Understanding age-induced alterations to the biomechanical barrier function of human stratum corneum

Central Nervous System Medications: Pharmacokinetic and Pharmacodynamic Considerations for Older Adults

Most drugs have not been evaluated in the older population. Recognizing physiological alterations associated with changes in drug disposition and with the ultimate effect, especially in central nervous system-acting drugs, is fundamental. While considering pharmacokinetics, it should be noted that the absorption of most drugs from the gastrointestinal tract does not change in advanced age. There are only few data about the effect of age on the transdermal absorption of medications such as fentanyl. Absorption from an intramuscular injection may be similar in older adults as in younger patients. The distribution of lipophilic drugs (such as diazepam) is increased owing to a relative increase in the percentage of body fat, causing drug accumulation and prolonged drug elimination following cessation. Phase I drug biotransformation is variably decreased in aging, impacting elimination, and hepatic drug clearance has been shown to decrease in older individuals by 10-40% for most drugs studied. Lower doses of phenothiazines, butyrophenones, atypical antipsychotics, antidepressants (citalopram, mirtazapine, and tricyclic antidepressants), and benzodiazepines (such as diazepam) achieve the same extent of exposure. For renally cleared drugs with no prior metabolism (such as gabapentin), the glomerular filtration rate appropriately estimates drug clearance. Important pharmacodynamic changes in older adults include an increased sedative effect of benzodiazepines at a given drug exposure, and a higher sensitivity to mu opiate receptor agonists and to opioid adverse effects. Artificial intelligence, physiologically based pharmacokinetic modeling and simulation, and concentration-effect modeling enabling a differentiation between the pharmacokinetic and the pharmacodynamic effects of aging might help to close some of the gaps in knowledge.

Considerations for managing elderly patients with atopic dermatitis

INTRODUCTION

Atopic dermatitis (AD) diagnosis in elderly is challenging, due to its clinical polymorphism and the lack of diagnostic biomarkers. Moreover, the chronicity of the disease and the complex pathogenetic mechanism, make elderly AD management challenging.

AREAS COVERED

A narrative review of the current literature was performed using the PubMed, Medline, Embase, and Cochrane Skin databases, by researching the following terms: 'atopic dermatitis,' 'clinical phenotypes,' 'eczema,' 'elderly patients,' 'elderly type atopic dermatitis,' 'eczema clinical presentation.' The aim was to report the current knowledge on pathogenesis, clinical presentation, and treatment options of elderly AD.

EXPERT OPINION

Elderly type AD has recently been identified as a separate entity, with an increasing prevalence. With aging, both immunosenescence and barrier alterations can cause or modify AD presentation. Moreover, a chronic proinflammatory state (so-called 'inflammaging') is often present in elderly subjects. Older patients with AD may present with peculiar immunophenotypic profile, making AD diagnosis challenging. Similarly, the chronicity of the disease and the complex pathogenetic mechanism, make AD management a challenge. Indeed, systemic therapies for AD are often contraindicated or not tolerated and the management of elderly type AD is often burdened with numerous difficulties, leading to undertreated disease. Even if dupilumab and tralokinumab represent a valuable therapeutic weapon, more data on safety of JAK inhibitors are required.

Characterisation of topographical, biomechanical and maturation properties of corneocytes with respect to anatomical location

BACKGROUND

The Stratum Corneum (SC) is the first barrier of the skin. The properties of individual cells are crucial in understanding how the SC at different anatomical regions maintains a healthy mechanical barrier. The aim of the current study is to present a comprehensive description of the maturation and mechanical properties of superficial corneocytes at different anatomical sites in the nominal dry state.

MATERIALS AND METHODS

Corneocytes were collected from five anatomical sites: forearm, cheek, neck, sacrum and medial heel of 10 healthy young participants. The surface topography was analysed using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The level of positive-involucrin cornified envelopes (CEs) and desmoglein-1 (Dsg1) were used as indirect measures of immature CEs and corneodesmosomes, respectively. In addition, AFM nanoindentation and stress-relaxation experiments were performed to characterise the mechanical properties.

RESULTS

Volar forearm, neck and sacrum corneocytes presented similar topographies (ridges and valleys) and levels of Dsg1 (13-37%). In contrast, cheek cells exhibited circular nano-objects, while medial heel cells were characterized by villi-like structures. Additionally, medial heel samples also showed the greatest level of immature CEs (32-56%, p < 0.001) and Dsg1 (59-78%, p < 0.001). A large degree of inter-subject variability was found for the Young's moduli of the cells (0.19-2.03 GPa), which was correlated with the level of immature CEs at the cheek, neck and sacrum (p < 0.05).

CONCLUSION

It is concluded that a comprehensive study of the mechanical and maturation properties of corneocytes may be used to understand the barrier functions of the SC at different anatomical sites.

Characterisation of superficial corneocyte properties over category I pressure ulcers: Insights into topographical and maturation changes

BACKGROUND

Pressure ulcers (PUs) are chronic wounds that are detrimental to the quality of life of patients. Despite advances in monitoring skin changes, the structure and function of skin cells over the site of pressure ulcers are not fully understood.

OBJECTIVE

The present study aims to evaluate local changes in the properties of superficial corneocytes in category 1 PU sites sampled from a cohort of hospitalised patients.

METHODS

Cells were collected from a PU-compromised site and an adjacent control area and their topographical, maturation and mechanical properties were analysed.

RESULTS

Corneocytes at the PU-compromised site were characterised by higher levels of immature cornified envelopes (p < 0.001) and greater amounts of desmoglein-1 (corneodesmosomal protein) (p < 0.001) compared to the adjacent control area. The cells at the control site presented the typical ridges-and-valleys topographical features of sacrum corneocytes. By contrast, the PU cells presented circular nano-objects at the cell surface, and, for some patients, the cell topography was deformed. CEs at the PU site were also smaller than at the control site. Although differences were not observed in the mechanical properties of the cells, those of the elderly patients were much softer compared with young subjects.

CONCLUSION

This is the first study investigating the changes in corneocyte properties in category I pressure ulcers. Superficial cells at the PU sites showed altered topographical and maturation characteristics. Further studies are required to elucidate if these changes are a consequence of early loss of skin integrity or a result of mechanical and microclimate insults to the skin surface.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

Sensory neuron activation from topical treatments modulates the sensorial perception of human skin

Neural signaling of skin sensory perception from topical treatments is often reported in subjective terms such as a sensation of skin "tightness" after using a cleanser or "softness" after applying a moisturizer. However, the mechanism whereby cutaneous mechanoreceptors and corresponding sensory neurons are activated giving rise to these perceptions has not been established. Here, we provide a quantitative approach that couples in vitro biomechanical testing and detailed computational neural stimulation modeling along with a comprehensive in vivo self-assessment survey to demonstrate how cutaneous biomechanical changes in response to treatments are involved in the sensorial perception of the human skin. Strong correlations are identified between reported perception up to 12 hours post treatment and changes in the computed neural stimulation from mechanoreceptors residing deep under the skin surface. The study reveals a quantitative framework for understanding the biomechanical neural activation mechanism and the subjective perception by individuals.

Combined Bipolar Radiofrequency and Non-Crosslinked Hyaluronic Acid Mesotherapy Protocol to Improve Skin Appearance and Epidermal Barrier Function: A Pilot Study

BACKGROUND

Age-associated changes in epidermal hydration, pigmentation, thickness and cell renewal influence skin appearance and can lead to laxity, dryness and poor skin tone. The aim of this pilot study was to assess the synergistic effects of a new bipolar radiofrequency plus non-crosslinked hyaluronic acid (HA) mesotherapy protocol compared with radiofrequency alone on skin appearance and markers of epidermal function.

METHODS

This prospective, single-center, split-face pilot study recruited women aged 25-65 years with dryness and laxity of the facial skin defined by a trans-epidermal water loss (TEWL) value of ≥26 g/m2/h. Subjects were treated with a bipolar radiofrequency device on both sides of the face. This was immediately followed by needle hyaluronic acid (HA) treatment on one side of the face with 2.5 mL of a non-crosslinked HA. Photographic documentation, analysis of epidermal barrier function parameters, and high frequency (HF) ultrasound analysis were performed prior to treatment and at 28 days.

RESULTS

Twenty female subjects with a mean age of 46 (range 29 to 54) years and dry and lax facial skin were included. TEWL was reduced and skin hydration improved to a greater extent with the combined radiofrequency plus mesotherapy protocol compared with radiofrequency alone (-5.8% vs. +3.9% and +23.1% vs. +1.0%, respectively). The combined protocol was also associated with greater improvements in melanin (-7.5% vs. -1.5%) and erythema values (-7.2% vs. +3.0%), respectively. Ultrasound measures of epidermal thickness and epidermal density were greater after the combined protocol compared with radiofrequency alone (12.0% vs. 5.6% and 57.7% vs. 7.1%, respectively). Both treatments were well-tolerated.

CONCLUSIONS

The combined bipolar radiofrequency and HA mesotherapy protocol provided greater improvements in skin hydration, firmness and tone compared with radiofrequency alone. The combination treatment was also associated with greater epidermal thickness and density and increased keratinocyte differentiation suggesting a synergistic effect of both treatments on epidermal homeostasis and barrier function. Both treatments were well-tolerated and led to improvements in facial appearance.

Dapsone-Loaded Mixed Micellar Gel for Treatment OF Acne Vulgaris

Mixed polymeric micelles are potential nanocarriers for topical drug delivery. Dapsone (DAP) is an antibacterial used as anti-acne agent, but challenged by low water solubility and poor skin permeability. In the present study, DAP-loaded mixed micellar gel was developed comprising Pluronics F-68 and F-127. Micelles were prepared by solvent evaporation method and particle size, ex vivo permeation, drug loading, and entrapment efficiency were determined. Central Composite Design was used to optimize formulation. Independent variables were concentration of Pluronics at three levels while micelle size and drug loading capacities were dependent variables. Droplet size ranged from 400 to 500 nm. Transmission electron microscopy revealed spherical morphology of micelles. Optimized micelles were incorporated into gel base using HPMC K100M, Sodium CMC, and Carbopol 980 as gelling agents. Gels were evaluated for pH, drug content, spreadability, rheology, syneresis, ex vivo permeation, and subacute dermal toxicity. Compared with solubility of free DAP (0.24+0.056 µg/ml), solubility in mixed micelles was 18.42±3.4 µg/ml in water at room temperature. Order of spreadability of gels was Na CMC < HPMC < Carbopol 980. Carbopol gels displayed thixotropy with index of 3.17. Syneresis for all gels from day 0 to day 30 was found to be in range of 4.2 to 15.6% w/w. Subacute dermal toxicity studies showed no signs of erythema and edema on rat skin until 21 days. These results suggest that mixed micelles can significantly increase solubility and permeability and sustain release of DAP and are suitable carriers for topical DAP delivery in anti-acne therapies.

Lipid Differences and Related Metabolism Present on the Hand Skin Surface of Different-Aged Asiatic Females-An Untargeted Metabolomics Study

This cross-sectional study aimed to investigate differences in skin surface lipids (SSL) and explore related metabolic pathways among females of different ages in Henan Province. Ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was used to determine the lipid composition of the skin surface of 58 female volunteers who were divided into three age groups. Statistical analysis was performed using Progenesis QI, Ezinfo, and MetaboAnalyst. Multivariate and enrichment analysis were used to identify the different SSL among the groups. A total of 530 lipid entities were identified and classified into eight classes. Among these, 63 lipids were significantly different between the groups. Lower levels of glycerolipids (GLs) and sphingolipids (SPs) were observed in the middle-aged group, while higher levels of GLs were found in the elder group. GLs belonged to the largest and statistically significant enrichment of lipid metabolic pathways, and the lipid individuals enriched to the sphingoid bases metabolism were the most and statistically significant. These findings suggest that there are differences in hand SSL among females of different ages, which may be related to GLs and sphingoid bases metabolism.

How do cells stiffen?

Cell stiffness is an important characteristic of cells and their response to external stimuli. In this review, we survey methods used to measure cell stiffness, summarize stimuli that alter cell stiffness, and discuss signaling pathways and mechanisms that control cell stiffness. Several pathological states are characterized by changes in cell stiffness, suggesting this property can serve as a potential diagnostic marker or therapeutic target. Therefore, we consider the effect of cell stiffness on signaling and growth processes required for homeostasis and dysfunction in healthy and pathological states. Specifically, the composition and structure of the cell membrane and cytoskeleton are major determinants of cell stiffness, and studies have identified signaling pathways that affect cytoskeletal dynamics both directly and by altered gene expression. We present the results of studies interrogating the effects of biophysical and biochemical stimuli on the cytoskeleton and other cellular components and how these factors determine the stiffness of both individual cells and multicellular structures. Overall, these studies represent an intersection of the fields of polymer physics, protein biochemistry, and mechanics, and identify specific mechanisms involved in mediating cell stiffness that can serve as therapeutic targets.

Human skin through the ages

As the largest organ of the human body the skin offers a protective role, providing a tough but pliable covering that provides the major barrier between the internal organs and the environment. It actively regulates water loss and is both oxygen and carbon dioxide permeable, and influences temperature regulation and immunological functions through its sensory properties. Both intrinsic and enhanced environmental factors contribute to the progressive deterioration of the skin with increasing age. Cutaneous problems are therefore an unavoidable and inevitable consequence of aging skin, which can prove to be both cosmetically unacceptable to those who succumb to these problems, as well as even life threatening if skin breakdown becomes chronic as is case with leg ulceration. This in turn has major implications for long-term impact on those looking after them (e.g., family, carers, etc.) and a huge burden on the health care system.

Polymeric Micelles: A Promising Pathway for Dermal Drug Delivery

Nanotechnology is an area in great development and with application in the most varied fields of science, including cosmetic and pharmaceutical industries. Because conventional formulations for topical application are not always able to effectively penetrate the physical barrier that human skin exerts against factors and compounds of the external environment, polymeric micelles appear as alternative carriers for drugs and active ingredients delivery, also allowing ingredients with lower solubility and higher lipophilicity to be delivered. In fact, the augmented bioavailability of drugs, greater efficacy even at a lower dose, and selective drug delivery in specific organelles are very interesting advantages of the polymeric micelles usage in cutaneous application. As a consequence, they show a reduction in many of the local and systemic adverse effects, which might lead to an increase in patient compliance to the therapeutics, constituting a promising alternative to conventional topical formulations.

Structural and Functional Changes and Possible Molecular Mechanisms in Aged Skin

Skin aging is a complex process influenced by intrinsic and extrinsic factors. Together, these factors affect the structure and function of the epidermis and dermis. Histologically, aging skin typically shows epidermal atrophy due to decreased cell numbers. The dermis of aged skin shows decreased numbers of mast cells and fibroblasts. Fibroblast senescence contributes to skin aging by secreting a senescence-associated secretory phenotype, which decreases proliferation by impairing the release of essential growth factors and enhancing degradation of the extracellular matrix through activation of matrix metalloproteinases (MMPs). Several molecular mechanisms affect skin aging including telomere shortening, oxidative stress and MMP, cytokines, autophagic control, microRNAs, and the microbiome. Accumulating evidence on the molecular mechanisms of skin aging has provided clinicians with a wide range of therapeutic targets for treating aging skin.

Ectoine disperses keratin and alters hydration kinetics in stratum corneum

Moisturizing compounds are commonly applied topically to human stratum corneum (SC). Many types of molecular species are employed, most commonly including humectants and occlusives. We find new evidence of keratin dispersion caused by the moisturizing compound ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid), and provide the first characterization of its impacts on the hydration kinetics and biomechanics of SC. A second compound, 2-(2-hydroxyethoxy)ethylguanidine succinate (HEG) was investigated for comparison. A suite of biomechanical and biochemical assays including FTIR, drying stress, and cellular cohesion were used. Studies were conducted on normal, lipid-extracted, and lipid plus natural moisturizing factor extracted SC. Ectoine was found to improve the dispersity and hydration of keratin bundles in corneocytes. It also decreased rates of stress development in lipid extracted SC when exposed to a dry environment by ∼30% while improving stress reduction during rehydration by ∼20%. Peak stresses were increased in harsh drying environments of <5% RH, but SC swelling measurements suggest that water retention was improved in ambient conditions. Further, changes up to ∼4 J/m² were seen in cohesion after ectoine treatments, suggesting corneodesmosome interactions. HEG was tested and found to disperse keratin without impacting corneodesmosomes. These results indicate that keratin dispersants produce beneficial effects on SC hydration kinetics, ultimately resulting in higher SC hydration under ambient conditions.

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First study demonstrating the biomechanical impact of keratin dispersion on human skin

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Ectoine disperses keratin bundles in human stratum corneum

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Rates of drying stress development are reduced in keratin-dispersed skin

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Rehydration rates are increased in keratin-dispersed skin

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Keratin dispersion alters corneocyte cohesion profiles

The precision of macroscale mechanical measurements is limited by the inherent structural heterogeneity of human stratum corneum

Biological tissues are structurally heterogenous mosaics at cellular and sub-cellular length scales. Some tissues, like the outermost layer of human skin, or stratum corneum (SC), also exhibit a rich topography of microchannels at larger mesoscopic length scales. Although this is well understood, modern studies continue to characterize the mechanical properties of biological tissues, including the SC, using macroscale techniques that assume these materials are homogenous in structure, thickness, and composition. Macroscale failure testing of SC is commonly associated with large sample to sample variability. We anticipate that microscale heterogeneities play an important role in defining the global mechanical response of the tissue. To evaluate the validity of the prevailing paradigm that macroscopic testing techniques can provide meaningful information about failure in soft heterogenous tissues, the macroscale work of fracture in isolated human SC samples is measured using conventional macroscale testing techniques and compared with the energy cost of creating new crack interfaces at the microscale, measured using a modified traction force microscopy technique. Results show that measured micro- and macroscale energy costs per unit crack path length are highly consistent. However, crack propagation is found to be guided by microscale topographical features in the tissue. This correlation reveals that macroscale mechanical sample to sample variability is caused by notable differences in crack propagation pathways. STATEMENT OF SIGNIFICANCE: Although designed to test homogeneous materials, macroscopic uniaxial tensometry is currently the gold standard for measuring the mechanical properties of biological tissues. All tissues, including human stratum corneum are structurally heterogeneous at the microscale and mechanical measurements are commonly highly variable, even for specimens from the same source. This study explores the fundamental causes of this disparity and evaluates the prevailing paradigm that macroscopic testing techniques can provide meaningful information about failure in soft heterogeneous tissues. Results conclude that the cause of large variability in mechanical work of fracture is due to inherent structural heterogeneities governing crack propagation pathways and altering the total crack length. Structural heterogeneities in tissue therefore limits the precision of macroscale biomechanical testing.

Increased Expression of 11β-Hydroxysteroid Dehydrogenase Type 1 Contributes to Epidermal Permeability Barrier Dysfunction in Aged Skin

Inactive cortisone is converted into active cortisol by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Excessive levels of active glucocorticoids could deteriorate skin barrier function; barrier impairment is also observed in aged skin. In this study, we aimed to determine whether permeability barrier impairment in the aged skin could be related to increased 11β-HSD1 expression. Aged humans (n = 10) showed increased cortisol in the stratum corneum (SC) and oral epithelium, compared to young subjects (n = 10). 11β-HSD1 expression (as assessed via immunohistochemical staining) was higher in the aged murine skin. Aged hairless mice (56-week-old, n = 5) manifested greater transepidermal water loss, lower SC hydration, and higher levels of serum inflammatory cytokines than the young mice (8-week-old, n = 5). Aged 11β-HSD1 knockout mice (n = 11), 11β-HSD1 inhibitor (INHI)-treated aged wild type (WT) mice (n = 5) and young WT mice (n = 10) exhibited reduced SC corticosterone level. Corneodesmosome density was low in WT aged mice (n = 5), but high in aged 11β-HSD1 knockout and aged INHI-treated WT mice. Aged mice exhibited lower SC lipid levels; this effect was reversed by INHI treatment. Therefore, upregulation of 11β-HSD1 in the aged skin increases the active-glucocorticoid levels; this suppresses SC lipid biosynthesis, leading to impaired epidermal permeability barrier.

Relating transdermal delivery plasma pharmacokinetics with in vitro permeation test (IVPT) findings using diffusion and compartment-in-series models

Increasing emphasis is being placed on using in vitro permeation test (IVPT) results for topical products as a surrogate for their in vivo behaviour. This study sought to relate in vivo plasma concentration - time pharmacokinetic (PK) profiles after topical application of drug products to IVPT findings with mechanistic diffusion and compartment models that are now widely used to describe permeation of solutes across the main skin transport barrier, the stratum corneum. Novel in vivo forms of the diffusion and compartment-in-series models were developed by combining their IVPT model forms with appropriate in vivo disposition functions. Available in vivo and IVPT data were then used with the models in data analyses, including the estimation of prediction intervals for in vivo plasma concentrations derived from IVPT data. The resulting predicted in vivo plasma concentration - time profiles for the full models corresponded closely with the observed results for both nitroglycerin and rivastigmine at all times. In contrast, reduced forms of these in vivo models led to discrepancies between model predictions and observed results at early times. A two-stage deconvolution procedure was also used to estimate the in vivo cumulative amount absorbed and shown to be linearly related to that from IVPT, with an acceptable prediction error. External predictability was also shown using a separate set of in vitro and in vivo data for different nitroglycerin patches. This work suggests that mechanistic and physiologically based pharmacokinetic models can be used to predict in vivo behaviour from IVPT data for topical products.

The diversity of shedder tests and a novel factor that affects DNA transfer

Since the first shedder test was formulated almost 20 years ago, a plethora of different test strategies has emerged. The amount of data generated so far is considerable. However, because of the limited reproducibility of its results, the reliability of the shedder concept is frequently questioned. This study provides a literature overview of applied shedder tests that capture the diversity of the concept. It is pointed out to what extent different classification criteria, workflows, and trace evaluation can impair the classification outcome. The robustness of shedder status was assessed by applying a promising approach established by Fonneløp et al. (Forensic Sci Int Genet 29:48-60, 21). Data provide similar results to those in recent studies but also ambiguous shedder classifications. The applied shedder test was adapted based on our own as well as the reviewed data. With novel classification parameters, promising results were achieved. This study reveals uncertainties and inconsistencies of the shedder concept. Recommendations for harmonization and transparency are proposed. Implementation of the recommendations may result in an increased impact on casework and transfer studies, including activity-level assessments. Furthermore, this study shows that moisturizers affect participants' shedder status as well as DNA transfer. The impact appears to remain relevant even 60 min post ointment application but depends greatly on the type of moisturizer applied.

Optimal configuration of confocal Raman spectroscopy for precisely determining stratum corneum thickness: Evaluation of the effects of polyoxyethylene stearyl ethers on skin

Properties regarding stratum corneum (SC), the outermost membrane of the skin, remain an active area in dermatologic and cosmetic research. The reduced thickness of SC is associated with varied adverse statuses such as skin lipid deficiency, skin barrier dysfunctions and skin deceases, etc. Emulsifiers with existing irritative effects on skin components also face the risk of decreasing SC thickness. We have been focusing on the effects of PEGylated emulsifiers on the skin and have an interest in finding the role of their polyethylene glycol (PEG)-chain length in tuning skin irritations. With this aim, PEG-stearyl ethers with different numbers of hydrophilic chains were applied on the skin, and their influence on skin thickness was discovered to determine their skin barrier effect. Confocal Raman spectroscopy (CRS) with extensive application in skin research was used here. To obtain the precise determination of skin thickness, our secondary aim was to find the optimal CRS configuration referring to varied objectives and pinhole sizes where further study is still in demand. Therefore, SC thickness measured via eddy current approach served as reference. The applied PEG-stearyl ethers formed the system to achieve varied thicknesses. Results confirmed that the skin interactions rose with increasing PEG-chain length, however only up to a certain limit, with decreasing effects recorded from PEG-40 stearyl ether and no effects observed from PEG-100 stearyl ether. Simultaneously, CRS combined with water immersion objective and 50 μm pinhole presented the most consistent values to the references and exhibited better spectral intensity and signal-to-noise ratio. Correlation plots involving different cases of configurations were calculated for error corrections. Taken together, this work helps to identify the potential mechanisms governing the interactions between PEG-stearyl ethers and skin and offers powerful evidence of using CRS as a reliable alternative to obtain accurate thickness values.

Regulation of Cell Polarity and Tissue Architecture in Epidermal Aging and Cancer

The mammalian skin is essential to protect the organism from external damage while at the same time enabling communication with the environment. Aging compromises skin function and regeneration, which is further exacerbated by external influences, such as UVR from the sun. Aging and UVR are also major risk factors contributing to the development of skin cancer. Whereas aging research traditionally has focused on the role of DNA damage and metabolic and stress pathways, less is known about how aging affects tissue architecture and cell dynamics in skin homeostasis and regeneration and whether changes in these processes promote skin cancer. This review highlights how key regulators of cell polarity and adhesion affect epidermal mechanics, tissue architecture, and stem cell dynamics in skin aging and cancer.

Autophagy Declines with Premature Skin Aging resulting in Dynamic Alterations in Skin Pigmentation and Epidermal Differentiation

Autophagy is a membrane traffic system that provides sustainable degradation of cellular components for homeostasis, and is thus considered to promote health and longevity, though its activity declines with aging. The present findings show deterioration of autophagy in association with premature skin aging. Autophagy flux was successfully determined in skin tissues, which demonstrated significantly decreased autophagy in hyperpigmented skin such as that seen in senile lentigo. Furthermore, an exacerbated decline in autophagy was confirmed in xerotic hyperpigmentation areas, accompanied by severe dehydration and a barrier defect, which showed correlations with skin physiological conditions. The enhancement of autophagy in skin ex vivo ameliorated skin integrity, including pigmentation and epidermal differentiation. The present results indicate that the restoration of autophagy can contribute to improving premature skin aging by various intrinsic and extrinsic factors via the normalization of protein homeostasis.

Impact of physiologically relevant temperatures on dermal absorption of active substances - an ex-vivo study in human skin

Skin temperature plays a certain role in the dermal absorption of substances, but the extent and mechanisms of skin temperatures-induced modulation in ranges caused by physiological thermoregulation or environmental conditions are largely unknown. The influence of dermal temperature on the absorption of the model lipophilic compound (anisole) and the model hydrophilic compounds (1,4-dioxane, ethanol) through human skin was investigated at three dermal temperatures (25, 32 and 39 °C) in an ex-vivo diffusion cell model. The substances were applied to the skin and transdermal penetration was monitored. All substances showed temperature dependent variations in their penetration behavior (3 h: 25-39 °C: 202-275% increase in cumulative, transdermally penetrated amounts). The relative differences in absorption in relation to temperature were greatest within 45 min after exposure (25-39 °C: 347-653% rise in cumulated penetration), although absolute amounts absorbed were small (45 min vs. 3 h: 4.5-14.5%). Regardless of blood circulation, skin temperature significantly influences the amount and kinetics of dermal absorption. Substance-dependent, temperature-related changes of the lipid layer order or the porous pathway may facilitate penetration. The early-stage modulation of transdermal penetration indicates transappendageal absorption, which may be relevant for short-term exposures. For both, toxicological evaluation and perfusion cell studies, it is important to consider the thermal influence on absorption or to perform the latter at a standardized temperature (32±1 °C).

The Pathobiology of Skin Aging: New Insights into an Old Dilemma

Long considered both physiologic and inevitable, skin aging is a degenerative phenomenon whereby both intrinsic and environmental factors conspire to produce an authentic disease. The consequences of this disorder are many and varied, ranging from atrophy and fragility to defective repair to deficient immunity and vulnerability to certain infections. The pathobiologic basis for skin aging remains poorly understood. At a cellular level, stem cell dysfunction and attrition appear to be key events, and both genetic and epigenetic factors are involved in a complex interplay that over time results in deterioration of our main protective interface with the external environment. Past and current understanding of the cellular and molecular intricacies of skin aging provide a foundation for future approaches designed to thwart the aging phenotype. Herein, the authors provide a review of current insights into skin aging, including the mechanisms of skin aging, the role of stem cells in skin aging and the implications of skin aging for the microbiome and for the development of cancer. Conquest of the oft overlooked disease of skin aging should have broad implications that transcend the integument and inform novel approaches to retarding aging and age-related dysfunction in those internal organs that youthful skin was designed to envelop and safeguard.

A Survey of Turkish Nurses' Knowledge of Incontinence-Associated Dermatitis

PURPOSE

The purpose of this study was to determine the knowledge of incontinence-associated dermatitis (IAD) among nurses working in intensive care units.

DESIGN

Descriptive study.

SUBJECTS AND SETTING

The study was conducted in 6 intensive care units of a 550-bed academic research hospital in Turkey. Licensed practical and registered nurses with a minimum of a Bachelor of Science in Nursing degree employed full-time on these units were invited to participate.

METHODS

The survey consisted of statements that examined the demographic characteristics (14 questions) and knowledge levels (59 statements) of the nurses. For each statement, nurses were required to mark only one of the following options: "correct," "incorrect," or "no knowledge." Data were collected from July to September 2016. The Shapiro-Wilk test, Mann-Whitney U test, Kruskal-Wallis H test, post hoc multiple comparison test, and Spearman's correlation coefficient were used to analyze the data.

RESULTS

Of the 126 RNs who participated in the study, 46.83% (n = 59) had an undergraduate degree in nursing. The majority (29.37%) practiced in gastroenterology surgery and urology intensive care units. The mean knowledge score was 33.05 ± 10.16 (min = 0, max = 59). The most correctly answered statement (94.44%; n = 119) was "The pH of the skin plays a role in skin barrier function." The statement with the most incorrect or "no knowledge" answers (96.03%; n = 120) was "The natural moisturizing factor found in the structure of corneocytes helps the skin to maintain its oil levels." Based on correctly answered statements, we found knowledge levels of the prevention and treatment of IAD were higher among nurses with a master of science degree in nursing (40.67 ± 4.32) and lower among licensed practical nursing (29.12 ± 10.08) (P < .05).

CONCLUSION

In this study, knowledge of the nurses on identification, prevention, and treatment of IAD was low. Comprehensive basic nursing education and in-service training programs on IAD are recommended.

Atopic dermatitis in the elderly: a review of clinical and pathophysiological hallmarks

BACKGROUND

Atopic dermatitis (AD) is a multifactorial and complex disease, characterized by an impaired skin barrier function and abnormal immune response. Many elderly patients present with pruritus and xerosis to dermatology, allergy and primary care clinics, and there is a lack of information available to clinicians regarding the proper diagnosis and management of these patients. Although the elderly are described as having a distinct presentation of AD and important comorbidities, most investigations and clinical care guidelines pertaining to AD do not include patients aged 60 years and older as a separate group from younger adults.

OBJECTIVES

To summarize current information on pathophysiology, diagnosis and management of AD in the elderly population and identify areas of insufficient information to be explored in future investigations.

METHODS

We carried out a systematic review of published literature, which assessed changes in the skin barrier and immune function with ageing and current information available for physicians to use in the diagnosis and treatment of AD in elderly patients.

RESULTS

Many age-related changes overlap with key hallmarks observed in AD, most notably a decline in skin barrier function, dysregulation of the innate immune system, and skewing of adaptive immunity to a type-2 T helper cell response, in addition to increased Staphylococcus aureus infection.

CONCLUSIONS

While general physiological alterations with ageing overlap with key features of AD, a research gap exists regarding specific ageing-related changes in AD disease development. More knowledge about AD in the elderly is needed to establish firm diagnostic and treatment methodologies. What's already known about this topic? Atopic dermatitis (AD) is a common inflammatory skin disease that causes significant burden worldwide. Recently, elderly patients have been considered a subgroup of patients with distinct AD manifestation. Limited studies have characterized the clinical presentation and role of IgE-mediated allergy in elderly patients with AD. What does this study add? This review offers a summary of age-related skin and immune alterations that correspond to pathogenic changes noted in patients with AD. The role of itch, environmental factors and skin microbiota in AD disease presentation in ageing patients is explored.

Brillouin Spectroscopy of Normal and Keratoconus Corneas

PURPOSE

To investigate the age dependence of Brillouin spectroscopy of the cornea and to compare normal and keratoconus corneas.

DESIGN

Retrospective case-control study.

METHODS

Study Population: Healthy patients and patients suffering from keratoconus seen at the Institut für Refraktive und Ophthalmo-Chirurgie (IROC) between December 2016 and March 2017. Brillouin frequency shifts of patients of 2 different groups were examined with Brillouin spectroscopy perpendicular to the corneal surface. Group 1 consisted of 47 healthy eyes, whereas Group 2 included 36 eyes with keratoconus of unclear progression. Besides Brillouin examinations, corneal tomographies were acquired so that correlations and comparisons between geometric parameters and Brillouin frequency shifts could be evaluated.

MAIN OUTCOME MEASURES

Corneal Brillouin frequency shifts averaged over full corneal thickness.

RESULTS

A significant correlation between age and central Brillouin frequency shift was identified (P = .011) with an increase in Brillouin frequency shift of 4 MHz per decade in normal corneas. Keratoconus corneas have a significantly reduced Brillouin frequency shift at the thinnest point compared to normal corneas (5.7072 ± 0.0214 vs 5.7236 ± 0.0146 GHz, P < .001). The Brillouin frequency shift at the point of maximum posterior elevation showed best correlation with geometry-derived keratoconus indices. The receiver operating characteristic curve analysis of Brillouin frequency shift showed substantially worse sensitivity and specificity compared to K_max and thinnest pachymetry for keratoconus detection.

CONCLUSION

Noninvasive Brillouin spectroscopy adds clinical information about the biomechanical state of the cornea perpendicular to the surface. An age-dependent stiffening of the cornea has been found and keratoconus corneas are statistically significantly different from normal corneas, but for precise differentiating of keratoconus stages (including normal corneas) the method is currently neither specific nor sensitive enough. Further development including standardized mapping and establishment of new indices may increase the potential of Brillouin spectroscopy substantially.

Xerosis cutis and associated co-factors in women with prurigo nodularis

BACKGROUND

Current data regarding the associated factors of prurigo nodularis are still uncertain, except for atopic predisposition.

OBJECTIVES

The purposes of this study were to (1) determine the frequencies of xerosis and other accompanying diseases of female patients with prurigo nodularis; (2) compare the demographic, clinical and accompanying disease characteristics by grouping these patients according to whether they have associated xerosis (who were subsequently subgrouped as atopic or non-atopic) or not.

METHODS

In this retrospective descriptive study, 80 females with PN were categorized according to the accompanying diseases (dermatological, systemic, neurological, psychogenic, mixed, or undetermined origin).

RESULTS

A total of 45 associated co-factors including dermatological in 63 (78.8%), systemic in 57 (71.3%), psychological in 33 (41.3%) and neurological co-factors in 14 (17.5%) of all patients with prurigo nodularis were detected. Xerosis was observed in 48 (60%) patients (non-atopic co-factors in 66.7% of them). The ratio of patients with mixed co-factors, dermatological+systemic co-factors and dermatological+systemic+psychological co-factors were found to be significantly higher in patients with xerosis compared to those without xerosis.

STUDY LIMITATIONS

Our study has certain limitations such as the absence of an age-matched control group, absence of follow-up data and the fact that the diagnosis of xerosis has not been based on objective methods.

CONCLUSIONS

Xerosis has been identified in more than half of the patients with PN and it has been determined that in most patients xerosis is associated especially with diabetes mellitus and other conditions related to prurigo nodularis.

Skin barrier and dry skin in the mature patient

Dry skin is the most common clinical manifestation of dermatologic diseases, and it presents with itching, redness, and desquamation-signs and clinical manifestations that are not only physically uncomfortable but also affect patients psychologically. The water content in the stratum corneum is largely dependent on the composition and amount of the intercellular lipids, which regulate the loss of water from the skin, and on the levels of hygroscopic substances of the natural moisturizing factors, which are responsible for retention of water in the stratum corneum. Prevention of water loss and penetration of potentially toxic substances and microorganisms into the body are the most important functions of the skin, which acts as a natural frontier between the inner organism and the environment. Skin barrier defects occur in several skin diseases, but the influence of aging on the skin barrier function is largely unknown and conflicting results have been reported. In this review, the structure and function of the barrier in relation to the aging process are discussed.

The global mechanical properties and multi-scale failure mechanics of heterogeneous human stratum corneum

The outermost layer of skin, or stratum corneum, regulates water loss and protects underlying living tissue from environmental pathogens and insults. With cracking, chapping or the formation of exudative lesions, this functionality is lost. While stratum corneum exhibits well defined global mechanical properties, macroscopic mechanical testing techniques used to measure them ignore the structural heterogeneity of the tissue and cannot provide any mechanistic insight into tissue fracture. As such, a mechanistic understanding of failure in this soft tissue is lacking. This insight is critical to predicting fracture risk associated with age or disease. In this study, we first quantify previously unreported global mechanical properties of isolated stratum corneum including the Poisson's ratio and mechanical toughness. African American breast stratum corneum is used for all assessments. We show these parameters are highly dependent on the ambient humidity to which samples are equilibrated. A multi-scale investigation assessing the influence of structural heterogeneities on the microscale nucleation and propagation of cracks is then performed. At the mesoscale, spatially resolved equivalent strain fields within uniaxially stretched stratum corneum samples exhibit a striking heterogeneity, with localized peaks correlating closely with crack nucleation sites. Subsequent crack propagation pathways follow inherent topographical features in the tissue and lengthen with increased tissue hydration. At the microscale, intact corneocytes and polygonal shaped voids at crack interfaces highlight that cracks propagate in superficial cell layers primarily along intercellular junctions. Cellular fracture does occur however, but is uncommon.

STATEMENT OF SIGNIFICANCE

Human stratum corneum protects the body against harmful environmental pathogens and insults. Upon mechanical failure, this barrier function is lost. Previous studies characterizing the mechanics of stratum corneum have used macroscopic testing equipment designed for homogenous materials. Such measurements ignore the tissue's rich topography and heterogeneous structure, and cannot describe the underlying mechanistic process of tissue failure. For the first time, we establish a mechanistic insight into the failure mechanics of soft heterogeneous tissues by investigating how cracks nucleate and propagate in stratum corneum. We further quantify previously unreported values of the tissue's Poisson's ratio and toughness, and their dramatic variation with ambient humidity. To date, skin models examining drug delivery, wound healing, and ageing continue to estimate these parameters.

Local cortisol/corticosterone activation in skin physiology and pathology

Cortisol and corticosterone are the endogenous glucocorticoids (GCs) in humans and rodents, respectively. Systemic GC is released through the hypothalamic-pituitary-adrenal (HPA) axis in response to various stressors. Over the last decade, extra-adrenal production/activation of cortisol/corticosterone has been reported in many tissues. The enzyme that catalyzes the conversion of hormonally inactive cortisone/11-dehydrocorticosterone (11-DHC) into active cortisol/corticosterone in cells is 11β-hydroxysteroid dehydrogenase (11β-HSD). The 11β-HSD1 isoform is predominantly a reductase, which catalyzes nicotinamide adenine dinucleotide phosphate hydrogen-dependent conversion of cortisone/11-DHC to cortisol/corticosterone, and is widely expressed and present at the highest levels in the liver, lungs, adipose tissues, ovaries, and central nervous system. The 11β-HSD2 isoform, which catalyzes nicotinamide adenine dinucleotide⁺-dependent inactivation of cortisol/corticosterone to cortisone/11-DHC, is highly expressed in distal nephrons, the colon, sweat glands, and the placenta. In healthy skin, 11β-HSD1 is expressed in the epidermis and in dermal fibroblasts. On the other hand, 11β-HSD2 is expressed in sweat glands but not in the epidermis. The role of 11β-HSD in skin physiology and pathology has been reported recently. In this review, we summarize the recently reported role of 11β-HSD in the skin, focusing on its function in cell proliferation, wound healing, inflammation, and aging.