Development of a stratum corneum and barrier function in an organotypic skin culture

The stratum corneum of human skin is responsible for maintaining the epidermal permeability barrier. We have developed a bilayered skin culture (SC) which forms a corneum 35 ± 1 cell layers thick 21 days after being raised to the air-liquid (A/L) interface. By the 7th day after raising to the A/L interface the corneocytes were irregularly shaped and had cross-sectional areas (CSA) of 300 m². By the 21st day the corneocytes had assumed polygonal shapes and had a CSA (100–250 m²) similar to that of human foreskin. The total lipid (TL) content of the corneum averaged 5–7% of the lyophilized weight. Ceramide content increased from 20% of TL at day 7 of A/L interface culture to 30% at day 21. Triglycerides decreased from 43% to 17% of TL during the same period. Free fatty acids comprised 5.5% of TL at day 21 of A/L interface culture. The intercorneocyte spaces contained stacks of lipid lamellae. However, the stacks lacked the Landmann unit repeat. Abnormal lamellar structures were observed in both the intra- and extracorneocyte spaces. Transepidermal water loss (TEWL) was >4 mg/cm² per h throughout the culture period. Lipid supplementation of the culture medium and culturing in a low humidity environment improved barrier function by 50%. However, the effects were not additive. The SC developed a near-normal corneum, but did not achieve barrier competence, due at least partially to abnormalities in lipid composition and organization. Improvement of barrier function with lipid supplementation or low humidity indicates that modifications of the culture environment may facilitate the SC in assembling a permeability barrier equivalent to human skin.     

Dry skin conditions, eczema and emollients in their management

Dry skin, which refers to roughened, flaky, or scaly skin that is less flexible than normal and dry to feel, is relatively common problem in all age groups, but is more common in elderly individuals. The water content of the stratum corneum is of paramount importance in maintaining the normal appearance and texture of human skin. The relative hydration of the stratum corneum is a composite of 3 factors viz. the rate of water transport from dermis to stratum corneum, the rate of surface loss of water and the rate of water binding ability of stratum corneum. Loss of integrity of the barrier function is a central factor in the development of dry skin conditions and eczema. The various factors involved in producing dry skin, various causes of dry skin and the role of emollients in the management of these conditions are discussed.     

Barrier lipid composition and response to plasma lipids: A direct comparison of mouse dorsal back and ear skin

The skin of the ear and the back are frequently selected sites in skin research using mouse models. However, distinct responses to treatment have been described between these two sites in several studies. Despite the crucial role of the stratum corneum (SC) in the skin barrier function of both dorsal back and ear skin, it remains unclear whether differences in lipid composition might underlie altered responses. Here, we compared the skin morphology and the barrier lipid composition of the ear with the back skin of wild-type mice. The ear contained more corneocyte layers in the SC and its barrier lipid composition was enriched with sphingosine ceramide subclasses, especially the short ones with a total chain length of 33-34 carbons. The free fatty acid (FFA) profile in the ear skin shifted towards shorter chains, significantly reducing the mean chain length to 23.3 vs 24.7 carbons in the back skin. In line, FFA species in the ear displayed a twofold increase in unsaturation index (P < .001). Gene expression in the ear skin revealed low expression of genes involved in lipid synthesis and uptake, indicating a reduced metabolic activity. Finally, the effects of hypercholesterolaemia on SC FFA composition was compared in ear and back skin of apolipoprotein E knockout (APOE^−/−) mice. Interestingly, the FFA profile in APOE^−/− ear skin was minimally affected, while the FFA composition in the back skin was markedly changed in response to hypercholesterolaemia. In conclusion, ear and back skin have distinct barrier lipids and respond differently to elevated plasma cholesterol.     

Stratum corneum sphingolipids and free amino acids in experimentally-induced scaly skin

Summary Stratum corneum sphingolipids are of particular importance in maintaining the water permeability barrier of mammalian epidermis. Free amino acids also play an important role in water retention in the stratum corneum. To clarify the way in which these substances affect scaly skin, stratum corneum sphingolipids and free amino acids collected from artificially-induced scaly skin were analysed. Scaly skin was induced by tape stripping. The total amount of sphingolipids was quantified by gas chromatography and five of sphingolipid fractions were isolated and quantified by thin-layer chromatography. Free amino acids were analysed using a high-speed amino analyser. The total amount of sphingolipid in scaly skin did not differ statistically from that in control skin. However, a significant change in the distribution of the five sphingolipid species was observed in scaly skin and the total amount of amino acids was decreased in scaly skin. These results suggest that the distribution of these five types of sphingolipid and the total amount of amino acids are responsible for scaly skin.     

Ceramides and skin function

Ceramides are the major lipid constituent of lamellar sheets present in the intercellular spaces of the stratum corneum. These lamellar sheets are thought to provide the barrier property of the epidermis. It is generally accepted that the intercellular lipid domain is composed of approximately equimolar concentrations of free fatty acids, cholesterol, and ceramides. Ceramides are a structurally heterogeneous and complex group of sphingolipids containing derivatives of sphingosine bases in amide linkage with a variety of fatty acids. Differences in chain length, type and extent of hydroxylation, saturation etc. are responsible for the heterogeneity of the epidermal sphingolipids. It is well known that ceramides play an essential role in structuring and maintaining the water permeability barrier function of the skin. In conjunction with the other stratum corneum lipids, they form ordered structures. An essential factor is the physical state of the lipid chains in the nonpolar regions of the bilayers. The stratum corneum intercellular lipid lamellae, the aliphatic chains in the ceramides and the fatty acids are mostly straight long-chain saturated compounds with a high melting point and a small polar head group. This means that at physiological temperatures, the lipid chains are mostly in a solid crystalline or gel state, which exhibits low lateral diffusional properties and is less permeable than the state of liquid crystalline membranes, which are present at higher temperatures. The link between skin disorders and changes in barrier lipid composition, especially in ceramides, is difficult to prove because of the many variables involved. However, most skin disorders that have a diminished barrier function present a decrease in total ceramide content with some differences in the ceramide pattern. Formulations containing lipids identical to those in skin and, in particular, some ceramide supplementation could improve disturbed skin conditions. Incomplete lipid mixtures yield abnormal lamellar body contents, and disorder intercellular lamellae, whereas complete lipid mixtures result in normal lamellar bodies and intercellular bilayers. The utilization of physiological lipids according to these parameters have potential as new forms of topical therapy for dermatoses. An alternative strategy to improving barrier function by topical application of the various mature lipid species is to enhance the natural lipid-synthetic capability of the epidermis through the topical delivery of lipid precursors.     

Influence of sportive activity on skin barrier function: a quantitative evaluation of 60 athletes

While sports‐related diseases are well documented in the literature, no study regarding the physiology of athlete's skin has been published yet. However, some evidence is given for impairment of the skin barrier due to sportive activity accompanied by an increase in sweating. In this explorative study, we investigated the effect of sportive activity on skin physiology, namely stratum corneum hydration, skin surface pH, and sebum content. A total of 60 healthy Caucasian volunteers (35 females, 25 males; mean 27.35 ± 4.09) were enrolled in this study. Measurements were done before and after 45 minutes of endurance cardio training at forehead, chest, forearm, and armpits. Hydration level, sebum secretion, and pH value of hydrolipid acid film were measured with worldwide‐acknowledged biophysical measuring methods. Stratum corneum hydration significantly increased after sportive activity. The increase was about 51.9% at the forearm and 31.9% at the chest. Sebum content at the forehead significantly decreased during exercising, from 87.36 μg/cm² to 62.41 μg/cm². At all investigated body sites, measured values for skin surface pH increased after sportive activity. Highest pH value was measured in armpits (pH 5.64–5.98) and lowest at forearm (pH 4.75–4.93). Sportive activity is accompanied by significant changes of skin physiology that could stress the barrier function of the skin. Higher skin surface pH and hyperhydration of the stratum corneum as well as increased lipid content on the skin surface are probably caused by an increased sweat production. The impaired skin barrier may also be the reason for some reported sports‐related dermatoses.     

Stratum corneum lipid abnormalities in surfactant-induced dry scaly skin

Sodium dodecyl sulfate (SDS) has been used to induce a dry scaly skin condition in human subjects. Measurements of stratum (s.) corneum hydration, scaliness, and lipid composition reveal in vivo surfactant perturbations on desquamation. Subjects (n = 10) were briefly treated daily with a 4% aqueous solution of SDS on one lower leg over a period of 2 weeks. The other control leg received no treatments. At the end of the treatment period, both lower legs were evaluated for hydration using an electrical impedance technique and examined by an independent dermatologist using a visually based grading scale for surface roughness and scaliness. Shave biopsies were then excised from each lower leg for analysis of s. corneum lipids. Treatment resulted in decreased s. corneum hydration and increased surface scale/roughness. These physical changes were accompanied by significant changes in s. corneum lipid composition. While surfactant treatments did not alter the total quantity of lipids per gram s. corneum protein, significant changes in specific lipid classes were observed. The free cholesterol to cholesterol ester ratio increased while the quantity of total sterols remained constant. The distribution of certain ceramide species were altered while the quantity of total ceramides remained constant. Free fatty acids were resolved into 2 distinct bands, only one of which diminished upon treatment. These results are interpreted in terms of a model for surfactant-induced perturbation of keratinization which leads to abnormal s. corneum lipids and altered desquamation.     

Advancements in the maintenance of skin barrier/skin lipid composition and the involvement of metabolic enzymes

The human skin barrier has an important role in protection and defense, reflected not only in the ability to resist entry of harmful substances into the human body, but also in the ability to prevent loss of water and nutrients. Once the skin barrier is damaged, the skin may become dry, scaly, and wrinkled, and a series of skin problems may occur. In this article, we review the composition of lipids, such as ceramides, cholesterol, and free fatty acids, in the skin and examine the expression of enzymes related to lipid metabolism, such as kallikreins, elongase of elongation of very long‐chain fatty acids, hydrolases, and lipid synthases. Additionally, we discuss the involvement of these proteins in skin barrier function and structure. The information presented in this review is expected to provide a theoretical basis for the development of skin care products facilitating the maintenance and repair of skin barrier function.     

The effect of liposomes on skin barrier structure.

The present work deals with the 'in vivo' stripping technique to evaluate the percutaneous absorption of sodium fluorescein (NaFl) vehiculized in two different liposome preparations formed by phosphatidylcholine (PC) and lipids mimicking the stratum corneum (SC; ceramides, cholesterol, palmitic acid and cholesteryl sulphate), respectively. Furthermore, the possible effect of these vesicles on the SC lipid alkyl chain conformational order were evaluated at different depths of SC by non-invasive biophysical techniques: Corneometer, Tewameter and especially ATR-FTIR. The results of NaFl percutaneous absorption indicate the highest penetration in the case of incorporation in PC liposomes, which could be related to the increase in SC lipid disorder detected by ATR-FTIR, i.e. a decrease in skin barrier function. On the other hand, SC lipid liposomes have been shown to have a higher affinity for SC owing to the high amount of NaFl found in this layer, suggesting a greater reservoir capacity of SC when similar lipid composition formulation is applied. A lipid order increase is observed by infrared spectroscopy, when these types of liposomes are topically applied, resulting in a strong barrier effect. These results could be useful in designing specific liposomal topical applications.     

Stratum corneum lipids in skin xerosis

Lipids of the stratum corneum are implicated in cohesion and desquamation of the stratum corneum as well as in the maintenance of normal barrier function. Evidence linking the intercellular lipids to such processes has mainly been derived from studies on acquired or inherited diseases of lipid metabolism manifesting abnormalities in the structure and the function of the stratum corneum. We have studied the composition of stratum corneum lipids in clinically normal individuals with typical xerosis or 'winter dry skin' in order to establish if the lipid composition differs from that of normal individuals, showing no signs of xerosis. The amount of total stratum corneum lipids was not related to xerosis (22.0 +/- 1.8 micrograms/cm2 for normal skin, and 26.3 +/- 2.9 micrograms/cm2 for severe xerosis), and no correlation was evident between polar lipids, cholesterol sulfate (2.8 +/- 0.5% for normal skin, and 1.6 +/- 0.2% for severe xerosis), or ceramides types I-VI, and dry skin. It therefore appears that dramatic changes in stratum corneum lipids are not detectable in normal 'winter dry' skin. However, a decreased proportion of neutral lipids (sterol esters, triglycerides), coupled to increased amounts of free fatty acids, were found associated to the severity of dry skin. Apart from a decline in the sebaceous function and in esterases activity, winter dry skin does not appear to be associated to dramatic changes in polar stratum corneum lipids.     

The importance of free fatty acid chain length for the skin barrier function in atopic eczema patients

An important feature of atopic eczema (AE) is a decreased skin barrier function. The stratum corneum (SC) lipids – comprised of ceramides (CERs), free fatty acids (FFAs) and cholesterol – fulfil a predominant role in the skin barrier function. In this clinical study, the carbon chain length distribution of SC lipids (FFAs and CERs) and their importance for the lipid organization and skin barrier function were examined in AE patients and compared with control subjects. A reduction in FFA chain length and an increase in unsaturated FFAs are observed in non‐lesional and lesional SC of AE patients. The reduction in FFA chain length associates with a reduced CER chain length, suggesting a common synthetic pathway. The lipid chain length reduction correlates with a less dense lipid organization and a decreased skin barrier function. All changes are more pronounced in lesional SC compared with non‐lesional skin. No association was observed between lipid properties and filaggrin mutations, an important predisposing factor for developing AE. The results of this study demonstrate an altered SC lipid composition and signify the importance of these changes (specifically regarding the CER and FFA chain lengths) for the impaired skin barrier function in AE. This provides insights into epidermal lipid metabolism as well as new opportunities for skin barrier repair.     

神经酰胺代谢途径对皮肤屏障功能影响研究进展

神经酰胺是角质层脂质的主要成分,是反映皮肤屏障功能的关键性物质,其含量的变化会使细胞间脂质结构发生变化,导致皮肤屏障功能障碍,而引发相关皮肤病。本文对神经酰胺的合成、分解、对皮肤屏障功能的影响及相关皮肤病进行综述。     

Skin barrier structure and function: the single gel phase model.

A new model for the structure and function of the mammalian skin barrier is postulated. It is proposed that the skin barrier, i.e., the intercellular lipid within the stratum corneum, exists as a single and coherent lamellar gel phase. This membrane structure is stabilized by the very particular lipid composition and lipid chain length distributions of the stratum corneum intercellular space and has virtually no phase boundaries. The intact, i.e., unperturbed, single and coherent lamellar gel phase is proposed to be mainly located at the lower half of stratum corneum. Further up, crystalline segregation and phase separation may occur as a result of the desquamation process. The single gel phase model differs significantly from earlier models in that it predicts that no phase separation, neither between liquid crystalline and gel phases nor between different crystalline phases with hexagonal and orthorhombic chain packing, respectively, is present in the unperturbed barrier structure. The new skin barrier model may explain: (i) the measured water permeability of stratum corneum; (ii) the particular lipid composition of the stratum corneum intercellular space; (iii) the absence of swelling of the stratum corneum intercellular lipid matrix upon hydration; and (iv) the simultaneous presence of hexagonal and orthorhombic hydrocarbon chain packing of the stratum corneum intercellular lipid matrix at physiologic temperatures. Further, the new model is consistent with skin barrier formation according to the membrane folding model of Norlén (2001). This new theoretical model could fully account for the extraordinary barrier capacity of mammalian skin and is hereafter referred to as the single gel phase model.     

Defective barrier function in melasma skin

Background Melasma is characterized by increased pigmentation and photodamaged features, which include solar elastosis. Recently, we detected the downregulation of the genes most associated with lipid metabolism using microarray analysis in melasma. These findings suggested that lesional skin may have different biophysical characteristics, and, in particular, an altered skin barrier function. Objective To determine the cutaneous biophysical characteristics of melasma. Methods The melanin index, erythema index, stratum corneum hydration, sebum content and transepidermal water loss (TEWL) were measured for lesional and perilesional normal skin of 16 melasma patients and then compared. In addition, a skin biopsy was performed on 11 of the 16 study subjects to measure stratum corneum thickness and to study the protein expressions of PPAR‐α and ALOX15B. Results Melanin index, erythema index and stratum corneum hydration were significantly higher in lesional skin than in perilesional normal skin. No significant difference was found between lesional and normal skin in terms of basal TEWL level or sebum content. However, the rate of TEWL after barrier perturbation was significantly higher for lesional skin, and the barrier recovery rate was significantly delayed. Furthermore, a trend towards thinned stratum corneum was observed for lesional skin, and this was correlated with barrier recovery rate. The expressions of PPAR‐α and ALOX15B were variable in the samples. Conclusions Melasma skin is characterized by impaired stratum corneum integrity and a delayed barrier recovery rate.     

Barrier function of the skin: "la raison d'être" of the epidermis

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.     

A comparison of techniques for the measurement of transepidermal water loss

Summary An Evaporimeter and a ventilated chamber technique have been compared in their ability to measure transepidermal water loss (TEWL) through rat skin. These techniques measure TEWL under very different conditions; the Evaporimeter measures the net TEWL under ambient relative humidity (RH) whereas the ventilated chamber employs a constant atmosphere, usually of low RH and thus measured the uni-directional diffusion of water. Paired Evaporimeter and ventilated chamber measurements were made of TEWL through normal skin and through skin whose barrier properties had been altered by tape-stripping (15 applications) or single applications of n-hexadecane (28.4 mol cm^–2). Both measuring techniques indicated the same level of TEWL through normal skin (mean 0.3 mg cm^–2 h^–1) and during increases in TEWL induced by n-hexadecane (max TEWL c 3.5 mg cm^–2 h^–1). However, the Evaporimeter was found to underestimate the higher rates of TEWL induced by tape-stripping, ie above TEWL rates of 7.5 mg cm^–2 h^–1. The Evaporimeter is portable, easy to use and suitable for measurements of net water loss up to 7.5 mg cm^–2 h^–1; it can only be used for comparative assessments of epidermal barrier function if used at a particular ambient RH. The more cumbersome ventilated chamber is to be preferred for accurate assessments of barrier function where high rates of TEWL occur.At this address during a period of industrial training     

Transepidermal water loss and skin capacitance alterations among workers in an ultra-low humidity environment

No studies have been performed evaluating skin barrier alterations in humans exposed to ultra-low humidity (ULH) in spite of several lines of evidence from animal experiments suggesting that the skin barrier is altered on exposure to ULH. The objectives of this study were to assess barrier function changes in workers occupationally exposed to ULH (relative humidity 1.5%), and to evaluate whether the exposure duration shows a dose-response relationship with transepidermal water loss (TEWL) and skin capacitance. A total of 49 male workers exposed to ULH for 12 h per working day were classified into five subgroups based on their ULH exposure duration (<0.5 months, 0.5–1.0 month, 1.1–10.0 months, 10.1–20.0 months, and >20.0 months). A group of 12 age-matched male laboratory workers from a normal humidity environment were recruited as a control group. TEWL and skin capacitance were measured to evaluate their skin barrier function. TEWL measurements showed a significant decline (8.3±0.4 vs 10.0±0.4 g m^–2 h^–1, P<0.05) but no differences were found in skin capacitance (39.7±1.3 a.u. vs 45.0±2.4 a.u., P=0.68) between the whole ULH exposure group and the control group. Maximum decreases in TEWL and skin capacitance were seen in the subgroups exposed for <0.5 months and 0.5–1.0 month, respectively. Almost completely natural recovery occurred in skin capacitance after 20 months ULH exposure, in contrast to less than 90% recovery in TEWL. Three stages were defined according to the pattern of alterations in TEWL and skin capacitance in relation to ULH exposure duration. A positive association between TEWL and skin capacitance occurred in the control group and stage I but a negative correlation in stage II. No correlation was found in stage III. Our study demonstrated that workers exposed to a ULH environment could exhibit skin barrier alterations. Both TEWL and skin capacitance decreased within 2 weeks of ULH exposure. The maximum alterations in TEWL and skin capacitance occurred during 0.5–1.0 months and 2 weeks, respectively. TEWL recovered partially and more slowly than skin capacitance which recovered earlier and almost completely.     

Comparison of structure and organization of cutaneous lipids in a reconstructed skin model and human skin: spectroscopic imaging and chromatographic profiling

The use of animals for scientific research is increasingly restricted by legislation, increasing the demand for human skin models. These constructs present comparable bulk lipid content to human skin. However, their permeability is significantly higher, limiting their applicability as models of barrier function, although the molecular origins of this reduced barrier function remain unclear. This study analyses the stratum corneum (SC) of one such commercially available reconstructed skin model (RSM) compared with human SC by spectroscopic imaging and chromatographic profiling. Total lipid composition was compared by chromatographic analysis (HPLC). Raman spectroscopy was used to evaluate the conformational order, lateral packing and distribution of lipids in the surface and skin/RSM sections. Although HPLC indicates that all SC lipid classes are present, significant differences are observed in ceramide profiles. Raman imaging demonstrated that the RSM lipids are distributed in a non‐continuous matrix, providing a better understanding of the limited barrier function.     

Near-infrared Fourier transform Raman spectroscopic analysis of proteins, water and lipids in intact normal stratum corneum and psoriasis scales

Previous biochemical studies demonstrated differences in the structure of lipids in normal skin and psoriatic lesions. Raman spectroscopy provides a unique possibility of studying the molecular structure of proteins, lipids and water in intact skin. Near-infrared Fourier transform Raman spectroscopy was used to study changes in molecular structure and conformation of proteins and lipids of stratum corneum in healthy persons and patients with psoriasis. In vitro Raman spectra were obtained from intact psoriatic scales in 11 patients and from normal stratum corneum of forearm, elbow and heel in a group of age-matched healthy persons. The spectra of stratum corneum differed between psoriasis and normal skin but not between investigated regions. No major changes of lipid band positions in Raman spectra were found, but the crystalline lipid structure was disrupted in psoriatic scales (assessed as the ratio of the symmetric methylene C-H stretching-mode intensities, S(lat)). Major spectral differences were seen in the molecular structure of the proteins. In the spectra of psoriatic scales, the peak position of the amide I band, in comparison with the normal skin, was shifted to higher wavenumbers, suggesting unfolding of proteins. Moreover, alterations in the disulfide stretch bonds of proteins were found in psoriasis scales, resulting in a less energetically favourable gauche-gauche-trans conformation (band around 520 cm(-1)). Psoriatic scales and normal stratum corneum did not statistically differ in their water content. The findings further define the molecular abnormalities in the stratum corneum in psoriasis.     

ATR-FTIR技术在面部敏感性皮肤角质层成分分析中的应用研究

【摘要】 目的 利用衰减全反射傅里叶变化红外光谱仪（ATR-FTIR）分析敏感性皮肤与正常皮肤角质层成分的差异,探讨该技术在敏感性皮肤发生机制研究中的应用价值。方法 自2018年12月至2019年2月,招募在上海市居住 ≥ 6年的148例志愿者,通过问卷调查、乳酸刺痛试验和辣椒素试验,将受试者分为正常皮肤组和敏感性皮肤组;同时,记录乳酸刺痛试验和辣椒素试验中受试者的总刺痛评分和总灼痛评分。应用ATR-FTIR检测角质层成分,包括天然保湿因子（NMF）、角质层脂质、游离脂肪酸（FFA）和β/α比值;同时应用其他无创技术测量经表皮失水率（TEWL）、角质层含水量、角质层脂质、皮肤pH值和3种周围感觉神经纤维的电流感觉阈值和浅表皮肤血流灌注量等皮肤生理参数。分析角质层成分与总刺痛评分和总灼痛评分的Spearman相关系数,以及与皮肤生理参数的Pearson相关系数。结果 73例志愿者完成全部试验,其中敏感性皮肤组34例,男15例,女19例,年龄（41.8 ± 8.9）岁;正常皮肤组39例,男19例,女20例,年龄（42.8 ± 9.4）岁。敏感性皮肤组和正常皮肤组角质层NMF分别为30.90 ± 7.38、37.01 ± 8.77（t = 3.193,P < 0.01）,FFA分别为14.90 ± 6.75和20.45 ± 11.76（t = 2.422,P < 0.05）,β/α值分别为3.17 ± 1.03和2.67 ± 0.56（t = -2.595,P < 0.05）,角质层脂质两组差异无统计学意义（t = 1.458,P > 0.05）。皮肤生理参数中,敏感性皮肤组TEWL显著高于正常皮肤组（t = -3.496,P < 0.001）,而5 Hz电流感觉阈值和表皮致密度显著低于正常皮肤组（P < 0.05）,角质层脂质差异无统计学意义（P > 0.05）。相关分析显示,NMF、FFA和β/α与TEWL（r值分别为-0.405、-0.562、0.503,均P < 0.01）和总刺痛评分（rs值分别为-0.401、-0.285、0.316,P < 0.01或0.05）均呈良好的相关性,同时,表皮致密度与NMF（r = 0.402,P < 0.01）和β/α比值（r = -0.369,P < 0.05）也呈良好的相关性。但NMF、FFA和β/α与角质层脂质、3种感觉神经纤维的电流感觉阈值、浅表皮肤血流灌注量及表皮厚度之间均无相关性（均P > 0.05）。结论 敏感性皮肤与正常皮肤角质层NMF、FFA和β/α存在显著差异,且NMF、FFA和β/α与部分角质层屏障功能生理参数之间具有良好的相关性。因此,ATR-FTIR是一种有效评价敏感性皮肤屏障功能的手段。