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At least 109 records · Page 6Linked to original sources
PubMed2004

The content of free amino acids in the stratum corneum is increased in senile xerosis.

Xerosis is one of the characteristics of aged skin. Xerosis may be caused by a decrease in the stratum corneum free amino acids which are natural moisturizing factors derived from filaggrin. In aged skin, filaggrin is immunohistochemically decreased compared with the levels in young skin. However, the differences in stratum corneum amino acids between aged and young skin have not been analyzed quantitatively. Therefore, in this study we determined the stratum corneum amino acids per 1000 stratum corneum cells in aged and young skin by high-performance liquid chromatography. The amount of filaggrin mRNA in the epidermis was also compared between aged and young skin using RT-PCR. The total amount of amino acids in the stratum corneum was larger in aged senile xerosis skin than in young skin. Only a few amino acids were found in the stratum corneum of ichthyosis vulgaris patients (control skin). The expression of filaggrin mRNA in aged skin was, however, similar to that in young skin. These findings suggest that the immunohistochemical decrease in filaggrin in aged skin may be caused by promotion of filaggrin proteolysis in the upper layers of the stratum spinulosum.

Adult↗
PubMed1999

Stratum corneum thiol protease (SCTP): a novel cysteine protease of late epidermal differentiation.

Proteolytic enzymes play crucial roles in the formation of the stratum corneum barrier tissue and in its subsequent maturation. Despite this, the proteases involved in stratum corneum physiology are not well characterized. Hence, studies were performed to identify these proteolytic enzymes present in the peripheral layers of this tissue using a combination of tape stripping and zymography. Using this approach, a novel human cysteine protease was identified and characterized, and named stratum corneum thiol protease (SCTP). Gelatin zymography revealed that SCTP is composed of two variants with apparent molecular weights of 34 and 35 kDa which do not correspond to any previously described stratum corneum protease. Mechanistically SCTP belongs to the cysteine proteinase class as shown by: (1) acid protease activity, (2) a requirement for mild reducing conditions, and (3) the specific inhibition of activity by E64 and Z-phe-ala-diazomethylketone. Further analysis using concanavalin A affinity chromatography demonstrated that the two 34 and 35 kDa variants are both glycoproteins, which, after removal of the oligosaccharide sidechains with the specific enzyme N-glycopeptidase F, reveal a single active core protease of 32 kDa. SCTP did not crossreact with antibodies raised against the lysosomal cysteine proteases cathepsins B, H or L, thereby distinguishing it from the classical cysteine cathepsins. Localization studies revealed that SCTP is present at all depths in the stratum corneum, thereby precluding microbial contamination as the enzyme source. Moreover, it was also present at all body sites investigated, except for the hyperkeratotic palmoplantar stratum corneum. SCTP was found to be a product of late differentiation in cultured human keratinocytes; the enzyme was synthesized by differentiated calcium-switched cells and secreted into the medium, whereas nondifferentiated basal keratinocytes did not produce this protease. Moreover, human fibroblast cultures did not produce the enzyme, suggesting that SCTP is not produced by the dermis and hence is epidermal specific. The function of SCTP is unknown, but the observed gelatinolytic activity coupled with its secretion into the medium by cultured keratinocytes indicates that physiologically it is responsible for the degradation of extracellular structural proteins. Furthermore, the optimal activity at acid pH suggests that it can function in the acidic environment of the stratum corneum. It remains to be elucidated whether this enzyme has a role in desquamation.

Blotting, Western↗
PubMed1996

Reinnervation of stratum lucidum by hippocampal mossy fibers is developmentally regulated.

Mossy fibers from dentate gyrus granule cells establish synapses on CA3 pyramidal neurons during the first 3 postnatal weeks in the rat. Mossy fiber synapses are primarily restricted to the stratum lucidum. When examined by Timm stain after 10-14 days in vitro, cultured hippocampal slices from postnatal day 4 rat pups show a similar mossy fiber termination pattern in stratum lucidum. Thus, axon guidance cues used by mossy fibers in vivo appear to be preserved in these cultured slices. Three experimental manipulations were performed on hippocampal slice cultures to examine whether the axon guidance cues used by mossy fibers are developmentally regulated. First, mossy fibers were transected on the day of culture or day 7 in vitro. Mossy fibers transected on either day were able to reestablish their synaptic pattern in stratum lucidum of CA3. Second, dentates and hippocampi of same age or different age were co-cultured. Same age co-cultures (P4 dentates to P4 hippocampi or P11 dentates to P11 hippocampi) showed good mossy fiber reinnervation of stratum lucidum, as did different age co-cultures from P4 dentates to P11 hippocampi. However, P11 dentates to P4 hippocampi co-cultures showed little mossy fiber reinnervation of stratum lucidum. Third, new P4 or P11 dentates were co-cultured onto hippocampal slices in which mossy fibers had been allowed to degenerate. New mossy fibers reinnervated these hippocampi, but did not reestablish their normal synaptic pattern in stratum lucidum. These three experimental manipulations suggest that mossy fiber axon guidance mechanisms are developmentally regulated, and that existing mossy fibers play a role in directing mossy fiber reinnervation of stratum lucidum.

Animals↗
PubMed1993

The location of Ted-R-1 antigen on the cell membrane of the stratum corneum: immunoelectron microscopic study.

As the Ted-R-1 monoclonal antibody yields fluorescence on the keratohyalin granules, in the cytoplasm of the lower stratum corneum cells and on the cell membrane region of the stratum corneum in indirect immunofluorescent examination, the location of the antigen of this Ted-R-1 monoclonal antibody was examined by the post-embedding, immunoelectron microscopic technique using gold labelled antibody. The number of gold particles located on the keratohyalin granules was 184.00 +/- 28.69 per micron2. In contrast, there were only a few gold particles in the nucleus and the cytoplasm of the stratum granulosum (3.85 +/- 1.34) and none were found in the intercellular spaces of these cells (< 1.00). On the other hand, they were diffusely located in the lower two to three cell layers of the stratum corneum (319.75 +/- 44.41) and on the inner surface of the marginal band of the upper cell layers of the stratum corneum, but only a few were located in the cytoplasm of the upper stratum corneum cells (12 +/- 7.00). These observations indicate that the Ted-R-1 antigen locates on both keratohyalin granules and the inner surface of the marginal band of the upper part of the stratum corneum cell layers.

Animals↗
PubMed2005

Epidermal cell culture model with tight stratum corneum as a tool for dermal gene delivery studies.

The purpose of this study was to evaluate the feasibility of organotypic cultures of rat epidermal cells as a tool to study non-invasive dermal gene delivery. Also, a novel transfection method employing liposomal pre-treatment of stratum corneum (SC) was evaluated. Rat epidermal cells were cultured on Transwell tissue culture inserts and formation of stratum corneum barrier was evaluated in permeability studies with two model compounds. Transfections were performed with naked pCMV-SEAP2 plasmid and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/dioleyl-phosphatidylethanolamine (DOPE)/DNA lipoplexes. Naked DNA was administered on the stratum corneum of the cell culture model with or without prior treatment of the stratum corneum with DOTAP/DOPE liposomes. Transfection was evaluated non-invasively by monitoring concentrations of secreted alkaline phosphatase (SEAP) in the culture medium of the basolateral compartment at 24-h intervals. Transfection with lipoplexes produced significant gene expression in rat epidermal keratinocyte (REK) epidermal culture model. Likewise, delivery of naked DNA on stratum corneum after DOTAP/DOPE liposome pre-treatment produced gene expression. Naked DNA alone did not result in detectable gene expression. In dermal gene delivery studies REK epidermal culture model is a suitable tool that includes tight stratum corneum and allows transgene expression in viable epidermis and non-invasive sampling of secreted gene product in the basolateral compartment. Liposomal pre-treatment of the stratum corneum augments transfection of viable epidermis.

Alkaline Phosphatase↗
PubMed2001

There is no influence of a temperature rise on in vivo adsorption of UV filters into the stratum corneum.

Temperature influences the stratum corneum adsorption of several topically applied compounds. This study was designed to evaluate the influence of the temperature on the stratum corneum adsorption of 3 UV filters. The UV filters were solubilized in two vehicles, an emulsion gel and petroleum jelly and applied at respectively, 31 and 40 degrees C during 30 min. In vivo stratum corneum UV filter content was measured using the tape stripping method. Similar amounts of UV filter were detected in the stratum corneum when comparing applications at the different temperatures. Application of the UV filters in the emulsion gel resulted in higher stratum corneum UV filter concentrations compared with application in the petroleum jelly. The application temperature did not influence the stratum corneum adsorption of the tested UV filters while the nature of the vehicle significantly influenced the amount of UV filters recovered from the stratum corneum.

Adult↗
PubMed1988

The role of protein and lipid domains in the uptake of solutes by human stratum corneum.

The uptake of a series of hydrocortisone esters varying in lipophilicity from water into untreated and delipidized human stratum corneum has been determined. The partition coefficients of solutes into fully hydrated stratum corneum are postulated to represent the separate contributions of three structurally distinct domains--the extractable lipids, protein, and the solvent domain. The solvent domain was assumed to have the properties of bulk water. The relative affinities of the protein and lipid domains of stratum corneum for solutes varying in structure were determined by comparing solute uptake in untreated and delipidized stratum corneum. Partitioning into the extracted lipids was also examined. Solute uptake into stratum corneum may be governed by the protein domain, the lipid domain, or a combination of the two, depending on solute lipophilicity. Due to differences in the selectivity of the two domains, a change in uptake mechanism occurs with increasing solute lipophilicity from protein-dominated uptake for hydrophilic solutes to lipid domain-dominated uptake for lipophilic solutes. The stratum corneum lipid content, which varies dramatically from individual to individual (3-46% in this study), is an important determinant of the affinity of the stratum corneum for highly lipophilic solutes but has no effect on the uptake of hydrophilic solutes.

Chromatography, Liquid↗
PubMed1994

Estradiol permeation from nonionic surfactant vesicles through human stratum corneum in vitro.

The permeation of estradiol from vesicular formulations through human stratum corneum was studied in vitro. The vesicles were composed of nonionic n-alkyl polyoxyethylene ether surfactants (CnEOm). The thermodynamic activity of estradiol present in each formulation was kept constant by saturating all formulations with estradiol. The effects of both the particle size and the composition of the formulation on estradiol permeation across excised human stratum corneum were investigated. Stratum corneum that was pretreated with empty surfactant carriers allowed for significantly higher estradiol fluxes compared with untreated stratum corneum. However, estradiol fluxes obtained in these pretreatment experiments appeared to be significantly lower than those obtained by the direct application of the estradiol-saturated carrier formulation on top of the stratum corneum. Furthermore, in the case of pretreatment of the stratum corneum, an increase in carrier size resulted in a decrease in estradiol flux. For direct application the opposite was found. Two mechanisms are proposed to play an important role in vesicle-skin interactions, i.e., the penetration enhancing effect of surfactant molecules and the effect of the vesicular structures that are most likely caused by adsorption of the vesicles at the stratum corneum-suspension interface.

Administration, Cutaneous↗
PubMed1999

A new computer-based evaporimeter system for rapid and precise measurements of water diffusion through stratum corneum in vitro.

It is important to have reliable methods for evaluation of skin barrier function when questions such as barrier perturbing effects of different agents and occlusive effects of different formulations are to be elucidated. A wealth of clinical work relates to measurements of transepidermal water loss in vivo, a method much affected by ambient air relative humidity, temperature, skin irritation processes, psychologic status of the subject, etc., factors that cause the method to suffer from low precision (i.e., high random error). Relating to these obstacles, we have developed a closed in vitro system for measurements of water diffusion rate through pieces of isolated stratum corneum at steady-state conditions, where the relative humidity and temperature is held constant and data can be collected continuously. Our evaporimeter-based in vitro system has a more than 3-fold higher precision (lower random error) ( approximately 10%) than measurements of transepidermal water loss in vivo ( approximately 35%). The results of our study show that: (i) the corneocyte envelopes contribute to the barrier capacity of stratum corneum; (ii) removal of the lipid intercellular matrix results in approximately a 3-fold increase in the water diffusion rate through the isolated stratum corneum (n = 20; p < 0.05), not a 100-fold as has previously been suggested; (iii) exposure to sodium dodecyl sulfate in water does neither alter the water diffusion rate (n = 10; p > 0.05) nor the water holding capacity (n = 10; p > 0.05) of stratum corneum; (iv) exposure to 1 M CaCl2 in water yields an increased water diffusion rate through stratum corneum (n = 10; p < 0.05); and (v) when applied to the stratum corneum in excess concentrations, the penetration enhancer Azone has occlusive effects on water diffusion through the stratum corneum (n = 6; p < 0.05).

Azepines↗
PubMed2002

Human epidermal glucosylceramides are major precursors of stratum corneum ceramides.

Ceramides are the major component of the stratum corneum, accounting for 30%-40% of stratum corneum lipids by weight, and are composed of at least seven molecular groups (designated ceramides 1-7). Stratum corneum ceramides, together with cholesterol and fatty acids, form extracellular lamellae that are responsible for the epidermal permeability barrier. Previous studies indicated that beta-glucocerebrosidase- and sphingomyelinase-dependent ceramide production from glucosylceramides and sphingomyelins, respectively, is important for epidermal permeability barrier homeostasis. A recent study indicated that sphingomyelins are precursors of two stratum corneum ceramide molecular groups (ceramides 2 and 5). In this study, we have examined the role of glucosylceramides in the generation of each of the seven stratum corneum ceramide molecular groups. First, the structures of various glucosylceramide species in human epidermis were determined by gas chromatography-mass spectrometry, fast atom bombardment-mass spectrometry, and nuclear magnetic resonance. The results indicate that total epidermal glucosylceramides are composed of six distinct molecular groups, glucosylceramides 1-6. Glucosylceramide 1 contains sphingenine and nonhydroxy fatty acids, glucosylceramide 2, phytosphingosine and nonhydroxy fatty acids, glucosylceramide 3, phytosphingosine with one double bond and nonhydroxy fatty acids, glucosylceramide 4, sphingenine and alpha-hydroxy fatty acids, glucosylceramide 5, phytosphingosine and alpha-hydroxy fatty acids, and glucosylceramide 6, phytosphingosine with one double bond and alpha-hydroxy fatty acids. The nonhydroxy fatty acids typically have 16-24-carbon-length chains, whereas alpha-hydroxy fatty acids are limited to 24-, 25-, and 26-carbon chains. The sphingosine bases are C18 or C20 chains. Next, acylglucosylceramides and glucosylceramides were treated with beta-glucocerebrosidase and the ceramides released were compared with stratum corneum ceramides. Ceramide moieties of acylglucosylceramides and glucosylceramides 1, 2, 4-6 correspond to stratum corneum ceramides 1-7. These results, together with those of our previous reports characterizing epidermal sphingomyelins, indicate that all ceramide species, including omega-hydroxy fatty-acid-containing ceramides, are derived from glucosylceramides, and fractions of ceramides 2 and 5 are from sphingomyelins. Furthermore, structural analysis of glucosylceramides revealed that human epidermal glycosphingolipids display a unique lipid profile that is rich in very long chain hydroxylated (alpha- and omega-hydroxy) fatty acids and phytosphingosine.

Adolescent↗
PubMed2003

Short-term glucocorticoid treatment compromises both permeability barrier homeostasis and stratum corneum integrity: inhibition of epidermal lipid synthesis accounts for functional abnormalities.

Prolonged exposure of human epidermis to excess endogenous or exogenous glucocorticoids can result in well-recognized cutaneous abnormalities. Here, we determined whether short-term glucocorticoid treatment would also display adverse effects, specifically on two key epidermal functions, permeability barrier homeostasis and stratum corneum integrity and cohesion, and the basis for such changes. In humans 3 d of treatment with a potent, commonly employed topical glucocorticoid (clobetasol), applied topically, produced a deterioration in barrier homeostasis, characterized by delayed barrier recovery and abnormal stratum corneum integrity (rate of barrier disruption with tape strippings) and stratum corneum cohesion (microg protein removed per stripping). Short-term systemic and topical glucocorticoid produced similar functional defects in mice, where the basis for these abnormalities was explored further. Both the production and secretion of lamellar bodies were profoundly decreased in topical glucocorticoid-treated mice resulting in decreased extracellular lamellar bilayers. These structural changes, in turn, were attributable to a profound global inhibition of lipid synthesis, demonstrated both in epidermis and in cultured human keratinocytes. The basis for the abnormality in stratum corneum integrity and cohesion was a diminution in the density of corneodesmosomes in the lower stratum corneum. We next performed topical replacement studies to determine whether lipid deficiency accounts for the glucocorticoid-induced functional abnormalities. The abnormalities in both permeability barrier homeostasis and stratum corneum integrity were corrected by topical applications of an equimolar distribution of free fatty acids, cholesterol, and ceramides, indicating that glucocorticoid-induced inhibition of epidermal lipid synthesis accounts for the derangements in both cutaneous barrier function and stratum corneum integrity/cohesion. These studies indicate that even short-term exposure to potent glucocorticosteroids can exert profound negative effects on cutaneous structure and function. Finally, topical replenishment with epidermal physiologic lipids could represent a potential method to reduce the adverse cutaneous effects of both topical glucocorticoid treatment and Cushing's syndrome.

Administration, Topical↗
PubMed2003

Water distribution and related morphology in human stratum corneum at different hydration levels.

This study focused on the water distribution in human stratum corneum and on the swelling of the corneocytes. For this purpose stratum corneum was hydrated to various levels and used either for Fourier transform infrared spectroscopy or for cryo-scanning electron microscopy. The images were analyzed with respect to water localization and cell shape. The Fourier transform infrared spectra were measured to study the water-lipid interactions. The results show that water only slightly changes the lipid transitions in the stratum corneum even at a hydration level of 300% wt/wt compared to stratum corneum and that water is inhomogeneously distributed in the stratum corneum. No gradual increase in water level was observed in depth. At 57%-87% wt/wt water content the hydration level in the central part of stratum corneum is higher than in the superficial and deeper cell layers. Water domains are mainly present within the corneocytes and not in the intercellular regions. At a very high hydration level (300% wt/wt), the corneocytes are strongly swollen except for the deepest cell layers adjacent to the viable epidermis. The corneocytes in these layers are not swollen. At 300% wt/wt hydration level water domains are also present in intercellular regions. Between 17% wt/wt and 300% wt/wt the cell thickness increases linearly with the hydration level suggesting that swelling of cells mainly occurs in the direction perpendicular to the skin surface. At an increased hydration level, the corneocyte envelope more efficiently surrounds the cell content compensating for the increased cell volume. The changes in stratum corneum morphology with increasing water level have also been observed in dermatomed skin.

Biopsy↗
PubMed2003

Ultrastructural evidence of stratum corneum permeabilization induced by photomechanical waves.

Photomechanical waves (high amplitude pressure transients generated by lasers) have been shown to permeabilize the stratum corneum in vivo and facilitate the transport of macromolecules into the viable epidermis. The permeabilization of the stratum corneum is transient and its barrier function recovers. Sites on the volar forearm of humans were exposed to photomechanical waves and biopsies were obtained immediately after the exposure and processed for electron microscopy. Electron microscopy showed an expansion of the lacunar spaces within the stratum corneum lipid bilayers but no changes in the organization of the secreted lamellar bodies at the stratum corneum-stratum granulosum boundary. The combination of photomechanical waves and sodium lauryl sulfate enhances the efficiency of transdermal delivery and delays the recovery of the barrier function of the stratum corneum. Electron microscopy from sites exposed to photomechanical waves and sodium lauryl sulfate showed that the lacunar spaces expanded significantly more and the secreted lamellar bodies also appeared to be altered. In either case, there were no changes in the papillary dermis. These observations support the hypothesis that the photomechanical waves induce the expansion of the lacunar spaces within the stratum corneum leading to the formation of transient channels.

Administration, Cutaneous↗
PubMed1989

Solute structure-permeability relationships in human stratum corneum.

The permeability coefficients (kp) of a series of methyl-substituted p-cresols were determined in human stratum corneum along with their partition coefficients (PC) between water and untreated stratum corneum, delipidized stratum corneum, octanol, and heptane. The PC values were identical in untreated and delipidized stratum corneum, suggesting that the stratum corneum/water PC data reflect the protein domain rather than the lipids. Although uptake into human stratum corneum was relatively insensitive to solute lipophilicity, reflecting the predominant role of proteins in the uptake, permeability coefficients were found to be more sensitive to lipophilicity, suggesting that transport is by a lipid pathway. A log-log plot of kp versus stratum corneum/water PC within the phenol series is linear, but with a slope of 3.6, indicating that kp is not directly proportional to PC. Functional group contributions to the free energy of the transfer process reflected in permeability or partitioning experiments were compared with group contribution data generated previously for the same substituents attached to the chain terminus of 21-esters of hydrocortisone. Within experimental error, a given functional group altered permeability by the same factor in either series of compounds. Group contributions of polar, hydrogen bonding substituents obtained from kp data were similar to those from octanol/water PC data, suggesting that the barrier microenvironment resembles that of a hydrogen bonding organic solvent. Comparison of the kp values of substituted p-cresols with those of hydrocortisone esters having similar lipophilicities also indicated a steep dependence of kp on molecular weight (log kp = constant + psi log PC - n log MW, n = 4.6) similar to the dependence observed in other biomembranes and isolated lipid bilayers.

Chemical Phenomena↗
PubMed1993

Surfactant-induced stratum corneum hydration in vivo: prediction of the irritation potential of anionic surfactants.

After repeated contact, many surfactants will cause skin irritation and, especially, dryness and scaliness. Earlier in vitro investigations suggested that the irritation potential of anionic surfactants was related to the induction of hydration of isolated stratum corneum membranes. We have now investigated early surfactant-stratum corneum interaction in vivo. Sodium salts of n-alkyl sulfates with variable carbon chain length (n = 8-14) were tested for the promotion of stratum corneum hydration by measurements of skin surface water loss and electrical capacitance measurements in healthy adult human volunteers. The surfactant-induced increase in water uptake was confirmed in vitro by means of isolated stratum corneum samples and surfactant solutions labeled with tritiated water. In a parallel experiment the irritation potential of these compounds was investigated by 24-h patch testing in human volunteers. The irritant responses were quantified non-invasively by erythema (skin color reflectance measurements) and transepidermal water loss measurements. Hydration of stratum corneum exposed for 5 min to surfactant solutions significantly exceeded that of controls (phosphate-buffered saline). It increased with application time and was concentration dependent, saturable with increasing concentration, and rapidly reversible. Baseline hydration was re-established only 10-15 min after treatment termination. Induction of hydration was closely correlated with the irritation potential of the investigated compounds. It initially increased with increasing carbon chain length. The maximum response was obtained for the C12 analogue (sodium lauryl sulfate). With further increases in molecular size induction of stratum corneum hydration subsequently decreased. We have demonstrated that anionic surfactants increase stratum corneum hydration in vivo. The present results suggest that the mechanisms responsible for the hydration are related to the irritation properties of these compounds.

Adolescent↗
PubMed1986

Hydration characteristics of pathologic stratum corneum--evaluation of bound water.

We measured in vitro the hygroscopicity and bound (non-freezing) water of various samples of pathologic horny layer obtained from the lesions of senile xerotic skin and psoriasis vulgaris and the normal horny layer from glabrous skin and plantar horny layer. The amount of water taken up by pathologic stratum corneum was much smaller than that by normal horny layer in an environment at a high relative humidity (RH). Tightly bound primary water to stratum corneum measured by Karl Fischer's method was about 5 mg/100 mg of dry stratum corneum in all the samples studied, while less tightly bound secondary water was much smaller in amount in pathologic stratum corneum than in the controls, i.e., 31.7 mg/100 mg dry scale from senile xerosis and 27.2 mg/100 mg dry psoriatic scale as compared with 38.2 mg/100 mg dry normal stratum corneum from glabrous skin and 37.3 mg/100 mg dry normal plantar stratum corneum. We believe that the low hygroscopicity of the pathologic stratum corneum is due to this smaller capacity for secondary bound water, which is responsible for the development of a dry scaly appearance even at high RH.

Adult↗
PubMed1987

Controlled removal of human stratum corneum by pulsed laser.

A new method is presented for controlled removal of the stratum corneum of human skin. An excimer laser (193 nm wavelength, 14 ns pulsewidth) was used to remove stratum corneum from in vitro human skin samples by an ablative process. The tritiated water (3H2O) permeability constant and electrical resistance of skin samples were measured in a diffusion chamber apparatus to quantify the enhancement of skin permeability. Each laser pulse ablates about a micrometer of stratum corneum, which allows controlled removal of tissue. The maximum specific enhancement of the 3H2O permeability constant obtained after complete stratum corneum removal depends on the laser pulse energy used. The most gentle laser ablation, achieved with a radiant exposure of 70 mJ/cm2 per pulse, produced a 124-fold enhancement, which is comparable to that achieved after stratum corneum removal by tape-stripping or removal of epidermis by mild heat treatment. Rapid tissue ablation occurred at higher radiant exposures of 170-480 mJ/cm2 per pulse, but only a 45-fold enhancement of permeability was achieved. The precision with which stratum corneum can be ablated using excimer laser pulses may allow further basic research on the internal structure of stratum corneum and on the re-epithelization in controlled wounds. The technique may prove useful clinically to enhance percutaneous transport in applications such as topical delivery of drugs, patch testing, and percutaneous blood gas monitoring.

Adult↗
PubMed1992

Comparison of lipids from epidermal and palatal stratum corneum.

Stratum corneum has been isolated by tryptic digestion of porcine epidermis and palatal epithelium, and the lipid concentrations and compositions have been compared by thin-layer chromatography in conjunction with photodensitometry. Palatal stratum corneum contained 47 +/- 6 micrograms lipid/mg tissue or 115 +/- 16 micrograms lipid per cm2 of stratum corneum surface, whereas epidermal stratum corneum contained 105 +/- 17 micrograms lipid/mg tissue or 135 +/- 16 micrograms/cm2. The difference in total lipid content does not account for the tenfold higher permeability constant for the permeation of water through the former tissue compared to the latter; therefore, the difference in permeability must be based on differences in lipid composition. In this regard, palatal stratum corneum includes 12.1% phospholipids, although phospholipids were undetected in epidermal stratum corneum. Differences in the content and location of non-polar liquid-phase lipids may also be of significance for permeability. Other factors that may contribute to the greater permeability of the palatal horny layer relative to epidermal stratum corneum include generally lower proportions of cholesterol, fatty acids, and ceramides, a dramatically lower proportion of the linoleate-containing acylceramide, and a tenfold lower content of covalently bound lipids associated with the corneocyte envelope.

Animals↗