Enhanced sodium absorption in middle ear epithelial cells cultured at air-liquid interface

Conclusion As we demonstrated previously that transcription of alpha-ENaC was correlated with oxygen tension in the culture medium, this study suggests that the increase in alpha-ENaC expression observed under ALI conditions may result from greater oxygenation of ME cells. Objective The physiology of the middle ear (ME) is primarily concerned with keeping the cavities fluid-free, to allow transmission of sound vibrations from the eardrum to the inner ear. ME epithelial cells are thought to play a key role in this process as they actively absorb sodium and water in order to clear any excess fluid present in the cavities. Material and methods As an air-liquid interface (ALI) model has been shown to improve differentiation and enhance sodium absorption in other respiratory epithelia, we established an ALI model for ME cells. Results ME cells cultured under ALI conditions exhibited a fourfold increase in sodium absorption, which was not related to either a metabolic effect or to enhanced morphological differentiation, but instead to an increase in expression of the alpha-subunit of the epithelial sodium channel (alpha-ENaC).