osteoprotegerin and Necrosis

The aim of this study is to evaluate and compare the response of bone tissue after osteotomy carried out with either rotating cutters or with piezoelectric terminals.Bioptic samples of bone tissue were taken during operations with rotating burs and piezoelectric terminals to increase bone volume before implantology. Samples first underwent histomorphometric analysis. Subsequently, osteoblastic cells, obtained from different samples, were placed in culture and allowed to proliferate to in vitro evaluate the time to initiate growth and to reach confluence. Finally, a molecular biologic study by reverse transcription polymerase chain reaction was performed to evaluate the expression of typical osteoblastic molecular markers, such as osteoprotegerin and osteopontin.Histomorphometric analysis showed that the width of necrotic line on the osteotomic margins from samples taken using different techniques did not vary significantly. Moreover, the times of initial growth and of confluence in cells from the 2 groups did not show any statistically significant differences. However, a highly significant correlation was revealed between the age of the patient and the initial growth time and the confluence. Similarly, reverse transcription polymerase chain reaction showed that the osteoprotegerin and osteopontin expression levels did not change significantly according to the surgical technique used.In conclusion, osteotomies carried out with either instrument do not seem to substantially influence the vitality of the bone tissue. The variability of the expression levels of typical osteoblastic markers seems to be linked more to other factors than to the surgical technique used.

Topics: Adolescent; Adult; Age Factors; Aged; Biopsy; Cell Proliferation; Cell Survival; Cells, Cultured; Child; Electrosurgery; Equipment Design; Female; Humans; Male; Mandible; Middle Aged; Necrosis; Osteoblasts; Osteopontin; Osteoprotegerin; Osteotomy; Reverse Transcriptase Polymerase Chain Reaction; Rotation; Young Adult

Osteocyte apoptosis due to microdamage and/or oxidative stress is related to increased local bone turnover and resorption observed in various bone diseases. Previous data on osteoblasts and osteoclasts have linked reactive oxygen species and antioxidants to bone remodelling. This study performs a comprehensive analysis on the effect of antioxidants such as glutathione (GSH), N-acetylcysteine and lipoic acid (LA) on starvation-induced osteocyte apoptosis and on cytokines involved in bone remodelling such as the receptor activator kB ligand (RANKL), osteoprotegerin (OPG) and sclerostin. For this study, apoptosis was induced by serum starvation in a murine osteocyte-like cell line MLO-Y4; this condition mimics in part osteocyte apoptosis due to microdamage. The results show that starvation-induced apoptosis and expression of RANKL, OPG and sclerostin are redox regulated processes. All antioxidants are able to inhibit the apoptosis due to starvation. They down-regulate the expression and the release of RANKL, the expression of sclerostin and RANKL/OPG ratio, whereas they only in part up-regulate OPG expression. Antioxidants mediate their effect on starvation-induced apoptosis by JNK signalling and on cytokine expression by both JNK and ERK1/2 activities. This study shows the possible involvement of biological antioxidants such as GSH and LA on redox regulated mechanisms related to apoptosis and expression of cytokines involved in bone remodelling. Moreover, it suggests that both JNK and ERK1/2 may be useful biological targets for drugs affecting bone diseases associated with increased oxidative stress.

Topics: Acetylcysteine; Adaptor Proteins, Signal Transducing; Animals; Antioxidants; Apoptosis; Bone Diseases; Bone Remodeling; Cell Line; Down-Regulation; Extracellular Signal-Regulated MAP Kinases; Glutathione; Glycoproteins; Hydrogen Peroxide; Intercellular Signaling Peptides and Proteins; MAP Kinase Kinase 4; Mice; Necrosis; Osteocytes; Osteoprotegerin; Oxidation-Reduction; Phosphorylation; RANK Ligand; Thioctic Acid

Osteoprotegerin (OPG), as an osteoclast antagonist, limits mineralised tissue resorption under physiological conditions. Previous work investigating OPG in a rat periodontal ligament (PDL) ankylosis model found no inhibitory effect on osteoclasts when OPG was administered at a dosage of 2.5mg/kg.. The object of this study was to determine whether dosages higher than 2.5 mg/kg of OPG were required to limit osteoclastic activity in an aseptic inflammatory model in rats.. Dry ice was applied for 15 minutes to the upper right first molar crown of eighteen, 8-week-old, male Sprague-Dawley rats. Three groups of 3 were injected with OPG at dosages of 2.5, 5.0 and 7.5 mg/kg of body weight immediately following the thermal insult. After 7 days, the rats were sacrificed and each maxilla processed for histological examination and stained for osteoclastic activity using tartrate-resistant acid phosphatase (TRAP). Osteoclast population numbers were estimated via light microscopy and results were analysed using a comparative mixed model statistical analysis.. Results showed OPG inhibited osteoclastic activity in a dose-dependent manner. From 2.5 mg/kg to 7.5 mg/kg, osteoclast populations were linearly reduced by 39.78% (p < 0.05). OPG did not appear to affect the inflammatory process and had varied efficacy in different regions of individual teeth.. Although osteoclastic activity reduced, it was not completely eliminated, perhaps because dosages were still inadequate, or additional factors might influence OPG and osteoclast activation in the aseptic inflammatory model.

Topics: Acid Phosphatase; Animals; Biomarkers; Cell Count; Disease Models, Animal; Dose-Response Relationship, Drug; Dry Ice; Freezing; Inflammation; Isoenzymes; Male; Maxilla; Molar; Necrosis; Odontoblasts; Osteoclasts; Osteoprotegerin; Rats; Rats, Sprague-Dawley; Root Resorption; Tartrate-Resistant Acid Phosphatase; Tooth Crown

Osteonecrosis of the jaw (ONJ) is associated with bisphosphonate (BP) therapy. BPs alter osteoblast production of mediators of osteoclastogenesis, including interleukin (IL)-6, RANKL and osteoprotegerin (OPG), a RANKL antagonist. This can inhibit bone turnover and lead to necrosis. There is little information on the contribution of gingival fibroblasts, near bone-resorption sites, to the IL-6/RANKL/OPG network, the effects of BPs, or fibroblast involvement in ONJ pathogenesis. Therefore, the objective of this study was to determine the effects of alendronate and pamidronate on the constitutive production, or the lipopolysaccharide (LPS)- or IL-1β-stimulated production, of IL-6, RANKL and OPG by human gingival fibroblasts.. Human gingival fibroblasts were derived from explants obtained from healthy individuals with noninflamed gingiva. Cytotoxicity was determined by measuring the activity of a mitochondrial enzyme. Fibroblasts were pre-incubated or not with BPs (0.01 nm-1 μm), then incubated or not with LPS or IL-1β. The concentrations of IL-6, OPG and RANKL were measured using ELISA. Data were analyzed using analysis of variance (ANOVA) and Scheffé's F procedure.. LPS and BPs were not cytotoxic. The cells produced IL-6, OPG and RANKL, all of which were stimulated by IL-1β or LPS (p ≤ 0.04). BPs generally increased the production of IL-6 and OPG (p ≤ 0.04) and decreased the production of RANKL (p ≤ 0.02). BPs generally further increased the production of LPS- or IL-1β-stimulated IL-6 (p ≤ 0.04) and had no effect on, or further increased, the production of LPS- or IL-1β-stimulated OPG (p ≤ 0.04). BPs decreased the production of LPS- or IL-1β-stimulated RANKL (p ≤ 0.04) and decreased constitutive, LPS-stimulated and IL-1β-stimulated RANKL/OPG ratios (p ≤ 0.02).. The action of alendronate and pamidronate on human gingival fibroblasts, through altering the production of RANKL and OPG, appears to contribute to a microenvironment favoring the inhibition of bone resorption and ONJ.

Topics: Alendronate; Analysis of Variance; Bone Density Conservation Agents; Bone Remodeling; Cells, Cultured; Diphosphonates; Fibroblasts; Gingiva; Humans; Interleukin-1beta; Interleukin-6; Lipopolysaccharides; Necrosis; Osteoclasts; Osteoprotegerin; Pamidronate; RANK Ligand; Statistics, Nonparametric