Estimation of external dose for wild Japanese macaques captured in Fukushima prefecture: decomposition of electron spin resonance spectrum.

The signal intensities of CO2- radicals in teeth can be utilised as an individual indicator of the cumulative external dose for animals. To accurately determine the external dose, it is desirable to analyse the CO2- radical intensity and improve its detection limit. We recently reported a dose-response in the range of 0-200 mGy and estimated the absorbed dose for seven wild Japanese macaques captured in/around the related areas to the Fukushima Daiichi Nuclear Power Plant accident. Herein, for further improvement of this method, we examined the electron spin resonance spectra of the teeth of these seven and an additional four macaques captured in Fukushima by applying two spectrum-decomposition algorithms.

Detection limit of electron spin resonance for Japanese deciduous tooth enamel and density separation method for enamel-dentine separation.

Electron spin resonance (ESR) dosimetry is one of the most powerful tools for radiation dose reconstruction. The detection limit of this technique using human teeth is reported to be 56 mGy or 67 mGy; however, the absorbed dose of Fukushima residents after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident was estimated to be lower than this detection limit. Our aim is to assess the absorbed radiation dose of children in Fukushima Prefecture after the accident; therefore, it is important to estimate the detection limit for their teeth. The detection limit for enamel of deciduous teeth of Japanese children separated by the mechanical method is estimated to be 115.0 mGy. The density separation method can effectively separate enamel from third molars of Japanese people. As we have collected thousands of teeth from children in Fukushima, the present technique may be useful to examine their external absorbed dose after the FNPP accident.

Radioactivity and radionuclides in deciduous teeth formed before the Fukushima-Daiichi Nuclear Power Plant accident.

The Fukushima-Daiichi Nuclear Power Plant (FNPP) accident in March of 2011 released substantial amounts of radionuclides into the environment. We collected 4,957 deciduous teeth formed in children before the Fukushima accident to obtain precise control data for teeth formed after the accident. Radioactivity was measured using imaging plates (IP) and epidemiologically assessed using multivariate regression analysis. Additionally, we measured 90Sr, 137Cs, and natural radionuclides which might be present in teeth. Epidemiological studies of IP showed that the amount of radioactivity in teeth from Fukushima prefecture was similar to that from reference prefectures. We found that artificial radionuclides of 90Sr and 137Cs, which were believed to have originated from past nuclear disasters, and natural radionuclides including 40 K and daughter nuclides in the 238U and 232Th series contributed to the generation of radioactivity in teeth. We also found no evidence to suggest that radionuclides originating from the FNPP accident significantly contaminated pre-existing teeth. This is the first large-scale investigation of radioactivity and radionuclides in teeth. The present findings will be indispensable for future studies of teeth formed after the FNPP accident, which will fall out over the next several years and might be more contaminated with radionuclides.

Changes in Oral Health Policies and Guidelines During the COVID-19 Pandemic.

The aim of this study was to describe the changes in oral health policies and guidelines in response to the Coronavirus disease 2019 (COVID-19) pandemic in different countries and regions around the world. Information on oral health policies and guidelines from 9 countries (Canada, China including Hong Kong, Egypt, India, Japan, New Zealand, Nigeria, Switzerland, and Thailand) were summarized, and sources of the information were mostly the national or regional health authorities and/or dental council/associations. The changes made to the oral health guidelines depended on the severity of the COVID-19 pandemic. This included suspension of non-emergency dental care services at the peak of the COVID-19 outbreak, and easing the restrictions on non-essential and elective dental care when the pandemic became under control. The COVID-19 risk mitigation strategies include strict adherence to infection control practices (use of hand sanitizers, facemask and maintaining social distancing), reducing the amount of aerosol production in the dental setting, and managing the quality of air in the dental treatment rooms by reducing the use of air conditioners and improving air exchange. The COVID-19 pandemic has shown a major impact on dental practice. Dental professionals are trying to adapt to the new norms, while the medium to long-term impact of COVID-19 on dentistry needs further investigation.

Structure-Dependent Effects of Bisphosphonates on Inflammatory Responses in Cultured Neonatal Mouse Calvaria.

Bisphosphonates (BPs) are classified into two groups, according to their side chain structures, as nitrogen-containing BPs (NBPs) and non-nitrogen-containing BPs (non-NBPs). In this study, we examined the effects of NBPs and non-NBPs on inflammatory responses, by quantifying the inflammatory mediators, prostaglandin E2 (PGE2) and nitric oxide (NO), in cultured neonatal mouse calvaria. All examined NBPs (pamidronate, alendronate, incadronate, risedronate, zoledronate) stimulated lipopolysaccharide (LPS)-induced PGE2 and NO production by upregulating COX-2 and iNOS mRNA expression, whereas non-NBPs (etidronate, clodronate, tiludronate) suppressed PGE2 and NO production, by downregulating gene expression. Additionally, [4-(methylthio) phenylthio] methane bisphosphonate (MPMBP), a novel non-NBP with an antioxidant methylthio phenylthio group in its side chain, exhibited the most potent anti-inflammatory activity among non-NBPs. Furthermore, results of immunohistochemistry showed that the nuclear translocation of NF-κB/p65 and tyrosine nitration of cytoplasmic protein were stimulated by zoledronate, while MPMBP inhibited these phenomena, by acting as a superoxide anion (O2-) scavenger. These findings indicate that MPMBP can act as an efficacious agent that causes fewer adverse effects in patients with inflammatory bone diseases, including periodontitis and rheumatoid arthritis.

Increase in bone metabolic markers and circulating osteoblast-lineage cells after orthognathic surgery.

Increased mineralisation rate and bone formation after surgery or fracture is the regional acceleratory phenomenon (RAP), and its systemic impact is the systemic acceleratory phenomenon (SAP). The proportion of circulating osteoblast lineage cells, including osteocalcin-positive (OCN+) cells, in the peripheral blood is markedly higher during pubertal growth and in patients with bone fractures. This study aimed to elucidate the dynamic changes in bone metabolic activity after orthognathic surgery by longitudinal prospective observation. Peripheral venous blood samples were collected from patients who had undergone orthognathic surgery, and serum bone metabolic markers and the proportion of OCN+ cells were measured. Orthognathic surgery induces systemic dynamic changes in bone metabolic activity by targeting steps in the bone healing process and related proteins, such as surgical stress/inflammation (C-reactive protein), bone resorption (type I collagen C-telopeptide), and bone formation (alkaline phosphatase and bone-specific alkaline phosphatase). During the early post-operative period, the population of OCN+ cells significantly increased. Confocal microscopy revealed that OCN proteins were localised in the cytoplasm in Triton X-100-treated OCN+ cells. Furthermore, OCN, ALP, and COL1A1 gene expression was detected in OCN+ cells, suggesting the contribution of the local maturation of bone marrow-derived OCN+ cells at the site of bone healing.

90Sr specific activity of teeth of abandoned cattle after the Fukushima accident - teeth as an indicator of environmental pollution.

90Sr specific activity in the teeth of young cattle that were abandoned in Kawauchi village and Okuma town located in the former evacuation areas of the Fukushima-Daiichi Nuclear Power Plant (FNPP) accident were measured. Additionally, specific activity in contaminated surface soils sampled from the same area was measured. (1) All cattle teeth examined were contaminated with 90Sr. The specific activity, however, varied depending on the developmental stage of the teeth during the FNPP accident; teeth that had started development before the accident exhibited comparatively lower values, while teeth developed mainly after the accident showed higher values. (2) Values of 90Sr-specific activity in teeth formed after the FNPP accident were higher than those of the bulk soil but similar to those in the exchangeable fraction (water and CH3COONH4 soluble fractions) of the soil. The findings suggest that 90Sr was incorporated into the teeth during the process of development, and that 90Sr in the soluble and/or leachable fractions of the soil might migrate into teeth and contribute to the amount of 90Sr in the teeth. Thus, the concentration of 90Sr in teeth formed after the FNPP accident might reflect the extent of 90Sr pollution in the environment.

Transfer of the bone morphogenetic protein 4 gene into rat periodontal ligament by in vivo electroporation.

OBJECTIVE: Regulation of alveolar bone metabolism is required in clinical dentistry. The aim of the present study was to establish a method for gene transfer into the periodontal ligament (PDL) by in vivo electroporation with a plasmid vector and to investigate the effects of BMP-4 transfer into the PDL. DESIGN: Plasmids containing mouse BMP-4 cDNA (pCAGGS-BMP4) were transfected into cultured rat PDL cells by in vitro electroporation, and BMP-4 production and secretion were detected by immunocytochemistry and western blotting. Next, pCAGGS-BMP4 was injected into the PDL of rats, and electroporation was performed in vivo, using original paired-needle electrodes. BMP-4 expression was examined by immunohistochemical staining 3, 7, 14, 21, and 28days after electroporation. Control groups were injected with pCAGGS by electroporation, injected with pCAGGS-BMP4 without electroporation, or subjected to neither injection nor electroporation. RESULTS: In vitro-transfected rat PDL cells exhibited production and secretion of the mature-form BMP-4. After in vivo electroporation of pCAGGS-BMP4, site-specific BMP-4 expression peaked on day 3, gradually decreased until day 14, and was absent by day 21. We observed no unfavorable effects such as inflammation, degeneration, or necrosis. CONCLUSIONS: Gene transfer by electroporation with plasmid DNA vectors has several advantages over other methods, including the non-viral vector, non-immunogenic effects, site-specific expression, simplicity, cost-effectiveness, and limited histological side effects. Our results indicate that the method is useful for gene therapy targeting the periodontal tissue, which regulates alveolar bone remodeling.

Gustatory Salivation Is Associated with Body Mass Index, Daytime Sleepiness, and Snoring in Healthy Young Adults.

The taste detection system for oral fatty acid may be related to obesity. In addition, sleep is intrinsically and closely related to food intake and metabolism. However, the association of gustatory salivation with body mass index (BMI), daytime sleepiness, or sleep habits is largely unknown. Therefore, we evaluated the relationship between gustatory salivation and BMI, Epworth sleepiness scale (ESS, a daytime sleepiness scale) or sleep habits among 26 healthy young individuals (20 males and 6 females; mean age: 26.0 ± 4.3 years). We also measured the saliva flow rate (SFR) that was induced by gum-chewing or each of three prototypical tastants (acetic acid, sucrose, and NaCl). Further, the SFR was induced by fatty acid, provided as oleic acid (OA) homogenized in non-fat milk. All participants showed normal rates of salivation during resting and gum-chewing states. The increase in the SFR induced by OA, but not by each of the three tastants, was associated with BMI. Moreover, both daytime sleepiness level and frequency of snoring were associated with the increase in the SFR induced by NaCl. These results suggest that BMI is associated with salivation induced by oral fatty acid exposure. Additionally, the regulatory mechanism for the NaCl-induced salivation reflex may have a relationship with impairments of the respiratory control system that are related to snoring during sleep and lead to daytime sleepiness because of insufficient sleep. Thus, measurement of gustatory salivation might contribute to the evaluation and prevention of obesity and sleep-related breathing disorders.

Vibrational stimulation induces osteoblast differentiation and the upregulation of osteogenic gene expression in vitro.

Vibrational stimulation is an accepted non-invasive method used to improve bone remodeling. However, the underlying mechanisms of this phenomenon remain unclear. In this study, we developed a new vibration-loading system to apply vibrational stimulation to cells based on a previously reported in vivo study. We hypothesized that osteoblasts respond to vibrational strain by expressing osteogenic marker genes, such as alkaline-phosphatase (ALP), Runx2, and Osterix. To test our hypothesis, we developed a vibration-loading system to apply a precise vibrational force to an osteoblast culture on a silicone membrane. The system regulated frequency and acceleration of the vibration, and strain on the silicone membrane culture surface was measured using the strain gauge method. After vibrational stimulation, cellular gene expression was analyzed using real-time polymerase chain reaction. We obtained clear strain signals from the culture surface at vibrational ranges of 1.0-10 m/s2 acceleration and frequencies of 30, 60, and 90 Hz, respectively. The strain increased in a linear fashion, depending on the acceleration magnitude. Vibrational stimulation also significantly upregulated expression of the osteogenic marker genes Runx2, Osterix, type I collagen, and ALP. In conclusion, we developed a new vibration-loading system that can precisely regulate frequency and acceleration, and we established the presence of dynamic cellular strain on a culture surface. Our findings suggest that vibrational stimulation may directly induce osteoblast differentiation.

The novel bisphosphonate disodium dihydrogen-4-[(methylthio) phenylthio] methanebisphosphonate increases bone mass in post-ovariectomy rats.

The novel bisphosphonate (BP) disodium dihydrogen-4-[(methylthio) phenylthio] methanebisphosphonate (MPMBP) is a non-nitrogen-containing BP with an antioxidant side chain that possesses anti-inflammatory properties. We investigated the systemic effects of this compound on bone loss induced by ovariectomy (OVX) in adult rats. Micro-computed tomography revealed that MPMBP increased bone mass and density in both the metaphysis and diaphysis, and improved the structural properties important for mechanical strength of osteoporotic bone. Sequential bone labeling with tetracycline and calcein indicated that MPMBP decreased longitudinal growth of the primary spongiosa (PS), but stimulated cortical bone formation in the diaphysis. MPMBP increased type I collagen accumulation in the PS, and decreased the number and size of adipocytes in the bone marrow, suggesting inhibition of increased bone marrow adipogenesis induced by OVX. Furthermore, MPMBP reduced the number of bone resorbing cathepsin K-positive osteoclasts induced by OVX. These results suggest that MPMBP could improve bone loss induced by estrogen deficiency. Both stimulation of bone formation and inhibition of bone resorption might play a role in the increase in bone mass and bone density after MPMBP treatment.

(90)Sr in teeth of cattle abandoned in evacuation zone: Record of pollution from the Fukushima-Daiichi Nuclear Power Plant accident.

Here we determined the (90)Sr concentrations in the teeth of cattle abandoned in the evacuation area of the Fukushima-Daiichi Nuclear Power Plant (FNPP) accident. (90)Sr activity concentrations in the teeth varied from 6-831 mBq (g Ca)(-1) and exhibited a positive relationship with the degree of radioactive contamination that the cattle experienced. Even within an individual animal, the specific activity of (90)Sr (Bq (g Sr)(-1)) varied depending on the development stage of the teeth during the FNPP accident: teeth that were early in development exhibited high (90)Sr specific activities, while teeth that were late in development exhibited low specific activities. These findings demonstrate that (90)Sr is incorporated into the teeth during tooth development; thus, tooth (90)Sr activity concentrations reflect environmental (90)Sr levels during tooth formation. Assessment of (90)Sr in teeth could provide useful information about internal exposure to (90)Sr radiation and allow for the measurement of time-course changes in the degree of environmental (90)Sr pollution.

Software development for estimating the concentration of radioactive cesium in the skeletal muscles of cattle from blood samples.

The 2011 earthquake severely damaged the Fukushima Daiichi Nuclear Power Plant (FNPP), resulting in the release of large quantities of radioactive material into the environment. The deposition of these radionuclides in rice straw as livestock feed led to the circulation of contaminated beef in the market. Based on the safety concern of the consumers, a reliable method for estimating concentrations of radioactive cesium in muscle tissue is needed. In this study, we analyzed the concentrations of radioactive cesium in the blood and skeletal muscle of 88 cattle, and detected a linear correlation between them. We then developed software that can be used to estimate radioactive cesium concentrations in muscle tissue from blood samples. Distribution of this software to the livestock production field would allow us to easily identify high-risk cattle, which would be beyond the safety regulation, before shipping out to the market. This software is planned to be released as freeware. This software would contribute to food safety, and aid the recovery of the livestock industry from the damage creacted by the 2011 Tohoku earthquake and tsunami.

Cesium radioactivity in peripheral blood is linearly correlated to that in skeletal muscle: analyses of cattle within the evacuation zone of the Fukushima Daiichi Nuclear Power Plant.

The accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) released a large amount of radioactive substances into the environment. Furthermore, beef contaminated with radioactive cesium above the 500 Bq/kg safety standard was circulated in the food chain in 2011. Japanese consumers remain concerned about the safety of radioactively contaminated food. In our previous study, we detected a linear correlation between radioactive cesium ((137) Cs) activity in blood and muscle around 500 to 2500 Bq/kg in cattle. However, it was unclear whether the correlation was maintained at a lower radioactivity close to the current safety standard of 100 Bq/kg. In this study, we evaluated 17 cattle in the FNPP evacuation zone that had a (137) Cs blood level less than 10 Bq/kg. The results showed a linear correlation between blood (137) Cs and muscle (137) Cs (Y = 28.0X, R(2) = 0.590) at low radioactivity concentration, indicating that cesium radioactivity in the muscle can be estimated from blood radioactivity. This technique would be useful in detecting high-risk cattle before they enter the market, and will contribute to food safety.

Periodontal tissue activation by vibration: intermittent stimulation by resonance vibration accelerates experimental tooth movement in rats.

INTRODUCTION: Accelerating the speed of orthodontic tooth movement should contribute to the shortening of the treatment period. This would be beneficial because long treatment times are a negative aspect of orthodontic treatment. In this study, we evaluated the effects of mechanical stimulation by resonance vibration on tooth movement, and we showed the cellular and molecular mechanisms of periodontal ligament responses. METHODS: The maxillary first molars of 6-week-old male Wistar rats were moved to the buccal side by using an expansive spring for 21 days (n = 6, control group), and the amount of tooth movement was measured. Additional vibrational stimulation (60 Hz, 1.0 m/s(2)) was applied to the first molars by using a loading vibration system for 8 minutes on days 0, 7, and 14 during orthodontic tooth movement (n = 6, experimental group). The animals were killed under anesthesia, and each maxilla was dissected. The specimens were fixed, decalcified, and embedded in paraffin. Sections were used for immunohistochemical analysis of receptor activator of NF kappa B ligand (RANKL) expression. The number of osteoclasts in the alveolar bone was counted by using TRAP staining, and the amount of root resorption was measured in sections stained with hematoxylin and eosin. RESULTS: The average resonance frequency of the maxillary first molar was 61.02 +/- 8.38 Hz. Tooth movement in the experimental group was significantly greater than in the control group (P <.05). Enhanced RANKL expression was observed at fibroblasts and osteoclasts in the periodontal ligament of the experimental group on day 3. The number of osteoclasts in the experimental group was significantly increased over the control group on day 8 (P <.05). Histologically, there were no pathological findings in either group or significant differences in the amount of root resorption between the 2 groups. CONCLUSIONS: The application of resonance vibration might accelerate orthodontic tooth movement via enhanced RANKL expression in the periodontal ligament without additional damage to periodontal tissues such as root resorption.

The manual function test: norms for 20- to 90-year-olds and effects of age, gender, and hand dominance on dexterity.

Stroke is the leading cause of long-term disability. Accurate assessment of motor function is important for documenting disability and the effectiveness of rehabilitative treatment. The Manual Function Test (MFT) was developed to evaluate unilateral manual performance in hemiparetic patients after stroke. This test consists of eight items, including the pegboard task, an item assessing dexterity. The total MFT score can range from 0 (severely impaired) to 32 (full function). We sought to determine normative data and explore influences of age, gender, and hand dominance. Three-hundred thirty-three healthy adult subjects between 20 and 90 years old were studied. Total MFT scores showed negative relationship to age. Compared with subjects in their 20s, those 50 or more years old had lower total MFT scores for dominant hands, as did those 40 or more years old for nondominant hands. For subjects in their 30s and 50s, total MFT scores for women were greater than for men concerning nondominant hands. No such gender difference in total MFT scores was noted for dominant hands. In the pegboard test, the number of pegs achieved for dominant hands was related to age when age was 50 or over, and when age 40 or over for nondominant hands. However, rates of decline in numbers of pegs achieved were similar between hands. In determining MFT norms, total score and items testing dexterity were influenced by age, gender, and hand dominance.

Local osteoprotegerin gene transfer to periodontal tissue inhibits lipopolysaccharide-induced alveolar bone resorption.

BACKGROUND AND OBJECTIVE: Osteoclastogenesis is primarily activated by receptor activator of nuclear factor kappaB ligand (RANKL) and is inhibited by osteoprotegerin (OPG). A previous study demonstrated that local OPG gene transfer to periodontal tissue inhibited RANKL-mediated osteoclastogenesis and experimental tooth movement. In the present study, we tested the hypothesis that local OPG gene transfer to the periodontium can neutralize RANKL activity induced by lipopolysaccharide injection, thereby inhibiting osteoclastogenesis and diminishing alveolar bone resorption in experimental periodontal disease. MATERIAL AND METHODS: Seven-week-old male Wistar rats received an injection of lipopolysaccharide or phosphate-buffered saline in the palatal gingiva of the upper first molars on both the right and left sides. An inactivated haemagglutinating virus of Japan (HVJ) envelope vector containing a mouse OPG expression plasmid [pcDNA3.1(+)-mOPG] or mock vector was injected periodically into the palatal periodontal tissue of the upper first molars. RESULTS: Lipopolysaccharide injection induced severe periodontal bone resorption. Local OPG gene transfer induced OPG production, and osteoclastogenesis was inhibited. Local OPG gene transfer significantly decreased alveolar bone resorption. CONCLUSION: Osteoprotegerin gene transfer to periodontal tissue inhibited osteoclastogenesis and alveolar bone resorption in lipopolysaccharide-induced experimental periodontal disease.

Cytoskeletal changes and the system of regulation of alkaline phosphatase activity in human periodontal ligament cells induced by mechanical stress.

The periodontal ligament (PDL) is a specialized, mechanically responsive tissue that adapts via cellular responses to equilibrate the effects of mechanical stress on teeth. However, the mechanism of remodelling by which individual cells in periodontal tissue detect and respond to mechanical stress is not well understood. To identify the cellular mechanisms induced by mechanical stress in the periodontal ligament, we examined the effects of cyclic stretching on periodontal ligament fibroblast-like cells (PDL cells). Furthermore, we investigated the effects of 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), and interaction with peripheral blood mononuclear cells (PBMCs) on mechanically-simulated PDL cells. PDL cells were cultured on type I collagen-coated silicon membranes with 10% FBS alpha-MEM, and then subjected to cyclic mechanical stimulation (1 s stretching/1 s relaxation, 15% maximum elongation). Alkaline phosphatase activity was monitored by cytochemical and spectrophotometric methods. Morphologically, the cells assumed a spindle shape, and the cytoskeletal components, including microtubules and F-actin filaments, were aligned perpendicular to the strain force vector. Cyclic stretching decreased ALPase activity in PDL cells. The anabolic systemic hormone 1,25(OH)(2)D(3) increased ALPase activity, but this effect was suppressed by cyclic stretching. ALPase activities were reduced by co-culture with PBMCs, including lymphocytes and monocytes. This PBMC-induced ALPase reduction was synergistically reduced by cyclic stretching. ALPase activity was decreased by co-culture with PBMCs, and ALPase activity was reduced synergistically by treatment with PBMCs and cyclic stretching. We conclude that PDL cells changed their shape and alignment in response to cyclic stretching. Furthermore, local factors, such as mechanical stress and PBMCs, showed synergistic suppressive effects on ALPase activity.

Establishment of Periodontal Ligament Cell Lines from Temperature-Sensitive Simian Virus 40 Large T-antigen Transgenic Rats.

Orthodontic tooth movement is controlled by various cell types in the periodontal ligament (PDL). Mechanical stresses, such as orthodontic force, are thought to induce differentiation of the mesenchymal cells in the PDL into osteoblasts and cementoblasts. The details of the process of differentiation, however, are not known, in part because adequate in vitro systems for their study do not yet exist. The purpose of this study was to establish and characterize immortalized PDL cell lines derived from the PDL of transgenic rats harboring the temperature-sensitive simian virus 40 T-antigen gene (TG rats). The PDL was removed from the molar roots of TG rats and incubated in tissue culture. Outgrowth cells from the PDL explant were passaged and cloned, depending on the shape of the colonies formed. The cell lines thus established were analyzed by reverse transcription-polymerase chain reaction for expression of type-I collagen, osteopontin, fibronectin, alkaline phosphatase (bone type), bone sialoprotein, the receptor activator of NF-kappa B ligand, and osteoprotegerin. In addition, the capacity for formation of mineralized nodules was assessed by incubating cells in calcification-promoting medium at 37 degrees C. A total of 15 stable cell lines were successfully established and characterized. These cell lines were classified into six groups based on their pattern of gene expression at 33 degrees C. Moreover, three of these clones were capable of forming calcified nodules. In conclusion, differential gene expression was demonstrated in 15 established PDL cell lines. Some cells had the potential to differentiate into cell types found in mineralized tissues, such as osteoblasts and cementoblasts, as well as cells expressing molecules that regulate osteoclast differentiation.

The induction of c-fos mRNA expression by mechanical stress in human periodontal ligament cells.

The periodontal ligament is subjected to mechanical loading during occlusion and mastication. Although internuclear transcription factors are associated with the regulatory pathway that converts these extracellular mechanical stimuli into a cellular response, there are no reports on these in human periodontal ligament fibroblasts. In this study, the amounts of c-fos mRNA in human periodontal ligament fibroblasts were investigated shortly after subjecting them to a cyclic tension force in vitro. The mRNA of alkaline phosphatase and the matrix proteins type I collagen, type III collagen, matrix Gla-protein, osteonectin, osteopontin, and osteocalcin were also examined. A significant, rapid, transient increase in c-fos mRNA was detected, which peaked 30 min after the application of mechanical force. However, there was no significant change in the mRNA for alkaline phosphatase or the matrix proteins. These results provide evidence that periodontal ligament fibroblasts and c-fos may play a critical part in the response of periodontal tissue to mechanical stimulation.