Abstract
The aim of this study is to investigate the properties of bone substrates which are responsible for induction of bone-resorptive behavior of osteoclasts. For this purpose, the recently developed culture system in which the bone-resorptive activity of isolated osteoclasts can be analized on various natural or artificial substrates has been utilized.
The results are follows:
1. Resorption pits by isolated osteoclasts occured on bovine enamel, bovine dentin, egg shell, clam shell and lingula shell, containing hydroxyapatite, calcite and aragonite respectively.
2. The resorptive activity of isolated osteoclasts was significantry lower on demineralized bone slices than that on untreated bone.
3. Extracellular calcium from 2mM to 3mM stimulated resorptive activity although 6mM or the above inhibited the activity in 15h of culture.
4. Although no resorption was seen on the surfaces of polycrystalline synthetic hydroxyapatite, geological single crystal hydroxyapatite and α-tricalcium phosphate, many pits were observed on octacalcium phosphate.
5. Resorption pits were created on the bone slices made anorganic by hydrazine treatment or sintering at 700°C and 900°C.
6. Electron microscopy revealed that elaborated ruffled border and clear zone developed in the osteoclasts on the mineralized bone, on the other hand, irregularly arranged ruffled border and poorly-organized appeared in the osteoclasts on the demineralzed bone.
These observations have suggested that bone mineral is responsible for induction of bone resorption by osteoclasts in close relation to development of ruffled border in osteoclasts.
