High concentrations of pamidronate on osteoblast growth

The aim of our study was to analyze the mechanism of osteoblast growth inhibition by high concentrations of pamidronate a nitrogen-containing bisphosphonate, on human osteoblast-like cells (MG-63).

Method:

The MG63 cellular line was cultured in Dulbecco’s modified Eagle medium with 10% fetal bovine serum (FBS). Cultures were kept at 37 ºC in a humidified atmosphere of 95% air and 5% CO₂.

The study of the mechanism of the osteoblast growth inhibition was determined through the analysis of cell cycle and induction of apoptosis/necrosis. MG-63 cells were incubated for 24 h with different doses (10^-4, 5x10^-5, 10^-5 M) of pamidronate (Sigma-Aldrich). Induction of apoptosis/necrosis was determined by flow cytometry and double staining with annexin V and propidium iodide. Cell cycle analysis was performed by a cytometric technique. Data were expressed as means ± standard deviation (SD) and compared using the Student’s t test. P < 0.05 was considered significant in all tests. At least three experiments were performed for each culture. SPSS version 20.0 (SPSS, Chicago, IL) was used for all data analyses.

Result:

Treatment with pamidronate at highest doses tested (10^-4, 5x10^-5) showed a significant increase (P <0.05) in apoptotic cell number compared to the control (non-treated cells). In the same way, the study of cell cycle showed that the percentage of cells in G₀/G₁ phase significantly increased at doses of treatment 10^-4, 5x10^-5 M. We did not detect a significative effect on induction of apoptosis and on cell cycle at lowest dose tested (10^-5M).

Conclusion:

High concentrations of pamidronate inhibits osteoblast growth through cell accumulation in G0/G1 phase of the cell cycle and induction of apoptosis.

These findings may be related with the osteonecrosis of the jaw because bisphosphonates have high affinity to the bone therefore they can rich high concentrations in bone.