Dentine Organic Matrices Effect on Osteoclastogenesis

Recently, the extracellular matrix (ECM), for example amelogenin , has been shown to play a role in osteoclastogenesis in root resorption process. We have reported that ECM from dentine has effects on osteoclastic activity, but the effect of dentine organic matrices on osteoclastogenesis has been still unknown. Objectives: We would like to investigate the effect of dentine organic matrices on osteoclastogenesis in root resorption. Methods: The unresorbed roots of bovine deciduous and permanent incisor were used. Dentine organic matrices were extracted using 0.6N HCl. Osteoblasts and bone marrow macrophages (BMMs) were co-cultured in 96-well dishes containing 10^-8M 1α, 25-dihydroxy vitamin D₃, and 10^-6M PGE₂. In some experiment, BMMs were cultured containing M-CSF 50 ng/ml, and RANKL 30 ng/ml. Protein extracts from root dentine (0.01%) were added and incubated for 5 days at 37°C 5% CO₂. TRAP positive cell count and TRAP activity were performed. The mRNA level of RANKL and OPG also assayed by real-time RT-PCR. Results: In co-culture system, multinucleated osteoclasts cultured with dentine organic matrices have shown to be suppressed in TRAP activity and the cell number when compared to the control. The mRNA level of RANKL/OPG in co-culture system was also decreased. In contrast, TRAP activity and multinucleated osteoclast number have been up-regulated in BMMs cultured with dentine organic matrices. Conclusion: These results may indicate that dentine organic matrices contain some factors that affect on osteoclastogenesis in root resorption process.