Abstract
To develop an alternative model for studying the regenerative capacity of olfactory neurons. An immunohistochemical analysis of mouse olfactory epithelium transplanted to the cerebral cortex. Strips of olfactory epithelium removed from donor mice at postnatal day 5 to day 20 were inserted into the parietal cortex of adult mice. Recipient animals were allowed to survive for 25 to 120 days and then perfused with 4% paraformaldehyde 1 hour after bromodeoxyuridine injection. The brains were processed, and frozen sections were obtained. Sections through transplant tissue were analyzed using immunohistochemistry and compared with normal olfactory epithelium. Graft survival approached 85% with mature olfactory neurons detected in 35% of the transplants stained for olfactory marker protein. Transplant epithelium resembled normal olfactory epithelium containing mature olfactory neurons and axon bundles. Studies of olfactory neuron regeneration have been limited by the inability to produce cultures with long-term viability. Olfactory epithelial grafts to the cerebral cortex provide an alternative approach to the study of olfactory neuron regeneration.
Highlights
It has been estimated that roughly two million Americans suffer from loss, decrease, or distortion of the sense of smell or taste, or both.[1]
Immunohistochemical reaction with antibodies directed against olfactory marker protein (OMP) labeled an area of cells below the supporting cell layer and above the basal stem cell layer within the olfactory epithelium (Fig. 2A)
All transplants with epithelium were found to contain dividing cells; a majority of transplants contained epithelium without mature olfactory neurons. This epithelium possibly could be composed of immature olfactory neurons that are not labeled with anti-OMP antibodies; we found that GAP-43 and neural cell adhesion molecule (NCAM) antibody staining is typically lacking as well in these cases
Summary
It has been estimated that roughly two million Americans suffer from loss, decrease, or distortion of the sense of smell or taste, or both.[1] The loss of olfaction can be debilitating. Anosmic individuals are unable to detect smoke, gas leaks, spoiled foods, or noxious chemicals, with possible disastrous outcomes. The psychological loss of pleasant olfactory experiences alone can cause depression,[2] and the inability to detect one’s own body odor or proper amount of perfumes or colognes can have a dramatic effect on social relations. Individuals in certain occupations, such as food preparers and perfumers, depend on their ability to smell.[2]. The sense of smell relies on receptor neurons in the olfactory epithelium that establish direct synaptic connections with cells in the brain. The stem cells of this epithelium have the ability to replace the entire cellular constituent of the epithelium including supporting cells and olfactory receptor neurons.[4,5] This pluripotent nature of the basal cells makes the olfactory epithelium a unique model for studying neuronal regeneration, as well as for studying chemosensory disease
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