out test. METHODS: The root canals of 40 human maxillary premolar teeth were instrumented and divided into four groups: (A) single cone (SC) followed by immediate post space preparation, (B) continuous wave of condensation (CWC) followed by immediate post space preparation, (C) SC followed by delayed post space preparation, and (D) CWC followed by delayed post space preparation. Micro-CT scans were performed for volumetric analysis of voids and filling materials in the apical 4-mm portion. A push-out test was performed, and failure modes (adhesive, cohesive, or mixed) were assessed. Data were analyzed using the Kruskal-Wallis test and one-way analysis of variance. RESULTS: No significant differences were observed among the four groups in terms of the percentage volume of voids of the apical 4 mm or the bond strength of apical gutta-percha. CONCLUSIONS: The percentage volume of voids and bond strength of apical gutta-percha were similar and were not significantly influenced by the timing of post space preparation or the obturation technique.