AN ULTRASTRUCTURAL-STUDY OF EXTRACELLULAR FIBRILLAR COMPONENTS OF DEVELOPING MOUSE MANDIBULAR CONDYLE WITH SPECIAL REFERENCE TO TYPE-VI COLLAGEN

The localization of type Vi collagen was examined from birth to 8 week s of age. Immunohistochemical staining with anti-type VI collagen anti body was strongly positive in the hypertrophic zone and moderately pos itive in the fibrous zone and the outer periphery of the proliferative zone, but negative in the inner area of the proliferative zone and ma ture zone. After ATP treatment, type VI collagen periodic fibrils with about 80-nm intervals were frequently observed but only in the fibrou s zone. They occurred mainly in the superficial area of this zone, whe re striated collagen fibrils were sparse, while a few were noted in th e inner area, where bundles of collagen fibrils were abundant. From th ese distributional differences of both components, a subzonation of th e fibrous zone into superficial and inner areas is suggested. Moreover , with ATP treatment there were fewer type VI collagen periodic fibril s formed with increasing age (8 weeks). Testicular hyaluronidase diges tion before ATP treatment facilitated the formation of periodic fibril s, in all the ages examined, in the intercellular space and around the fibroblastic cells. The interaction of type VI collagen with other co mponents such as collagen fibrils, glycosaminoglycans or proteoglycans may play a part in maintaining the structural integrity of extracellu lar matrix in the mouse mandibular condyle.