Effect of simvastatin on gentamicin-induced hair cell damage. Photograph of organs of Corti (OCs). Overview on the left (scale bar 100 μm) and high magnification on the right (sale bar 20 μm). Untreated OCs (A), OCs exposed to 100 μM simvastatin (B), and OCs exposed to 100 μM mevalonate demonstrate three orderly rows of outer hair cells (OHC) and a single row of inner hair cells (IHC). OCs cultured with gentamicin showed significant loss of hair cells (C). Treatment with increasing concentrations of simvastatin in addition to gentamicin resulted in dose dependent significant decrease in hair cell loss compared with gentamicin treatment only (D-F). Mevalonate reverses the protective effect of simvastatin on gentamicin-induced hair cell damage. OCs cultured with mevalonate in addition to gentamicin and OCs cultured with simvastatin 10 μM and mevalonate showed the same degree of hair cell loss as OCs cultured with gentamicin only (H,I).