Characterisation of topographical, biomechanical and maturation properties of corneocytes with respect to anatomical location

BACKGROUND: The Stratum Corneum (SC) is the first barrier of the skin. The properties of individual cells are crucial in understanding how the SC at different anatomical regions maintains a healthy mechanical barrier. The aim of the current study is to present a comprehensive description of the maturation and mechanical properties of superficial corneocytes at different anatomical sites in the nominal dry state. MATERIALS AND METHODS: Corneocytes were collected from five anatomical sites: forearm, cheek, neck, sacrum and medial heel of 10 healthy young participants. The surface topography was analysed using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The level of positive‐involucrin cornified envelopes (CEs) and desmoglein‐1 (Dsg1) were used as indirect measures of immature CEs and corneodesmosomes, respectively. In addition, AFM nanoindentation and stress‐relaxation experiments were performed to characterise the mechanical properties. RESULTS: Volar forearm, neck and sacrum corneocytes presented similar topographies (ridges and valleys) and levels of Dsg1 (13–37%). In contrast, cheek cells exhibited circular nano‐objects, while medial heel cells were characterized by villi‐like structures. Additionally, medial heel samples also showed the greatest level of immature CEs (32–56%, p < 0.001) and Dsg1 (59–78%, p < 0.001). A large degree of inter‐subject variability was found for the Young's moduli of the cells (0.19–2.03 GPa), which was correlated with the level of immature CEs at the cheek, neck and sacrum (p < 0.05). CONCLUSION: It is concluded that a comprehensive study of the mechanical and maturation properties of corneocytes may be used to understand the barrier functions of the SC at different anatomical sites.