Splitting culture medium by air-jet and rewetting for the assessment of the wettability of cultured epithelial cell surfaces

This study found that the phenomenon of rewetting after squeezing culture medium varied in different culture conditions for rat oral mucosal epithelial cells. When culture medium covering over cultured cells was squeezed by an air-jet application, the motion of squeezed culture medium was able to be observed by using a commercially available movie camera. Squeezed width on cells cultured in keratinocyte culture medium (KCM), which contained with fetal bovine serum, was one-sixth of that in FBS-free KCM. This result corresponded to the mucous layer staining statuses of cultured cells in both cases; positive in KCM and negative in FBS-free medium. Furthermore, the gene expression of mucous glycoprotein MUC4 in KCM was 100 times higher than that in FBS-free medium, and the expression of MUC4 protein only showed on the apical surface of cells cultured in KCM. The relative gene expression levels of MUC1, 13, 15, and 16 in both the normal and FBS-free medium were found to be no more than one-thirtieth of that of MUC4 in KCM. The main factor of the wettability difference between KCM and FBS-free medium was speculated to be the difference of MUC4 expression between both media. This method can be a simple technique for testing not only the surface wettability but also the mucous formation of cultured cells.