Nitrogen-containing bisphosphonates modulate the antigenic profile and inhibit the maturation and biomineralization potential of osteoblast-like cells

Abstract

Objectives: The aim was to evaluate the effect of three nitrogen-containing bisphosphonates at different concentrations on osteoblast growth, differentiation, and antigenic profile, using the MG-63 cell line as 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 10(-5), 10(-7), or 10(-9) M of pamidronate, alendronate, or ibandronate. Proliferative capacity of the osteoblasts was determined by spectrophotometry (MTT) at 24 and 48 h of culture. Flow cytometry was used to study antigenic profile (CD54, CD80, CD86, HLA-DR) and phagocytic activity. Cell differentiation was evaluated at 7, 15, and 21 days by the study of nodule formation and alkaline phosphatase activity (ALP) at 24 h by spectrophotometric assay.

Results: Pamidronate, alendronate, and ibandronate each exerted a significant stimulatory effect on MG63 proliferation that depended on the dose and treatment duration (p < 0.05). In general, a significantly decreased expression of CD54, CD80, and HLA-DR membrane antigens was observed after 24 h of treatment with each nitrogen-containing bisphosphonate (p < 0.05), but there was no significant difference in phagocytic activity versus controls. A decrease in ALP activity was observed after 24 h of treatment and a decrease in calcium deposition after 15 and 21 days (p < 0.05).

Conclusion: Nitrogen-containing bisphosphonates can increase the proliferation of MG-63 osteoblast-like cells, modulate their expression of co-stimulatory molecules associated with immune function, and decrease their differentiation capacity, generally at low doses.

Clinical relevance: These findings suggest that low doses of nitrogen-containing bisphosphonates exert their effect on osteoblasts by altering their physiology, which would explain the disruption of their repair capacity and may be directly related to the development of BRONJ.