The Concept of the Onychodermis: An Embryological Assessment and Comparative Analysis with the Hair Follicle

The study introduced the concept of the onychodermis, a specialized mesenchymal substructure unique to the nail organ, characterized by its expression of CD10. Through immunohistochemical analysis, the researchers compared adult and fetal hair follicles with fetal nail organs, focusing on the expression of CD10, CD34, and nestin. They found that the CD10-positive/CD34-negative onychodermis was prominent by the end of the second trimester, with no corresponding structure in hair follicles. The onychodermis was suggested to play a role in anchoring the nail bed and possibly in inducing hard keratins, contributing to nail plate formation.