Extreme acid resistance of human cheek epithelial cells.

Human cheek epithelial cells, despite residing in an almost neutral environment of the mouth, are exposed to many acidic stimuli, so these cells may possess acid resistance. Our researchs objective is to find out if isolated human cheek epithelial cells can survive in highly acidic conditions, and whether there is any difference in acid resistance between cheek epithelial cells of males and females; and to establish a protocol. We collected 3 buccal swab samples from each male or female participant and gave following 3 different treatments to their samples: (i) Milli-Q water (ii) HCl with pH of -0.48 (iii) HCl with pH of - 0.48 and, then, rehydration with Milli-Q water. Staining and microscopic analysis showed that cheek epithelial cells did not burst after acid treatment. However, they slightly shrunk in size and were stained substantially darker. Moreover, cells that were rehydrated after acid treatment, provided further evidence of their survival because these cells, as a result of rehydration, had substantially regained bigger size as well as lighter staining. Furthermore, at pH of -0.48, no difference was observed in acid resistance of the cells from the two genders. Results of this study, which is the only one to incubate cheek epithelial cells at pH < 2.0, manifest that the human cheek epithelial cells, isolated from any of the two genders, are extremely acid-resistant and do not burst in highly acidic conditions. Besides, these cells may also be useful as model cells for the study of acid-resistant pathogens and acid-resistant cancer cells.