Differential Expression of Mucins in Murine Olfactory Versus Respiratory Epithelium

Mucins are a key component of the airway surface liquid and serve many functions. Given the numerous differences in olfactory versus respiratory nasal epithelia, we hypothesized that mucins would be differentially expressed between these two areas. Secondarily, we evaluated for changes in mucin expression with radiation exposure, given the clinical observations of nasal dryness, altered mucus rheology, and smell loss in radiated patients. Immunofluorescence staining was performed in a mouse model to determine the expression of mucins 1, 2, 5AC and 5B in nasal respiratory and olfactory epithelia of control mice and one week after exposure to 8 gy of radiation. Mucins 1, 5AC and 5B exhibited differential expression between olfactory and respiratory epithelium while mucin 2 showed no difference. Within the olfactory epithelium, mucin 1 was located in a lattice-like pattern around gaps corresponding to dendritic knobs of olfactory sensory neurons, whereas in respiratory epithelium it was only intermittently expressed. Mucin 5AC was expressed by subepithelial glands in both epithelial types but to a higher degree in the olfactory epithelium. Mucin 5B was expressed by submucosal glands in the olfactory epithelium but by surface epithelial cells in respiratory epithelium. At one-week after exposure to single-dose 8 gy of radiation, no qualitative effects were seen on mucin expression. Our findings demonstrate that murine olfactory and respiratory epithelia express mucins differently, and characteristic patterns of mucins 1, 5AC, and 5B can be used to define the underlying epithelium. Radiation (8 gy) does not appear to affect mucin expression at one week. Author Roles Christopher Kennel conceived, organized and executed the study, performed the analysis, and contributed to the manuscript. Elizabeth Gould conceived and executed the study, and contributed to the manuscript. Diego Restrepo conceived and executed the study, supervised the experiments, reviewed the analysis, and contributed to the manuscript. Ernesto Salcedo performed experiments and reviewed the manuscript. Thad Vickery performed experiments and reviewed the manuscript. Eric Larson performed experiments and reviewed the manuscript. Vijay Ramakrishnan conceived and executed the study, reviewed the analysis, and contributed to the manuscript. All authors discussed the results and implications and contributed to the final manuscript.