Effect of endotoxin on cultured human middle ear epithelium

The effect of endotoxin was investigated on air-exposed cultured human middle ear epithelium. Concentrations of 0, 1 and 100 ng/ml endotoxin were used. Complete differentiation of the cells was not reached at 12 days. After 21 days, endotoxin had induced an increased proliferation of the epithelial layer. Furthermore, an increase in the number of secretory cells and in the amount and length of microvilli was observed at this time. There were no significant morphological differences between the high and the low endotoxin concentrations, which supports our hypothesis that endotoxin induces an all-or-nothing reaction. These findings are in agreement with our previous results on serially submerged cultured rat middle ear epithelium. From these results we conclude that endotoxin is an important factor in the disturbance of the morphology of the middle ear epithelium, which may lead to chronic otitis media with effusion. In addition, our tissue culture method proved to be a good model for further studies on human middle ear mucosa.