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ARTICLE

Ultrastructural analysis shows persistence of adhesion and tight junction proteins in mature human hair

LORENZO ALIBARDI¹, BERND NOECKER²

1 Comparative Histolab Padova and Department of Biology, University of Bologna, Bologna, 40126, Italy
2 KAO Europe Research Laboratories, Kao Germany GmbH, Darmstadt, 64297, Germany

* Address correspondence to: Lorenzo Alibardi,

BIOCELL 2021, 45(4), 1013-1022. https://doi.org/10.32604/biocell.2021.013913

Received 26 August 2020; Accepted 16 November 2020; Issue published 22 April 2021

Abstract

The differentiation of cells composing mature human hairs produces layers with different corneous characteristics that would tend to flake away one from another, as in the corneous layer of the epidermis, without anchoring junctions. It is likely that cell junctions established in the forming cells of the hair bulb are not completely degraded like in the corneous layer of the epidermis but instead remain in the hair shaft to bind mature cuticle, cortex, and medulla cells into a compact hair shaft. During cell differentiation in hairs, cell junctions seem to disappear, and little is known about the fate of junctional proteins present in the mature human hair shaft. The present ultrastructural immunogold study has detected some marker proteins of adhesion junction (cadherin and beta-catenin) and tight junctions (occludin and cingulin) that are still present in cornified hairs where numerous isopeptide bonds are detected, especially in the medulla. This qualitative ultrastructural study indicates that aside from the cell membrane complex, a long corneo-desmosome bonding cortex and cuticle cells, also sparse adherens and tight junction remnants are present. It is suggested that the cornification of these junctions with the incorporation of their proteins within the mature corneous material of the hair shaft likely contributes to maintaining the integrity of the mature hair. This information will also allow us to evaluate the effects of different chemical components present in hair formulations and stains on these junctional proteins and the consequent integrity of the hair shaft.

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