Stratum corneum hydration: Phase transformations and mobility in stratum corneum, extracted lipids and isolated corneocytes

Abstract

The outermost layer of skin, stratum corneum (SC), functions as the major barrier to diffusion. SC has the architecture of dead keratin filled cells embedded in a lipid matrix. This work presents a detailed study of the hydration process in extracted SC lipids, isolated corneocytes and intact SC. Using isothermal sorption microcalorimetry and relaxation and wideline (1)H NMR, we study these systems at varying degrees of hydration/relative humidities (RH) at 25 degrees C. The basic findings are (i) there is a substantial swelling both of SC lipids, the corneocytes and the intact SC at high RH. At low RHs corneocytes take up more water than SC lipids do, while at high RHs swelling of SC lipids is more pronounced than that of corneocytes. (ii) Lipids in a fluid state are present in both extracted SC lipids and in the intact SC. (iii) The fraction of fluid lipids is lower at 1.4% water content than at 15% but remains virtually constant as the water content is further increased. (iv) Three exothermic phase transitions are detected in the SC lipids at RH=91-94%, and we speculate that the lipid re-organization is responsible for the hydration-induced variations in SC permeability. (v) The hydration causes swelling in the corneocytes, while it does not affect the mobility of solid components (keratin filaments).

Developmental plasticity of cutaneous water loss and lipid composition in stratum corneum of desert and mesic nestling house sparrows

“…Therefore, the proper combination of ceramides and cerebrosides in the SC of desert birds appears to be crucial for the dual function of the SC of water conservation and thermoregulation in this environment (13,14). Lipids can also change their phase behavior in response to humidity (15). High levels of hydration of the SC lead to increased fluidity of intercellular lipids.…”

“…Changes in the ratios of lipid classes in the SC might influence CWL in birds (14). Apparently, appropriate ratios of ceramides, cerebrosides, and FFAs are necessary for the formation of intracellular lipid bilayers, called lamellae, and the molecular organization of these lamellae affects CWL (14,15).…”

“…We chose to study the effect of humidity on the SC, given that the properties of the permeability barrier, at least in mammals, change in response to the level of hydration of the SC (14,15,26). Our study showed that, regardless of environmental origin, nestling house sparrows had a more permeable skin than that of adults exposed to their natural environment.…”

In vivo confirmation of hydration-induced changes in human-skin thickness, roughness and interaction with the environment

“…8 The hydration level of the SC can vary depending on environmental conditions, as corneocytes can take up water until the hydration level of the SC is in equilibrium with the environment. 12 The hydration level of the SC is responsible for the physiology and homeostasis of the skin. 13 The examples of the importance of hydration on the functions and properties of the skin are its influence on the mechanical toughness of skin, its barrier functions, and the regulation of enzyme activity.…”

Microwave: Effects and Implications in Transdermal Drug Delivery

“…7(a), (c), (d)). Oleic acid is an unsaturated fatty acid with a cis double bond at C9 induces a kink in its hydrocarbon chain [45][46][47]. Owing to the Table 1.…”