Fig. 3. Optn^−/− cells are more sensitive to H2O2-induced cytotoxicity.

a Cell viability of osteoclast precursors in response to various concentrations of H₂O_2. Each graph indicates a different treatment duration (1, 2, and 3 days). Quantitation of live b, apoptotic c, and necrotic d cells following treatment with various concentrations of H₂O₂. The cells are shown as a ratio of treated versus control untreated cells. The cells were treated with H₂O₂ for 1 day and then stained with Annexin V for apoptosis and necrosis before quantitation by flow cytometry. WT, Optn^+/+ preosteoclasts; KO, Optn^−/− preosteoclasts; Cont, control (growth media only); n = 3 experiments. Data are presented as the mean ± SEM. *p < 0.05, **p < 0.01 compared to Optn^+/+ within each dosage group.