Comparison of Culture Media for in-vitro Expansion of Oral Epithelial Keratinocytes: Implications for Testing E-liquid Flavors

Background: Expansion of OKF6/TERT-2 oral epithelial cells in vitro is important for studying the molecular biology of disease and pathology affecting the oral cavity. Keratinocyte Serum-Free Medium (KSFM) is the medium of choice for this cell line. This study compares three media for OKF6/TERT-2 cultures: KSFM, Dulbecco’s Modified Eagle Medium/Nutrient Mixture of Hams F-12 (DMEM/F12) and a composite medium comprised of DMEM/F-12 and KSFM (1:1 v/v), referred as DFK. The toxicological effects of electronic cigarette liquids (E-liquids) on OKF6/TERT-2 cells cultured in these media were also compared. Methods: Cells were cultured in KSFM, DMEM/F12 or DFK and cellular morphology, growth, wound healing and gene expression of mucins and tight junctions were evaluated. Additionally, cytotoxicity was determined after E-liquid exposures. Results: Switching from KSFM to DMEM/F12 or DFK 24-hours post-seeding leads to typical cellular morphologies, and these cultures reach confluency faster than those in KSFM. Wound-healing recovery occurred fastest in DFK. Except for claudin-1, there is no difference in expression of the other genes tested. Additionally, E-liquid cytotoxicity appears to be amplified in DFK cultures. Conclusions: DMEM/F12 and DFK are alternative media for OKF6/TERT-2 cell culture to study molecular biology of disease and pathology, provided cells are initially seeded in KSFM.