Expression of Clara cell secretory protein in experimental otitis media in the rat

Conclusion. These results suggest that CCSP is upregulated in OME and may play a protective role in the pathogenesis of OME. Objective. Clara cell secretory protein (CCSP) is an abundant 16-kDa homodimeric protein and is secreted by non-ciliated secretory epithelial cells in the lung. It has an important protective role against the intrapulmonary inflammatory process. The aim of this study was to investigate the expression of CCSP in endotoxin-induced otitis media with effusion (OME) in the rat. Material and methods. We instilled endotoxin and saline (control) into the middle ear cavity of the rat. Middle ear mucosa were taken at 0, 1, 3, 6 and 12 h and 1, 3, 7 and 14 days, and the expression of both CCSP mRNA and protein were then evaluated using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry. Results. RT-PCR revealed that the expression of CCSP was first identified at 1 h after endotoxin instillation, was dramatically increased between 1 h and Day 1, with maximal expression at 12 h, and then decreased after Day 3. The expression pattern of CCSP protein identified by means of Western blotting was similar to the CCSP mRNA patterns observed using RT-PCR. Expression of CCSP at both mRNA and protein levels was not detected in either normal middle ear mucosa or saline-instilled middle ear mucosa. Immunohistochemistry revealed that some epithelial cells in the middle ear mucosa were stained.