(99)Tc-MDP-induced human osteoblast proliferation, differentiation and expression of osteoprotegerin

The aim of the present study was to examine the influence of technetium methylenediphosphonate ((99)Tc-MDP) on the proliferation and differentiation of human osteoblasts. Human iliac cancellous bone was isolated and cultured with either (99)Tc-MDP, β fibroblast growth factor (as a positive control) or medium only (as a negative control). Proliferation was assessed by direct cell counting, CCK-8 assay and bromodeoxyuridine staining. The cell cycle and rate of apoptosis was assessed by propidium iodide staining and flow cytometry. Alkaline phosphatase (ALP) activity was assessed by the p-nitrophenyl phosphate method and mineralized nodules were stained with Alizarin Red. Expression of osteocalcin (OCN) and bone morphogenetic protein-2 (BMP-2) was assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and expression levels of osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) were assessed by RT-qPCR and ELISA. Isolated human osteoblasts stained positively for ALP and developed mineralized nodules. Treatment with 10(−5)-10(−10) M (99)Tc-MDP enhanced proliferation and 48 h incubation with 10(−8) M (99)Tc-MDP increased the proportion of cells in S-phase, decreased the proportion in G(0)/G(1) phase, and increased the cell proliferation index. The rate of apoptosis also increased, but the increase was not significant. Cells incubated with 10(−6)-10(−9) M (99)Tc-MDP for 3–9 days exhibited increased ALP activity and mineralized nodule development. 10(−8) M (99)Tc-MDP increased BMP-2 and OPG expression levels and OPG secretion, but OCN mRNA expression levels and RANKL secretion were not significantly altered at 72 h. (99)Tc-MDP treatment induced osteoblast proliferation and differentiation without affecting apoptosis. These findings provide proof of concept for the future use of (99)Tc-MDP in the treatment of bone-destructive diseases.