MDCK Cell Culture.

MDCK cells were cultured at 37○C in an atmosphere of 5% CO2. Cells were passaged at a 1:5 ratio every 3 to 4 d using standard cell culture protocols and disposed of after 25 passages. The culture medium was composed of high-glucose Dulbecco’s Modified Eagle Medium (Thermo Fisher Scientific) supplemented with 10% FBS (Sigma) and 1% penicillin-streptomycin (Thermo Fisher Scientific).