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

Abstract

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). 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 48h 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 21days by the study of nodule formation and alkaline phosphatase activity (ALP) at 24h by spectrophotometric assay. 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 24h 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 24h of treatment and a decrease in calcium deposition after 15 and 21days (p < 0.05). 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. 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.