Gentamicin negatively influenced osteogenic function in vitro

Local delivery of gentamicin is an accepted method of infection prophylaxis in the surgery of open fractures. However, the few reports of studies into the effect of locally applied gentamicin on osteoblasts used inadequate methods. In our study, we used the well-characterised C2C12 cell line with reproducible differentiation pathway into the osteoblast lineage. We investigated the viability, cell number, alkaline phosphatase activity, and the expression of osteogenic genes of C2C12 cells after exposure to gentamicin at concentrations of 12.5–800 μg/ml for 48 h. Exposure of C2C12 cells to gentamicin (12.5–800 mg/ml) for 48 h showed no significant changes in the cell number, but cell viability was decreased by one-third at the tested concentrations of 200–800 μg/ml. The alkaline phosphatase activity was significantly decreased by one-third to one-half at any tested concentration (12.5–800 μg/ml) of gentamicin. Any tested concentration of gentamicin up to 800 μg/ml for 48 h did not inhibit or decrease the osteogenic gene expression of osterix and alkaline phosphatase of the C2C12 cells. In conclusion, gentamicin at high concentrations as achieved by local application reduced cellular viability and alkaline phosphatase activity in vitro and therefore may be detrimental for bone healing and repair in vivo.