Masahiko Yokozeki

Function and Regulation of Osteopontin in Response to Mechanical Stress

Extensive histological study revealed the impairment of bone remodeling caused by mechanical stress in OPN knockout mice in a tooth movement system. Analysis of OPN promoter transgenic mice showed the mechanical stress response element(s) in the 5.5‐kb upstream region. These results were also obtained with the primary cultured cells.

Interferon-γ inhibits the myofibroblastic phenotype of rat palatal fibroblasts induced by transforming growth factor-β1 in vitro

Interferon‐γ (IFN‐γ), a multifunctional cytokine, has been noted as a potential therapeutic agent for various fibrotic disorders, including excessive scar tissue formation. We previously reported that transforming growth factor‐β1 (TGF‐β1) induced the myofibroblastic phenotype in palatal fibroblasts derived from palatal mucosa, and that such effects might have a close link to palatal scar formation. In the present study, we examined the effects of IFN‐γ on TGF‐β1‐pretreated palatal fibroblasts for the purpose of clarifying the suppressive potency against myofibroblastic phenotype expression in vitro. IFN‐γ significantly altered the spindle morphology of TGF‐β1‐pretreated palatal fibroblasts into the polygonal one that was similar to the non‐treated palatal fibroblasts. This change was parallel with a decrease in the expression of α‐smooth muscle actin protein, a marker for myofibroblast, as determined by immunoblot analysis. Northern blot analysis showed that IFN‐γ inhibited proα2(I) collagen mRNA expression that was stimulated by TGF‐β1 pretreatment for 24 h. Furthermore, IFN‐γ decreased the cell contractility enhanced by TGF‐β1 pretreatment for 24 h in a three‐dimensional collagen gel culture system. These results suggest that IFN‐γ may have negative effects with regard to controlling the myofibroblastic phenotype induced by TGF‐β1 in palatal fibroblasts.

Smad3 is required for enamel biomineralization

Smad3 is an intracellular signaling molecule that mediates the signal from transforming growth factor-beta (TGF-beta) and activin receptors. In this study, we reveal hypomineralized enamel in mice with the targeted deletion of the Smad3 gene. The Smad3 (-/-) mice had chalky white incisor enamel, while the enamel of the wild-type or Smad3 (+/-) mice was yellow-brown. Histological analysis of the undecalcified sections showed that the enamel thickness of the maxillary incisors in the Smad3 (-/-) mice was similar to that of the wild-type and Smad3 (+/-) mice while that the enamel of the maxillary molars in Smad3 (-/-) mice was disrupted in places. Microcomputed tomography (microCT) analysis revealed that the mineralization of the maxillary incisors and mandibular molars in the Smad3 (-/-) mice showed significant reduction in the degree of mineralization when compared to that of the wild-type and Smad3 (+/-) mice. Scanning electron microscopic (SEM) analysis of the mandibular incisors revealed that the enamel surface of the Smad3 (-/-) mice was irregular and disrupted in places and showed images similar to decalcified mature enamel. The histological analysis of the decalcified sections showed that distinct morphological changes in the ameloblasts at the secretory and maturational stages were not observed between the Smad3 (-/-) and Smad3 (+/-) or wild-type mice, while the enamel matrix was observed in the decalcified sections of the mandibular molars in the Smad3 (-/-) mice. These results suggested that Smad3 was required for enamel biomineralization, and TGF-beta and activin signaling might be critical for its process.

An Orthodontic Case of Transposition of the Upper Right Canine and First Premolar

Tooth transposition is a rare and severe positional anomaly that may create many orthodontic problems from both esthetic and functional points of view. In this report, we describe a case of the orthodontic management of a transposition of the upper canine and premolar with congenital absence of the upper lateral incisor. The patient was treated with a multibracket appliance and the extraction of three premolars, and treatment was completed without a need for any prosthetic replacement.

Segmental Distraction of the Midface in a Patient With Crouzon Syndrome

We treated midface hypoplasia in a 20-year-old woman with Crouzon syndrome using a rigid external distraction device. The patient showed severe exophthalmos and maxillary retrusion, although relatively good occlusion had been achieved by long-term orthodontic procedures. We considered that our patients particular condition could not be resolved by the usual Le Fort III osteotomy/midface distraction procedure, so we devised a segmental approach. The midface, mobilized by Le Fort III osteotomy, was divided into two segments by Le Fort I osteotomy; each fragment was connected to the rigid external distraction device to be distracted separately. Distraction was begun after 1 day at 1 mm/day. The upper and lower segments were distracted over 17 and 12 days, respectively. The patients occlusion was fully corrected, and her facial contour was significantly improved. After 3 weeks of consolidation, we removed the distraction device. The clinical course was without complication, and no relapse was observed on the cephalogram or computed tomography scan obtained 1 year after the procedure. Our modified technique was helpful in increasing the usefulness of the external distraction system and in refining the midface distraction procedure.

Oral rehabilitation of an orthodontic patient with cleft lip and palate and hypodontia using secondary bone grafting, osseo-integrated implants, and prosthetic treatment.

Objective Complete skeletal and dental reconstruction of the anterior maxilla is of great importance to patients with cleft lip and palate. Accordingly, osseo-integrated implants have been utilized for dental reconstruction after secondary bone grafting. In this report, the orthodontic management of a patient with unilateral cleft lip and plate with associated hypodontia is described. The patient was treated with comprehensive orthodontic treatment in addition to secondary bone grafting, and dental reconstruction was achieved with a combination of osseo-integrated implants and fixed prosthodontic treatment.

Analysis of gene expression profiles in human periodontal ligament cells under hypoxia: The protective effect of CC chemokine ligand 2 to oxygen shortage

Periodontal ligament (PDL) cells appear to play important functional roles in response to mechanical stress. We hypothesized that hypoxia caused by a deformation of blood vessels and the following ischaemia may play a crucial role in differential gene expression in PDL cells affected by mechanical stress. Gene induction in cultured human PDL cells by hypoxia was analyzed using cDNA array, followed by RT-PCR analysis. Eleven hypoxia-responsive genes were found differentially expressed under low-oxygen conditions in PDL cells. Among them, CCR2, CC chemokine ligand 2 (CCL2) receptor was studied in more detail since little information is available on the role of chemokines in adaptive responses of PDL cells under hypoxia. Here we investigate whether CCR2 mediates the signalling to maintain the homeostasis of PDL cells. We found that cell death of PDL cells was induced under hypoxia with down-regulation of CCL2 mRNA expression. However, the exogenous CCL2 prevented PDL cell death under oxygen shortage with the increment of cellular inhibitor of apoptosis (cIAP) mRNA expression. The present study demonstrated substantial effects of hypoxia on gene expression of CCL2 and CCR2 in PDL cells, indicating that mechanical loading accompanied with mild hypoxia allows PDL cells to elicit adaptive responses with up-regulation of CCR2.

Identification of a novel frameshift mutation (383insT) in the RUNX2 (PEBP2 α/CBFA1/AML3) gene in a Japanese patient with cleidocranial dysplasia

Abstract Cleidocranial dysplasia (CCD) is an autosomal dominant disorder due to mutations in runt-related gene 2 (RUNX2)/polyomavirus enhancer-binding protein 2αA (PEBP2αA)/core-binding factor A1 (CBFA1)/acute myeloid leukemia 3 (AML3). To investigate the RUNX2 mutations in a Japanese patient with classic CCD, we analyzed the RUNX2 gene using polymerase chain reaction (PCR)–single-strand conformation polymorphism and PCR–restriction fragment length polymorphism. The patient had hypoplasia of the clavicles, patent fontanelles, short stature, supernumerary teeth, and retention of deciduous dentition. We identified a 1-bp insertion (383insT) at codon 128 of the RUNX2 gene. The 383T insertion affects the conserved residue in the runt domain and results in premature termination in the runt domain.

Prognostic implications of nasal cavity and cleft morphology in secondary bone grafting

OBJECTIVE To examine the prognostic significance of the skeletal morphology around the nasal cavity and the alveolar cleft in secondary bone grafting (SBG). DESIGN AND SETTING Fifty-one alveolar clefts in 41 patients (10 bilateral and 31 unilateral cleft lips and palates) registered in the Tokushima University Dental Hospital were examined in this study. METHOD Evaluation of the bony bridge after SBG using dental radiographs at 1 year after surgery. The clefts were divided into two groups: group I (54.9%) in which the upper border of the bony bridge was preferably maintained on or above the horizontal reference line (RL) constructed at the level of the root apex of the upper central incisor adjacent to the cleft, and group II (45.1%) in which the bone level was lower than the RL. Presurgical cleft width was determined by the dental radiographs. The cleft/nasal cavity ratio; the value of the cleft width divided by the nasal cavity width on the cleft side, which was analyzed by frontal cephalograms before the SBG; and the cleft/apertura piriformis ratio, the value analyzed by computed tomography, were used. RESULTS AND CONCLUSION The age, sex, and eruptive stage of the canine teeth at the time of the SBG showed no significant difference between groups. The presurgical cleft width also showed no significant difference between group I (6.6 +/- 3.1 mm) and group II (7.9 +/- 3.3 mm). The cleft/nasal cavity ratio showed a significant difference between groups I and II (0.42 +/- 0.14, 0.75 +/- 0.25; p < .05). Furthermore, the cleft/apertura piriformis ratio also showed a significant difference between groups I and II (0.32 +/- 0.12, 0.65 +/- 0.26; p < .05). These results suggested that measurements of the skeletal morphology around the nasal cavity and alveolar cleft might aid in predicting the stability of the bony bridge after SBG.

Longitudinal Evaluation of Secondary Bone Grafting Into the Alveolar Cleft

Objective To longitudinally evaluate the outcome of secondary bone grafting (SBG) using computed tomograms (CTs) and conventional dental radiographs. Subjects Nineteen alveolar clefts from 17 patients were used in this study. Method A two-dimensional evaluation of SBG was performed using dental radiographs at 1 year after SBG by assigning scores of 1 to 4 (from very good to poor) based on postoperative marginal bone level on the alveolar side. On the basis of postoperative marginal bone levels on the nasal side, clefts were also assigned to groups with the bony bridge on or above (group I) or below (group II) a horizontal reference line. Three-dimensional evaluation of the SBG was performed on horizontal CT slices with the residual cortical bone (RCB) ratio before SBG (T0) as well as 1.5 (T1), 3 (T2), 6 (T3), and 12 months (T4) after SBG. Results The RCB ratio at T4 in the group with scores 1 and 2 was significantly smaller than that of score 3. Furthermore, the mean RCB ratio at T4 in group I was significantly smaller than that in group II. Nineteen alveolar clefts were divided into two groups, A and B, based on a cluster analysis of the RCB ratios. Group A showed a continuous decrease in the RCB ratio from T0 to T2, but group B showed a significant decrease only in the period from T0 to T1. Conclusion These results suggested that the RCB ratio might be a useful parameter for evaluation of the bony bridge after SBG.