High doses of bisphosphonates reduce osteoblast-like cell proliferation by arresting the cell cycle and inducing apoptosis.

OBJECTIVES

The study objective was to evaluate the effect on osteoblast growth of high concentrations of three nitrogen-containing bisphosphonates (pamidronate, alendronate, and ibandronate) and one non-nitrogen-containing bisphosphonate (clodronate), using the MG-63 cell line as an osteoblast model, in order to determine the role of osteoblasts in bisphosphonate-related osteonecrosis of the jaw (BRONJ).

MATERIALS AND METHODS

Osteoblasts were incubated in culture medium with different doses of pamidronate, alendronate, ibandronate or clodronate. The proliferative capacity of the osteoblasts was determined by spectrophotometry (MTT-based) at 24 h of culture. Flow cytometry was used to determine the percentage of cells in each cell cycle phase (G0/G1, G2/M, and S) and to discriminate apoptotic cell death from necrotic cell death in the cell cycle at 24 h of treatment.

RESULTS

All the bisphosphonates assayed produced a significant and dose-dependent reduction in MG-63 proliferation at the high doses assayed (10(-4) and 5 × 10(-5) M) in comparison with controls (p <0.001). Cell cycle study revealed that all assayed bisphosphonates significantly arrested the cell cycle in phase G0/G1 at doses of 10(-4) and 5 × 10(-5) M, increasing the percentage of cells in this phase (p <0.05). Apoptosis/necrosis studies showed significant changes compared with control cells, with an increased percentage of cells in apoptosis after treatment with 10(-4) or 5 × 10(-5) M of pamidronate, alendronate, ibandronate, or clodronate (p <0.05).

CONCLUSIONS

High doses of nitrogen-containing or non-nitrogen-containing bisphosphonates can reduce the proliferation of MG-63 osteoblast-like cells by arresting the cell cycle and inducing apoptosis/necrosis.