Ablation of AQP5 gene in mice leads to olfactory dysfunction caused by hyposecretion of Bowman's gland.

Smell detection depends on nasal airflow, which can make absorption of odors to the olfactory epithelium by diffusion through the mucus layer. The odors then act on the chemo-sensitive epithelium of olfactory sensory neurons (OSNs). Therefore, any pathological changes in the olfactory area, for instance, dry nose caused by Sjögren's Syndrome (SS) may interfere with olfactory function. SS is an autoimmune disease in which aquaporin (AQP) 5 autoantibodies have been detected in the serum. However, the expression of AQP5 in olfactory mucosa and its function in olfaction is still unknown. Based on the study of the expression characteristics of AQP5 protein in the nasal mucosa, the olfaction dysfunction in AQP5 knockout (KO) mice was found by olfactory behavior analysis, which was accompanied by reduced secretion volume of Bowman's gland by using in vitro secretion measure system, and the change of acid mucin in nasal mucus layer was identified. By excluding the possibility that olfactory disturbance was caused by changes in OSNs, the result indicated that AQP5 contributes to olfactory functions by regulating the volume and composition of OE mucus layer, which is the medium for the dissolution of odor molecules. Our results indicate that AQP5 can affect the olfactory functions by regulating the water supply of BGs and the mucus layer upper the OE that can explain the olfactory loss in the patients of SS, and AQP5 KO mice might be used as an ideal model to study the olfactory dysfunction.