Periodontal treatment and microbiome-targeted therapy in management of periodontitis-related nonalcoholic fatty liver disease with oral and gut dysbiosis.

A growing body of evidence from multiple areas proposes that periodontal disease, accompanied by oral inflammation and pathological changes in the microbiome, induces gut dysbiosis and is involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). A subgroup of NAFLD patients have a severely progressive form, namely nonalcoholic steatohepatitis (NASH), which is characterized by histological findings that include inflammatory cell infiltration and fibrosis. NASH has a high risk of further progression to cirrhosis and hepatocellular carcinoma. The oral microbiota may serve as an endogenous reservoir for gut microbiota, and transport of oral bacteria through the gastro-intestinal tract can set up a gut microbiome dysbiosis. Gut dysbiosis increases the production of potential hepatotoxins, including lipopolysaccharide, ethanol, and other volatile organic compounds such as acetone, phenol and cyclopentane. Moreover, gut dysbiosis increases intestinal permeability by disrupting tight junctions in the intestinal wall, leading to enhanced translocation of these hepatotoxins and enteric bacteria into the liver through the portal circulation. In particular, many animal studies support that oral administration of Porphyromonas gingivalis, a typical periodontopathic bacterium, induces disturbances in glycolipid metabolism and inflammation in the liver with gut dysbiosis. NAFLD, also known as the hepatic phenotype of metabolic syndrome, is strongly associated with metabolic complications, such as obesity and diabetes. Periodontal disease also has a bidirectional relationship with metabolic syndrome, and both diseases may induce oral and gut microbiome dysbiosis with insulin resistance and systemic chronic inflammation cooperatively. In this review, we will describe the link between periodontal disease and NAFLD with a focus on basic, epidemiological, and clinical studies, and discuss potential mechanisms linking the two diseases and possible therapeutic approaches focused on the microbiome. In conclusion, it is presumed that the pathogenesis of NAFLD involves a complex crosstalk between periodontal disease, gut microbiota, and metabolic syndrome. Thus, the conventional periodontal treatment and novel microbiome-targeted therapies that include probiotics, prebiotics and bacteriocins would hold great promise for preventing the onset and progression of NAFLD and subsequent complications in patients with periodontal disease.

Development and use of a mouth gag for oral experiments in rats.

OBJECTIVE: Rodent models such as mice and rats are often used in investigations of the oral cavity in the fields of periodontology and dental anesthesiology. When various treatments are performed in the oral cavity, it is very important to secure the visual field while keeping the animal's mouth fully opened, in order to ensure the consistency of experimental procedures. Therefore, we developed a standardized gag conforming to various degrees of oral cavity size of different aged rats. DESIGN: The gag was composed of a rectangular incisor-opening frame constructed from a stainless steel wire with retractors and a dial to alter the opening amounts. Wistar rats (n = 5) aged 4, 8, and 12 weeks were used to evaluate the suitability of the gag in oral cavity. As tests for application of gag in intraoral experiments, the ligature placement around the molars, drug injection into the gingiva, measurement of gingival blood flow rate, and installation of stimulation an electrode for somatosensory-evoked potentials into the molar were performed. RESULTS: Adjusting the opening dial enabled both the maintenance of open state and more favorable intraoral observation compared with tweezers as a control device in all different types of rats. Furthermore, our gag made it possible to facilitate the insertion of diverse instruments into the oral cavity and to achieve various experimental purposes. The stainless-steel gag can also be autoclaved and dry-heat sterilized. CONCLUSION: It was revealed that our mouth gag can be widely applied to various oral experiments in different old aged rats.

Effects of theaflavins on tissue inflammation and bone resorption on experimental periodontitis in rats.

BACKGROUND AND OBJECTIVE: Theaflavins (TFs), the major polyphenol in black tea, have the ability to reduce inflammation and bone resorption. The aim of this study was to evaluate the effects of TFs on experimental periodontitis in rats. MATERIAL AND METHODS: Thirty rats were divided into five groups: Control (glycerol application without ligation), Ligature (glycerol application with ligation), TF1 (1 mg/mL TF application with ligation), TF10 (10 mg/mL TF application with ligation), and TF100 (100 mg/mL TF application with ligation). To induce experimental periodontitis, ligatures were placed around maxillary first molars bilaterally. After ligature placement, 100 µL glycerol or TFs were topically applied to the rats daily, and rats were euthanized 7 days after ligature placement. Micro-computed tomography was used to measure bone resorption in the left side of the maxilla, and quantitative polymerase chain reaction was used to measure the expression of interleukin (IL)-6, growth-regulated gene product/cytokine-induced neutrophil chemoattractant (Gro/Cinc-1, rat equivalent of IL-8), matrix metalloproteinase-9 (Mmp-9), receptor activator of nuclear factor-kappa Β ligand (Rankl), osteoprotegerin (Opg), and the Rankl/Opg ratio in gingival tissue. With tissue from the right side of the maxilla, hematoxylin and eosin staining was used for histological analysis, immunohistochemical staining for leukocyte common antigen (CD45) was used to assess inflammation, and tartrate-resistant acid phosphatase (TRAP) staining was used to observe the number of osteoclasts. RESULTS: The TF10 and TF100 groups, but not the TF1 group, had significant inhibition of alveolar bone loss, reduction in inflammatory cell infiltration in the periodontium, and significantly reduced numbers of CD45-positive cells and TRAP-positive osteoclasts compared with the Ligature group. Correspondingly, the TF10 and TF100 groups had significantly downregulated gene expression of IL-6, Gro/Cinc-1(IL-8), Mmp-9, and Rankl, but not of Opg. Consequently, Rankl/Opg expression was significantly increased in the Ligation group but was attenuated in the TF10 and TF100 groups. CONCLUSION: The results of this study suggest that topical application of TFs may reduce inflammation and bone resorption in experimental periodontitis. Therefore, TFs have therapeutic potential in the treatment of periodontal disease.

Osteogenic potential of rat stromal cells derived from periodontal ligament.

Various mesenchymal stromal cells (MSCs) have been applied to regenerative medicine. MSCs derived from periodontal tissue could also be a useful cell source for alveolar bone regeneration. However, only a few attempts of direct comparisons have been made between MSCs from periodontal tissues and those from other somatic tissues. The purpose of this study was to clarify the osteogenic characteristics of mesenchymal stromal cells derived from bone marrow (BMSCs), adipose tissue (ASCs) and periodontal ligament (PDLSCs). BMSCs, ASCs and PDLSCs were isolated from Fisher 344 rats. After 1 week of primary culture, stromal cells were subjected to cell surface analysis and osteogenic differentiation. The cells were subcultured for 2 weeks with and without osteogenic supplements (OS), followed by biochemical and histological analyses. With regard to cell surface antigens, all MSCs were positive for CD29 and CD90 and negative for CD45. With regard to osteogenic differentiation, BMSCs with OS had the highest ALP activity, calcium uptake and osteocalcin content. Without OS, PDLSCs had the highest levels of these bone differentiation markers. RT-PCR analysis and histological analysis showed similar trends. These results indicate that PDLSCs are an ideal candidate for alveolar bone regeneration.

The effects of oral xylitol administration on bone density in rat femur.

To examine the effects of oral xylitol administration on rat femur bone density, 36 four-week-old male Wistar rats divided into three groups were fed CE-2 diet (control, n = 12) alone or supplemented with 10% (n = 12) or 20% (n = 12) dietary xylitol for 40 days. Biochemical, morphological, and histological analyses were performed. The 10% and 20% xylitol groups showed higher levels of both serum Ca and alkaline phosphatase activity and lower levels of serum tartrate-resistant acid phosphatase than the control group. Although no significant differences in the three-dimensional bone structure or trabecular bone structure of the femur were observed, both xylitol groups showed significantly higher bone density than the control group. Compared to the control group, the 10% and 20% xylitol groups showed an increase in trabeculae. Thus, oral administration of xylitol appears to affect bone metabolism, leading to increased bone density in rat femur.