A novel statistical model for mandibular helical axis analysis.

The purpose of this study was to establish a new statistical method for the analysis of noisy mandibular helical axis parameters, especially the position vector of the finite helical axis (FHA). The subjects were children with anterior cross-bite who had received orthodontic treatment. Maximum mouth-opening was measured by means of an opto-electronic motion analysis system. These movements were compared with similar movement in the same group after treatment of their anterior cross-bite. Each curve of FHA position vectors was modelled as a spline function with random coefficients. To determine the optimal number of knots, two criteria were used: deviance information criteria (DIC) and mean squared prediction error (MSE). We were interested in estimating a typical curve for a population. Self-modelling regression (SEMOR) was extended to three dimensions to model groups of three-dimensional curves. Each curve was modelled as a spline function using nine knots. Population average curves were created using SEMOR. This study provided detailed information about jaw movement for comparing cross-bite to normal occlusion by calculating the population mean curves of the position vector of the FHA. Our results suggested that the two population mean curves for the position vector of the FHA were significantly different in the closing phase. The combination of a spline function with random coefficients and SEMOR extended to three dimensions can be used not only for FHA analysis but also for the analysis of other jaw movements.

X-ray diffraction study of low-temperature phase transformations in nickel-titanium orthodontic wires.

OBJECTIVES: Employ conventional X-ray diffraction (XRD) to analyze three clinically important nickel-titanium orthodontic wire alloys over a range of temperatures between 25 and -110 degrees C, for comparison with previous results from temperature-modulated differential scanning calorimetry (TMDSC) studies. METHODS: The archwires selected were 35 degrees C Copper Ni-Ti (Ormco), Neo Sentalloy (GAC International), and Nitinol SE (3M Unitek). Neo Sentalloy, which exhibits superelastic behavior, is marketed as having shape memory in the oral environment, and Nitinol SE and 35 degrees C Copper Ni-Ti also exhibit superelastic behavior. All archwires had dimensions of 0.016in.x0.022in. (0.41 mm x 0.56 mm). Straight segments cut with a water-cooled diamond saw were placed side-by-side to yield a 1 cm x 1cm test sample of each wire product for XRD analysis (Rint-Ultima(+), Rigaku) over a 2theta range from 30 degrees to 130 degrees and at successive temperatures of 25, -110, -60, -20, 0 and 25 degrees C. RESULTS: The phases revealed by XRD at the different analysis temperatures were in good agreement with those found in previous TMDSC studies of transformations in these alloys, in particular verifying the presence of R-phase at 25 degrees C. Precise comparisons are not possible because of the approximate nature of the transformation temperatures determined by TMDSC and the preferred crystallographic orientation present in the wires. New XRD peaks appear to result from low-temperature transformation in martensite, which a recent transmission electron microscopy (TEM) study has shown to arise from twinning. SIGNIFICANCE: While XRD is a useful technique to study phases in nickel-titanium orthodontic wires and their transformations as a function of temperature, optimum insight is obtained when XRD analyses are combined with complementary TMDSC and TEM study of the wires.

Relationship between the pharyngeal airway space and craniofacial morphology, taking into account head posture.

This study assessed the relationship between craniofacial characteristics and the size of the pharyngeal airway space (PAS), taking into account head posture. Sixty dental students 25-30 years of age (30 men and 30 women) were examined by lateral cephalometry. The data were corrected with the use of appropriate regression equations for the PAS. The PAS significantly correlated with hyoid position, maxillary and mandibular size, maxillary and mandibular prognathism, and mandibular inclination. A large, anteriorly positioned mandible was associated with a large PAS-TP (the most proximal distance between the posterior pharyngeal wall and the tongue base). Uvula length and PNS-Ba (the distance between the most posterior point of the hard palate and the most inferior point of the anterior foramen magnum) correlated with PAS-UP (the most proximal distance between the posterior pharyngeal wall and uvula). Our results suggest that the anteroposterior dimension of the PAS is substantially affected by the size of the enclosure surrounding the PAS, including the maxilla, mandible and soft palate.

Generation of virtual models for planning orthognathic surgery using a modified multimodal image fusion technique.

Streak artefacts caused by dental metals deteriorate the quality of computed tomography (CT) images. We developed and evaluated a method for generating three-dimensional virtual models to plan orthognathic surgery in patients with multiple dental materials, to avoid the adverse effects of metal artefacts in image fusion. The method basically consists of four procedures: (1) fabrication of a splint in the open-mouth position with fiducial markers, (2) reconstruction of a virtual skull model in the open-mouth position from CT scanning, (3) reconstruction of two virtual dental models in the open-mouth position and either the intercuspal position (ICP) or centric relation (CR) from surface scanning, and (4) three serial steps of image registration and subsequent repositioning of the mandible to the ICP or CR. This method allows for the registration of skull and dental models under artefact-free conditions. To validate the method, CT and dental cast data from 30 patients were used. The registration accuracy was 0.080 mm for the initial registration, 0.033 mm for the second registration, and 0.028 mm for the third registration. The present method can be used to determine the occlusal relationships and craniofacial morphology of patients with dental metals and can be applied to computer-assisted diagnosis and surgery.

Proteoglycan expression is influenced by mechanical load in TMJ discs.

The expression and assembly of the extracellular matrix are profoundly associated with adaptive and pathological responses of the temporomandibular joint (TMJ). To better understand the adaptive responses of the TMJ disc to mechanical loading, we examined the expression of 2 modular proteoglycans and 10 small leucine-rich proteoglycans (SLRPs) at the mRNA and protein levels and determined the contents of proteoglycan-related glycosaminoglycans (GAGs) in rat TMJ discs in response to altered mechanical loading caused by an incisal bite plane. One hundred thirty 7-week-old male Wistar rats were assigned to control and bite plane groups. TMJ disc thickness and the intensity of toluidine blue staining of metachromasia increased in the posterior band after 2 weeks of wearing the bite plane. GAG content increased significantly in the bite plane group after 2 weeks. Quantitative real-time RT-PCR (reverse transcription polymerase chain reaction) analysis indicated that biglycan and chondroadherin mRNA levels increased after 2 weeks and that the level of decorin mRNA increased at 4 weeks. Versican mRNA levels increased after 3 weeks, particularly for the V0 and V1 versican isoforms, which carry more GAG attachment sites than do the V2 and V3 isoforms. Western analysis demonstrated a corresponding increase in the levels of versican, biglycan, and decorin core proteins at 4 weeks in the bite plane group. These results indicate that mechanical loading differentially influences proteoglycan mRNA expression and protein accumulation in the TMJ disc. The change in proteoglycan mRNA and protein levels may lead to the modulation of matrix-matrix and cell-matrix interactions and has important biological significance for adaptation to complicated biomechanical requirements and for tissue maintenance in the TMJ disc.

Effects of expansive force on the differentiation of midpalatal suture cartilage in rats.

In an attempt to clarify the effects of biomechanical tensional force on chondrogenic and osteogenic differentiation of secondary cartilage, the midpalatal sutures of 4-week-old Wistar male rats were expanded by orthodontic wires which applied 20 g force for 4, 7, 10, and 14 days. The differentiation pathways in the midpalatal suture cartilage were examined by immunohistochemistry for osteocalcin, type I and type II collagen, and von Kossa histochemistry. Although the midpalatal sutures of the control animals consisted mainly of two separate secondary cartilages with mesenchyme-like cells at their midlines, type I collagen-rich fibrous tissue began to appear at day 4 and increased at the midline of the cartilage with days of experiment. At the end of the experiment, type I collagen-rich and calcified bone matrix appeared at the boundary between the precartilaginous and the cartilaginous cell layers. Most of the cartilaginous tissues were separated from each other and the midpalatal suture was replaced by osteocalcin-positive intramembranous bone and fibrous sutural tissue. These results strongly suggest that tensional force changed the phenotypic expression of collagenous components in secondary cartilage, which may reflect the differentiation pathway of osteochondro progenitor cells.

Micro X-ray diffraction study of superelastic nickel-titanium orthodontic wires at different temperatures and stresses.

The phase transformation behavior in three commercial nickel-titanium orthodontic wires having different transformation temperatures was studied by micro X-ray diffraction (micro-XRD). Micro-XRD spectra were obtained at three different included bending angles (135 degrees, 146 degrees and 157 degrees) and three different temperatures (25 degrees C, 37 degrees C and 60 degrees C). The regions analyzed by micro-XRD were within the separate areas of a given wire specimen that experienced only tensile or compressive strain. The intensity ratio (M002/A110) between the 002 peak for martensitic NiTi and the 110 peak for austenitic NiTi was employed as the index to the proportions of the martensite and austenite phases. The ratio of martensite to austenite increased in all three nickel-titanium wires with decreasing included bending angle (greater permanent bending deformation), and was lower within the compression area for all wires at all bending angles than within the tension area. Micro-XRD provides an effective method for quantitative evaluation of the proportions of these two phases in nickel-titanium orthodontic wires, even though considerable preferred crystallographic orientation exists because of the wire drawing process.

Micro-X-ray diffraction observation of nickel-titanium orthodontic wires in simulated oral environment.

A micro-X-ray diffraction (micro-XRD) technique has been employed to determine the phases in two superelastic nickel-titanium orthodontic wires that exhibit shape memory in the oral environment and one superelastic nickel-titanium wire that does not exhibit shape memory in vivo. The micro-XRD analyses were performed over the clinically relevant temperature range of 0-55 degrees C, which corresponds to the ingestion of cold and hot liquids, and both straight and bent (135 degrees ) test samples were analyzed. The results showed that for straight (as-received) test samples, the rhombohedral phase (R-phase) was definitely present in one shape memory wire product and perhaps in the other shape memory wire product, but was apparently absent in the superelastic wire product that did not display shape memory. Martensite was observed in all three wire products after bending. Phase transformations occurred with temperature changes simulating the oral environment for straight test samples of the two shape memory wires, but the micro-XRD pattern changed minimally with temperature for straight test samples of the superelastic wire and for bent test samples of all three wire products. The phase transformations revealed by micro-XRD were consistent with results recently found by temperature-modulated differential scanning calorimetry.

Differential expression of human beta-defensin 2 in keratinized and non-keratinized oral epithelial lesions; immunohistochemistry and in situ hybridization.

Human beta-defensin(hBD)-2, an antimicrobial peptide, is produced by various epithelial cells. Because hBD-2 expression in the oral epithelium has not been assessed, we investigated its localization in normal oral epithelium and epithelial lesions. hBD-2 expression was studied using immunohistochemistry and in situ hybridization on formalin-fixed, paraffin-embedded tissue sections from 30 cases of squamous cell carcinoma and 6 cases of leukoplakia. Immunostaining for hBD-2 was more intense in hyperkeratinized than in ortho- or non-keratinized epithelium. In contrast, signals for hBD-2 mRNA were frequently stronger in non-keratinized epithelium than in hyper- or ortho-keratinized epithelium. The results suggest that keratinization in oral epithelium plays an important role in the biological function of hBD-2 both at the mRNA level and in the retention of the peptide in the epithelium.

Confocal microscopy of cementocytes and their lacunae and canaliculi in rat molars.

The present study was designed to analyze the morphological characteristics of cementocytes and osteocytes. The maxillae of 10-week-old Wistar rats were used for observations. Non-decalcified ground sections stained vitally with fluorescence dyes and decalcified frozen sections stained with FITC-phalloidin were examined by confocal microscopy. Calcein and alizarin red stained the calcification front of bone, cementum, and dentin intensely. In addition, lacunae and canaliculi of cementocytes and osteocytes as well as dentinal canals were stained with the fluorescent dyes. The staining of lacunae and canaliculi was less intense than that of the calcification front of bone, cementum and dentin. The canaliculi of cementocytes and osteocytes were connected with the canaliculi extending from the calcification front of cementum and bone, respectively. The canalicular density was less in the cellular cementum than in the bone. Areas devoid of canaliculi were numerous in the cellular cementum, whereas areas devoid of canaliculi were scarce in the alveolar bone. Further, the lacunae of cementocytes showed various shapes, from oval to tubular, while the lacunae of osteocytes were invariably oval. The cell body and the cytoplasmic processes of cementocytes were positive for FITC-phalloidin within the extracellular matrix of cellular cementum, which was negative. The distribution of actin filaments in the osteocytes and the cementocytes was predominantly cortical and appeared to be closely associated with the cell membrane of the cell bodies and the cytoplasmic processes. Intense staining was seen at the proximal part of the cytoplasmic processes in both osteocytes and cementocytes, showing a punctuated structure of the cells that was more frequent in osteocytes than in cementocytes. The stress fiber known to be present in most of the cultured cells was not evident in the these cells in situ. The cells incorporated in the cementodentinal junction were strongly stained with FITC-phalloidin. The distribution pattern of the cytoplasmic processes stained with FITC-phalloidin was similar to that of the canaliculli stained vitally. The cytoplasmic processes of osteocytes and cementocytes were connected with those of cells lining the surface of bone and cementum. The present result-that lacunae and canaliculi of cementocytes were stained vitally with the fluorescence dyes-suggests that cementocytes may have a role in secondary calcification of cellular cementum. Further, the lower density of cytoplasmic processes in cementocytes than in osteocytes suggests a lack of complexity in the intercellular network within the cellular cementum.

Localization of types I, II and III collagen and glycosaminoglycans in the mandibular condyle of growing monkeys: an immunohistochemical study.

In order to analyse the regional and age-related variations of primate condyles, immunohistochemical techniques were used to examine the localization of types I, II and III collagen and a variety of glycosaminoglycans in distinct anteroposterior regions of the mandibular condyle of two growing female rhesus monkeys (Macaca mulatta). In the juvenile monkey staining for types I and III collagen was weak in the fibrous tissue layer, intense in the pre-cartilaginous tissue layer and faint in the cartilaginous tissue layer; staining was significantly more intense in the posterosuperior and posterior regions than in the anterior region. Similarly, staining for cartilage-characteristic extracellular matrices, including type II collagen and keratan sulfate, was intense in the cartilaginous tissue layer of the posterior condyle. In contrast, in the late-adolescent monkey staining for the extracellular matrices was more intense in the anterior half of the condyle (i.e. from the anterior to the posterosuperior region) than in the posterior region, and most intense in the posterosuperior region. The results demonstrate that marked regional differences exist in the phenotypic expression of the extracellular matrices in the mandibular condyles of growing monkeys and that these differences vary between different developmental stages. The variations probably reflect the predominance of competing growth and articulatory functions in the mandibular condyles.

Confocal microscopy of Tomes' granular layer in dog premolar teeth.

Tomes' granular layer is the hypomineralized area of radicular dentin, but knowledge concerning it is limited. The present study was designed to investigate the structural characteristics of Tomes' granular layer in the dog's teeth by confocal microscopy. Permanent premolars of four beagles, two at 7 months and the other two at 14 months of age, were used for observation. During premolar root formation, the 7-month-old dogs were injected with calcein and alizarin red S for vital staining of dentin, and ground sections of the teeth were prepared. Both ground and decalcified-paraffin sections were made from the teeth of the 14-month-old dogs and stained with basic fuchsin or with hematoxylin and eosin. All sections were examined by fluorescence and confocal microscopy. In the ground sections, granules of Tomes' layer and dentinal tubules were stained with basic fuchsin and with calcein. The granules of Tomes' layer stained with calcein were seen only near the labeling lines by calcein. The granules of Tomes' layer appeared as bright spots in cross sections, and as lines in longitudinal sections. When the sections were cut tangentially through the surface of dentin, the granules of Tomes' layer showed a reticular structure. Most of the dentinal tubules were seen to pass between the granules and terminated in the dentin-cementum junction. Looped tubules were not found in this area. In the paraffin sections stained with hematoxylin and eosin, extracellular matrix of dentin showed fluorescence of various intensities and dentinal tubules appeared dark. At the surface of the radicular dentin, the granules of Tomes' layer appeared as fluorescent fibers running parallel to the surface of dentin in the longitudinal sections. The fibers appeared as bright spots in the cross sections and as a mesh in the tangential sections. In the periodontal ligament, collagen fibers showed intense fluorescence, whereas most cells were negative. From these results we conclude that Tomes' granular layer of dog's teeth may be the collagen fiber bundles that remained uncalcified or hypocalcified within the radicular dentin.

The process of calcification during development of the rat tracheal cartilage characterized by distribution of alkaline phosphatase activity and immunolocalization of types I and II collagens and glycosaminoglycans of proteoglycans.

The rat tracheal cartilage was shown to calcify during development. The process of calcification was characterized in terms of distribution of alkaline phosphatase (ALP) activity and alterations to immunolocalization of types I and II collagens and glycosaminoglycans of proteoglycans during the development of the tracheal cartilage, in comparison with calcification of the epiphyseal growth plate cartilage. ALP activity was not identified in the tracheal cartilage in the course of calcification, which therefore differed from that in the growth plate. The tracheal cartilage matrix was not resorbed or invaded by type I collagen during calcification. This suggests that no osteogenesis is involved in calcification of the cartilage. Immunoreactivity for type II collagen became weaker in the central region of the tracheal cartilage during development. No net loss of proteoglycans was identified with Alcian blue staining after calcification of the tracheal cartilage. Immunoreactivity for chondroitin 4-sulphate increased in the calcified tracheal cartilage, while reactivity for chondroitin 6-sulphate was weaker in the calcified area than in the surrounding uncalcified region of the tracheal cartilage. The alteration of the extracellular matrices during development may be involved in the calcification of the rat tracheal cartilage.

Expression of major bone extracellular matrix proteins during embryonic osteogenesis in rat mandibles.

It is not known how bone proteins appear in the matrix before and after calcification during embryonic osteogenesis. The present study was designed to investigate expressions of the five major bone extracellular matrix proteins--i.e. type I collagen, osteonectin, osteopontin, bone sialoprotein and osteocalcin--during osteogenesis in rat embryonic mandibles immunohistochemically, and their involvement in calcification demonstrated by von Kossa staining. Wistar rat embryos 14 to 18 days post coitum were used. Osteogenesis was not seen in 14-day rat embryonic mandibles. Type I collagen was localized in the uncalcifed bone matrix in 15-day mandibles, where no other bone proteins showed immunoreactivity. Osteonectin, osteopontin, bone sialoprotein and osteocalcin appeared almost simultaneously in the calcified bone matrix of 16-day mandibles and accumulated continuously in 18-day mandibles. The present study suggested that type I collagen constitutes the basic framework of the bone matrix upon which the noncollagenous proteins are oriented to lead to calcification, whereas the noncollagenous proteins are deposited simultaneously by osteoblasts and are involved in calcification cooperatively.

Distribution of type I collagen, type II collagen and PNA binding glycoconjugates during chondrogenesis of three distinct embryonic cartilages.

Previous studies of chondrogenesis have been focused on limb bud cartilage, whereas little is known about chondrogenic processes of other cartilages with different developmental fates. We hypothesize that cartilages with various developmental fates might show identical characteristics of chondrogenesis. The chondrogenic processes in the nasal septum, the mandible, and the limb bud of the mouse were examined by means of PNA-binding glycoconjugate, and types I and II collagen expression. Swiss-Webster mouse embryos of 11 days (E11) to 14 days (E14) gestation were fixed and processed for immuno- and lectin histochemistry. The blastema of mesenchymal cell aggregates stained positively with anti-type I collagen, but very weakly with anti-type II collagen in all three models at E12, whereas PNA bound to the blastema in the limb bud but not in nasal septum or mandible. Types I and II collagens coexisted in cartilages at E13. Type II collagen was predominant in E14; type I collagen was confined to the peripheral region. The synchronized transitional expression of the collagen phenotypes in all three embryonic cartilages may be systemically regulated. The presence or absence of the PNA-binding glycoconjugates may be involved in characterizing the nature of the cartilages.

Presence of chondroid bone on rat mandibular condylar cartilage. An immunohistochemical study.

Immunohistochemical techniques were used to examine the locations of type I and type II collagens in the the most anterior and the posterosuperior regions of the mandibular condylar cartilages of young and adult rats. Large ovoid and polygonal cells, which were morphologically different from any of the neighboring cells, e.g., mature or hypertrophied chondrocytes, osteoblasts, or fibroblasts, were observed at the most anterior margin of the young and adult condylar cartilages. In the extracellular matrix (ECM) of this area, an eosinophilic staining pattern similar to that in bone matrix was observed, while the peripheral ECM showed basophilic staining and very weak reactivity to Alcian blue. Immunohistochemical examination showed that the ECM was stained heavily and diffusely for type I collagen, while a staining for type II collagen was faint and limited to the peripheral ECM. Two different staining patterns for type II collagen could be recognized in the ECM: one pattern revealed a very faint and diffuse reaction while the other showed a wak rim-like reaction. These staining patterns were markedly different from those in the cartilaginous cell layer in the posterosuperior area of the condylar secondary cartilage, which showed faint staining for type I collagen and a much more intense staining for type II collagen. These observations reveal the presence of chondroid bone, a tissue intermediate between bone and cartilage tissues, in the mandibular condylar cartilage, and suggest the possibility of osteogenic transdifferentiation of mature chondrocytes.

Chondrocytes synthesize type I collagen and accumulate the protein in the matrix during development of rat tibial articular cartilage.

The present study was designed to investigate whether or not chondrocytes in articular cartilage express type I collagen in vivo under physiological conditions. Expressions of the gene and the phenotype of type I collagen were examined in rat tibial articular cartilage in the knee joint during development. Knee joints of Wistar rats at 1, 5, and 11 weeks postnatal were fixed in 4% paraformaldehyde with or without 0.5% glutaraldehyde and decalcified in 10% EDTA. After the specimens were embedded in paraffin and serial sections made, adjacent sections were processed for immunohistochemistry and in situ hybridization for type I collagen. The epiphysis of the tibia was composed of cartilage in week- 1 rats. Formation of articular cartilage was in progress in week 5 as endochondral ossification proceeded and was completed in week 11. Anti-type I collagen antibody stained only the superficial area of the epiphysis in week 1, but the immunoreactivity was expanded into the deeper region of the articular cartilage with development in weeks 5 and 11. Hybridization signals for pro-alpha 1 (I) collagen were seen in some of chondrocytes in the epiphysis of the week-1 tibia. The most intense signals were identified in chondrocytes in week 5 and the signals appeared weaker in week 11. The present study demonstrated that chondrocytes synthesize type I collagen and accumulate the protein in the matrix during development of the articular cartilage.

Age-related changes in the localization of glycosaminoglycans in condylar cartilage of the mandible in rats.

There is little information available regarding the morphological and biomolecular characteristics of mandibular condylar cartilage. The purpose of this study was to determine the age-related changes in the morphology and immunolocalization of glycosaminoglycans (GAGs) in mandibular condyles. The mandibular condylar cartilages from 4-, 8-, 16-, 32-, and 64-week-old Wistar male rats were examined to verify the localization of chondroitin-4-sulfate (Ch-4S), chondroitin-6-sulfate (Ch-6S) and keratan sulfate (KS) using an indirect immunofluorescent technique with three monoclonal antibodies for glycosaminoglycans, 2-B-6, 3-B-3 and 5-D-4, respectively. Morphologically, the condylar cartilage was a growth cartilage during growing periods, began to differentiate into articular cartilage from the central area of 16-week-old condyles, and became mature articular cartilage at 32 weeks of age. A regional difference was found in the morphological features and distribution of GAGs between the anterior, central, postero-superior and posterior areas of the condyles at each age. The immunohistochemical localizations of these three glycosaminoglycans showed age-related, morphology-dependent changes, from growth cartilage to articular cartilage-like cartilage. Immunoreactions for all of the antibodies decreased progressively with age in the interterritorial matrix, while the pericellular and territorial matrix in the condylar cartilage of the mandible maintained relatively higher immunoreactivity. In conclusion, age-related and regional differences in the localization of glycosaminoglycans Ch-4S, Ch-6S, and KS were found in the mandibular condyles in rats, and these changes are believed to be related to functional and developmental requirements.

Type X collagen is not localized in hypertrophic or calcified cartilage in the developing rat trachea.

Our previous studies have shown that rat tracheal chondrocytes become larger and hypertrophic, and that the cartilage matrix calcifies during development. Type X collagen is a short collagen molecule identified in hypertrophic and calcified cartilage in the growth plate of long bones during endochondral ossification. The present study was designed to investigate the distribution of type X collagen in rat tracheal cartilage during development before and after hypertrophization and calcification. Tracheas from postnatal Wistar rats, newborn, and at 4, 8 and 10 weeks were fixed along with hind limbs from newborn rats. Serial sections were made and adjacent sections were processed for von Kossa staining or immunohistochemistry for type X collagen. In addition, the immunoreactivity to type II collagen was examined as a control. The anti-type X collagen antibody stained hypertrophic and/or calcified cartilage in the newborn rat tibia. The immunoreaction for type X collagen was localized in the uncalcified peripheral region of tracheal cartilage in 4, 8 and 10-week-old rats. In contrast, the anti-type X collagen antibody did not show immunoreactivity to hypertrophic or calcified cartilage in the central region of the 10-week-old rat tracheal cartilage. The present study has suggested that type X collagen is not involved in hypertrophization of chondrocytes or calcification of the matrix in developing rat tracheal cartilage.

Localization of types I, II and X collagen and osteocalcin in intramembranous, endochondral and chondroid bone of rats.

Chondroid bone is a unique calcified tissue intermediate between bone and cartilage. To clarify its characteristics, we examined the distributions of the ECMs associated with chondrogenic differentiation and matrix calcification in the chondroid bone of the rat glenoid fossa, and compared them to those in two typical bone tissues, alveolar bone of the maxilla (intramembranous bone) and the growth plate of long bone (endochrondral bone), using immunofluorescence techniques. Morphologically, the glenoid fossa consisted of the fibrous, progenitor and cartilaginous cell layers and the cartilaginous cell layer was further divided into the superficial non-hypertrophic layers (secondary cartilage) and the deep hypertrophic cell layers (chondroid bone). The co-distribution of type I and type II collagens was observed in secondary cartilage and chondroid bone, whereas type X collagen was restricted to the pericellular matrix of hypertrophied cells (chondroid bone). Osteocalcin, which was absent from the calcified cartilage of endochondral bone formation, was also present in the ECM of the chondroid bone, but not in cells. These results demonstrate that chondroid bone of rats, which is adjacent to secondary-type cartilage in the glenoid fossa, has phenotypic expressions associated with both hypertrophied chondrocytes and osteocytes.