Stratum Corneum Hydration Level Research Articles

Stratum corneum keratin structure, function and formation – a comprehensive review

A comprehensive review on stratum corneum keratin organization, largely based on the recently published cubic rod-packing and membrane templating model [J. Invest. Dermatol., 123, 2004, 715], is presented. Keratin is the major non-aqueous component (wt/wt) of stratum corneum. As 90-100% of the stratum corneum water is thought to be located intracellularly one may presume that keratin also is a major factor (together with filaggrin-derived free amino acids) determining stratum corneum hydration level and water holding capacity. This water holding capacity depends in turn on the structural organization of the corneocyte keratin intermediate filament network. The cubic rod-packing model for the structure and function of the stratum corneum cell matrix postulates that corneocyte keratin filaments are arranged according to a cubic-like rod-packing symmetry. It is in accordance with the cryo-electron density pattern of the native corneocyte keratin matrix and could account for the swelling behaviour and the mechanical properties of mammalian stratum corneum. The membrane templating model for keratin dynamics and for the formation of the stratum corneum cell matrix postulates the presence in viable epidermal cellular space of a highly dynamic small lattice parameter (<30 nm) membrane structure with cubic-like symmetry, to which keratin is associated. It further proposes that membrane templating, rather than spontaneous self-assembly, is responsible for keratin intermediate filament formation and dynamics. It is in accordance with the cryo-electron density patterns of the native keratinocyte cytoplasmic space and could account for the characteristic features of the keratin network formation process, the dynamic properties of keratin intermediate filaments, the close lipid association of keratin, the insolubility in non-denaturating buffers and pronounced polymorphism of keratin assembled in vitro, and the measured reduction in cell-volume and hydration level between stratum granulosum and stratum corneum.

Correlations between Dermal Torque Meter®, Cutometer®, and Dermal Phase Meter® measurements of human skin.

The Dermal Torque Meter® (DTM) and the Cutometer® are instruments that measure mechanical properties of skin. The NOVA(tm) Dermal Phase Meter® (DPM) measures the stratum corneum (SC) hydration level. The objectives of this study were to determine which parameters of the DTM data curves were most sensitive to changes in SC hydration level, which of the two instruments (Cutometer or DTM) was most sensitive, and what correlations existed between the Cutometer and DTM data. Dry leg skin was created on nine subjects by washing with soap and using no moisturizers for one week. The skin was then treated with moisturizing lotions for two weeks. Measurements were made with the Cutometer, DTM, and DPM pre- and post-treatment. Significant changes in DPM, DTM, and Cutometer measurements were found after the moisturizer treatment. However, correlations were not found between mechanical property data and DPM data. The DTM had the two parameters with the highest sensitivity of all of the DTM and Cutometer parameters. Finally, correlations between the two instruments existed for only three of the ten parameters investigated. While measurements with all three instruments significantly changed in response to skin hydration, neither the DTM nor Cutometer data tended to correlate with DPM data, perhaps due to the differences in the depths into the skin which each instrument measures. Furthermore, the mechanical properties measured by the two instruments do not correlate well between the instruments. Finally, the DTM was found to have the most sensitive parameters.

Electroperturbation of the human skin barrier in vitro: II. Effects on stratum corneum lipid ordering and ultrastructure.

In transdermal iontophoresis, drugs can be driven across the skin by electrorepulsion, but their transport can also be enhanced by electrical perturbation of the skin barrier. Our objective was to study perturbing effects of electrical current on human stratum corneum lipid fine structure combining techniques including freeze-fracture electron microscopy. Human stratum corneum was subjected to pulsed constant currents, varying from 0.013-13 mA.cm-2. The voltage across the stratum corneum was high-frequency-sampled and s.c. impedence values derived from it. Upon termination of the current, skin samples were rapidly frozen and processed for freeze-fracture electron microscopy or subjected to X-ray diffraction analysis. Initially a rapid decrease of the resistance and, overall, a rapid increase of the capacitances was observed; generally, these effects became more pronounced with increasing current density. Wide- and small-angle X-ray diffractograms of human stratum corneum exposed for 1 h to the highest current indicated a disordering of both the lateral packaging arrangement and long-range lamellar stacking of the intercellular lipids of stratum corneum. Furthermore, an increase in the stratum corneum hydration level as a result of electrical current application was observed. On electron micrographs of freeze-fracture replicas of human stratum corneum, exposed for 1 h to current densities between 0.013 and 13 mA.cm-2, perturbations of the intercellular lipid structure were observed in accordance with the results of X-ray diffraction; these perturbations aggravated with increasing current density. Together, the data suggest that both the lateral and the longitudinal disordering of the intercellular lipids observed with X-ray diffraction may be responsible for the appearance of perturbed structures observed with freeze-fracture electron microscopy. The lipid disordering may be due to polarization of the lipid head groups induced by the electrical field, followed by mutual repulsion.

Sensitivity of cutometer data to stratum corneum hydration level

The cutometer is an instrument that measures mechanical properties of skin. The NOVA dermal phase meter (DPM) measures the stratum corneum (SC) hydration level. The objectives of this study were to determine which parameters of the cutometer data curves were most sensitive to changes in SC hydration level, and to determine if lowering the skin stress applied by the cutometer would increase the instrument's sensitivity to SC hydration. In two studies, the volar forearms of ten and six subjects, respectively, were hydrated with wet paper towels for ten min. Measurements were made with the cutometer at various vacuum levels, and with the DPM. In another study, leg skin of nine subjects was hydrated by applying moisturizing lotions for 2 weeks. Measurements were made with the cutometer and DPM. Significant changes in DPM and cutometer measurements were found after hydrating skin in each study. However, only three correlations were found between cutometer data and DPM data. The lack of correlation was perhaps due to the differences in the depth into the skin which the two instruments measure. It is not clear which cutometer data parameters are generally most sensitive to hydration level, since different parameters were found to be most sensitive in each of the three studies. Finally, lowering the cutometer vacuum level generally did not increase the sensitivity of the measurements to changes in hydration levels.

Pruritus and skin hydration during dialysis

Dry skin is frequently observed in uraemic patients and a link with the common complaint of pruritus has been suggested. Objective data on skin dryness in haemodialysed patients is sparse and equivocal. No such information exists for the many patients now receiving peritoneal dialysis. We assessed the prevalence and severity of both pruritus and skin dryness in a uraemic population receiving maintenance dialysis. Forty-eight haemodialysis and 24 peritoneal dialysis patients were examined and skin dryness assessed by clinical grading and measurement of stratum corneum hydration using a corneometer. Forty age- and sex-matched controls were also assessed. Several biochemical parameters with possible relevance to pruritus were measured. Regular emollient therapy was prescribed to pruritic dialysis patients and efficacy assessed. Dialysis patients overall had clinically drier skin than controls, especially the peritoneal dialysis group. Stratum corneum hydration levels were significantly reduced in the peritoneal dialysis (P<0.004), but not the haemodialysis, population. Twenty-seven per cent of haemodialysed and 54% of peritoneal dialysis patients complained of pruritus. Pruritic patients in each dialysis group had significantly lower hydration than non-pruritic patients (P<0.05). Regular emollient use in pruritic patients produced a marked reduction in severity of pruritus, abolishing the symptom in nine of 21 patients treated. Reduced stratum corneum hydration correlates with pruritus in patients on maintenance haemodialysis and peritoneal dialysis, and may be alleviated by simple emollient therapy.

Electrical methods for skin moisture assessment.

Skin sites on 8 test subjects were treated with moisturizers, and different electrical measuring methods were compared regarding their quality in the assessment of the induced changes in the stratum corneum hydration level. Low frequency susceptance measurements were found preferable to high frequency admittance measurements, and the advantages of monopolar measurements with the three-electrode system are described.