Expression of tenascin-Xon rat TMJ in functional property

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The tenascin family including tenascin-C, -X, -R, and N is known as one of extracellular matrix. Mainly tenascin-X, which is detected in ligaments and tendon of the joint hyperextensibility, and tenascin-C, which is associated with cell adhesion and conjugation, are observed. in this study, we investigated the transcription and translation levels of tenascin-C and -X in rat TMJ and masseter muscle during TMJ forming period, and on soft diet.1.Distribution of tenascin during development : Tenascin-C and X were detected in masseter muscle, connective tissue, and the bone matrix in the mandibular condyle and the mandibular fossa, on 18-days gestation. On 20-days gestation, tenascin-X was detected in the upper side of the TMJ disk in contrast to that of tenascin-C. During postnatal period, while tenascin-C was detected on masseter muscle and the middle region of the disk, tenascin X was detected mainly on the myotendinous junction, middle and outer regions of the disk and the bone matrix i … More n the mandibular fossa. These results suggest that in the period from 20-days gestation to postnatal, the localization of the tenascin family changes, at the same time cell movement and adhesion take place, resulting in the developed TMJ. Tenascin-C mRNA expressed more than tenascin-X mRNA in the newborn period, although the expression level of these had no difference in other periods. This suggests that in the newborn period these two play different roles. it seems according to the observation on the different localization of tenascin-C and -X in the TMJ disk that tenascin-C and -X are specially related to TMJ disk development.2.The effect of a soft diet : After weaning, one group was fed on a soft diet, while the other group was fed on a normal diet for three weeks. Tenascin-C was detected mainly on anterior and posterior regions of the disk in both groups. Especially the strong reaction was observed on the middle region of the disk in soft diet group in the first week. Tenascin-X was revealed the same region of tenascin-C in both groups and in soft diet group, the strong reaction was observed on the upper side of the disk in the first week. The PCNA-positive cell was observed on cartilage of mandibular condyle and inner and outer region of the disk in control group. In soft diet group, the number of the PCNA-positive cells decreased in the first week, then increased in the third week. The apoptosis-positive cell was observed on the bone matrix in the mandibular fossa and the mandibular condyle, in both groups in soft diet group the apoptosis-positive cells was also observed on cartilage of the condyle in the second week, and on cartilage cells and epithelial tissues in the eighth week. This suggests that the distribution of tenascin -C and -X, and cells and tissues composed of TMJ were changed by the stress of a soft diet for three weeks, and that mechanical stress causes cell movement and separation. Less