Variation of Stratum Corneum Biophysical and Molecular Properties with Anatomic Site

Several serine protease enzymes are known to be involved in both normal desquamation and the inflammatory processes of the skin. Alteration in the activity of these proteases should also affect corneocyte maturity and size as well as stratum corneum thickness. The aim of the present work was to characterise the baseline changes in corneocyte size, corneocyte maturity, selected protease activity (specifically, Kallikreins-5 and 7, tryptase), protein content and trans-epidermal water loss (TEWL) as a function of anatomic site. The anatomic sites investigated were: cheek, abdomen, wrist and mid-ventral forearm. TEWL values were highest for the cheek (p < 0.05). The TEWL values were also significantly higher (p < 0.05) for cheek and wrist compared with other sites. Protein content was significantly lower for wrist (p < 0.05) compared with other sites. Corneocyte maturity and surface area were significantly (p < 0.05) lower for cheek and wrist compared with other sites. An excellent correlation (r2 = 0.99) was obtained for maturity and surface area measurements. Kallikrein-5 and tryptase activity were significantly higher for the cheek compared with other sites but Kallikrein-7 values were uniform across sites. The findings have significant implications for skin permeability to drugs and other substances such as environmental toxins depending on the anatomic site of delivery or exposure.