Interferon-γ enhances the efficacy of autogenous bone grafts by inhibiting postoperative bone resorption in rat calvarial defects.

PURPOSE: Interferon (IFN)-γ is a major cytokine produced by immune cells that plays diverse roles in modulating both the immune system and bone metabolism, but its role in autogenous bone grafting remains unknown. Here, we present that local IFN-γ administration improved the efficacy of autogenous bone graft treatment in an experimental rat model. METHODS: An autogenous bone graft model was prepared with critically sized rat calvariae defects. Four weeks (w) after bone graft implantation, rats were treated locally with IFN-γ or were not treated. The effect of IFN-γ on bone formation was evaluated for up to 8w with micro-computed tomography, quantitative histomorphometry, and Von Kossa staining. Osteoclastogenesis was assessed by tartrate-resistant acid phosphatase staining. Immunohistochemistry staining or quantitative polymerase chain reactions were used to estimate the expression of osteoclast differentiation factor and inflammatory cytokines including tumor necrosis factor (TNF)-α, a well-known stimulant of osteoclastogenesis and an inhibitor of osteoblast activity, in defects. RESULTS: Newly formed bone gradually replaced the autogenous bone grafts within 4w, although severe bone resorption with osteoclastogenesis and TNF-α expression occurred after 6w in the absence of IFN-γ administration. IFN-γ administration markedly attenuated bone loss, osteoclastogenesis, and TNF-α expression, while it enhanced bone formation at 8w. CONCLUSION: Local IFN-γ administration promoted bone formation in autogenous bone grafts possibly via regulating osteoclastogenesis and TNF-α expression. The data provide insights into the potential roles of IFN-γ in autogenous bone grafting.

The increased ratio of 11ß-hydroxysteroid dehydrogenase type 1 versus 11ß-hydroxysteroid dehydrogenase type 2 in chronic periodontitis irrespective of obesity.

11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), which converts inactive cortisone to active cortisol, has been reported to play an important role in metabolic diseases as well as chronic inflammatory diseases. The involvement of 11ß-HSD1 in chronic periodontitis was investigated in the present study. The relationship between the levels of 11ß-HSD1, chronic periodontitis, and body mass index (BMI) was analyzed. The expression of 11ß-HSD1 mRNA was significantly higher in the chronic periodontitis group than in the control group. Since the expression of 11ß-HSD2, which converts active cortisol to inactive cortisone, was slightly lower in the chronic periodontitis group than in the controls, the ratio of 11ß-HSD1 versus 11ß-HSD2 was significantly higher in the chronic periodontitis group than in the controls. A correlation was not observed between BMI and the level of 11ß-HSD1 or between BMI and the ratio of 11ß-HSD1 versus 11ß-HSD2. These results suggested that an increase in the ratio of 11ß-HSD1 versus 11ß-HSD2 was associated with chronic periodontitis irrespective of obesity.

Cell survival and gene expression under compressive stress in a three-dimensional in vitro human periodontal ligament-like tissue model.

This study investigated cell survival and gene expression under various compressive stress conditions mimicking orthodontic force by using a newly developed in vitro model of human periodontal ligament-like tissue (HPdLLT). The HPdLLT was developed by three-dimensional culturing of human periodontal ligament fibroblasts in a porous poly-L-lactide matrix with threefold increased culture media permeability due to hydrophilic modification. In vitro HPdLLTs in experimental groups were subjected to 5, 15, 25 and 35 g/cm(2) compressive stress for 1, 3, 7 or 14 days; controls were cultured over the same periods without compressive stress. Cell morphology and cell apoptosis in the experimental and control groups were investigated using scanning electron microscopy and caspase-3/7 detection. Real-time polymerase chain reaction was performed for seven osteogenic and osteoclastic genes. Similar extracellular matrix and spindle-shaped cells were observed inside or on the surface of in vitro HPdLLTs, with no relation to compressive stress duration or intensity. Similar caspase-3/7 activity indicating comparable apoptosis levels was observed in all samples. Receptor activator of nuclear factor kappa-B ligand and bone morphogenetic protein 2 genes showed characteristic "double-peak" expression at 15 and 35 g/cm(2) on day 14, and alkaline phosphatase and periodontal ligament-associated protein 1 expression peaked at 5 g/cm(2) on day 14; other genes also showed time-dependent and load-dependent expression patterns. The in vitro HPdLLT model system effectively mimicked the reaction and gene expression of the human periodontal ligament in response to orthodontic force. This work provides new information on the effects of compressive stress on human periodontal ligament tissue.

Effects of tryptophan-rich breakfast and light exposure during the daytime on melatonin secretion at night.

BACKGROUND: The purpose of the present study is to investigate effects of tryptophan intake and light exposure on melatonin secretion and sleep by modifying tryptophan ingestion at breakfast and light exposure during the daytime, and measuring sleep quality (by using actigraphy and the OSA sleep inventory) and melatonin secretion at night. METHODS: Thirty three male University students (mean ± SD age: 22 ± 3.1 years) completed the experiments lasting 5 days and 4 nights. The subjects were randomly divided into four groups: Poor*Dim (n = 10), meaning a tryptophan-poor breakfast (55 mg/meal) in the morning and dim light environment (<50 lx) during the daytime; Rich*Dim (n = 7), tryptophan-rich breakfast (476 mg/meal) and dim light environment; Poor*Bright (n = 9), tryptophan-poor breakfast and bright light environment (>5,000 lx); and Rich*Bright (n = 7), tryptophan-rich breakfast and bright light. RESULTS: Saliva melatonin concentrations on the fourth day were significantly lower than on the first day in the Poor*Dim group, whereas they were higher on the fourth day in the Rich*Bright group. Creatinine-adjusted melatonin in urine showed the same direction as saliva melatonin concentrations. These results indicate that the combination of a tryptophan-rich breakfast and bright light exposure during the daytime could promote melatonin secretion at night; further, the observations that the Rich*Bright group had higher melatonin concentrations than the Rich*Dim group, despite no significant differences being observed between the Poor*Dim and Rich*Dim groups nor the Poor*Bright and Rich*Bright groups, suggest that bright light exposure in the daytime is an important contributor to raised melatonin levels in the evening. CONCLUSIONS: This study is the first to report the quantitative effects of changed tryptophan intake at breakfast combined with daytime light exposure on melatonin secretion and sleep quality. Evening saliva melatonin secretion changed significantly and indicated that a tryptophan-rich breakfast and bright light exposure during the daytime promoted melatonin secretion at this time.

An inhibitory role for caspase-3 at the late stage of RANKL-induced osteoclast differentiation in RAW264 cells and mouse bone marrow macrophages.

Osteoclast differentiation/activation is involved in orthodontic tooth movement at the compression sites of the alveolar bone. RANKL, a member of the TNF family expressed in osteoblasts, binds to RANK, a member of the TNF receptor family expressed on preosteoclasts, resulting in differentiation of preosteoclasts into mature osteoclasts. Several members of the TNF family, such as TNF and Fas ligand, can induce apoptosis by activation of caspase-3. We have investigated whether caspase-3 be involved in the late stage of RANKL-induced osteoclast differentiation. Increased active caspase-3 was found in mouse monocytic RAW264 cells differentiated into mature osteoclasts by treatment with RANKL for 3 days. Co-treatment with Z-Asp-CH2-DCB, a caspase-3-specific inhibitor, augmented RANKL-induced osteoclast differentiation in RAW264 cells, also seen in mouse bone marrow macrophages. This suggests that activation of caspase-3 may play an inhibitory role at the late stage of RANKL-induced osteoclast differentiation.

In vitro human periodontal ligament-like tissue formation with porous poly-L-lactide matrix.

This study aimed to establish an in vitro human periodontal ligament-like tissue (HPdLLT) by three-dimensional culturing of human periodontal ligament fibroblasts (HPdLFs) in a porous poly-L-lactide (PLLA) matrix modified hydrophilically with ammonia solution. After ammonia modification, the surface roughness and culture-medium-soaking-up ability of the PLLA matrix increased, whereas the contact angle of water drops decreased. The thickness, porosity, and pore size of the PLLA matrix were 400±50 µm, 83.3%, and 75-150 µm, respectively. HPdLFs (1×10(5) cells) were seeded on the modified PLLA matrix and centrifuged to facilitate seeding into its interior and cultured for 14 days. Scanning electron microscope (SEM) observation, proliferation assay, picrosirius-red staining, and real-time polymerase chain reaction (RT-PCR) for type-1 collagen (COL1), periodontal ligament associated protein-1 (PLAP-1), fibroblast growth factor-2 (FGF-2), and alkaline phosphatase (ALP) mRNA were conducted on days 1, 3, 7, and 14. HPdLFs were observed entirely from the surface to the rear side of the matrix. Cell proliferation analysis, SEM observation, and picrosirius-red staining showed both progressive growth of 3D-cultured HPdLFs and extracellular matrix maturation by the secretion of COL1 and type 3 collagen (COL3) from days 1 to 14. Expressions of COL1, PLAP-1, and FGF-2 mRNA suggested the formation of cellular components and supplementation of extracellular components. Expressions of ALP, COL1, and PLAP-1 mRNA suggested the osteogenic potential of the HPdLLT. The results indicated in vitro HPdLLT formation, and it could be used in future periodontal ligament tissue engineering to achieve optimal periodontal regeneration.