Wnt signalling in oral and maxillofacial diseases

Anti-inflammatory role of low-intensity pulsed ultrasound in inhibiting lipopolysaccharide-induced M1 polarization of RAW264.7 cells via Wnt2b/AXIN/β-catenin

Background

Low-intensity pulsed ultrasound (LIPUS) is a special type of low-intensity ultrasound. In periodontal disease, LIPUS is applied as an adjuvant and non-invasive treatment. It has been reported that LIPUS significantly shifts the macrophage phenotype from M1 to M2, but the specific mechanism behind this shift is still unknown.

Methods

RAW264.7 cells were induced to M1/M2 polarization with lipopolysaccharide (LPS)/interleukin-4 (IL4). LIPUS was performed for 25 min two times, 24 h apart, at an intensity of 45 mW/cm2 to stimulate RAW264.7 cells. PolyA mRNA sequencing was conducted of both the LPS-induced RAW264.7 cells and the LPS-induced RAW264.7 cells with LIPUS treatment. The expression of Wnt2b in RAW264.7 cells was downregulated by siRNA. The macrophage surface markers and downstream inflammatory cytokines were detected using flow cytometry. The relative expression of proteins in the Wnt2b/AXIN/β-catenin pathway was assessed using reverse transcription real-time polymerase chain reaction (RT-qPCR) and Western blot.

Results

LIPUS reversed the M1 polarization of RAW264.7 cells, with decreased expression of CD80 and CD86. In addition, LIPUS enhanced the M2 polarization of RAW264.7 cells, with upregulated expression of CD163 and CD206. The polyA mRNA sequencing results indicated that the Wnt signaling pathway participated in the M1 polarization of LIPUS-treated RAW264.7. The results of the RT-qPCR showed a higher expression of Wnt2b in LIPUS-treated and M1- or M2-polarized RAW264.7 cells. Knocking down Wnt2b was shown to reverse the inhibitory effect of LIPUS on M1 polarization and increase the expression of CD80 and CD86. Wnt2b knockdown also regulated downstream AXIN, β-catenin, and inflammatory factors such as tumor necrosis factor alpha (TNFα) and interleukin-6 (IL6).

Conclusions

LIPUS plays an anti-inflammatory role by inhibiting LPS-induced M1 polarization of RAW264.7 cells in a Wnt2b/AXIN/β-catenin-dependent way. LIPUS may play a therapeutic role in periodontal diseases by inhibiting inflammation through the regulation of macrophage differentiation.

Research Trends in the Relationship Between Orofacial Cleft and Cancer: A Bibliometric and Network Visualization Study

OBJECTIVE

To use the bibliographic data of publications regarding the association between orofacial cleft (OC) and cancer to examine the implications of publication growth, co-citation, co-words, and authorship networks using bibliometric indicators and network visualization.

METHODS

Bibliometric study analyzed documents related to the association between OC and cancer. Data were obtained in October 2023 from the Scopus, Pubmed, Web of Science. The search strategy was developed, and data obtained were imported into R ("bibliometrix") for analysis. Results: 70 documents were found from 1977 to 2023. Most were journal articles (90.0%) designed as case-control studies (42.8%). American Journal of Epidemiology was the most relevant source. The most cited document was Frebourg T, et al. (2006). Vieira A, Martelli-Junior were the most cited author. Most authors were affiliated to Brazil (University of Montes Claros) and United States (University of Pittsburgh). Research in this thematic has included children and adults of both sexes. Research trend points to gastric cancer, leukemia and breast cancer as the most investigated cancers in association to OC.

CONCLUSION

This bibliometric analysis helps fill research gaps regarding the knowledge of the relationship between OC and cancer, providing some clues for selecting future research in this topic.

Dissecting specific Wnt components governing osteogenic differentiation potential by human periodontal ligament stem cells through interleukin-6

Periodontal ligament stem cells (PDLSCs) play a significant role on periodontal tissue and alveolar bone homeostasis. During inflammation, interleukin (IL)-6 serves as one of key cytokine players controlling tissue reaction as well as alveolar bone tissue remodeling. It is believed that periodontal tissue inflammation causes periodontium degradation, especially alveolar bone. However, in this study, we show that an inflammatory mediator, IL-6, may serve another direction on alveolar bone homeostasis during inflammatory condition. We found that, IL-6 at 10 and 20 ng/mL was not cytotoxic and dose-dependently exerted beneficial effects on osteogenic differentiation of human PDLSCs (hPDLSCs), as demonstrated by increased alkaline phosphatase activity, mRNA expression of osteogenic markers, and matrix mineralization. The presence of physiological and inflammatory level of IL-6, the osteogenic differentiation potential by hPDLSCs was enhanced by several possible mechanisms including transforming growth factor (TGF), Wnt, and Notch pathways. After in-depth and thorough exploration, we found that Wnt pathway serves as key regulator controlling osteogenic differentiation by hPDLSCs amid the IL-6 presentation. Surprisingly, apart from other mesenchymal stem cells, distinct Wnt components are employed by hPDLSCs, and both canonical and non-canonical Wnt pathways are triggered by different mechanisms. Further validation by gene silencing, treatment with recombinant Wnt ligands, and β-catenin stabilization/translocation confirmed that IL-6 governed the canonical Wnt/β-catenin pathway via either WNT2B or WNT10B and employed WNT5A to activate the non-canonical Wnt pathway. These findings fulfill the homeostasis pathway governing periodontal tissue and alveolar bone regeneration and may serve for further therapeutic regimen design for restoring the tissues.

Wnt4 prevents apoptosis and inflammation of dental pulp cells induced by LPS by inhibiting the IKK/NF‑κB pathway

Wnt4 has been shown to promote the recovery of odontogenic differentiation of dental pulp stem cells under inflammatory conditions, but its role in inflammation and apoptosis of pulpitis remains to be elucidated. Lipopolysaccharide (LPS) (10 µg/ml) was applied to treat the human dental pulp cells (HDPCs) for 24 h. Western blotting measured the expressions of inflammatory cytokines and apoptosis-related proteins. Cell apoptosis was measured by flow cytometry. The level of Wnt4 was evaluated by reverse transcription-quantitative PCR and western blotting. The results indicated that LPS could promote inflammatory response and apoptosis in HDPCs and downregulated Wnt4 expression was found in LPS-HDPCs. Overexpression of Wnt4 ameliorated cell inflammatory response and apoptosis, presented by reduced expressions of IL-8, IL-6, TNF-α, IL-1β, Bax, cleaved-caspase 3 and enhanced Bcl-2 expression as well as decreased apoptosis rate. Moreover, overexpression of Wnt4 reduced the phosphorylation levels of IKK2, IκBα and p65 proteins upregulated by LPS. Finally, overexpression of IKK2 reversed the effects of Wnt4 on inflammation and apoptosis of LPS-HDPCs and NF-κB inhibitor reversed the effect of IKK2 overexpression in LPS-HDPCs. Wnt4 inhibited LPS-triggered inflammation and apoptosis in HDPCs via regulating the IKK/NF-κB signaling pathway, which provided a new viewpoint for understanding the pathological mechanism of pulpitis.

An Overlooked Bone Metabolic Disorder: Cigarette Smoking-Induced Osteoporosis

Cigarette smoking (CS) leads to significant bone loss, which is recognized as an independent risk factor for osteoporosis. The number of smokers is continuously increasing due to the addictive nature of smoking. Therefore it is of great value to effectively prevent CS-induced osteoporosis. However, there are currently no effective interventions to specifically counteract CS-induced osteoporosis, owing to the fact that the specific mechanisms by which CS affects bone metabolism are still elusive. This review summarizes the latest research findings of important pathways between CS exposure and bone metabolism, with the aim of providing new targets and ideas for the prevention of CS-induced osteoporosis, as well as providing theoretical directions for further research in the future.