Critical roles of periostin in the process of orthodontic tooth movement.

AIM: The process of orthodontic tooth movement (OTM) involves multiple mechanisms of action including bone and extracellular matrix remodelling, although the role of periodontal ligament (PDL) in this process is largely unknown. Periostin, which is highly expressed in the PDL, is known to be responsible for mechanical stimulation in maintaining the integrity of periodontal tissues. We hypothesize that this protein plays an important role during OTM. MATERIAL AND METHODS: By using spring in 4-week-old wild-type (WT) and periostin null mice, the rate of tooth movement and mineralization were evaluated. For the evaluation, double labelling, expression of sclerostin (SOST), number of TRAP-positive cells, and quality of collagen fibrils by Sirius red were analysed and compared between these two groups. RESULTS: Our findings showed that the distance of the tooth movement and mineral deposition rates were significantly reduced in periostin null mice (P < 0.05), with a lack of expression changes in SOST as observed in the WT group. The arrangement, digestion, and integrity of collagen fibrils were impaired in periostin null mice. The number of osteoclasts reflected by expressions of TRAP (tartrate-resistant acid phosphatase) in the null mice was also significantly lower than the WT control (P < 0.05). CONCLUSION: Periostin plays a stimulatory role in both SOST and TRAP responses to OTM in the compassion site, although it is not clear if this role is direct or indirect during orthodontic loading.

Inactivation of a novel FGF23 regulator, FAM20C, leads to hypophosphatemic rickets in mice.

Family with sequence similarity 20,-member C (FAM20C) is highly expressed in the mineralized tissues of mammals. Genetic studies showed that the loss-of-function mutations in FAM20C were associated with human lethal osteosclerotic bone dysplasia (Raine Syndrome), implying an inhibitory role of this molecule in bone formation. However, in vitro gain- and loss-of-function studies suggested that FAM20C promotes the differentiation and mineralization of mouse mesenchymal cells and odontoblasts. Recently, we generated Fam20c conditional knockout (cKO) mice in which Fam20c was globally inactivated (by crossbreeding with Sox2-Cre mice) or inactivated specifically in the mineralized tissues (by crossbreeding with 3.6 kb Col 1a1-Cre mice). Fam20c transgenic mice were also generated and crossbred with Fam20c cKO mice to introduce the transgene in the knockout background. In vitro gain- and loss-of-function were examined by adding recombinant FAM20C to MC3T3-E1 cells and by lentiviral shRNA-mediated knockdown of FAM20C in human and mouse osteogenic cell lines. Surprisingly, both the global and mineralized tissue-specific cKO mice developed hypophosphatemic rickets (but not osteosclerosis), along with a significant downregulation of osteoblast differentiation markers and a dramatic elevation of fibroblast growth factor 23 (FGF23) in the serum and bone. The mice expressing the Fam20c transgene in the wild-type background showed no abnormalities, while the expression of the Fam20c transgene fully rescued the skeletal defects in the cKO mice. Recombinant FAM20C promoted the differentiation and mineralization of MC3T3-E1 cells. Knockdown of FAM20C led to a remarkable downregulation of DMP1, along with a significant upregulation of FGF23 in both human and mouse osteogenic cell lines. These results indicate that FAM20C is a bone formation "promoter" but not an "inhibitor" in mouse osteogenesis. We conclude that FAM20C may regulate osteogenesis through its direct role in facilitating osteoblast differentiation and its systemic regulation of phosphate homeostasis via the mediation of FGF23.

Evaluation of oral mucosa epithelium in type II diabetic patients by an exfoliative cytology method.

Diabetes mellitus is a common metabolic disease that causes chronic hyperglycemia and disturbances in carbohydrate, lipid, and protein metabolism. Although diabetes can cause considerable cellular changes, this field has attracted little research. We therefore decided to evaluate the quantitative and qualitative changes in oral epithelial cells using an exfoliative cytology method. In 30 control individuals and 30 patients with type II diabetes, smears were obtained from two distinct oral sites: the buccal mucosa and tongue dorsum. The oral smears were stained using Papanicolaou solution. Quantitative and qualitative changes were evaluated in each slide. For this purpose, 50 clearly defined cells in each slide were microscopically evaluated, and photographs were subjected to computerized morphometric analysis. Cytoplasmic and nuclear areas in the diabetic group were significantly higher than in the control group. The cytoplasmic/nuclear ratio was lower in the control group. At both smear sites, the proportion of cells with nuclear changes was higher in the diabetic group. Diabetes mellitus can cause alterations in the oral epithelium that are detectable with this exfoliative cytology method. The method may be viable in evaluating this disease.

Dentin matrix protein 1 and phosphate homeostasis are critical for postnatal pulp, dentin and enamel formation.

Deletion or mutation of dentin matrix protein 1 (DMP1) leads to hypophosphatemic rickets and defects within the dentin. However, it is largely unknown if this pathological change is a direct role of DMP1 or an indirect role of phosphate (Pi) or both. It has also been previously shown that Klotho-deficient mice, which displayed a high Pi level due to a failure of Pi excretion, causes mild defects in the dentinal structure. This study was to address the distinct roles of DMP1 and Pi homeostasis in cell differentiation, apoptosis and mineralization of dentin and enamel. Our working hypothesis was that a stable Pi homeostasis is critical for postnatal tooth formation, and that DMP1 has an antiapoptotic role in both amelogenesis and dentinogenesis. To test this hypothesis, Dmp1-null (Dmp1(-/-)), Klotho-deficient (kl/kl), Dmp1/Klotho-double-deficient (Dmp1(-/-)/kl/kl) and wild-type (WT) mice were killed at the age of 6 weeks. Combinations of X-ray, microcomputed tomography (µCT), scanning electron microscopy (SEM), histology, apoptosis and immunohistochemical methods were used for characterization of dentin, enamel and pulp structures in these mutant mice. Our results showed that Dmp1(-/-) (a low Pi level) or kl/kl (a high Pi level) mice displayed mild dentin defects such as thin dentin and a reduction of dentin tubules. Neither deficient mouse line exhibited any apparent changes in enamel or pulp structure. However, the double-deficient mice (a high Pi level) displayed severe defects in dentin and enamel structures, including loss of dentinal tubules and enamel prisms, as well as unexpected ectopic ossification within the pulp root canal. TUNEL assay showed a sharp increase in apoptotic cells in ameloblasts and odontoblasts. Based on the above findings, we conclude that DMP1 has a protective role for odontoblasts and ameloblasts in a pro-apoptotic environment (a high Pi level).

Protective roles of DMP1 in high phosphate homeostasis.

PURPOSE: Dmp1 (dentin matrix protein1) null mice (Dmp1(-/-)) display hypophosphatemic rickets with a sharp increase in fibroblast growth factor 23 (FGF23). Disruption of Klotho (the obligatory co-receptor of FGF23) results in hyperphosphatemia with ectopic calcifications formed in blood vessels and kidneys. To determine the role of DMP1 in both a hyperphosphatemic environment and within the ectopic calcifications, we created Dmp1/Klotho compound deficient (Dmp1(-/-)kl/kl) mice. PROCEDURES: A combination of TUNEL, immunohistochemistry, TRAP, von Kossa, micro CT, bone histomorphometry, serum biochemistry and Scanning Electron Microscopy techniques were used to analyze the changes in blood vessels, kidney and bone for wild type control, Dmp1(-/-), Klotho deficient (kl/kl) and Dmp1(-/-)kl/kl animals. FINDINGS: Interestingly, Dmp1(-/-)kl/kl mice show a dramatic improvement of rickets and an identical serum biochemical phenotype to kl/kl mice (extremely high FGF23, hyperphosphatemia and reduced parathyroid hormone (PTH) levels). Unexpectedly, Dmp1(-/-)kl/kl mice presented elevated levels of apoptosis in osteocytes, endothelial and vascular smooth muscle cells in small and large blood vessels, and within the kidney as well as dramatic increase in ectopic calcification in all these tissues, as compared to kl/kl. CONCLUSION: These findings suggest that DMP1 has an anti-apoptotic role in hyperphosphatemia. Discovering this novel protective role of DMP1 may have clinical relevance in protecting the cells from apoptosis in high-phosphate environments as observed in chronic kidney disease (CKD).

Salvadora Persica extract chewing gum and gingival health: improvement of gingival and probe-bleeding index.

Previous studies showed that Persica extracts have antibacterial activity against cariogenic and periodontopathic bacteria and can develop periodontal health; however, the clinical effects of gum as a delivery device for Persica to periodontal health in human, have not yet been investigated. The objective of this study was to evaluate the effect of chewing gum containing Persica extract on periodontal health in a double-masked, randomized trial. From a high school in Babol, 72 cases with plaque induced moderate gingivitis were randomly assigned to the 2 weeks trial in the following groups: S+/P+ (n = 18): use of Persica extract chewing gum for 2 weeks and two sessions of scaling; S+/P- (n = 18): use of placebo chewing gum two sessions of scaling; S-/P+ (n = 18): use of Persica extract chewing gum; and S-/P- (n = 18): use of placebo chewing gum. Plaque index (PI), gingival index (GI), and bleeding index (BI), were measured at days 0, 7, and 14. Data was analyzed with t test or Mann-Whitney U test. Seven patients from Persica scaling group and five patients from Persica no scaling (S-/P+) group were excluded for complaining about the taste and irritation. The effects of extract chewing gum was statistically significant in reduction of GI, and BI but not for PI in Persica groups compared with the placebo groups in the days of 7 and 14 after the beginning of trial. Persica extract chewing gum had a considerable effect on GI, and BI. The use of Salvadora persica extract chewing gum may promote periodontal health.