The evaluation of nitrogen containing bisphosphonate?s effect on oral mucosa cell culture

Bisphosphonate related osteonecrosis of the jaw (BRONJ) has become one of the most obstinate and complicated pathology in oral and maxillofacial surgery. Defective or delayed epithelialization of soft tissue has been observed in almost every BRONJ case. Whether BRONJ starts from bone or soft tissue is still controversial. It has been hypothesized that the soft tissue of the oral mucosa could play a significant role in BRONJ. In order to support or reject this hypothesis, our study was planned to investigate and compare the in vitro effects of alendronate and pamidronate on human gingival fibroblasts. Primary fibroblast cultures were set up from 6 healthy volunteers? oral mucosa biopsy under standard cell culture conditions. The cytotoxic concentrations of alendronate and pamidronate were determined by MTT assay. Alendronate and pamidronate were added to culture medium at concentrations of 10-4 to 10-7M for at 6, 12, 24, 48 and 72 hours. Cell proliferation and induction of apoptosis were evaluated and compared with immunohistochemically by Ki-67 and caspase-3 staining, respectively. Both pamidronate and alendronate induced apoptosis and inhibited cell proliferation in a dose and time dependent manner compared to untreated control cells. Although cell proliferation ratios were similar for both drugs, caspase activation in every application time and dose was significantly higher in pamidronate than alendronate (p:0.046). Bisphosphonates induce apoptosis via caspase-3 pathway on human gingival fibroblasts in a dose and time dependent manner emphasizing the importance of soft tissue in BRONJ.