Effects of long-term unilateral naris closure on the olfactory epithelia of adult mice

Abstract

This study investigated the effects of long-term unilateral naris closure on the olfactory epithelia of adutt mice. The results support and extend the findings of our previous paper in which we examined the effects of unilateral closure for up to 3 months. In the present study naris closures were performed for 4, 5, 6, 7 or 8 months. The observed effects depended on the length of closure and the position of the sampling site along the rostral-caudal axis of the olfactory epithelium. The closed sides appeared to be unaffected by naris closure at all time points when compared to controls. A number of time-dependent changes were characteristic of the open-side olfactory epithelium. The most deleterious effects occured in the rostral regions of the epithelium where there were dramatic losses of receptor neurons at 3 months, regrowth at 4 months, and losses at 5, 6, 7 and 8 months of closure. The effects of naris closure on the morphology of the epithelium on the open sides were often striking. In mice that had significant losses of receptor neurons, the epthhelium frequently had only supporting and basal cell layers with virtually the entire neuronal layer absent. Depending on the length of closure, the middle regions of the open side showed either no effect, losses, or else an increase in the number of receptor neurons. Naris closure resulted in an increase in the number of receptor neurons in the caudal regions of the open side at all time points. In the 7 and 8 month closure groups, 2 additional abnormalities were observed on the open sides. Some animals showed an increased rugosity of the olfactory epithelial surface. In others large numbers of polymorphonuclear leukocytes were visible on the epithelial surface indicating active inflammation.