Occlusal hypofunction causes changes of proteoglycan content in the rat periodontal ligament

The biological functions of proteoglycans and glycosaminoglycans are closel y associated with mechanical stress on the tissue. In order to reveal the r elationship between proteoglycans in the periodontal ligament and mechanica l stress such as occlusal stimuli, occlusal hypofunction of rat unilateral mandibular molars was induced by extraction of the opposing first, second a nd third maxillary molars. Immunohistochemical analyses were performed usin g antibodies for chondroitin sulfate, decorin, biglycan, heparan sulfate an d keratan sulfate, and hyaluronic acid-binding protein. Chondroitin sulfate , observed more strongly in the cervical side than in the apical side of th e periodontal ligament of the unextracted sides of mandible, and uniformly present in the extracellular matrix of the periodontal ligament, decreased significantly from I wk post-extraction of the antagonists, with a decrease in thickness and disarrangement in fibrous components. Decorin core protei n, uniformly present in the periodontal ligament of the unextracted sides, decreased as early on as 2 d post-extraction. Heparan sulfate, mainly local ized on the cell surface of vascular endothelial cells and osteoclastic cel ls as well as in the extracellular matrix of the unextracted sides, decreas ed significantly in association with the decreased number of blood vessels and osteoclastic cells as early on as 2 d post-extraction. Biglycan, kerata n sulfate and hyaluronic acid, uniformly distributed in the periodontal lig ament of the unextracted sides, showed little change after the extraction. These: results demonstrate that occlusal hypofunction causes tissue remodel ing of the periodontal ligament, with a significant decrease of chondroitin sulfate, decorin and heparan sulfate.