Chinese Journal of Dental Research, 03/2024

Short-chain fatty acids (SCFAs) are the metabolites identified in both the oral cavity and the gut. They play an important role in the triggering, development and progression of systemic diseases. SCFAs can alter the gut microbial components, intestinal epithelium and host immune system, and are also associated with cancer incidence. Salivary SCFAs, produced by the oral microbiome, are correlated with some oral diseases. The occurrence of systemic diseases associated with gut SCFAs is more clearly defined than oral SCFAs. Salivary SCFAs can enter the bloodstream directly via inflamed gingiva to cause continuous low-grade systemic inflammation. Hence, salivary SCFAs could be an indicator for the early diagnosis of systemic diseases. Furthermore, they provide a basis for understanding the oral-systemic axis driven through salivary SCFAs in the pathogenesis of several diseases. Keywords: gut microbiome, oral diseases, oral microbiome, salivary metabolites, SCFAs

Objective: To investigate the biological regulatory function of Gremlin1 (GREM1) and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein eta (YWHAH) in dental pulp stem cells (DPSCs), and determine the underlying molecular mechanism involved. Methods: Alkaline phosphatase (ALP) activity, alizarin red staining, scratch migration assays and in vitro and in vivo osteo-/dentinogenic marker detection of bone-like tissue generation in nude mice were used to assess osteo-/dentinogenic differentiation. Coimmunoprecipitation and polypeptide microarray assays were employed to detect the molecular mechanisms involved. Results: The data revealed that knockdown of GREM1 promoted ALP activity, mineralisation in vitro and the expression of osteo-/dentinogenic differentiation markers and enhanced osteo-/ dentinogenesis of DPSCs in vivo. GREM1 bound to YWHAH in DPSCs, and the binding site was also identified. Knockdown of YWHAH suppressed the osteo-/dentinogenesis of DPSCs in vitro, and overexpression of YWHAH promoted the osteo-/dentinogenesis of DPSCs in vitro and in vivo. Conclusion: Taken together, the findings highlight the critical roles of GREM1-YWHAH in the osteo-/dentinogenesis of DPSCs. Keywords: dental pulp stem cells, Gremlin1, tooth regeneration, YWHAH

Objective: To investigate whether bone marrow mesenchymal stem cells (BMMSCs) modulate periodontal bone repair through the hydroxylase domain-containing protein 2 (PHD2)/hypoxia- inducible factor-1 (HIF-1) signalling pathway in response to inflammatory conditions. Methods: Osteogenic differentiation of PHD2 shRNA-modified BMMSCs and the possible mechanism were explored in an inflammatory microenvironment stimulated by porphyromonas gingivalis lipopolysaccharide (Pg-LPS) in vitro. The effect of PHD2 gene-modified BMMSCs on periodontal bone loss was evaluated with experimental periodontitis. Results: Pg-LPS stimulation greatly impaired the osteogenic differentiation of BMMSCs, whereas the silence of PHD2 significantly enhanced the osteogenesis of BMMSCs. More importantly, increased level of vascular endothelial growth factor (VEGF) was detected under Pg-LPS stimulation, which was verified to be associated with the augmented osteogenesis. In experimental periodontitis, PHD2-modified BMMSCs transplantation elevated osteogenic parameters and the expression of VEGF in periodontal tissue. Conclusion: This study highlighted that PHD2 gene silencing could be a feasible approach to combat inflammatory bone loss by rescuing the dysfunction of seed cells. Keywords: BMMSCs, HIF-1, inflammation, PHD2, VEGF

Objective: To reveal the role and mechanism of cannabinoid receptor 1 (CB1) and mitochondria in promoting osteogenic differentiation of periodontal ligament stem cells (PDLSCs) in the inflammatory microenvironment. Methods: Bidirectional mitochondrial transfer was performed in bone mesenchymal stem cells (BMSCs) and PDLSCs. Laser confocal microscopy and quantitative flow cytometry were used to observe the mitochondrial transfer and quantitative mitochondrial transfer efficiency. Realtime reverse transcription polymerase chain reaction (RT-PCR) was employed to detect gene expression. Alkaline phosphatase (ALP) activity, alizarin red staining (ARS) and quantitative calcium ion analysis were used to evaluate the degree of osteogenic differentiation of PDLSCs. Results: Bidirectional mitochondrial transfer was observed between BMSCs and PDLSCs. The indirect co-culture system could simulate intercellular mitochondrial transfer. Compared with the conditioned medium (CM) for BMSCs, that for HA-CB1 BMSCs could significantly enhance the mineralisation ability of PDLSCs. The mineralisation ability of PDLSCs could not be enhanced after removing the mitochondria in CM for HA-CB1 BMSCs. The expression level of HO-1, PGC-1α, NRF-1, ND1 and HK2 was significantly increased in HA-CB1 BMSCs. Conclusion: CM for HA-CB1 BMSCs could significantly enhance the damaged osteogenic differentiation ability of PDLSCs in the inflammatory microenvironment, and the mitochondria of CM played an important role. CB1 was related to the activation of the HO-1/PGC-1α/NRF-1 mitochondrial biogenesis pathway, and significantly increased the mitochondrial content in BMSCs. Keywords: bone marrow mesenchymal stem cells, CB1, mitochondrial transfer, osteogenic differentiation, periodontal membrane stem cells

Objective: To establish an animal model of oral squamous cell carcinoma invading the mandible through multi-sample experiments that verified the stability, repeatability, tumorigenicity and mandible destruction rate of the model. Methods: Oral squamous cell carcinoma cell suspension was injected into the outer side of the mandible through the anterior edge of the masseter muscle of naked mice to observe the tumourforming process. Then, the anatomical, histological and imaging examinations were carried out to determine whether the tumour had invaded the mandible. By comparing the tumour growth of multiple groups of various squamous cell carcinoma cells (CAL27, HN6 and HN30 cells), the changes in body weight and characteristics of tumour formation were compared, and the experience was summarised to further verify the stability, repeatability, tumour formation rate and arch damage rate of the model. Results: The subsequent specimens of tumour-bearing nude mice were validated once the model had been established. In vitro, tumour tissue wrapped around the mandible’s tumour-bearing side, and the local texture was tough with no resistance to acupuncture. Haematoxylin and eosin staining revealed that squamous cells were infiltrating the mandible in both the horizontal and sagittal planes. Microcomputed tomography results showed that the mandible on the tumour-bearing side displayed obvious erosion damage. Cell lines with various passage rates clearly had diverse tumour-bearing life cycles. Conclusion: This study successfully established an animal model of oral squamous cell carcinoma invasion of the mandible. The model has excellent biological stability, repeatability, tumorigenesis rate and mandible destruction rate. Keywords: animal model, invade, life cycle, mandible, oral squamous cell carcinoma

Objective: To investigate the antioxidant enzyme status in biological samples of patients with oral squamous cell carcinoma (OSCC) and compare them with biological samples of healthy people through a systematic review and meta-analysis. Methods: Antioxidant enzymes of catalase (CAT), sodium dismutase (SOD) and glutathione peroxide (GPx) were included in the analysis. A literature search was conducted of the PubMed, Science Direct, Scopus, Web of Science and Wiley Online Library databases for studies published between January 1999 and December 2022. A total of 831 articles were selected, of which 131 were found to be relevant. Finally, the full texts of 12 studies were screened and included. Studies that evaluated other antioxidant enzymes were excluded. Standardised mean difference (SMD) was derived to conduct a meta-analysis using comprehensive meta-analysis v3 (Biostat, Englewood, NJ, USA). A random effects model with 95% confidence interval (CI) was used to estimate the effect size. P < 0.05 was considered significant. Results: CAT levels were measured in eight studies (n = 567) and the mean values for the OSCC and control groups were 4.81 ± 2.57 and 10.02 ± 1.81, respectively (SMD 3.18, 95% CI 1.01 to 1.42; P = 0.001). SOD level was evaluated in 11 studies (n = 762) and the values for the OSCC and control groups were 3.78 ± 1.45 and 7.34 ± 1.79, respectively (SMD 3.66, 95% CI 1.51 to 1.94; P = 0.001). GPx level was evaluated in 10 studies (n = 697) and the values for the OSCC and control groups were 13.33 ± 1.42 and 16.54 ± 2.9, respectively (SMD 1.91, 95% CI 1.34 to 1.77; P = 0.001). The heterogeneity between the studies was severe (I2 ≥ 90%). The risk of bias between studies was low to moderate. Conclusion: Analysis revealed that the levels of antioxidant enzymes decreased in biological samples of patients with OSSC as compared to healthy controls. Understanding the pathological progress of OSCC by analysing the level of antioxidant enzymes is beneficial in formulating a personalised, targeted pro-oxidant therapy for cancer treatment. Keywords: antioxidant enzymes, oral squamous cell carcinoma, pathogenesis

Objective: To examine the increased use of chairside CAD/CAM among Chinese dental practitioners, and to explore the existing barriers influencing its further application and satisfaction levels. Methods: A semi-structured questionnaire was developed to gather respondents’ demographic information, as well as their experiences and behaviours regarding the implementation of chairside CAD/CAM. A specialised web-based survey system and WeChat were used to display and distribute the final questionnaire. Then, the data were analysed with Chi-square tests and regression analyses to determine the effects of various demographic variables on chairside CAD/ CAM applications. Results: A total of 1,969 questionnaire responses were included in the analyses. Chairside CAD/ CAM systems were used by 36.9% of participants, with a higher usage rate observed among prosthodontists (60.0%) and dental practitioners holding a PhD degree (57.7%). Chairside CAD/ CAM-fabricated prostheses were most commonly used in the posterior maxilla (83.3%) and mandible (86.0%), followed by the anterior maxilla and mandible (63.8% and 48.6%, respectively). Major barriers to further application included high initial investment, frequent updates of equipment and software programs, and a lack of expertise in chairside CAD/CAM usage. Conclusion: Most dental practitioners did not use chairside CAD/CAM systems. The application rate was significantly influenced by sex, location, educational background, department and type of healthcare facility. Chairside CAD/CAM users showed limited satisfaction with the aesthetic performance of the fabricated prostheses. To improve the popularity of chairside CAD/CAM systems, especially among dental practitioners lacking advanced academic degrees, it is highly advisable to optimise CAD software programs and offer comprehensive training opportunities. Keywords: chairside CAD/CAM restoration, cross-sectional study, dental practitioners, survey