Mucociliary differentiation according to time in human nasal epithelial cell culture

Knowledge of the state of differentiation, cell phenotype, and expression of genes for mucus production at the time of study is important because these may vary at different times during the culture period. The primary purpose of this study was to determine whether the number of ciliated cells increases as a function of differentiation in NHNE cells. If we observed an increase in the number of ciliated cells, the composition ratio of ciliated and secretory cells according to the culture duration was determined. The levels of mucin and lysozyme secretion and their gene expression at this time were also examined. The presence of ciliated cells was not evident up to 2 days after confluence. However, 3.1 +/- 0.2 %, 7.4 +/- 0.5 %, and 14.5 +/- 0.6 % of the cells were ciliated on the 7th, the 14th, and the 28th day after confluence, respectively. Meanwhile, the percentage of secretory cells were 35.6 +/- 2.8 %, 32.8 +/- 2.5 %, 32.8 +/- 2.5 %, and 49.4 +/- 1.4 % on the 2nd, the 7th, 14th, and 28th day after confluence. The amount of secreted mucin showed an abruptly increasing pattern by the 14th day after confluence but showed no significant changes thereafter. The amount of secreted lysozyme increased as a function of differentiation. MUC5AC and MUC5B mRNA were mainly expressed between the 7th and the 14th day after confluence with relatively weak MUC8 and lysozyme expression. By the 28th day after confluence however, as the MUC5AC mRNA expression became weaker, MUC5B, MUC8, and lysozyme mRNA expression became stronger. In conclusion, we speculate that in in vitro studies with NHNE cells, the time point of treatment should vary according to the purpose of the study. In addition, the MUC5B and MUC8 gene may play an important role in mucin secretion in fully differentiated human nasal epithelial cells.