Distribution of type I and type III collagen in the developing periodontal ligament of mice

In order to localize type I and type III collagen in developing periodontal ligament, immunofluorescent and immunoelectron microscopic examinations were undertaken. The materials used were the maxillary molars of CF1 mice, 13 days to 6 months old. The antibodies used were monospecific polyclonal antibodies against type I or type III collagen raised in rabbits or guinea pigs, respectively. Single- and double-staining methods were employed in immunofluorescent as well as immunoelectron microscopic examinations. In immunofluorescent examinations, during the development of the periodontal ligament, periodontal fibers showed intense and homogenous staining for both type I and type III collagen; while Sharpey's fibers in the alveolar bone showed a heterogenous staining in cross and longitudinal sections for both types of collagen. In immunoelectron microscopic examinations, fibrils of periodontal fibers showed positive staining for type I and type III collagen simultaneously and had characteristic cross-banding and had a large diameter (ranging 40 approximately 80 nm) which remained constant during development. Sharpey's fibers in the alveolar bone or in the cementum showed the same staining pattern as the periodontal fibers, except for an afibrillar area which showed negative staining for both type I and type III collagen. The results obtained suggest that periodontal fibers and Sharpey's fibers consist of cofibrils of at least type I and type III collagen.