Modulation of the skin environment after stratum corneum (SC) perturbation has profound effects on the rate and effectiveness of barrier repair. Intermediate water exposure, e.g. moderate relative humidity, may provide the optimum water gradient for SC repair. More rapid recovery with semipermeable (SP) films in vivo was associated with increased hydration measured as moisture accumulation rate. We hypothesized that (i) damaged SC recovering under the high water exposure of full occlusion (FO) would have lower free amino acids (FAA) than sites with low hydration (no occlusion, NO) and semi-occlusion (SP, semipermeable film, intermediate hydration) and (ii) SC under semi-occlusion would have higher FAA than with low hydration. Volar forearm sites in 15 healthy adults were perturbed via cellophane tape stripping and treated with SP, FO and NO for five days. Barrier recovery rate, hydration, dryness and erythema were determined. Serial SC samples (n=15) were collected on day 5 and FAA quantified using reverse-phase HPLC and fluorescence detection. The cumulative protein removed was higher for SP than the control, NO and FO. FAA as total, individual amino acids and citrulline were consistently higher in the control than the three damaged sites. Generally, FAA was higher in NO than FO. Citrulline was higher for NO than SP and FO over the sampled SC. Levels were higher for SP than FO in certain, but not all of the FAAs. FAA was inversely correlated to barrier integrity. Skin hydration was relatively constant at the external microenvironment of the SP site, whereas the NO and FO had a reduction, i.e. a gradient, over the time. Overall, barrier recovery under conditions of a decreasing hydration gradient produced SC with higher levels of FAA than did conditions of full occlusion.
[Show abstract][Hide abstract] ABSTRACT: Neonatal skin hydration decreases rapidly postnatally and then increases, indicating adaptive changes in stratum corneum water handling properties. Transition from high to low humidity at birth may initiate filaggrin proteolysis to free amino acids. Neonatal skin with vernix caseosa retained is more hydrated than skin with vernix removed. This study examines the potential roles of free amino acids and vernix in postnatal adaptation of infant stratum corneum in vivo. Specifically, the ontogeny of free amino acid generation in neonatal stratum corneum and the role of vernix caseosa in postnatal adaptation were examined using high performance liquid chromatography. Free amino acids were quantified for infant skin samples collected at (i) birth and 1 month and (ii) birth and 24 hours after vernix caseosa retention or removal and compared to neonatal foreskin, vernix caseosa, and adult stratum corneum using t-tests, analysis of variance, or univariate procedures. Free amino acids were extremely low at birth, significantly higher 1 month later but lower than in adults. Vernix caseosa retention led to significantly higher free amino acids 24 hours after birth compared to infants with vernix caseosa removed, and it paralleled the higher stratum corneum hydration of vernix caseosa-retained skin. Vernix caseosa contained free amino acids, with glutamic acid and histidine levels higher than in infants. Free amino acids in vernix caseosa-retained skin appear to originate from vernix caseosa. Free amino acids were lower in neonatal foreskin than adult forearm stratum corneum. Arginine was higher than citrulline at birth, but levels were comparable in older infants. The free amino acid increase at 1 month may be initiated by the humidity transition at birth and supports results in animals. The findings have implications for infant skin care practices.
[Show abstract][Hide abstract] ABSTRACT: Patients with a prosthetic limb report negative skin effects, including irritation, rash and chafing, which can lead to infection, discomfort and reduced wear time to significantly impact normal activities. The aims were to examine the epidermal integrity (transepidermal water loss, TEWL), stratum corneum (SC) hydration [moisture accumulation rate (MAT)], friction and biomechanical properties in active below the knee amputees and to determine the effects of an inert sock liner on skin condition. The liner reduced hydration, TEWL and friction and increased elasticity versus the amputee's conventional skin care methods. Residual limb TEWL was increased and MAT was reduced versus the contralateral normal skin. In a second study, we hypothesized that complete occlusion would decrease free amino acids (FAA) and quantified them by high performance liquid chromatography in an adult volar forearm model. Occlusion with a water vapor impermeable wet dressing led to increased TEWL, erythema and dryness and reduced MAT versus normal skin, comparable to the results in the amputees. The FAA levels were significantly reduced for the occluded sites. The results suggest that residual limb occlusion in amputees may block the formation of FAA in the upper SC. Therapies based on replacement of water binding FAAs, may alleviate the consequences of long-term occlusion.
Archives for Dermatological Research 03/2011; 303(2):117-24. DOI:10.1007/s00403-010-1111-y · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Premature infants lack the vernix caseosa, have an incompetent stratum corneum (SC) barrier and are predisposed to infection. Use of topical agents to improve barrier function has had mixed outcomes. The aim was to determine the effect of vernix versus common barrier creams on the rate and quality of the epidermal barrier repair following controlled wounding.
Minor wounds were created with (1) laser ablation in the minipig and (2) tape stripping of mother's volar skin as a model for premature skin. Native vernix was applied to the mother's tape-stripped skin. Treatments were no occlusion (NO), vernix and a petrolatum-based cream (PBC) in the pig, and NO, vernix, PBC, an oil-in-water cream (OWC), a semipermeable film (SP) and full occlusion (FO) in adults.
Outcomes for both trials were barrier recovery and skin hydration (moisture accumulation rate, MAT), initial hydration, erythema and dryness in adults. Vernix and PBC produced greater barrier repair than NO in the pig. SP produced greater recovery than NO and FO in adults. Vernix yielded greater recovery than FO and was similar to PBC, OWC and NO. Vernix had a directionally higher MAT than OWC and directionally higher initial hydration than NO.
The findings suggest that vernix-based topical creams would be effective for the treatment of epidermal wounds and show promise to augment SC repair and maturation in infants.
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