Maintenance of Immortalized Mouse Auditory Cells

HEI-OC1 auditory cells were kindly provided by Dr. D. Lim (House Research Institute, Los Angeles, CA, USA). This conditionally immortalized mouse auditory cell line was established by Kalinec et al. [27 (link)], and is a well-established in vitro system for investigating cellular and molecular mechanisms. Cells were maintained in low-glucose Dulbecco's modified medium (DMEM; Wako, Osaka, Japan) supplemented with 10% fetal bovine serum (FBS; HyClone, UT, USA), 1% penicillin streptomycin, and 1% kanamycin (MP Biomedicals, Ohio, USA) at 33°C in a humidified incubator with 10% CO₂. This culturing medium also served as the control medium in the population doubling experiments. Maintaining HEI-OC1 cells at this temperature and CO₂ concentration is referred to as “permissive conditions” by Kalinec et al. [27 (link)], because lower basal apoptotic rates are present.