Effects of periodontal and bisphosphonate treatment on the gingival crevicular levels of sclerostin and dickkopf-1 in postmenopausal osteoporosis with and without periodontitis

Signalling interaction between β-catenin and other signalling molecules during osteoarthritis development

Osteoarthritis (OA) is the most prevalent disorder of synovial joint affecting multiple joints. In the past decade, we have witnessed conceptual switch of OA pathogenesis from a 'wear and tear' disease to a disease affecting entire joint. Extensive studies have been conducted to understand the underlying mechanisms of OA using genetic mouse models and ex vivo joint tissues derived from individuals with OA. These studies revealed that multiple signalling pathways are involved in OA development, including the canonical Wnt/β-catenin signalling and its interaction with other signalling pathways, such as transforming growth factor β (TGF-β), bone morphogenic protein (BMP), Indian Hedgehog (Ihh), nuclear factor κB (NF-κB), fibroblast growth factor (FGF), and Notch. The identification of signalling interaction and underlying mechanisms are currently underway and the specific molecule(s) and key signalling pathway(s) playing a decisive role in OA development need to be evaluated. This review will focus on recent progresses in understanding of the critical role of Wnt/β-catenin signalling in OA pathogenesis and interaction of β-catenin with other pathways, such as TGF-β, BMP, Notch, Ihh, NF-κB, and FGF. Understanding of these novel insights into the interaction of β-catenin with other pathways and its integration into a complex gene regulatory network during OA development will help us identify the key signalling pathway of OA pathogenesis leading to the discovery of novel therapeutic strategies for OA intervention.

Identification of potential cell death-related biomarkers for diagnosis and treatment of osteoporosis

BACKGROUND

This study aimed to identify potential biomarkers for the diagnosis and treatment of osteoporosis (OP).

METHODS

Data sets were downloaded from the Gene Expression Omnibus database, and differentially programmed cell death-related genes were screened. Functional analyses were performed to predict the biological processes associated with these genes. Least absolute shrinkage and selection operator (LASSO), support vector machine (SVM), and random forest (RF) machine learning algorithms were used to screen for characteristic genes, and receiver operating characteristics were used to evaluate the diagnosis of disease characteristic gene values. Gene set enrichment analysis (GSEA) and single-sample GSEA were conducted to analyze the correlation between characteristic genes and immune infiltrates. Cytoscape and the Drug Gene Interaction Database (DGIdb) were used to construct the mitochondrial RNA-mRNA-transcription factor network and explore small-molecule drugs. Reverse transcription real-time quantitative PCR (RT-qPCR) analysis was performed to evaluate the expression of biomarker genes in clinical samples.

RESULTS

In total, 25 differential cell death genes were identified. Among these, two genes were screened using the LASSO, SVM, and RF algorithms as characteristic genes, including BRSK2 and VPS35. In GSE56815, the area under the receiver operating characteristic curve of BRSK2 was 0.761 and that of VPS35 was 0.789. In addition, immune cell infiltration analysis showed that BRSK2 positively correlated with CD56dim natural killer cells and negatively correlated with central memory CD4 + T cells. Based on the data from DGIdb, hesperadin was associated with BRSK2, and melagatran was associated with VPS35. BRSK2 and VPS35 were expectably upregulated in OP group compared with controls (all p < 0.05).

CONCLUSIONS

BRSK2 and VPS35 may be important diagnostic biomarkers of OP.

Gingival crevicular fluid periodontal ligament-associated protein-1, sclerostin, and tumor necrosis factor-alpha levels in periodontitis

BACKGROUND

In periodontitis, the equilibrium between bone formation and resorption skews in favor of bone loss. Periodontal ligament-associated protein-1 (PLAP-1) and sclerostin play a significant role in the suppression of bone formation. Tumor necrosis factor-alpha (TNF-α) is a central proinflammatory cytokine related to periodontal bone loss. This study aims to assess gingival crevicular fluid (GCF) PLAP-1, sclerostin, and TNF-α levels in individuals with periodontal disease.

METHODS

Seventy-one individuals diagnosed with generalized stage III grade C periodontitis (n = 23), gingivitis (n = 24), and periodontal health (n = 24) were included in the study. Full-mouth clinical periodontal measurements were performed. PLAP-1, sclerostin, and TNF-α total amounts in GCF were quantified by ELISA. Nonparametric methods were used for the data analyses.

RESULTS

Periodontitis group exhibited significantly higher GCF PLAP-1, sclerostin and TNF-α levels compared with gingivitis and periodontally healthy groups (p < 0.05). GCF PLAP-1 and TNF-α levels of gingivitis group were higher than healthy controls (p < 0.05) whereas GCF sclerostin levels were similar in two groups (p > 0.05). Significant positive correlations were found between GCF PLAP-1, sclerostin and TNF-α levels and all clinical parameters (p < 0.01).

CONCLUSIONS

To our knowledge, this is the first study showing GCF PLAP-1 levels in periodontal health and disease. Increased GCF PLAP-1 and sclerostin levels and their correlations with TNF-α in periodontitis imply that those molecules might be involved in the pathogenesis of periodontal disease. Further studies in larger mixed cohorts are needed to enlighten the possible role of PLAP-1 and sclerostin in periodontal bone loss.

Sclerostin deficiency effectively promotes bone morphogenetic protein-2-induced ectopic bone formation

BACKGROUND AND OBJECTIVE

Severe periodontitis causes alveolar bone resorption, resulting in tooth loss. Developments of tissue regeneration therapy that can restore alveolar bone mass are desired for periodontal disease. The application of bone morphogenetic protein-2 (BMP-2) has been attempted for bone fractures and severe alveolar bone loss. BMP-2 reportedly induces sclerostin expression, an inhibitor of Wnt signals, that attenuates bone acquisition. However, the effect of sclerostin-deficiency on BMP-2-induced bone regeneration has not been fully elucidated. We investigated BMP-2-induced ectopic bones in Sost-knockout (KO) mice.

METHODS

rhBMP-2 were implanted into the thighs of C57BL/6 (WT) and Sost-KO male mice at 8 weeks of age. The BMP-2-induced ectopic bones in these mice were examined on days 14 and 28 after implantation.

RESULTS

Immunohistochemical and quantitative RT-PCR analyses showed that BMP-2-induced ectopic bones expressed sclerostin in osteocytes on days 14 and 28 after implantation in Sost-Green reporter mice. Micro-computed tomography analysis revealed that BMP-2-induced ectopic bones in Sost-KO mice showed a significant increased relative bone volume and bone mineral density (WT = 468 mg/cm³ , Sost-KO = 602 mg/cm³ ) compared with those in WT mice on day 14 after implantation. BMP-2-induced ectopic bones in Sost-KO mice showed an increased horizontal cross-sectional bone area on day 28 after implantation. Immunohistochemical staining showed that BMP-2-induced ectopic bones in Sost-KO mice had an increased number of osteoblasts with osterix-positive nuclei compared with those in WT mice on days 14 and 28 after implantation.

CONCLUSION

Sclerostin deficiency increased bone mineral density in BMP-2-induced ectopic bones.