Isolation and characterization of an immortalized oral keratinocyte cell line of mouse origin

Objective: To establish an oral epithelial cell line of mouse origin for molecular and biochemical assays. Design: Epithelial cells were isolated from the oral cavity of adult mice and established as a spontaneously immortalized cell line in culture, designated immortalized oral keratinocyte cells (IMOK cells). The cells were then characterized for growth characteristics, differentiation potential, karyotype, transfectability, susceptibility to viral infection and responses to siRNA. Results: The IMOK cells exhibit robust growth in both serum-containing and serum-free medium for at least 100 population doublings. IMOK cells have a near diploid karyotype, express keratinocyte marker proteins and can be induced to undergo differentiation by the addition of high levels of calcium to the medium. The differentiation process is characterized by morphological changes and by the induction of oral epithelium specific differentiation marker proteins such as K4 and K13. Transient transfection analyses reveal that IMOK cells are highly transfectable and that several promoters of epithelial cells are active in these cells. Moreover, upon differentiation with calcium, there is an up-regulation of differentiation specific K4 and Elf5 promoter activity. Finally, we show that the oral keratinocytes are also amenable to infection with retroviruses and to siRNA-based knockdown of gene expression. Conclusions: Our study is the first to establish an immortalized oral keratinocyte cell line of murine origin that can recapitulate the oral epithelium differentiation program and thus could serve as a useful tool for toxicological and molecular analyses of the oral tissue. (C) 2008 Elsevier Ltd. All rights reserved.