Epilife basal medium

hOMK were purchased from Cell Research Corp. (Singapore, Republic of Singapore) and cultured in an epithelial culture medium (EpiLife basal medium supplemented with EpiLife Defined Growth Supplement, Thermo Fisher Science, Waltham, MA, USA), at 37 °C in a humidified atmosphere of 95% air and 5% CO₂. hOMK were seeded at a density of 1, 3 × 10⁴, 1 × 10⁵, or 1 × 10⁶ cells/well in 96-well plates, 24-well plates, or six-well plates, depending on the experiment, and then stimulated with 5-FU ((0.5 μg/mL or 0.01–10 μg/mL) (Kyowa Kirin, Tokyo, Japan)) and β-cry ((1 × 10⁻⁷ M) (CaroteNature, Lupsingen, Switzerland)). In some experiments, the combination of LPS ((1 μg/mL) from P. gingivalis (InvivoGen, San Diego, CA, USA)), RA ((10 nM) (Sigma, St. Louis, MI, USA)) and indomethacin ((10 μg/mL) (Nacalai, Kyoto, Japan)) were also used and dissolved in DMSO.

The impedance spectroscopy measurement was performed as previously described^{30 (link)}. In brief, a sinusoidal electrical current I(f) [A] was generated and the potential difference U(f) [V] was measured by an impedance spectrometer LCR HiTESTER 3522-50 (HIOKI E.E. Corporation, Nagano, Japan) to record the impedance spectra Z(f) of biological samples. A custom-made user interface, programmed in LabVIEW (National Instruments, Austin, TX USA) calculated Z(f) according to the equation Z(f) = U(f)/I(f).
RHE, mRHE, and RCE models were measured in a 24-well plate (Brand, Wertheim, Germany) with an in-house-developed measuring chamber (Supplementary Fig. 1). The insert and the well were filled with 0.5 ml EpiLife® basal medium (Thermo Fisher Scientific, Waltham, MA USA) to ensure contact with the electrodes. For each well, impedance was measured over a frequency range from 1 Hz to 100 kHz at 40 logarithmically distributed sampling points.