Skin Compartments Research Articles

Single-cell RNA sequencing of chronic idiopathic erythroderma defines disease-specific markers.

Chronic erythroderma is a potentially life-threatening condition that can be caused by a variety of diseases, but approximately 30% of cases remain idiopathic, often with insufficient treatment options. To establish a molecular disease map of chronic idiopathic erythroderma. We performed single-cell RNA sequencing combined with T-cell receptor sequencing of blood and skin from 5 chronic idiopathic erythroderma (CIE) patients and compared results with 8 cases of erythrodermic cutaneous T-cell lymphoma (eCTCL), 15 moderate-to-severe atopic dermatitis (AD), 10 psoriasis and 20 healthy control (HC) individuals. In erythrodermic CTCL, we found strong expansion of CD4+ malignant clones with a CCR7+SELL+ central memory phenotype. By contrast, CIE exhibited a pattern of low-level, but consistent expansion of CD8A+KLRK1+ T-cell clones, both in blood and skin. KLRK1 was also expressed by CCR10+FUT7+ skin-homing CIE blood T-cells that had increased proliferation rates and were absent in all other conditions. While CIE and CTCL patients lacked the strong type 2 or type 17 immune skewing typically found in AD or psoriasis, respectively, they were characterized by upregulation of MHC II genes (HLA-DRB1, HLA-DRA, CD74) in keratinocytes and fibroblasts, most likely in an IFNG-dependent fashion. However, we found strongest upregulation of type 1 immune mediators in CIE samples, both in the expanded CD8A+ clones, as well as in the tissue microenvironment. Despite the notion that CIE might be a mere bundle of various yet uncharacterized disease processes, we found specific pathogenic signatures in these patients, that were different from other forms of erythroderma. These data might help to improve our pathogenic understanding of the blood and skin compartments of CIE, aiding in discovery of future treatment targets.

Analysis of Immunohistochemical Expression of Bcl-2 in Cases of Psoriasis and Psoriasiform Dermatitis.

Introduction Psoriasis involves rapid cell growth and abnormal differentiation of skin cells. Dysregulation of apoptosis has been proposed in the pathogenesis of psoriasis. The role of Bcl-2 as an anti-apoptotic proteinin pathogenesis has not been studied in detail in these cases.Our study aims to evaluate the expression of Bcl-2 in different skin compartments in psoriasis and psoriasiform dermatitis cases. Materials and methodology An analytical cross-sectional study was performed using paraffin blocks of psoriasis and psoriasiform dermatitis patients between 2022 and 2023. For light microscopy screening, sections were initially stained with hematoxylin and eosin stains. In further sections, a primary antibody against Bcl-2 was applied. The level of Bcl-2 expression in keratinocytes of supra-basal and basalepidermal layers and dermal lymphocytes was evaluated using a scoring system. Results Sixty patients, 30 with psoriasis and 30 with psoriasiform dermatitis were included. Among the histopathological features, parakeratosis (p - 0.038), Munro's microabscesses (p - 0.001), supra-papillary plate thinning (p - 0.004), and increased dermal vasculature (p - 0.001) were significantly associated with psoriasis when compared with psoriasiform dermatitis. Most psoriatic lesions had hypogranulosis whereas it was alternating hypo and hypergranulosis in psoriasiform dermatitis (p - 0.001). Acanthosis was regular in psoriasis lesions (p - 0.036). Bcl-2 expression was seen in dermal lymphocytes in all psoriasis and psoriasiform lesions with significantly stronger positive expression compared to basal and supra-basal layers. Psoriasis cases demonstrated more significant Bcl-2 positivity in dermal lymphocytes and basal layers than psoriasiform dermatitis cases. Conclusion Bcl-2 has stronger expression in dermal lymphocytes and basal layers than supra-basal layers, which comply with the proposed pathogenesis. Increased Bcl-2 expression in psoriasis cases compared with other psoriasiform dermatitis lesions implies the more chronic and recurrent nature of the disease.

Effect of vehicle on the in vitro penetration and metabolism of genistein and daidzein in ex vivo skin explants and the Phenion full-thickness skin model.

In a read-across assessment of the safety of genistein and daidzein in cosmetic products, additional information was required to account for differences in their systemic exposure after topical application in a typical body lotion formulation. Therefore, we measured the penetration and metabolism of two doses (3 and 30 nmoles/cm2) of genistein and daidzein applied in ethanol and in a body formulation to fresh pig skin, fresh and frozen human skin, and PhenionFT models. Both chemicals readily penetrated all skin models when applied in ethanol. The same sulfate and glucuronide metabolites were formed in fresh pig skin, fresh human skin, and PhenionFT models, which also all demonstrated that (a) these pathways could be saturated between 3 and 30 nmoles/cm2 and (b) the extent of metabolism of daidzein was lower than genistein. Although the relative amounts of radiolabeled chemical in human skin and medium compartments were altered by freezing, their overall bioavailability was not affected. The greatest impact on the bioavailability and distribution of both chemicals was observed when they were applied in the formulation. Most of the dose applied in the formulation was retained on the skin surface, especially at 30 nmoles/cm2 (60%-90%), resulting in much lower amounts in the medium and/or skin. In conclusion, all four skin models demonstrated first-pass metabolism of genistein and daidzein and a marked alteration in their disposition by applying them in a body lotion formulation. This supports the use of fresh pig skin and PhenionFT models as alternatives to human skin for investigating skin metabolism and formulation effects for these two chemicals. The results were used to develop the dermal module of a PBPK model and dose setting for organ-on-chip experiments. They could also be used to refine internal exposure estimates in regulatory safety assessments.

A Comprehensive Ultrasound Investigation of Lower Facial and Neck Structure.

The jawline and neck significantly influence facial aesthetics. Botulinum toxin and filler are highly favored as minimally invasive jawline rejuvenation procedures. However, little evidence exists on the age-related skin and superficial fat tissue transformations in healthy individuals to guide targeted interventions. A quantitative sonographic assessment was conducted on 51 patients. Total soft tissue thickness (the skin and superficial fat compartments) was measured at eight sites along the jawline and four sites at the neck. Among them, 21 patients received botulinum toxin A (BTX-A) injections for jawline lift. Three-dimensional images and questionaries were obtained before and after the treatment. In this ultrasound study, total superficial soft tissue thickness decreased significantly from the prejowl sulcus to the lateral cheek, with the jowl showing the greatest thickness. Vertically, significant differences in thickness were noted between superior and inferior points, especially at the inferior prejowl sulcus for the middle-aged and the jowl for the elderly group when comparing across age groups. Soft tissue thickness at the neck decreased from zones 1 to 3, consistent in all age groups. BMI and age positively correlated with soft tissue thickness at the jawline and neck. Regarding BTX-A injections, participants described a pain-free injection process, of which 85.7% reported substantial aesthetic improvement and sharpening of the submental-cervical angle. This study quantified age-related changes in superficial soft tissues at the jawline and neck regions with ultrasound imaging. With aging, soft tissue thickness alters with high region-specificity. Tailoring interventions to the specific alterations within each age group can achieve optimal results with enhanced safety. This study provided a quantitative analysis of skin and superficial fat compartment thicknesses for the young, middle-aged, and elderly groups. This study illustrated how skin and superficial fat compartments change with age in a regionally specific manner for both the jawline and neck regions. This study revealed a positive association between BMI and age with skin and superficial fat tissue thicknesses, especially in areas like the jowl, submental, and neck. This study provided guidance for a safe and effective botulinum toxin. A injection method focusing on the injection depths and regions to achieve optimal jawline rejuvenation outcomes and patient experience. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Photo-neuro-immuno-endocrinology: How the ultraviolet radiation regulates the body, brain, and immune system

Ultraviolet radiation (UVR) is primarily recognized for its detrimental effects such as cancerogenesis, skin aging, eye damage, and autoimmune disorders. With exception of ultraviolet B (UVB) requirement in the production of vitamin D3, the positive role of UVR in modulation of homeostasis is underappreciated. Skin exposure to UVR triggers local responses secondary to the induction of chemical, hormonal, immune, and neural signals that are defined by the chromophores and extent of UVR penetration into skin compartments. These responses are not random and are coordinated by the cutaneous neuro-immuno-endocrine system, which counteracts the action of external stressors and accommodates local homeostasis to the changing environment. The UVR induces electrical, chemical, and biological signals to be sent to the brain, endocrine and immune systems, as well as other central organs, which in concert regulate body homeostasis. To achieve its central homeostatic goal, the UVR-induced signals are precisely computed locally with transmission through nerves or humoral signals release into the circulation to activate and/or modulate coordinating central centers or organs. Such modulatory effects will be dependent on UVA and UVB wavelengths. This leads to immunosuppression, the activation of brain and endocrine coordinating centers, and the modification of different organ functions. Therefore, it is imperative to understand the underlying mechanisms of UVR electromagnetic energy penetration deep into the body, with its impact on the brain and internal organs. Photo-neuro-immuno-endocrinology can offer novel therapeutic approaches in addiction and mood disorders; autoimmune, neurodegenerative, and chronic pain-generating disorders; or pathologies involving endocrine, cardiovascular, gastrointestinal, or reproductive systems.

A physiologically based pharmacokinetic model of diethyl phthalates in humans

Phthalates are a family of industrial and consumer product chemicals, among which diethyl phthalate (DEP) has been widely used. DEP is metabolized into the active metabolite monoethyl phthalate (MEP) and exposure to DEP may induce male reproductive toxicity, developmental toxicity and hepatotoxicity. To better assess the toxicity of DEP and MEP, it is important to understand and predict their internal concentrations, especially in reproductive organs. Here we present a human physiologically based pharmacokinetic (PBPK) model of DEP. Implemented in R, the PBPK model consists of seven tissue compartments, including blood, gut, liver, fat, skin, gonad, and rest of body (RB). In the blood both DEP and MEP partition into free and bound forms, and tissue distribution is considered as blood flow-limited. DEP is metabolized in the gut and liver into MEP which is further glucuronidated and cleared through the urine. The chemical-specific parameters of the model were predicted in silico or estimated based on published human urinary MEP data after exposure to DEP in the air at 250 or 300 μg/m3 for 3 or 6 h through inhalation and dermal absorption. Sensitivity analysis identified important parameters including partition coefficients of DEP for fat, RB, and skin compartments, and the rate constants for glucuronidation of MEP and urinary excretion, with regard to Cmax, area under the curve (AUC), and clearance half-lives of DEP and MEP. A subset of the sensitive parameters was then included in hierarchical population Bayesian Markov chain Monte Carlo (MCMC) simulations to characterize the uncertainty and variability of these parameters. The model is consistent with the notion that dermal absorption represents a significant route of exposure to DEP in ambient air and clothing can be an effective barrier. The developed human PBPK model can be utilized upon further refinement as a quantitative tool for DEP risk assessment.

Matricellular Proteins in the Homeostasis, Regeneration, and Aging of Skin.

Matricellular proteins are secreted extracellular proteins that bear no primary structural functions but play crucial roles in tissue remodeling during development, homeostasis, and aging. Despite their low expression after birth, matricellular proteins within skin compartments support the structural function of many extracellular matrix proteins, such as collagens. In this review, we summarize the function of matricellular proteins in skin stem cell niches that influence stem cells' fate and self-renewal ability. In the epidermal stem cell niche, fibulin 7 promotes epidermal stem cells' heterogeneity and fitness into old age, and the transforming growth factor-β-induced protein ig-h3 (TGFBI)-enhances epidermal stem cell growth and wound healing. In the hair follicle stem cell niche, matricellular proteins such as periostin, tenascin C, SPARC, fibulin 1, CCN2, and R-Spondin 2 and 3 modulate stem cell activity during the hair cycle and may stabilize arrector pili muscle attachment to the hair follicle during piloerections (goosebumps). In skin wound healing, matricellular proteins are upregulated, and their functions have been examined in various gain-and-loss-of-function studies. However, much remains unknown concerning whether these proteins modulate skin stem cell behavior, plasticity, or cell-cell communications during wound healing and aging, leaving a new avenue for future studies.

Simulating of human physiological supersystems: interactions of cardiovascular, thermoregulatory and respiratory systems

Special quantitative model of the human thermoregulatory system (MTS) functioning with cardiovascular and lung systems is created. These systems form a human physiological supersystem (HPSS). MTS describes thermoregulatory responses to alterations of both external environmental physical characteristics and internal biological characteristics. Algorithms provide designing of scenarios including simulation of either short-time or long-time (hours or days) observations. Input data include different combinations of environmental variables (air or water temperature, air humidity, wind or water flow speed, light intensity, infrared radiation) for a naked or wear human, as well as for given dynamics of biological characteristics (rate of heat production including its components associated with metabolism and ATP molecules leasing during mental and physical activities). Human body is presented by a core, blood, and a skin compartments. Skin and lung evaporation are under hypothalamic control based on afferent impulse patterns from internal, and skin heat and cold receptors. Dynamic output data include blood, hypothalamic, and skin temperatures, hemodynamic parameters like heart rate, cardiac output, regional blood flows, vascular resistances, blood pressures, and regional blood volumes. Serotonin and melatonin concentrations modulating biological heat production rate are associated with a day/night light intensity. Currently, the PCbased simulator is autonomous software to be used both for educational purposes and for providing of special computer research. In a near future, this simulator has to be widened by models of kidneys, and a mechanism of liverpancreas interaction.

A CASE SERIES OF PATIENTS WITH CUTANEOUS T‐CELL LYMPHOMA TREATED WITH COMBINATION MOGAMULIZUMAB AND OTHER THERAPIES AFTER SINGLE AGENT MOGAMULIZUMAB

Introduction: Mogamulizumab (moga) is an anti-CCR4, monoclonal antibody approved as monotherapy for the treatment of relapsed/refractory mycosis fungoides (MF) and Sezary syndrome (SS). Combination therapies are frequently utilized in cutaneous T-cell lymphoma (CTCL), in part due to the variation in response across blood, nodal, and skin compartments. Little is known about moga in combination with other therapies. Methods: We conducted a single institution retrospective analysis of MF/SS patients who were treated with moga in combination with other systemic therapies, including peginterferon alpha-2a (IFNα), bexarotene, extracorporeal photopheresis (ECP), and oral methotrexate between March 2019 and March 2023. Baseline characteristics and clinical outcomes were recorded and summarized. Responses were assessed by Olsen staging criteria (Olsen et al., 2022). Results: We identified 9 patients treated with moga combination therapy at our institution (Table 1). Six of 7 patients transitioned from mono to combination therapy due to progressive disease or stable disease with uncontrolled symptom burden. Median time to next treatment was 157.5 days (range 42-330) for moga monotherapy. The best response observed in the 8 patients to single agent moga was classified as: 4 (50%) partial responses (PR), 3 (37.5%) stable disease (SD), and 1 (12.5%) progressive disease (PD). We identified a total of 7 different treatment combinations in our 9 patients (6 systemic therapies and 2 skin-directed), which included IFNα (n = 4), bexarotene (2), ECP (2), total skin electron beam radiation (TSEB) (2), narrow band ultraviolet-B therapy (NBUVB) (1), IFNα + ECP (2), and oral methotrexate (1). Multiple patients received more than one combination treatment. Among the combination therapies, the median time to next treatment was 137 days (range 24-224 days) with 2 out of 6 patients having ongoing responses to moga + IFNα +/- ECP. The patient with PR on moga + IFNα received 7 prior therapies. His skin involvement improved from T4 to T1 but significant disease in the blood persisted (B2). He continues moga + IFNα now 846 days later. Conclusions: Mogamulizumab has improved outcomes for MF/SS patients, but global complete responses are rare with the best responses seen in blood. In our series, the addition of IFNα provided clinical benefits to patients with SD or PD on single agent moga. One patient achieved a lengthy partial response despite persistent disease seen in peripheral blood samples. We speculate the combination of moga + IFNα may augment antibody-dependent cellular cytotoxicity thereby improving efficacy of moga. Additionally, combinatorial approaches may improve responses in skin, nodes, and viscera where lower responses are observed to single agent moga. Further investigations of moga combinations are needed. Keywords: Combination Therapies, Cutaneous non-Hodgkin lymphoma No conflicts of interests pertinent to the abstract.

Targeting lymphoid-derived IL-17 signaling to delay skin aging

Skin aging is characterized by structural and functional changes that contribute to age-associated frailty. This probably depends on synergy between alterations in the local niche and stem cell-intrinsic changes, underscored by proinflammatory microenvironments that drive pleotropic changes. The nature of these age-associated inflammatory cues, or how they affect tissue aging, is unknown. Based on single-cell RNA sequencing of the dermal compartment of mouse skin, we show a skew towards an IL-17-expressing phenotype of T helper cells, γδ T cells and innate lymphoid cells in aged skin. Importantly, in vivo blockade of IL-17 signaling during aging reduces the proinflammatory state of the skin, delaying the appearance of age-related traits. Mechanistically, aberrant IL-17 signals through NF-κB in epidermal cells to impair homeostatic functions while promoting an inflammatory state. Our results indicate that aged skin shows signs of chronic inflammation and that increased IL-17 signaling could be targeted to prevent age-associated skin ailments.

Boosting hair growth through follicular delivery of Melatonin through lecithin-enhanced Pickering emulsion stabilized by chitosan-dextran nanoparticles in testosterone induced androgenic alopecia rat model

The strategy in this work was loading Melatonin (MEL), the powerful antioxidant photosensitive molecule, in novel Pickering emulsions (PEs) stabilized by chitosan-dextran sulphate nanoparticles (CS-DS NPs) and enhanced by lecithin, for treatment of androgenic alopecia (AGA). Biodegradable CS-DS NPs dispersion was prepared by polyelectrolyte complexation and optimized for PEs stabilization. PEs were characterized for droplet size, zeta potential, morphology, photostability and antioxidant activity. Ex-vivo permeation study through rat full thickness skin was conducted with optimized formula. Differential tape stripping trailed by cyanoacrylate skin surface biopsy was executed, for quantifying MEL in skin compartments and hair follicles. In-vivo evaluation of MEL PE hair growth activity was performed on testosterone induced AGA rat model. Visual inspection followed by anagen to telogen phase ratio (A/T) and histopathological examinations were conducted and compared with marketed 5% minoxidil spray “Rogaine ®”. Data showed that PE improved MEL antioxidant activity and photostability. Ex-vivo results displayed MEL PE high follicular deposition. In-vivo study demonstrated that MEL PE treated testosterone induced AGA rat group, restored hair loss and produced maximum hair regeneration along with prolonged anagen phase amongst tested groups. The histopathological examination revealed that MEL PE prolonged anagen stage, increased follicular density and A/T ratio by 1.5-fold. The results suggested that lecithin-enhanced PE stabilized by CS-DS NPs was found to be an effective approach to enhance photostability, antioxidant activity and follicular delivery of MEL. Thus, MEL-loaded PE could be a promising competitor to commercially marketed Minoxidil for treatment of AGA.

Influence of Molecular Structure and Physicochemical Properties of Immunosuppressive Drugs on Micelle Formulation Characteristics and Cutaneous Delivery.

The aim of this study was to investigate whether subtle differences in molecular properties affected polymeric micelle characteristics and their ability to deliver poorly water-soluble drugs into the skin. D-α-tocopherol-polyethylene glycol 1000 was used to prepare micelles containing ascomycin-derived immunosuppressants-sirolimus (SIR), pimecrolimus (PIM) and tacrolimus (TAC)-which have similar structures and physicochemical properties and have dermatological applications. Micelle formulations were prepared by thin-film hydration and extensively characterized. Cutaneous delivery and biodistribution were determined and compared. Sub-10 nm micelles were obtained for the three immunosuppressants with incorporation efficiencies >85%. However, differences were observed for drug loading, stability (at the highest concentration), and their in vitro release kinetics. These were attributed to differences in drug aqueous solubility and lipophilicity. Differences between the cutaneous biodistribution profiles and drug deposition in the different skin compartments pointed to the impact of differences in thermodynamic activity. Therefore, despite their structural similarities, SIR, TAC and PIM did not demonstrate the same behaviour either in the micelles or when applied to the skin. These outcomes indicate that polymeric micelles should be optimized even for closely related drug molecules and support the hypothesis that drugs are released from micelles prior to skin penetration.

Psoriatic Resolved Skin Epidermal Keratinocytes Retain Disease-Residual Transcriptomic and Epigenomic Profiles.

The disease-residual transcriptomic profile (DRTP) within psoriatic healed/resolved skin and epidermal tissue-resident memory T (TRM) cells have been proposed to be crucial for the recurrence of old lesions. However, it is unclear whether epidermal keratinocytes are involved in disease recurrence. There is increasing evidence regarding the importance of epigenetic mechanisms in the pathogenesis of psoriasis. Nonetheless, the epigenetic changes that contribute to the recurrence of psoriasis remain unknown. The aim of this study was to elucidate the role of keratinocytes in psoriasis relapse. The epigenetic marks 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) were visualized using immunofluorescence staining, and RNA sequencing was performed on paired never-lesional and resolved epidermal and dermal compartments of skin from psoriasis patients. We observed diminished 5-mC and 5-hmC amounts and decreased mRNA expression of the ten-eleven translocation (TET) 3 enzyme in the resolved epidermis. SAMHD1, C10orf99, and AKR1B10: the highly dysregulated genes in resolved epidermis are known to be associated with pathogenesis of psoriasis, and the DRTP was enriched in WNT, TNF, and mTOR signaling pathways. Our results suggest that epigenetic changes detected in epidermal keratinocytes of resolved skin may be responsible for the DRTP in the same regions. Thus, the DRTP of keratinocytes may contribute to site-specific local relapse.

Dermal appendage-dependent patterning of zebrafish atoh1a+ Merkel cells.

Touch system function requires precise interactions between specialized skin cells and somatosensory axons, as exemplified by the vertebrate mechanosensory Merkel cell-neurite complex. Development and patterning of Merkel cells and associated neurites during skin organogenesis remain poorly understood, partly due to the in utero development of mammalian embryos. Here, we discover Merkel cells in the zebrafish epidermis and identify Atonal homolog 1a (Atoh1a) as a marker of zebrafish Merkel cells. We show that zebrafish Merkel cells derive from basal keratinocytes, express neurosecretory and mechanosensory machinery, extend actin-rich microvilli, and complex with somatosensory axons, all hallmarks of mammalian Merkel cells. Merkel cells populate all major adult skin compartments, with region-specific densities and distribution patterns. In vivo photoconversion reveals that Merkel cells undergo steady loss and replenishment during skin homeostasis. Merkel cells develop concomitant with dermal appendages along the trunk and loss of Ectodysplasin signaling, which prevents dermal appendage formation, reduces Merkel cell density by affecting cell differentiation. By contrast, altering dermal appendage morphology changes the distribution, but not density, of Merkel cells. Overall, our studies provide insights into touch system maturation during skin organogenesis and establish zebrafish as an experimentally accessible in vivo model for the study of Merkel cell biology.

Physiologically based modelling of dermal absorption and kinetics of consumer-relevant chemicals: A case study with exposure to bisphenol A from thermal paper

Bisphenol A (BPA) is one of the best studied industrial chemicals in terms of exposure, toxicity, and toxicokinetics. This renders it an ideal candidate to exploit the recent advancements in physiologically based pharmacokinetic (PBPK) modelling to support risk assessment of BPA specifically, and of other consumer-relevant hazardous chemicals in general. Using the exposure from thermal paper as a case scenario, this study employed the multi-phase multi-layer mechanistic dermal absorption (MPML MechDermA) model available in the Simcyp® Simulator to simulate the dermal toxicokinetics of BPA at local and systemic levels. Sensitivity analysis helped to identify physicochemical and physiological factors influencing the systemic exposure to BPA. The iterative modelling process was as follows: (i) development of compound files for BPA and its conjugates, (ii) setting-up of a PBPK model for intravenous administration, (iii) extension for oral administration, and (iv) extension for exposure via skin (i.e., hand) contact. A toxicokinetic study involving hand contact to BPA-containing paper was used for model refinement. Cumulative urinary excretion of total BPA had to be employed for dose reconstruction. PBPK model performance was verified using the observed serum BPA concentrations. The predicted distribution across the skin compartments revealed a depot of BPA in the stratum corneum (SC). These findings shed light on the role of the SC to act as temporary reservoir for lipophilic chemicals prior to systemic absorption, which inter alia is relevant for the interpretation of human biomonitoring data and for establishing the relationship between external and internal measures of exposure.

Epidermal/Dermal Separation Techniques and Analysis of Cell Populations in Human Skin Sheets

Human skin consists of three compartments, each endowed with a particular structure and the presence of several immune and nonimmune cells that together comprise a protective shield and orchestrate multiple processes in the skin. Appropriate processing of human skin samples acquired from healthy volunteers or patients is essential for successful analysis in basic, translational, and clinical research to obtain accurate and reliable results, despite differences between individuals. From the wide range of available assays and methods, it is necessary to select the suitable method for separation of skin compartments, which will provide preservation or high viability of skin cells or whole structures that will be analyzed or further processed. In this paper, we review and discuss skin separation methods and compare their features such as processing time, cell viability, location of the basement membrane after detachment of the epidermis from the dermis, and their application. Furthermore, we visualize different cell populations and structures in epidermal and dermal sheets using confocal microscopy. It is aimed to provide an overview of the optimal processing of human skin samples and their possible application.

Deep learning for the detection of anatomical tissue structures and neoplasms of the skin on scanned histopathological tissue sections.

Basal cell carcinoma (BCC), squamous cell carcinoma (SqCC) and melanoma are among the most common cancer types. Correct diagnosis based on histological evaluation after biopsy or excision is paramount for adequate therapy stratification. Deep learning on histological slides has been suggested to complement and improve routine diagnostics, but publicly available curated and annotated data and usable models trained to distinguish common skin tumors are rare and often lack heterogeneous non-tumor categories. A total of 16 classes from 386 cases were manually annotated on scanned histological slides, 129,364 100 x 100 µm (~395 x 395 px) image tiles were extracted and split into a training, validation and test set. An EfficientV2 neuronal network was trained and optimized to classify image categories. Cross entropy loss, balanced accuracy and Matthews correlation coefficient were used for model evaluation. Image and patient data were assessed with confusion matrices. Application of the model to an external set of whole slides facilitated localization of melanoma and non-tumor tissue. Automated differentiation of BCC, SqCC, melanoma, naevi and non-tumor tissue structures was possible, and a high diagnostic accuracy was achieved in the validation (98%) and test (97%) set. In summary, we provide a curated dataset including the most common neoplasms of the skin and various anatomical compartments to enable researchers to train, validate and improve deep learning models. Automated classification of skin tumors by deep learning techniques is possible with high accuracy, facilitates tumor localization and has the potential to support and improve routine diagnostics.

015 Clonal sharing of skin T cells within different skin compartments and blood

The human skin harbors a heterogenous pool of cytotoxic tissue-resident memory T (TRM) cells seeded during infections and inflammation. TRM cells are retained at the site of viral infections and provide local immunity. These cells persist for years in the skin after bone marrow transplantation but circulating ex-TRM cells indicate several potential fates. Here, we explored the clonal relationships between human T cells in different skin compartments and circulation. 10x Genomics 5 prime immune profiling coupled with feature barcoding technology was employed to investigate the clonal relationship, transcriptomic and proteomic profiles of single T cells sorted from blood, subcutis, dermis, and epidermis.

Tackling the challenges of developing microneedle-based electrochemical sensors.

Microneedles provide unique advantages in biomedical areas, particularly biosensing, because of their opportunities for minimally invasive and convenient detection. This review introduces concepts of electrochemical microneedle-based sensors for minimally invasive analysis together with insights into skin compartments for designing successful microneedles. We discuss requirements for developing microneedle-based biosensors, including electrical and electrochemical behaviors of materials (such as metals, nanomaterials, and conducting polymers) which are the key factors for sensitive biosensors. We further emphasize immobilization strategies to attach biorecognition elements to electrode materials. Moreover, we detail advanced techniques that require state-of-the-art fabrications and materials to realize porous, biodegradable, and antifouling materials to enhance biosensing performances. We also emphasize studies of cytotoxicity and damage to the skin to elucidate biocompatible potentials. Furthermore, we highlight the latest advances in microneedles published from 2019 to 2022. This review also includes an overview of key remaining obstacles and opportunities where developments will push the advances continuously. The conclusion and outlook on the status of laboratory and commercial availability are added. We prospect that microneedle sensors will be integrated into a closed-loop system biodevice for diverse applications, e.g., detection and therapy. This review discusses concepts of electrochemical microneedle-based sensors for minimally invasive monitoring. We discuss requirements including geometry, mechanical, electrical, electrochemical properties, and immobilization strategy. We illustrate advanced techniques and materials to enrich biosensor features, e.g., porosity, dissolvable ability, and anti-fouling capability. Concern of toxicity is highlighted. We also illustrate recent applications and outlooks of recently published study that exploits microneedle-based biosensors.

Daptomycin Physiology-Based Pharmacokinetic Modeling to Predict Drug Exposure and Pharmacodynamics in Skin and Bone Tissues.

Daptomycin has been recommended in the treatment of bone and joint infection. Previous work showed that the approved dosage of daptomycin may be insufficient to achieve optimal exposure in patients with bone and joint infection. However, those studies assumed that bone exposure was similar to steady-state daptomycin-free plasma concentrations. We sought to establish a physiologically based pharmacokinetic (PBPK) model of daptomycin to describe the dynamics of daptomycin disposition in bone and skin tissue. A PBPK model of daptomycin was built using PK-Sim®. Daptomycin concentrations in plasma and bone were obtained from three previously published studies. Physicochemical drug characteristics, mass balance, anthropometrics, and experimental data were used to build and refine the PBPK model. Internal validation of the PBPK model was performed using the usual diagnostic plots. The final PBPK model was then used to run simulations with doses of 6, 8, 10, and 12 mg/kg/24 h. Pharmacokinetic profiles were simulated in 1000 subjects and the probabilities of target attainment for the area under the concentration-time curve over the bacterial minimum inhibitory concentration were computed in blood, skin, and bone compartments. The final model showed a good fit of all datasets with an absolute average fold error between 0.5 and 2 for all pharmacokinetic quantities in blood, skin and bone tissues. Results of dosing simulations showed that doses ≥10 mg/kg should be used in the case of bacteremia caused by Staphylococcus aureus with a minimum inhibitory concentration >0.5 mg/L or Enterococcus faecalis with a minimum inhibitory concentration >1 mg/L, while doses ≥12 mg/kg should be used in the case of bone and joint infection or complicated skin infection. When considering a lower minimum inhibitory concentration, doses of 6-8 mg/kg would likely achieve a sufficient success rate. However, in the case of infections caused by E. faecalis with a minimum inhibitory concentration >2 mg/L, a higher dosage and combination therapy would be necessary to maximize efficacy. We developed the first daptomycin PBPK/pharmacodynamic model for bone and joint infection, which confirmed that a higher daptomycin dosage is needed to optimize exposure in bone tissue. However, such higher dosages raise safety concerns. In this setting, therapeutic drug monitoring and model-informed precision dosing appear necessary to ensure the right exposure on an individual basis.