Bone changes its shape adaptively according to the mechanical environment, suggesting a close relationship between the bone remodeling and the stress induced in bones. We measured the geometries of the canine radius after partial resection of the ulna with X-ray CT and microscopic study with fluorescent labeling. The experimental animals were six beagle dogs aged three months. The midshaft of their right ulna was partially resected. The experimental period of them was 6, 12 and 24 weeks. Sectional images of their antebrachium were taken every 2 or 4 weeks with X-ray CT. The bone was labeled with Calcein and Xylenol Orange each week. From CT observation, significant bone growth was observed at cranial lateral, caudal-medial side and resected ulnar side at 6 weeks after surgery. At 12 weeks, the thickness of cortical bone was increased. At 24 weeks, the cross-section changed to an oval or round shape. From confocal laser microscope observation, significant new bone formation was identified under the periosteum at the cranial lateral and resected ulnar side from 2 weeks after surgery. On the control side, lamellar bone formation took place in an orderly manner, whereas on the experimental side, there was a large quantity of rapid woven bone formation filling the cavities of the resected ulna, followed by the lamellar bone formation. The bone formations took place to compensate for the mechanical functions of the lost ulna, suggesting the adaptive nature of bone remodeling.
The aim of this study was to define transcriptional changes that occur during dexamethasone induced in vitro osteoblastic differentiation using human mesenchymal stem cells (hMSCs) . Bone marrow derived hMSCs from three individual donors were grown in DMEM containing 10% fetal bovine serum and antibiotics (basal media, BM) . At confluence (Day 0), cells were grown in BM or BM plus ascorbic acid, β-glycerophosphate and dexamethasone (OS) . At 0, 3, 7 and 14 days, total RNA was isolated from hMSCs, and 32P-labelled probes were synthesized. Atlas 1.2 gene arrays (Clontech) were hybridized with donor specific cDNA probes. Acquired data were analyzed using GeneSpring Software (Silicon Genetics) enabling normalization and averaging of donorspecific data sets at each time point. Only 8, 31, and 27 genes were upregulated more than 3-fold at 3, 7 and 14 days, respectively. Over 50 genes were downregulated at each time point. Interestingly, the results of this study did not reflect commonly identified genes that are frequently considered in cellular differentiation along the osteoblastic lineage. Instead, some interesting genes were upregulated. Seven days exposure to OS media resulted in the relatively high induction of several genes, including growth factors and receptors which affect adipocyte, chondrocyte and osteoblast differentiation. IGF II and FGFR 3, FGFR 2 were upregulated in the middle of 14 days' induction. Examination of gene expression at day 14 also revealed a number of receptors (LEPR) and transcription factors (RORa) were upregulated during 14 days. These could be of importance to the process of early stage differentiation.
To fabricate a prosthesis which is functionally harmonized with the stomatognathic system, the interocclusal relationship must be reproduced as accurately as possible. This study investigated the influence of the occlusal contacts upon tooth displacement and clarified the optimal occlusal contacts for the prosthesis. The displacement paths of six maxillary left first molars of six adults in good general health were measured in this study. We gave each test tooth eight patterns of artificial occlusal contacts by attaching platinum foil on the occlusal surface. Subjects were asked to perform clenching at the intercuspal position (=ICP) with medium occlusal forces, and 3-dimensional tooth displacement paths were measured by the Type M-3 tooth displacement transducer. The following conclusions were obtained. 1. Using the Student's t-test for statistical analysis, it was suggested that the difference of the buccolingual location of occlusal contacts influenced the direction of the tooth displacement. 2. The tooth which had occlusal contact in the buccal cusp displaced in the mesio-buccal direction, so this may create a wide dental arch and a slight discrepancy was generated at the distal interproximal contact area of the tooth. 3. It was shown that the tooth which had occlusal contact in the buccal cusp rotated in the buccoapical direction in reverse to the natural tooth.
The aim of this study was to identify genes responsible for the formation and maintenance of cartilage tissue. For this purpose, gene expression patterns were compared between differentiating and dedifferentiating chondrocytes by cDNA macroarray analysis. A total of 1, 186 genes were examined, and at least 7 genes were identified as candidate genes having critical roles in cartilages. Three of them encode well-known cartilage matrix molecules : aggrecan, decorin and type IX collagen, and others were preproenkephalin A, Early Growth Response-1, Early Growth Response-3, and basigin. All these genes were expressed at high level in mature cartilage, but their expressions were suppressed in response to dedifferentiation of chondrocytes. Meanwhile, transcription factor ALY, variant in the kinase (vik), and syndecan 2 genes were newly activated during the process of chondrocyte dedifferentiation. A similar process is somewhat observed in osteoarthritis. Therefore, activation of these genes might be closely related to the progression of osteoarthritis and would be a useful marker for it.