Rena Okawa

Phex Mutation Causes the Reduction of Npt2b mRNA in Teeth

Hyp mice (murine homologue of human X-linked hypophosphatemia) have a disorder in phosphate homeostasis, and display hypomineralization in bones and teeth. We investigated whether a mutation of Phex (phosphate regulating gene homologies to endopeptidase on the X chromosome) has an effect on the expression level of type II sodium-dependent phosphate co-transporter (Npt2) in the developing teeth of the Hyp mouse. Quantitative RT-PCR analyses revealed that the amount of Npt2b mRNA, an isoform of Npt2, in Hyp mouse tooth germs was significantly lower than that in wild-type mice, in both in vivo and in vitro experiments. In addition, tooth germs from wild-type mice cultured in medium supplemented with antisense oligo-deoxynucleotide for Phex also showed a reduction of Npt2b mRNA expression. These findings suggest that the loss of Phex function is related to the defect of Npt2b expression in teeth, and Npt2b reduction is an intrinsic defect of Hyp murine teeth.

Bacterial profiles of oral streptococcal and periodontal bacterial species in saliva specimens from Japanese subjects

OBJECTIVE Recent developments in molecular biological techniques have increased understanding of the distribution of oral bacterial species in clinical specimens, though few investigations have been conducted to simultaneously detect oral streptococcal and periodontal species in the same specimens. The purpose of the present study was to investigate the distribution and correlation of 6 oral streptococcal and 6 periodontal species in saliva specimens taken from children and their mothers. DESIGN Seventy-four pairs of children and their mothers were approved to participate in this study. Saliva specimens were collected and bacterial DNA extracted, which was subjected to PCR analyses using species-specific sets of primers. The combinations of species able to be detected simultaneously were determined by statistical analyses. RESULTS Streptococcus sobrinus and Porphyromonas gingivalis were detected more often in the mothers than the children. Streptococcus mutans, Streptococcus sanguinis, and Streptococcus oralis were detected simultaneously in a significant number of specimens, while the presence of Campylobacter rectus was correlated with the presence of at least one of the red complex species (P. gingivalis, Treponema denticola and Tannerella forsythensis). On the other hand, no correlation was shown between the rates of detection of oral streptococcal and periodontal species. CONCLUSIONS Our results indicate that among streptococcal and periodontal species, several are able to coexist in saliva, while the presence of both does not have an influence on each other.

Distribution of periodontopathic bacterial species in Japanese children with developmental disabilities

BackgroundRecent developments in molecular biological techniques have enabled rapid detection of periodontopathic bacterial species in clinical specimens. Accumulated evidence suggests that detection of specific bacterial species enables identification of subjects at high risk for the onset of periodontitis. We investigated the distribution of 10 selected periodontopathic bacterial species in dental plaque specimens obtained from children with disabilities who were attending daycare centers.MethodsA total of 187 children (136 boys, 51 girls) aged 1-6 years old and diagnosed with such disabilities as mental retardation, cerebral palsy, and autism, participated in the study. Subgingival dental plaque specimens were collected from the buccal side of the maxillary left second primary molar after a clinical examination. Bacterial DNA was extracted from the specimens and PCR analyses were carried out to detect 10 selected periodontopathic species using specific primers for each. In addition, statistical analyses were performed to analyze the correlations among clinical parameters and the detected species.ResultsThe most frequently detected species was Capnocytophaga sputigena (28.3%), followed by Aggregatibacter actinomycetemcomitans (20.9%) and Campylobacter rectus (18.2%). Eikenella corrodens, Capnocytophaga ochracea, and Prevotella nigrescence were detected in approximately 10% of the specimens, whereas Treponema denticola, Tannerella forsythia, and Prevotella intermedia were rarely found, and Porphyromonas gingivalis was not detected in any of the subjects. The total numbers of detected species were positively correlated with the age of the subjects. There were 10 subjects with positive reactions for T. denticola and/or T. forsythia, in whom the total number of bacterial species was significantly higher as compared to the other subjects. Furthermore, subjects possessing C. rectus showed significantly greater values for periodontal pocket depth, gingival index, and total number of species.ConclusionWe found that approximately one-fourth of the present subjects with disabilities who possessed at least one of T. denticola, T. forsythia, and C. rectus were at possible risk for periodontitis. Follow-up examinations as well as preventive approaches should be utilized for such individuals.

Hyper-expression of Osteocalcin mRNA in Odontoblasts of Hyp Mice

The Hyp mouse is a murine homologue of human X-linked hypophosphatemia that displays hypo-mineralization in bone and dentin. In this study, we tested the hypothesis that the defect in Hyp mice leads to alterations in the expression of dentin matrix proteins that may be associated with the hypo-mineralization changes in the tissues. Quantitative RT-PCR analyses showed that expression of the osteocalcin gene in Hyp mice tooth germ samples was significantly higher than in wild-type mice, whereas the gene expressions of osteonectin, osteopontn, dentin matrix protein 1, and type I collagen in both types of mice were similar. Further, cultured Hyp mice tooth germ samples exhibited a higher expression of the osteocalcin gene than did those from wild-type mice, which was in accord with the results of our in vivo analysis. These findings suggest that osteocalcin mRNA is highly expressed in Hyp mice odontoblasts and may be associated with dentin hypo-mineralization.

Aggravation of inflammatory bowel diseases by oral streptococci

OBJECTIVES Streptococcus mutans can aggravate colitis in mice. We evaluated the virulence of colitis using type strains as well as blood isolates of several oral streptococcal species. MATERIALS AND METHODS We investigated the susceptibility of blood isolates of several oral streptococci to phagocytosis, adhesion to and invasion of hepatic cells and interferon-γ secretion. A mouse model of dextran sodium sulphate-induced colitis was used to evaluate bacterial aggravation of colitis. In addition, interferon-γ antibody was administered to mice with prominent aggravation of colitis. RESULTS In vitro analyses showed that Streptococcus sanguinis ATCC 10556 was a possible virulent strain among type strains of several oral streptococci, and that analysis of blood isolates of S. sanguinis TW289 revealed a potential virulent strain. Intravenous administration of ATCC 10556 and TW289 caused prominent aggravation of dextran sodium sulphate-induced colitis, and histopathological examinations showed that interferon-γ secretion due to infection of hepatic cells caused colitis aggravation. Administration of interferon-γ antibody suppressed TW289-induced colitis. CONCLUSION These results suggest that some virulent oral streptococcal strains are associated with the aggravation of colitis induced by enhanced secretion of interferon-γ when they invade the bloodstream.

Oral manifestations of patients with hypophosphatasia

Abstract Hypophosphatasia is a rare inherited disorder characterized by defective bone mineralization and deficiency of tissue non-specific alkaline phosphatase (TNSALP) activity. The disease is caused by mutations in the liver/bone/kidney alkaline phosphatase gene ( ALPL ) encoding TNSALP. As for dental manifestations, premature loss of deciduous teeth due to disturbed cementum formation is well known. However, few reports of multiple cases have been presented. The oral manifestations of patients diagnosed with hypophosphatasia were analyzed by collecting clinical records of cases from a nationwide survey of pediatric dentistry clinics affiliated with 29 university dental hospitals in Japan. We inquired regarding the number of cases and clinical findings of diagnosed patients. We obtained information for 9 children diagnosed with hypophosphatasia from our university and 10 from 6 other universities. The main oral manifestation was early exfoliation of deciduous teeth, which was found in 15 of the 19 cases. Early exfoliation of mandibular deciduous anterior teeth was recognized in 14, whereas there were no cases of early exfoliation of a permanent tooth. The main oral finding of hypophosphatasia was early exfoliation of deciduous teeth, predominantly in the mandibular anterior region of children aged 1 to 4 years old.

Inverted maxillary second primary molar and permanent successor teeth: X-ray photographic evaluations

A 10-year-and-4-month old girl was shown to have inverted maxillary right second primary molar and permanent successor teeth, after being referred to our clinic for examination of an unerupted maxillary right second primary molar. Orthopantomograph images taken at the age of 7Y4M showed an impacted maxillary second primary molar and ambiguous tooth germ of its permanent successor, while images obtained at the age of 10Y4M exhibited the tooth germ of the permanent successor in a position on top of the impacted primary molar. Orthopantomographs were obtained twice during the next year, which showed development of the second premolar. The dental age of the entire dentition, except for the maxillary right second premolar, at 7Y4M was considered to be consistent with her chronological age, whereas it was approximately 6 months to 1 year behind of chronological age when determined at the age of 10Y4M, 11Y4M, and 12Y3M. The dental age of the permanent second premolar gradually increased, however, remained approximately 4 years behind chronological age. At 12Y3M, computed tomography examinations were performed to clarify the three-dimensional positions of the second primary molar and its permanent successor. At that time, the impacted primary molar was located close to the inferior part of the maxillary sinus, while the tooth germ of the permanent successor was located in the apex region of the adjacent first permanent premolar and first permanent molar. We decided to carry out the periodical examinations to observe the maxillary right second primary molar and premolar.

Report of Two Dental Patients Diagnosed with Hypophosphatasia

Hypophosphatasia is a rare inherited skeletal disorder characterized by defective bone mineralization and tissue non-specific alkaline phosphatase (TNSALP) deficiency, with mutations in the gene encoding the TNSALP isozyme the cause. As for dental manifestations, premature loss of primary teeth due to disturbed cementum formation is well known and tooth roots in affected patients are not able to adequately attach to absorbed alveolar bone due to malformed cementum. We report spontaneous early exfoliation along with mild to severe mobility of primary anterior teeth in 2 child patients referred to pediatric dentists from a general dental practitioner. Case 1 was a 1-year-7- month-old boy with 3 mandibular incisors exfoliated, while Case 2 was a 3-year-3-month-old girl with 1 mandibular central incisor exfoliated. The possibility of hypophosphatasia was considered and the patients were referred to the Pediatric Clinic of Osaka University Medical Hospital, where each was diagnosed with hypophosphatasia (odonto type). We performed repeated periodontal treatments and applied removable partial dentures in both cases, which solved esthetic and functional problems. Although the incidence is quite low, it is important to diagnose hypophosphatasia as early as possible for planning general and dental preventive approaches. In patients with mild forms, such as odonto and childhood types, early exfoliation of primary teeth identified in a dental examination can occasionally lead to early diagnosis of hypophosphatasia. In addition, dental findings obtained by a dentist are useful to identify patients with a risk of hypophosphatasia, who can then be immediately referred to a pediatrician for more detailed systemic examinations. Thus, a cooperative relationship between pediatricians and pediatric dentists should be regarded as necessary. This is the first known report to describe cases of hypophosphatasia diagnosed after referral from a pediatric dentist because of typical dental findings for the disorder.

Longitudinal comparison of Streptococcus mutans-induced aggravation of non-alcoholic steatohepatitis in mice

ABSTRACT Background: We previously reported that intravenous administration of Streptococcus mutans strain TW871 caused typical non-alcoholic steatohepatitis (NASH)-like findings in a high-fat diet (HFD) mouse model at 16 weeks after initiating the experiment. Objective: The purpose of the present study was to analyse mice administered S. mutans TW871 fed a HFD for various periods of time. Methods: First, 6-week-old C57BL/6J mice were fed an HFD for 4 weeks, then TW871 (1 × 107 CFU) or phosphate-buffered saline (PBS) were intravenously administered. Mice were euthanized 12, 16, 20, and 48 weeks after starting the experiment, and conventional clinical and histopathological evaluations were performed. Results: Typical NASH-like findings were not identified in the mice at 12 weeks, while they were observed in the TW871 group at 16 weeks, and the severity of NASH symptoms were increased at 20 weeks. Furthermore, signs of severe NASH were also observed at 48 weeks. In contrast, in the PBS-administered group, the NASH findings were identified only at 48 weeks and no typical NASH features were observed at 12, 16, or 20 weeks. Conclusion: These results suggest that intravenous administration of a specific S. mutans strain aggravates NASH in a time-dependent manner in the mice in contrast to mice without S. mutans exposure.

Successful application of molecular biological technique for evaluation of changes in periodontopathic bacteria in Japanese children with developmental disabilities

Abstract Developments in molecular biological techniques enables rapid and easy identification of periodontopathic bacterial species in clinical specimens. However, there are few reports regarding their application for community dentistry. The aim of this study was to show successful application of a molecular biological technique for evaluation of changes in periodontal bacterial species in children at daycare centers. We studied 187 children who received oral examinations in 2009 and 186 who received examinations in 2010, among whom 102 were examined in both years. Clinical parameters regarding periodontal conditions were evaluated and the distribution of 10 periodontopathic species in dental plaque specimens were determined by polymerase chain reaction. Periodontal pocket depth values in the 2010 group were significantly smaller than those in 2009. When the subjects were divided into those with (positive group) and without (negative group) Porphyromonas gingivalis , Treponema denticola , Tannerella forsythia , or Campylobacter rectus in 2009, the positive group had significantly smaller periodontal pocket values than the negative group. In addition, the rate of subjects with P. gingivalis , T. denticola , T. forsythia , or C. rectus in the positive group in 2010 was significantly reduced. Our findings demonstrate that molecular biological methods provide more information as compared to a standard clinical examination when evaluating changes of periodontal conditions in the field of community dentistry.