A new approach to assess the effect of photodamage on corneocyte envelope maturity using combined hydrophobicity and mechanical fragility assays

Abstract

The combined method developed allows characterization of CE maturity based on hydrophobicity per unit surface area and rigidity rather than a simple ratio of lipid to involucrin. A more robust and sensitive measurement has therefore been developed addressing the limitations of earlier protocols.

12R‐lipoxygenase activity is reduced in photodamaged facial stratum corneum. A novel activity assay indicates a key function in corneocyte maturation

“…The presence of the eLOX3 antibody was ineffective in reducing the detected fluorescence which revealed that the inhibition by 12R‐LOX antibody is not owing to an unspecific spatial blockage by the antibody but an antigen‐specific blocking of 12R‐LOX. A parallel study investigated the impact of 12R‐LOX antibody in ex vivo CE maturation showing that CE rigidity improved while CE hydrophobicity remained unchanged in all tested samples (data not shown).The lower 12R‐LOX activity in PE samples is consistent with the reduced 12R‐LOX protein mass levels in PE cheek compared to PP post‐auricular sites as well as reduced CE maturation on this site . Decreased 12R‐LOX activity and reduced corneocyte maturation ex vivo demonstrate the importance of this enzyme for the SC maturation by influencing the CE hydrophobicity (D. Guneri, unpublished data).…”

“…The importance of these metabolic products, their formation and role in CLE formation was highlighted by the work of Brash and collaborators who focused on 12R‐LOX as the first enzyme in ceramide EOS linoleate oxidation . However, we were interested in this enzyme because of the known reduced maturation of facial SC corneocytes as reduced mass levels of 12R‐LOX were recently reported in Caucasian facial SC . This finding was accompanied with lower 12R‐LOX mass levels in Albino Africans compared to Black Africans and Caucasians .…”

“…Transepidermal water loss (TEWL) was measured at baseline and 30 ± 5 s after the third, sixth and ninth tape strippings to ensure consistent SC integrity (Aquaflux AF102; Biox Systems Ltd, London, U.K.). The first and ninth tapes were used to analyse the relative CE maturity (RCEM) while the second and eighth tapes were allocated for the 12R‐LOX enzyme assay.…”

“…The crosslinking of proteins and the attachment of lipids are mediated then by transglutaminases (TGs) . These two processes contribute to the gain in rigidity and hydrophobicity of CEs defining their maturity . The maturity of corneocytes contribute to the integrity and cohesion of the SC in order to support its function .…”

Assessing the skin barrier via corneocyte morphometry

“…With the tactile working principle of AFM, mechanical properties like rigidity (Young's modulus) became accessible on subcellular level and have been reported for corneocytes as well . While dry corneocytes conceivably are more rigid than living keratinocytes (water makes soft), it is not predictable, how the contributions of cytoskeletal fibres or proteins or lipid mixture alter their rigidity in diseased states.…”