Water-holding Capacity Of Stratum Corneum Research Articles

아미노산 동시분석을 통한 피부보습능과 각질 중 아미노산 함량과의 상관관계 연구

천연보습인자(NMF, natural moisturizing factor)는 정상 피부 내의 각질층에 존재하는 수용성, 친수성 성분을 총칭하는 말로 외부로부터 수분을 흡수하고 각질층의 수분보유능을 증가시키며 피부가 건조해지는 것을 방지하여 피부의 유연성과 가수성을 유지하는 기능을 한다. NMF는 주로 아미노산과 아미노산의 대사산물로 구성되며 이들은 필라그린(filaggrin)이 분해되면서 생성된다. 본 연구에서는 피부 각질층의 22종의 개별 아미노산의 함량분석을 통하여 피부보습능과 개개의 아미노산과의 상관관계를 연구하였다. 15명의 건강한 지원자들의 전박과 이마로부터 tape stripping한 각질 시료 중 22종의 아미노산 함량을 UPLC-PDA를 이용하여 동시 분석하였다. 그 결과 각질 표면보다는 안쪽에서의 아미노산들의 함량이 높음을 확인하였다. 또한 신체 부위별 비교에서 전박이 이마에 비해 아미노산 함량이 1.5배 정도 높음을 확인하였다. 전박부위의 아미노산 총 함량과 보습능(TEWL)과의 상관 관계분석을 통해서는 보습능이 클수록 총아미노산 함량이 높은 것으로 확인되었으며 특히 Ser, Glu, Gly, Ala 및 Thr은 각질 내 존재하는 주요 아미노산 성분으로 보습에 긍정적인 영향을 주는 성분으로 확인되었다. 이상의 결과로써 NMF의 주성분인 아미노산의 함량은 각질 생리기능과 밀접한 관련을 가지고 있음을 확인할 수 있었으며 본 연구를 통해 얻은 각질층의 아미노산의 통합적인 분석법은 보습, 노화, 미백, 피부 염증질환 등 다양한 피부 상태와 아미노산류들의 변화와의 관계를 깊이 이해하고 피부 기능과 관련된 새로운 분자적 타겟을 발굴하고 증명하는데 기초적인 방법으로써 사용될 수 있을 것으로 사료된다. Natural moisturizing factors (NMFs) are hydrophilic and water-soluble components in stratum corneum of the skin. NMFs absorb water from outer environment and enhance the water-holding capacity of stratum corneum and thereby, prevent the dryness and increase flexibility and plasticity of skin. NMFs are mainly composed of amino acids and their metabolites that are produced from the degradation of filaggrin. Here we established a simultaneous quantification method for 22 amino acids in tape-stripped stratum corneum samples using UPLC-PDA. With this method, we analyzed amino acid contents from tape-stripped stratum corneum samples of forearm and forehead regions from 15 healthy volunteers. Amino acid contents of inner (or upper) region were higher than outer (or lower) region of stratum corneum. Amino acid contents of stratum corneum of forearm were higher by 1.5 fold than forehead region. Of note, total amino acid contents were significantly and inversely correlated with trans-epidermal water loss (TEWL), an index for skin barrier function. Especially, Ser, Glu, Gly, Ala and Thr were determined to positively affect skin mositurizing activities. In conclusion, we could demonstrate that amino acid contents of stratum corneum are closely linked with skin barrier and moisturizing function, providing an important and fundamental methodology for the study of amino acids in skin physiology.

Environmental dew point and skin and lip weathering

Xerosis represents a physiological response of the stratum corneum (SC) to environmental threats. The influence of the environmental dew point (DP) is not fully understood. This parameter is the air temperature at which the relative humidity is maximum. This study aimed to assess the relationship between the environmental DP and the water-holding capacity of the skin and lower lip vermilion. For comparison, SC property was evaluated after occlusive application of cooled and uncooled hydrogel pads. Electrometric measurements using a dermal phase meter (DPM) device were performed on the back of the hands, the cheeks and the lower lip of 40 healthy menopausal women. Assessments were performed in the outdoor conditions during winter and spring. The same measurements were recorded after hydrogel pads, at room temperature or cooled to 4 degrees C, were placed for 15 min on the test sites. The environmental DP was recorded at each evaluation time. The SC water-holding capacity was discretely influenced by the DP. In the open-air environmental conditions, a positive linear relationship was found on the cheeks between the DP and DPM values. The relationship was weaker on the lips. Conversely, a consistent increase in DPM values was recorded immediately after removal of the cooled and uncooled hydrogel pads. The observations made in the open-air testing conditions are consistent with the predicted events following the Arrhenius law. By contrast, the combination of cooling and occlusion by the hydrogel pads is responsible for the reverse effect on the SC.

Effects of glycerol on human skin damaged by acute sodium lauryl sulphate treatment

Glycerol, widely used as humectant, is known to protect against irritants and to accelerate recovery of irritated skin. However, most studies were done with topical formulations (i.e. emulsions) containing glycerol in relatively high amounts, preventing drawing conclusions from direct effects. In this study, acute chemical irritations were performed on the forearm with application of a 10% sodium lauryl sulphate (SLS) aqueous solution under occlusion for 3 h. Then, glycerol aqueous solutions from 1 to 10% were applied under occlusion for 3 h. After elimination of moist excess consecutive to occlusive condition, in ambient air for 15 and 30 min, skin barrier function was investigated by dual measurement of skin hydration and transepidermal water loss (TEWL). Treatments with SLS solution under occlusion significantly increased TEWL and decreased skin hydration as assessed by capacitance measurements. The SLS irritant property was raised by the occlusion and the water barrier function as well as water content appeared impaired. Recovery with glycerol at low doses was remarkable through a mechanism that implies its hygroscopic properties and which is saturable. This precocious effect acts through skin rehydration by enhancing water-holding capacity of stratum corneum that would facilitate the late physiological repair of impaired skin barrier. Thus, glycerol appears to substitute for natural moisturizing factors that have been washed out by the detergent action of SLS, enhancing skin hydration but without restoring skin barrier function as depicted by TEWL values that remained high. Thus, irritant contact dermatitis treated with glycerol application compensate for skin dehydration, favouring physiological process to restore water barrier function of the impaired skin. Empirical use of glycerol added topical formulations onto detergent altered skin was substantiated in the present physicochemical approach.

Effect of Regular Sauna on Epidermal Barrier Function and Stratum Corneum Water-Holding Capacity in vivo in Humans: A Controlled Study

During the last few years, sauna has become the epitome of wellness. Besides studies in general medicine evaluating the health benefit of sauna, e.g. on the cardiovascular system, no systematic study regarding skin physiology has been published. The present exploratory study was intended to analyse the effect of regular Finnish sauna on skin physiology. The effect of regular sauna bathing was assessed with non-invasive instruments: stratum corneum water-holding capacity, skin redness, transepidermal water loss and surface skin pH were analysed in 41 healthy volunteers, aged 20–49 years, in a group with regular sauna exposure compared to a control group with no regular sauna exposure. A more stable epidermal barrier function, an increase in stratum corneum hydration, a faster recovery of both elevated water loss and skin pH after exposure to 2 × 15 min sauna at 80°C could be demonstrated in volunteers with regular sauna. Heart beat rate and ionic concentration in sweat as well as epidermal blood perfusion showed a training effect under regular sauna. A decrease in casual skin sebum content on the skin surface of the forehead was observed in these volunteers. The present data suggest a protective effect of regular sauna on skin physiology, especially surface pH and stratum corneum water-holding capacity.

Effects of Osmosis on Water-Holding Capacity of Stratum corneum and Skin Hydration

The stratum corneum (SC) is characterized by highly hydrophilic compounds exhibiting osmotic properties. The role of osmosis in iontophoretic transdermal drug delivery has been a subject in numerous studies. However, the effects of osmosis on the water-holding capacity (WHC) of SC and skin hydration need to be clarified. In the present study, the WHC and skin hydration were found to be correlated with osmotic pressure and the SC permeability of osmolytes. The WHC and skin hydration enhancement were related to the increase in SC osmolality. A mathematical model was proposed to predict the WHC and skin hydration from physicochemical parameters of compounds.

Quantitative assessments of physiological and biological parameters in psoriatic lesions and its correlations to the clinical severity of psoriasis.

Twenty-nine psoriatics were examined using a model with clinical, physiological and pathological assessment parameters. The three parts in this assessment model include: (1) clinical assessment: psoriasis area and severity index (PASI); (2) assessment of skin physiology and microcirculation: water content of stratum corneum, water-holding capacity of stratum corneum, transepidermal water loss, intravital dynamic videocapillaroscopy-measuring the capillary diameters and blood cell velocity in proximal nailfold of ring finger, and fluorescence angiography-measuring transcapillary Na-fluorescein(NAF) diffusion; and (3) immunohistochemistry examination: markers of proliferation (Ki67Ag), differentiation (involucrin), and inflammation (neutrophil elastase, intercellular adhesion molecule-1(ICAM-1), endothelial leukocyte adhesion molecule-1(ELAM-1)). Our results showed both the transcapillary diffusion of NAF and the expression of cell markers-dermal neutrophil elastase, epidermal ELAM-1 and Ki67Ag--correlated significantly to PASI scores (P < 0.05, linear regression). According to our results, the increased capillary permeability and inflammation markers, and enhanced expression of Ki67Ag correlated very well with PASI score. These markers could serve as alternative methods for assessment of the clinical severity of psoriatic patients.

Effects of site and menstrual cycle on barrier function and stratum corneum water-holding capacity.

Areas of the skin with similar anatomical structure may have different functional behaviour. In vivo barrier function and stratum corneum water-holding capacity during the menstrual cycle on two sites of the volar forearm (upper and lower) and on the anterior aspect of the thigh were evaluated using the plastic occlusion stress test (POST). 13 healthy women (age 31 ± 4) with regular menses entered the study. POST was performed by applying a plastic chamber (1.8 cm diameter) on the skin for 24 h. After removal the skin surface water loss (SSWL) was measured using an evaporimeter (EP1-Servomed, Sweden) every 5 min for 30 min. Measurements were taken on the 10th and 25th day of the menstrual cycle. Statistical analysis was performed using one-factor Anova for repeated measures. Free and bound water compartments of evaporation were also analysed. Higher hydration and SSWL were detectable on the 25th day of the cycle. However, no significant influence of menstrual cycle was found. Significant differences between the upper and lower volar foream were detected (P < 0.001). The differences observed were mainly related to the evaporation of bound water, confirming a different barrier function at the sites investigated; therefore, it must be taken into account that adjacent skin sites with equal structure may have different functional behaviour.

Effects of systemic treatment with statins on skin barrier function and stratum corneum water-holding capacity.

Topical application of inhibitors of HMGCoA reductase, the rate-limiting enzyme of cholesterol synthesis, has been shown to induce impairment of barrier function. Assessing whether oral administration of statins used for reducing blood levels of cholesterol induces functional changes in stratum corneum barrier. 69 subjects of both sexes under-going treatment for hypercholesterolemia (mean age 48 +/- 11 years) entered the study; 43 had been treated with simvastatin and 11 with pravastatin for 6 months; 15 only on dietary regimen served as controls. Efficiency of stratum corneum water barrier was evaluated by transepidermal water loss (TEWL) measurement using an evaporimeter; water-holding capacity of the stratum corneum was assessed by the sorption-desorption test measured by capacitance. Statistical analysis was performed using ANOVA. No differences were found between the groups (simvastatin, pravastatin, diet) concerning both basal TEWL and the dynamic of water binding in the stratum corneum. Prolonged treatment with cholesterol-lowering drugs based on inhibition of HMGCoA reductase does not alter the permeability barrier of the skin.

Plastic Occlusion Stress Test as a Model to Investigate the Effects of Skin Delipidization on the Stratum corneum Water Holding Capacity in vivo

The purpose of the study was to develop an in vivo model to study the effects of lipid removal on skin barrier. 16 subjects (age 41 +/- 8) were delipidized in vivo on the volar forearm using respectively ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1). A third site served as control. Water holding capacity (WHC) was measured according to the plastic occlusion stress test (POST) procedure: the water desorption curve after removal of the occlusion was recorded in terms of skin surface water loss (SSWL) using an evaporimeter for 30 min. In the central part of the evaporation curve (bound water) the CM-treated site is significantly different from control and EA-treated sites (p < 0.01). The SSWL decay constants reflecting the desorption rate of water from SC are higher in the CM-treated site (p < 0.01). The data are consistent with the effect of CM delipidization (polar lipids) on bound water. No differences are recorded in the evaporation of free water. We conclude that polar lipids have a key role in modulating barrier function and WHC of the stratum corneum. The POST can represent a useful in vivo model to study the effects of lipid extraction on skin function.

Effect of Occlusive Dressings on the Stratum Corneum Water Holding Capacity

Occlusion of the skin is used in clinical dermatology to promote wound healing and to increase the transcutaneous penetration of topically applied drugs. These effects are related to the degree of occlusion exerted and depend on the physicochemical nature of the dressing. We have evaluated the effects of four different materials on the skin barrier and the stratum corneum water holding capacity (WHC) using the Plastic Occlusion Stress Test (POST). The following materials were compared: hydrocolloid dressing, polyurethane film, polyethylene film, and a plastic chamber. These devices were applied on the volar forearm for 24 hours in 10 healthy volunteers (mean age 32 +/- 4 years). Upon their removal, the stratum corneum WHC, measured as skin surface water loss (SSWL), was recorded continuously for 25 minutes using an Evaporimeter. SSWL decay curves showed significant differences between the occlusive materials (analysis of variance, p less than 0.01). Higher SSWL values were recorded in sites occluded with the plastic chamber, whereas the polyurethane film resulted in poor occlusive capacity. Hydrocolloid dressing and polyethylene gave similar responses with higher WHC values compared to polyurethane (p less than 0.05). The relevance of these findings to clinical dermatology in terms of wound healing and drug absorption is discussed.