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PubMed2001

Development of stratum intermedium and its role as a Sonic hedgehog-signaling structure during odontogenesis.

Stratum intermedium is a transient and subtle epithelial structure closely associated with inner dental epithelium in tooth germs. Little is known about its development and roles. To facilitate analysis, we used bovine tooth germs, predicting that they may contain a more conspicuous stratum intermedium. Indeed, early bell stage bovine tooth germs already displayed an obvious stratum intermedium with a typical multilayered organization and flanking the enamel knot. Strikingly, with further development, the cuspally located stratum intermedium underwent thinning and involution, whereas a multilayered stratum intermedium formed at successive sites along the cusp-to-cervix axis of odontogenesis. In situ hybridization and immunohistochemistry showed that stratum intermedium produces the signaling molecule Sonic hedgehog (Shh). Maximal Shh expression was invariably seen in its thickest multilayered portions. Shh was also produced by inner dental epithelium; expression was not constant but varied with development and cytodifferentiation of ameloblasts along the cusp-to-cervix axis. Interestingly, maximal Shh expression in inner dental epithelium did not coincide with that in stratum intermedium. Both stratum intermedium and inner dental epithelium expressed the Shh receptor Patched2 (Ptch2), an indication of autocrine signaling loops. Shh protein, but not RNA, was present in underlying dental mesenchyme, probably resulting from gradual diffusion from epithelial layers and reflecting paracrine loops of action. To analyze the regulation of Shh expression, epithelial and mesenchymal layers were separated and maintained in organ culture. Shh expression decreased over time, but was maintained in unoperated specimens. Our data show for the first time that stratum intermedium is a highly regulated and Shh-expressing structure. Given its dynamic and apparently interactive properties, stratum intermedium may help orchestrate progression of odontogenesis from cusp to cervix.

Animals↗
PubMed2003

pH-induced modifications to stratum corneum lipids investigated using thermal, spectroscopic, and chromatographic techniques.

The effects of nonphysiological pH on stratum corneum lipid content and structure have been studied. Human stratum corneum samples were soaked in solutions at pH 1, 2, 6, 11, or 12 for up to 24 h. After removal of the stratum corneum, the buffer solutions were analyzed for lipid composition using thin-layer chromatography analysis and the stratum corneum sheets were examined using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The results demonstrate that only buffers of pH 11 or higher affect the stratum corneum lipids. No large difference in the contents of ceramides and cholesterol extracted by buffers of varying pH was observed. In contrast, free fatty acid extraction was pH dependent; amounts removed by 24-h treatment with pH 11 or 12 buffers were comparable, and were similar to amounts extracted with a methanol-chloroform mixture for 15 min. No appreciable changes in DSC and FTIR spectra were detected between untreated stratum corneum and stratum corneum samples treated with buffers at pHs in the range 1-6. For tissue treated with pH 11 and 12, the position of the endothermal melting peak T2 shifted from 72 to 74 degrees C on the DSC thermograms. Small changes in the broadness of spectral peaks at 2855 cm(-1) [attributable to upsilon(CH(2)) stretching of stratum corneum lipids and 1655 cm(-1) upsilon(C=O) stretching amide I band] can be seen in the FTIR spectra from the treated stratum corneum samples, although no shifts in peak positions were observed. Intensity changes in peaks from extraneous lipids [upsilon(C=O) stretching mode at 1735 cm(-1)] were observed after buffer treatments. The changes provoked by the alkaline buffers are not dramatic and it may be concluded that the stratum corneum appears remarkably resilient to extended exposure in both highly acidic (pH 1) and highly alkaline (pH 12) environments.

Adult↗
PubMed1986

Filaggrin breakdown to water binding compounds during development of the rat stratum corneum is controlled by the water activity of the environment.

Filaggrin is a specific epidermal protein which is the precursor of the free amino acids, urocanic acid and pyrrolidone carboxylic acid which are largely responsible for the ability of the stratum corneum of the skin to remain hydrated at low environmental humidity. The distribution of filaggrin shown by immunofluorescence in the stratum corneum of the rat changed dramatically during the first hours of postnatal life. During late foetal development, filaggrin accumulated through the entire thickness of the stratum corneum, indicating that there was a block on the subsequent processing of the protein which normally would convert it to free amino acids. Immediately after birth this block was lifted and normal proteolysis of the filaggrin took place in the outer part of the stratum corneum, leaving the normal adult pattern of a thin zone of cells containing filaggrin at the bottom of the stratum corneum. This activation of filaggrin proteolysis was dependent on the drop in external water activity caused by the transition from an aqueous environment in utero to a dryer environment after birth and it could be blocked by maintaining a 100% humidity atmosphere around the newborn rat after birth. In isolated stratum corneum in vitro, filaggrin proteolysis took place only between 80 and 95% relative humidity, both higher and lower relative humidity blocked the proteolysis. Application of occlusive patches to adult rats prevented the normal proteolysis of filaggrin, indicating that this mechanism controls not only the massive filaggrin proteolysis occurring after birth but also the proteolysis occurring during normal stratum corneum maturation. The stratum corneum therefore has the ability to respond to changes in external humidity by altering the level of the stratum corneum where it converts its reserves of filaggrin into water binding amino acids, such that under humid conditions water binding components will be produced in only the most superficial stratum corneum, or even not produced at all.

Aging↗
PubMed2000

Hyaluronan exists in the normal stratum corneum.

Hyaluronan is well known to exist as a water-sorbed macromolecule in the extracellular matrix. We here examined whether hyaluronan exists in the normal stratum corneum. High performance liquid chromatography was used to quantify hyaluronan content in the stratum corneum, epidermis (including stratum corneum), and dermis of mice, with the resulting dry weights being 22.3 +/- 2.9, 15.1 +/- 1.5, and 738.6 +/- 31.6 microg per g, respectively. Normal mouse skin was then labeled with [3H]-glucosamine in an organ culture, and accumulation of [3H]-labeled hyaluronan and its molecular mass were determined separately for the stratum corneum, epidermis, and dermis. In the stratum corneum, [3H]-labeled hyaluronan was accumulated linearly over the 3-d culture period. After the 3-d culture period, the epidermis synthesized twice the amount (expressed as dpm per mg dry weight) of [3H]-labeled hyaluronan as the dermis, whereas the stratum corneum and dermis showed nearly the same content of [3H]-labeled hyaluronan. The molecular mass of [3H]-labeled hyaluronan was highest (>1.0 x 106) in the dermis and clearly lower (<6.0 x 104) in the stratum corneum. Based on these results, we here confirm that hyaluronan is supplied from keratinocytes beneath the stratum corneum layer, and is present in the normal stratum corneum. We speculate that hyaluronan may play a role in moisturizing the stratum corneum and/or regulating its mechanical properties.

Animals↗
PubMed2003

Characteristics of the epidermis and stratum corneum of hairless mice with experimentally induced diabetes mellitus.

Diabetes mellitus induces many pathophysiologic changes in the skin. Even so, dermatologists still lack an animal model of diabetes that enables the direct evaluation of the various functional properties of the skin. Our group induced two types of an experimental type 1 diabetes model in hairless mice by administering either streptozotocin or alloxan, in order to examine the properties of the stratum corneum and epidermis of these animals. The plasma glucose concentrations of the mice at 3 wk after their i.v. injection were significantly higher than those of control mice (streptozotocin, 3.2-fold; alloxan, 3.7-fold). The stratum corneum water content was significantly reduced in both types of diabetic mice, whereas the transepidermal water loss remained unchanged. The amino acid content with normal epidermal profilaggrin processing was either normal or elevated in the stratum corneum of the streptozotocin-treated mice. In contrast, the stratum corneum triglyceride content in the streptozotocin-treated mice was significantly lower than the control level, even though the levels of ceramides, cholesterols, and fatty acids in the stratum corneum were all higher than the control levels. The streptozotocin-treated group also exhibited decreases in basal cell proliferation and epidermal DNA content linked with an increase in the number of corneocyte layers in the stratum corneum, suggesting that the rates of epidermal and stratum corneum turnover were slower in the streptozotocin-treated animals than in the normal controls. In contrast, there were no remarkable changes in any of the epidermal differentiation marker proteins examined. This finding in diabetic mice, namely, reduction in both the epidermal proliferation and stratum corneum water content without any accompanying impairment in the stratum corneum barrier function, is similar to that found in aged human skin. Our new animal model of diabetes will be useful for the study of diabetic dermopathy as well as the mechanisms of stratum corneum moisturization.

Alloxan↗
PubMed2003

Glycerol regulates stratum corneum hydration in sebaceous gland deficient (asebia) mice.

The only known function of human sebaceous glands is the provocation of acne. We assessed here whether sebum influences stratum corneum hydration or permeability barrier function in asebia J1 and 2 J mice, with profound sebaceous gland hypoplasia. Asebia J1 mice showed normal permeability barrier homeostasis and extracellular lamellar membrane structures, but they displayed epidermal hyperplasia, inflammation, and decreased (>50%) stratum corneum hydration, associated with a reduction in sebaceous gland lipids (wax diesters/monoesters, sterol esters). The triglyceride content of both asebia and control stratum corneum was low, consistent with high rates of triglyceride hydrolysis within the normal pilosebaceous apparatus, despite high rates of triglyceride synthesis. Although a mixture of synthetic, sebum-like lipids (sterol/wax esters, triglycerides) did not restore normal stratum corneum hydration to asebia skin, topical glycerol, the putative product of triglyceride hydrolysis in sebaceous glands, normalized stratum corneum hydration, and the glycerol content of asebia stratum corneum was 85% lower than in normal stratum corneum. In contrast, another potent endogenous humectant (urea) did not correct the abnormality. The importance of glycerol generation from triglyceride in sebaceous glands for stratum corneum hydration was demonstrated further by (i) the absence of sebaceous-gland-associated lipase activity in asebia mice, whereas abundant enzyme activity was present in the glands of control mice; and (ii) the inability of high concentrations of topical triglyceride to correct the hydration abnormality, despite the presence of abundant lipase activity in asebia stratum corneum. These results show that sebaceous-gland-derived glycerol is a major contributor to stratum corneum hydration.

Animals↗
PubMed1995

Functional changes in human stratum corneum induced by topical glycolic acid: comparison with all-trans retinoic acid.

The effects of topical glycolic acid and all-trans retinoic acid on stratum corneum barrier function and hydration of human skin were investigated in 6 healthy volunteers utilizing non-invasive techniques. In addition, changes in stratum corneum turnover time induced by the substances were examined using the dansyl chloride fluorescence test. Twelve percent glycolic acid in water and 0.1% retinoic acid in ethanol, respectively, were applied for 60 min once daily, over a period of 2 weeks (5 consecutive days weekly) on dansyl chloride-labelled skin and on untreated skin. During a 10-day application period, both glycolic acid and retinoic acid similarly induced a significant increase in TEWL. However, after discontinuing treatment, TEWL in retinoic acid-exposed skin remained increased. Glycolic acid significantly reduced stratum corneum hydration from day 11 to day 18 (p < 0.05), while retinoic acid induced skin dryness after 9 days of treatment, which persisted until day 18 (p < 0.005). Whereas glycolic acid rapidly induced an intense erythema implying a direct non-specific inflammatory response, the retinoic acid-exposed skin gradually developed erythema. Retinoic acid caused scaling to a greater extent than did glycolic acid, even after treatment cessation. Both glycolic acid and retinoic acid significantly decreased stratum corneum turnover time and stratum corneum turnover time50 (the time in days from labelling until approximately 50% of fluorescence disappeared), compared with the vehicle controls. However, glycolic acid shortened stratum corneum turnover time (12.8 +/- 0.9 days) as well as stratum corneum turnover time50 (7.3 +/- 0.7 d) significantly more than did retinoic acid (15.8 +/- 0.7 d and 9 +/- 0.8 d, respectively). While ethanol (vehicle of retinoic acid) slightly but significantly decreased stratum corneum turnover time (p < 0.05), water (vehicle of glycolic acid) did not. This study showed that both glycolic acid and retinoic acid induced certain functional changes in stratum corneum, mirroring their irritation potential. However, changes at retinoic acid-exposed sites appeared longer-lasting, implying a distinct mode of action. An increase in stratum corneum turnover induced by the substances may be, in part, linked with their irritation properties.

Adult↗
PubMed1991

Intercellular lamellar lipids in plantar stratum corneum.

Plantar stratum corneum was examined by means of transmission electron microscopy after conventional osmium fixation and after fixation with ruthenium tetroxide. The latter fixative was used in order to reveal the possible existence of lamelarly ordered lipids in the intercellular space, as has previously been demonstrated for non-palmo-plantar stratum corneum. A major part of the plantar stratum corneum intercellular space was occupied by extracellular parts of desmosomes. In specimens fixed with ruthenium tetroxide the intercellular space not occupied by desmosomes was found to contain multiple alternating electron dense and electron lucid bands, suggestive of membraneous structures. This pattern appeared to be similar to that previously described for non-palmo-plantar stratum corneum. It is suggested that the intercellular lipids of palmo-plantar stratum corneum may be qualitatively similar to the intercellular lipids of non-palmo-plantar stratum corneum. The lower lipid content, expressed as weight per unit weight of tissue, in palmo-plantar stratum corneum as compared to non-palmo-plantar stratum corneum may be related to the fact that a larger portion of the intercellular space of the former tissue is occupied by desmosomes. The relatively high water permeability of palmo-plantar stratum corneum implies that desmosomes, i.e. non-lipid regions of the intercellular space, may have a high water permeability and hence could establish a hydrophilic route through the stratum corneum.

Body Water↗
PubMed2002

Two-photon fluorescence lifetime imaging of the skin stratum corneum pH gradient.

Two-photon fluorescence lifetime imaging is used to identify microdomains (1-25 microm) of two distinct pH values within the uppermost layer of the epidermis (stratum corneum). The fluorophore used is 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), whose lifetime tau (pH 4.5, tau = 2.75 ns; pH 8.5, tau = 3.90 ns) is pH dependent over the pH range of the stratum corneum (pH 4.5 to pH 7.2). Hairless mice (SKH1-hrBR) are used as a model for human skin. Images (< or =50 microm x 50 microm) are acquired every 1.7 microm from the stratum corneum surface to the first viable layer (stratum granulosum). Acidic microdomains (average pH 6.0) of variable size (~1 microm in diameter with variable length) are detected within the extracellular matrix of the stratum corneum, whereas the intracellular space of the corneocytes in mid-stratum corneum (25 microm diameter) approaches neutrality (average pH 7.0). The surface is acidic. The average pH of the stratum corneum increases with depth because of a decrease in the ratio of acidic to neutral regions within the stratum corneum. The data definitively show that the stratum corneum acid mantle results from the presence of aqueous acidic pockets within the lipid-rich extracellular matrix.

Animals↗
PubMed2001

Aberrant lipid organization in stratum corneum of patients with atopic dermatitis and lamellar ichthyosis.

There are several skin diseases in which the lipid composition in the intercellular matrix of the stratum corneum is different from that of healthy human skin. It has been shown that patients suffering from atopic dermatitis have a reduced ceramide content in the stratum corneum, whereas in the stratum corneum of lamellar ichthyosis patients, the amount of free fatty acids is decreased and the ceramide profile is altered. Both patient groups also show elevated levels of transepidermal water loss indicative of an impaired barrier function. As ceramides and free fatty acids are essential for a proper barrier function, we hypothesized that changes in the composition of these lipids would be reflected in the lipid organization in stratum corneum of atopic dermatitis and lamellar ichthyosis patients. We investigated the lateral lipid packing using electron diffraction and the lamellar organization using freeze fracture electron microscopy. In atopic dermatitis stratum corneum, we found that, in comparison with healthy stratum corneum, the presence of the hexagonal lattice (gel phase) is increased with respect to the orthorhombic packing (crystalline phase). In lamellar ichthyosis stratum corneum, the hexagonal packing was predominantly present, whereas the orthorhombic packing was observed only occasionally. This is in good agreement with studies on stratum corneum lipid models that show that the presence of long-chain free fatty acids is involved in the formation of the orthorhombic packing. The results of this study also suggest that the ceramide composition is important for the lateral lipid packing. Finally, using freeze fracture electron microscopy, changes in the lamellar organization in stratum corneum of both patient groups could be observed.

Dermatitis, Atopic↗
PubMed1998

Normalization of epidermal calcium distribution profile in reconstructed human epidermis is related to improvement of terminal differentiation and stratum corneum barrier formation.

Calcium plays an important role in the regulation of cellular differentiation and desquamation of epidermal keratinocytes. In this study, we examined the calcium distribution in reconstructed epidermis in an attempt to understand the physiology of keratinocyte differentiation and desquamation in vitro. Ion capture cytochemistry (the potassium oxalate-pyroantimonate method) was employed to localize ionic calcium in reconstructed epidermis generated under three different culture conditions (in serum-containing medium, serum-free medium, and serum-free medium supplemented with retinoic acid), allowing a comparison of the physiology of incompletely and well-differentiated keratinocytes. The reconstructed epidermis generated in serum-containing medium showed features of incomplete differentiation, and compared with the native skin, a high calcium content within incompletely differentiated cells in the stratum corneum. Use of serum-free medium containing vitamin and lipid supplements led to a marked improvement of the stratum corneum ultrastructure and penetration pathway across the stratum corneum, indicating improved barrier formation of the reconstructed epidermis. In parallel, the calcium distribution pattern was normalized showing the highest levels of calcium in the stratum granulosum and low levels in the inner stratum corneum. Addition of retinoic acid to the serum-free medium resulted in an altered keratinocyte differentiation and re-appearance of large quantities of calcium precipitates in the stratum corneum. Proton probe X-ray microanalysis was applied to investigate the calcium distribution quantitatively in native and reconstructed epidermis generated in serum-free medium, and verified the calcium distribution demonstrated by the precipitation technique. Regardless of the presence or absence of calcium in the stratum corneum, all examined culture systems exhibited insufficient desquamation, which correlates with the finding that stratum corneum chymotryptic enzyme was present predominantly as an inactive precursor. This study demonstrates that improvement of the stratum corneum barrier properties in vitro is concurrent with the normalization of the epidermal calcium gradient, whereas deregulation of terminal differentiation correlates with an accumulation of calcium ions within incompletely differentiated corneocytes.

Adult↗
PubMed2003

Hydration disrupts human stratum corneum ultrastructure.

Using transmission and cryo-scanning electron microscopy, we confirm that extended water exposure leads to extensive disruption of stratum corneum intercellular lipid lamellae. We define the in vivo swelling behavior of the stratum corneum: exposure to water for 4 or 24 h results in a 3- or 4-fold expansion of the stratum corneum thickness, respectively. Corneocytes swell uniformly with the exception of the outermost and inner two to four corneocyte layers, which swell less. We show that hydration induces large pools of water in the intercellular space, pools that can exceed the size of water-swollen corneocytes. By 4 h of water exposure there are numerous small and large intercellular pools of water ("cisternae") present throughout the stratum corneum, and at 24 h these cisternae substantially increase in size. Within cisternae the lipid structure is disrupted by lamellar delamination ("roll-up"). Cisternae appear to be disk-shaped structures that do not obviously communicate. Cisternae appear to contain considerable lipidic and other material and to contain a substantial fluid volume that can rival the volume of the dry stratum corneum. Similar results are obtained following urine exposure. With urine exposure, cisternae communicate with salts in the external solution. This study illustrates the disruptive effect of overhydration on the stratum corneum intercellular space, identifies large and numerous unanticipated intercellular cisternal structures, defines the magnitude of stratum corneum swelling, and identifies stratum corneum cell layers that swell less. The study suggests the stratum corneum is a more chaotic structure than previously envisioned, and provides a framework for better understanding desquamation, irritancy, and percutaneous transport.

Adult↗
PubMed2003

Antioxidant enzyme activity in human stratum corneum shows seasonal variation with an age-dependent recovery.

The stratum corneum, as the body's principal barrier to the environment, is continuously exposed to environmental sources of reactive oxygen species like ultraviolet light, ozone, and pollution. Reactive oxygen species are believed to be involved in cancer, aging, and inflammatory skin disorders. We have developed a method to measure catalase and superoxide dismutase activity on tape strippings from the human stratum corneum and demonstrated a gradient of antioxidant enzyme activity across the stratum corneum with decreasing levels towards the skin surface. Sun exposure resulted in a seasonal variation of the catalase activity in stratum corneum, with low activities in summer and higher activities in winter for the same person, whereas superoxide dismutase activity in stratum corneum did not seem to vary in those conditions. Exposure of human skin to broadband ultraviolet-A resulted in a dose-dependent deactivation of the catalase activity in stratum corneum within 24 h, whereas exposure to ultraviolet-B had no effect. Superoxide dismutase activity in stratum corneum was not affected by ultraviolet-A or ultraviolet-B irradiation within 24 h. After exposure to a dose of 15 J per cm2 broadband ultraviolet-A, full recovery of the catalase activity occurred in 3-4 wk at an age-dependent rate. We conclude that sun exposure results in a disturbed catalase to superoxide dismutase ratio in the stratum corneum. This may lead to an increased vulnerability to oxidative damage in stratum corneum barrier components. These results therefore stress the importance of providing efficient protection for this internal defense mechanism in sun-exposed areas of the skin.

Adult↗
PubMed2003

pH directly regulates epidermal permeability barrier homeostasis, and stratum corneum integrity/cohesion.

Both exposure of stratum corneum to neutral pH buffers and blockade of acidification mechanisms disturb cutaneous permeability barrier homeostasis and stratum corneum integrity/cohesion, but these approaches all introduce potentially confounding variables. To study the consequences of stratum corneum neutralization, independent of hydration, we applied two chemically unrelated superbases, 1,1,3,3-tetramethylguanidine or 1,8-diazabicyclo [5,4,0] undec-7-ene, in propylene glycol:ethanol (7:3) to hairless mouse skin and assessed whether discrete pH changes alone regulate cutaneous permeability barrier function and stratum corneum integrity/cohesion, as well as the responsible mechanisms. Both 1,1,3,3-tetramethylguanidine and 1,8-diazabicyclo [5,4,0] undec-7-ene applications increased skin surface pH in parallel with abnormalities in both barrier homeostasis and stratum corneum integrity/cohesion. The latter was attributable to rapid activation (<20 min) of serine proteases, assessed by in situ zymography, followed by serine-protease-mediated degradation of corneodesmosomes. Western blotting revealed degradation of desmoglein 1, a key corneodesmosome structural protein, in parallel with loss of corneodesmosomes. Coapplication of serine protease inhibitors with the superbase normalized stratum corneum integrity/cohesion. The superbases also delayed permeability barrier recovery, attributable to decreased beta-glucocerebrosidase activity, assessed zymographically, resulting in a lipid-processing defect on electron microscopy. These studies demonstrate unequivocally that stratum corneum neutralization alone provokes stratum corneum functional abnormalities, including aberrant permeability barrier homeostasis and decreased stratum corneum integrity/cohesion, as well as the mechanisms responsible for these abnormalities.

Animals↗
PubMed1988

Membrane structural alterations in murine stratum corneum: relationship to the localization of polar lipids and phospholipases.

During the formation of the mammalian epidermal permeability barrier, lipids are sequestered in the stratum corneum intercellular spaces, transforming from a relatively polar lipid mixture to predominantly nonpolar species. Certain lipid catabolic enzymes, which co-localize with these lipids, may regulate this process. In order to localize the sites within the outer epidermis where polar lipids are catabolized, and their relationship to the alterations in membrane structure that occur in these layers, we compared the biochemical localization of polar lipids, the ultrastructure, and freeze-fracture morphology, as well as the localization of phospholipases within the outer epidermis. Both histochemical staining of frozen sections and biochemical studies of protease- and tape-stripped whole stratum corneum demonstrated small amounts of polar lipids in the stratum compactum, while in contrast, the stratum disjunctum was devoid of both phospholipids and glycosphingolipids. Phospholipase activity was present within lamellar bodies, among secreted lamellar body disks at the granular-cornified layer interface, and within the intercellular spaces of the stratum compactum. Both the depletion of polar lipids from the stratum compactum and deletion of these substances from the stratum disjunctum correlated with sequential changes in membrane structure observed by transmission electron microscopy and freeze-fracture. Thus, a phospholipase-mediated attack on phospholipids (with a parallel assault by other lipid catabolic enzymes on other polar species), may induce both the initial fusion and elongation of lamellar body disks and the subsequent formation of the hydrophobic membrane bilayers found in the mid-to-outer stratum corneum. These studies also may require modification of traditional views of the stratum corneum as a metabolically inert tissue, revealing its intercellular lipid domains to be partially in an active state of flux.

Animals↗
PubMed1991

Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin?

Stratum corneum lipids are an important determinant for both water-retention function and permeability-barrier function in the stratum corneum. However, their major constituent, ceramides, have not been analyzed in detail in skin diseases such as atopic dermatitis that show defective water-retention and permeability-barrier function. In an attempt to assess the quantity of ceramides per unit mass of the stratum corneum in atopic dermatitis, stratum corneum sheet was removed from the forearm skin by stripping with cyanoacrylate resin and placed in hexane/ethanol extraction to yield stratum corneum lipids. The stratum corneum was dispersed by solubilization of cyanoacrylate resin with dimethylformamide, and after membrane filtration, the weight of the stratum corneum mass was measured. The ceramides were quantified by thin-layer chromatography and evaluated as microgram/mg stratum corneum. In the forearm skin of healthy individuals (n = 65), the total ceramide content significantly declined with increasing age. In atopic dermatitis (n = 32-35), there was a marked reduction in the amount of ceramides in the lesional forearm skin compared with those of healthy individuals of the same age. Interestingly, the non-lesional skin also exhibited a similar and significant decrease of ceramides. Among six ceramide fractions, ceramide 1 was most significantly reduced in both lesional and non-lesional skin. These findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.

Adolescent↗
PubMed2005

Stratum corneum hydration and flexibility are useful parameters to indicate clinical severity of congenital ichthyosis.

To determine any correlation between the stratum corneum barrier function and the phenotypic severity of congenital ichthyosis, we studied stratum corneum hydration, flexibility, thickness and transepidermal water loss (TEWL) in patients with congenital ichthyosis. Seven patients with congenital ichthyosis aged 2-46 years and age-matched controls were included in the present study. We divided seven patients into two groups; patients with non-bullous type (non-bullous congenital ichthyosiform erythroderma patients) and patients with the bullous type of congenital ichthyosis (bullous congenital ichthyosiform erythroderma and ichthyosis bullosa of Siemens). Stratum corneum hydration, thickness and flexibility were measured using a Corneometer ASA-M2. The stratum corneum thickness was also examined using a skin biopsy technique. TEWL was measured using Evaporimeter AS-TW1. The clinical severity of ichthyosis phenotype was evaluated using a visual analogue scale (VAS). Stratum corneum hydration and flexibility were significantly reduced in both congenital ichthyosis patient groups. Stratum corneum thickness was significantly increased in both groups. In the patient group with non-bullous congenital ichthyosis, significant negative correlations were confirmed between the VAS score and stratum corneum hydration and between the VAS score and flexibility. A significant, positive correlation was also observed between the VAS score and stratum corneum thickness. There was a positive correlation between the VAS score and TEWL on both the extensor and flexor sides of the forearm and back. We conclude that stratum corneum hydration, flexibility and thickness measured by the corneometer, and TEWL on the arm may be a useful indicator of the severity of ichthyosis phenotype.

Adolescent↗
PubMed1996

A critical comparison of methods to quantify stratum corneum removed by tape stripping.

Skin surface stripping with adhesive tape has been used to study the barrier function of the stratum corneum. Usually, the amount of stratum corneum removed by stripping is not linearly proportional to the number of strips removed. The generally accepted quantitative method to determine the amount of stratum corneum material on a tape strip is weighing. This method however has certain drawbacks, it is time consuming and laborious because tape strips have to be weighed twice and sometimes it cannot be used to determine concentration profiles in the skin of active substances in topically applied vehicles. In this paper, the accuracy and reliability of an alternative method to determine the amount of stratum corneum removed by tape stripping of the skin was investigated and compared to weighing. It is based on the spectrophotometric examination of the tape. The light absorption by the proteins on the tape is correlated to the weight of the stratum corneum material. This method was found to be easier and faster than weighing, but it was less reliable because the light scattering of the stratum corneum on the tape largely overshadowed the absorption of the proteins. The light scattering showed a linear increase with an increasing amount of material on the tape, but with a large variability, resulting in calibration curves with correlations of 0.8400. However, direct spectroscopic analysis of stratum corneum tape strips has some distinct advantages even if it cannot be used for the exact quantification of stratum corneum proteins. With direct spectroscopic measurements, a tape strip can be laterally examined to inspect its homogeneity. Direct spectroscopic measurements on tape strips might also be employed to investigate the lateral and in-depth distribution of strongly light-absorbing substances in the stratum corneum.

Adhesives↗