Introduction The epithelial barrier formed by the nasal mucosa provides efficient protection against inhaled substances. Patients with chronic rhinosinusitis show a damaged barrier function. In own preliminary investigations significant epithelial damage could be shown by the ubiquitously present environmental pollutant NO2. The aim of the study was to investigate the temporal course of the development of the epithelial barrier.
Methods Nasal mucosa was obtained from 12 patients. The isolated primary mucosal cells were cultured in the air-liquid interface. To assess the quality and expression of the epithelial barrier, transepithelial resistance and paracellular permeability were determined at several points in time. PCR was used for the analysis of molecular markers for cell-cell contacts such as Zonula occludens and Occludin.
Results Already after 7 days mRNA of Zonula occludens and Occludin could be detected in the PCR. The mean time until an efficient epithelial barrier with adequate transepithelial resistance and moderate paracellular flow was built up was 20 days in vitro. A stable epithelial barrier is formed between weeks 3 and 4 of cultivation.
Discussion In our in vitro system an efficient epithelial integrity could be demonstrated after 20 days, which remained stable over the further cultivation period of 4 weeks. All experiments with primary nasal mucosal cells should therefore only take place after 20 days of cultivation, otherwise adequate cell exposure will be disturbed by an incomplete barrier. The results represent an important basis for further toxicological investigations of epithelial barrier damage.
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