Search for Olfactory Cells Within the Fetal Ethmoid Epithelium

The recent rhinological functional approach known as "Evo-Devo" leads us to consider the nose not as a single organ, but as the construction of a specifically olfactory organ within which functional respiratory structures have developed over the course of species evolution in the same way they develop during human embryogenesis.

In adult humans, the olfactory structures are limited to two narrow regions situated at the upper part of the nasal passages known as olfactory clefts. Nevertheless, phylogenetic evidence indicates that these olfactory clefts are vestiges of an olfactory organ that once occupied the entire ethmoid bone in the front of the skull base.

The hypothesis of this study posits that, during the embryological development of the ethmoid bone, it would initially be covered with olfactory mucosa, which would gradually diminish as the lateral masses of the ethmoid formed, eventually persisting exclusively within the olfactory clefts of the ethmoid by the conclusion of the first trimester (end of organogenesis). Besides their fundamental interest, the results of this study could help understand the still unknown pathogenesis of nasal polyposis, a chronic anosmic disease with a prevalence of 2 to 4% in the French and European population.

This study requires a series of ethmoidal samples from human fetuses at various ages between 7 and 15 weeks of gestational age. Specific immunohistological labeling techniques under standard optical microscopy will be used to search for and quantify olfactory nerve cells within the fetal ethmoidal mucosa.