Remodeling of the sagittal suture in osteopetrotic (op/op) mice associatedwith cranial flat bone growth

It is well known that cranial flat bone experiences growth and development at the sutural interface, which is regarded as a neutral zone to control me chanical stimuli. In osteopetrotic (op/op) mice, meanwhile, cranial deforma tion is produced by the deficiency of osteoclasts and the subsequent defect of bone resorption. It would be a reasonable assumption that such disturba nce in bone remodeling affects sutural modification and the relevant crania l flat bone development. The present study was thus conducted to examine hi stological features of the sagittal sutures in op/op mice, with special ref erence to the relevant bone remodeling. The sagittal sutures in 10-, 15-, 3 0-, and 60-day-old normal and op/op mice were observed microscopically. Fur thermore, osteoclastic activity was evaluated on the sections stained with tartrate-resistant acid phosphatase (TRAP). The sutures of 15-day-old op/op mice showed stenosis and synostosis, and less-developed collagen fibers as sociated with an irregular arrangement of fibroblasts, whereas these change s were rarely found in normal mice. Osteoclasts were hardly detected in the parietal bones around the sutures of op/op mice, although the number was n umerous in normal mice. These results emphasize that congenital deficiency in osteoclast produces unbalanced bone remodeling at the sutural interface and on the surfaces of the cranial bones, which is assumed to be closely re lated to cranial bone deformity in op/op mice.