Ex Vivo Live Full-Thickness Porcine Skin Model as a Versatile In Vitro Testing Method for Skin Barrier Research

Nanotopology-Enabled On-Site Pathogen Detection for Managing Atopic Dermatitis

Atopic dermatitis (AD), a prevalent skin condition often complicated by microbial infection, poses a significant challenge in identifying the responsible pathogen for its effective management. However, a reliable, safe tool for pinpointing the source of these infections remains elusive. In this study, a novel on-site pathogen detection that combines chemically functionalized nanotopology with genetic analysis is proposed to capture and analyze pathogens closely associated with severe atopic dermatitis. The chemically functionalized nanotopology features a 3D hierarchical nanopillar array (HNA) with a functional polymer coating, tailored to isolate target pathogens from infected skin. This innovative nanotopology demonstrates superior pathogenic capture efficiency, favorable entrapment patterns, and non-cytotoxicity. An HNA-assembled stick is utilized to directly retrieve bacteria from infected skin samples, followed by extraction-free quantitative loop-mediated isothermal amplification (direct qLAMP) for validation. To mimic human skin conditions, porcine skin is employed to successfully capture Staphylococcus aureus, a common bacterium exacerbating AD cases. The on-site detection method exhibits an impressive detection limit of 103 cells mL-1. The HNA-assembled stick represents a promising tool for on-site detection of bacteria associated with atopic dermatitis. This innovative approach enables to deepen the understanding of AD pathogenesis and open avenues for more effective management strategies for chronic skin conditions.

Glycolic acid-induced disruption of epidermal homeostasis in a skin equivalent model: Insights into temporal dynamics and mechanisms

Glycolic acid (GA) is extensively used in cosmetic formulations and skin peeling treatments but its adverse effects, notably severe disruption of epidermal structure, limit its clinical utility. However, the detailed impact of GA on epidermal homeostasis, including changes in structure and protein expression over time, is not fully understood. This study employed a reconstructed human epidermis (RHE) model to assess the effects of varying GA concentrations on epidermal proliferation, differentiation, and desquamation at different time points. Through histology, immunofluorescence, and immunohistochemistry, we observed that 35% GA concentration adversely caused abnormal epidermal homeostasis by affecting epidermal proliferation, differentiation and desquamation. Our findings reveal time-specific responses of key proteins to GA: Filaggrin, Involucrin, Loricrin, and Ki67 showed very early responses; KLK10 an early response; and AQP3 and K10 late responses. This research provides a detailed characterization of GA's effects in an RHE model, mimicking clinical superficial peeling and identifying optimal times for detecting GA-induced changes. Our results offer insights for designing interventions to mitigate GA's adverse effects on skin, enhancing the safety and efficacy of GA peeling treatments.

Polymeric micelle gel with luliconazole: in vivo efficacy against cutaneous candidiasis in Wistar rats

The objective of this research was focused on the design and development of luliconazole-loaded polymeric micelle hydrogel (LUL-PM-CHG) using quality by design (QbD) principle to improve the penetration and retention of LUL in the skin. The optimization of the formulation involved the utilization of a Box-Behnken design with three factors and three levels. The impact of specific formulation variables, namely the ratio of poloxamer P123 and F127, sonication time, and the quantity of drug, was investigated in terms of particle size, micellar incorporation efficiency, and polydispersity index. The LUL-loaded P123/F127 mixed micelles involved the thin film hydration method for thin preparation. The characteristics of optimized formulation include a particle size of 226 ± 8.52 nm, a polydispersity index (PDI) of 0.153 ± 0.002, a zeta potential (ZP) of 30.15 ± 2.32 mV, and a micellar incorporation efficiency (MIE) of 88.38 ± 3.84%. In vitro release studies indicated a sustained release of LUL-PM-CHG for a duration of up to 8 h. The MIC, GI50, and GI90 of different formulations on Candida albicans were determined using both the microtiter broth dilution method and the plate method and showed that LUL-PM-CHG exhibited the highest antifungal activity compared to the other formulations, with MIC values of 3.25 ± 0.19 ng/mL, GI50 values of 37.11 ± 2.89, and GI90 values of 94.98 ± 3.41 The study also measured the % of inhibition activity and the generation of intracellular reactive oxygen species (ROS) using flow cytometry. LUL-PM-CHG showed the highest percentage of inhibition (75.5%) and ROS production (MFI-140951), indicating its enhanced activity compared to LUL-CHG and LUL. Fungal infection was induced in Wistar rats using immunosuppressant's treatment followed by exposure to C. albicans. Finally, in vivo fungal scaling and histopathological studies indicated a reduction in fungal infection in Wistar rat skin after treatment. The obtained results suggested that LUL-PM can serve as a promising formulation to enhance luliconazole antifungal activity and increase patient compliance.

Effect of Penetration Enhancer on the Structure of Stratum Corneum: On-Site Study by Confocal Polarized Raman Imaging

Keratin and lipid structures in the stratum corneum (SC) are closely related to the SC barrier function. The application of penetration enhancers (PEs) disrupts the structure of SC, thereby promoting infiltration. To quantify these PE-induced structural changes in SC, we used confocal Raman imaging (CRI) and polarized Raman imaging (PRI) to explore the integrity and continuity of keratin and lipid structures in SC. The results showed that water is the safest PE and that oleic acid (OA), sodium dodecyl sulfate (SDS), and low molecular weight protamine (LMWP) disrupted the ordered structure of keratin, while azone and liposomes had less of an effect on keratin. Azone, OA, and SDS also led to significant changes in lipid structure, while LMWP and liposomes had less of an effect. Establishing this non-invasive and efficient strategy will provide new insights into transdermal drug delivery and skin health management.

Development of an ex vivo porcine skin model for the preclinical evaluation of subcutaneously injected biomacromolecules

Subcutaneous administration is used to deliver systemically-acting biotherapeutics, e.g. antibodies, and locally-acting biomacromolecules, e.g. hyaluronic acid. However, few preclinical models are available to evaluate post-injection behaviour in the tissue microenvironment. In vivo animal studies are costly, time-consuming, and raise obvious ethical concerns. In vitro models are cost-efficient, high-throughput solutions, but cannot simulate complex skin structure and biological function. An ex vivo model (containing hypodermis) with an extended culture period that enabled longitudinal studies would be of great interest for both the pharmaceutical and cosmeceutical industries. We describe the development of one such ex vivo model, using viable full-thickness porcine skin. Structural integrity was evaluated using a histological scoring system: spongiosis and epidermal detachment were identified as discriminating parameters. Ki67 and Claudin-1 expression reported on epidermal cell proliferation and barrier function, respectively and their expression decreased as a function of incubation time. After optimization, the system was used to investigate the fate/impact of subcutaneously administered hyaluronic acid (HA) formulations. The results showed that HA was localized at the injection site and adjacent adipocytes were well preserved during 5 days' incubation and confirmed that the full-thickness ex vivo porcine skin model could provide a platform for preclinical evaluation of subcutaneously injected biomacromolecules.

Liquid crystalline nanogel targets skin cancer via low-frequency ultrasound treatment

The potential of low-frequency ultrasound (LFU) combined with nanotechnology-based formulations in improving skin tumors topical treatment was investigated. The impact of solid lipid nanoparticles (SLN) and hydrophilic nanogels as coupling media on LFU-induced skin localized transport regions (LTR) and the penetration of doxorubicin (DOX) in LFU-pretreated skin was evaluated. SLN were prepared by the microemulsion technique and liquid crystalline nanogels using Poloxamer. In vitro, the skin was pretreated with LFU until skin resistivity of ∼1 KΩ.cm2 using the various coupling media followed by evaluation of DOX penetration from DOX-nanogel and SLN-DOX in skin layers. Squamous cell carcinoma (SCC) induced in mice was LFU-treated using the nanogel with the LFU tip placed 5 mm or 10 mm from the tumor surface, followed by DOX-nanogel application. LFU with nanogel coupling achieved larger LTR areas than LFU with SLN coupling. In LFU-pretreated skin, DOX-nanogel significantly improved drug penetration to the viable epidermis, while SLN-DOX hindered drug transport through LTR. In vivo, LFU-nanogel pretreatment with the 10 mm tip distance induced significant tumor inhibition and reduced tumor cell numbers and necrosis. These findings suggest the importance of optimizing nanoparticle-based formulations and LFU parameters for the clinical application of LFU technology in skin tumor treatment.

Photoactivated Gallium Porphyrin Reduces Staphylococcus aureus Colonization on the Skin and Suppresses Its Ability to Produce Enterotoxin C and TSST-1

Staphylococcus aureus is a key pathogen in atopic dermatitis (AD) pathogenicity. Over half of AD patients are carriers of S. aureus. Clinical isolates derived from AD patients produce various staphylococcal enterotoxins, such as staphylococcal enterotoxin C or toxic shock syndrome toxin. The production of these virulence factors is correlated with more severe AD. In this study, we propose cationic heme-mimetic gallium porphyrin (Ga3+CHP), a novel gallium metalloporphyrin, as an anti-staphylococcal agent that functions through dual mechanisms: a light-dependent mechanism (antimicrobial photodynamic inactivation, aPDI) and a light-independent mechanism (suppressing iron metabolism). Ga3+CHP has two additive quaternary ammonium groups that increase its water solubility. Furthermore, Ga3+CHP is an efficient generator of singlet oxygen and can be recognized by heme-target systems such as Isd, which improves the intracellular accumulation of this compound. Ga3+CHP activated with green light effectively reduced the survival of clinical S. aureus isolates derived from AD patients (>5 log10 CFU/mL) and affected their enterotoxin gene expression. Additionally, there was a decrease in the biological functionality of studied toxins regarding their superantigenicity. In aPDI conditions, there was no pronounced toxicity in HaCaT keratinocytes with both normal and suppressed filaggrin gene expression, which occurs in ∼50% of AD patients. Additionally, no mutagenic activity was observed. Green light-activated gallium metalloporphyrins may be a promising chemotherapeutic to reduce S. aureus colonization on the skin of AD patients.

Methodologies to Evaluate the Hair Follicle-Targeted Drug Delivery Provided by Nanoparticles

Nanotechnology has been investigated for treatments of hair follicle disorders mainly because of the natural accumulation of solid nanoparticles in the follicular openings following a topical application, which provides a drug "targeting effect". Despite the promising results regarding the therapeutic efficacy of topically applied nanoparticles, the literature has often presented controversial results regarding the targeting of hair follicle potential of nanoformulations. A closer look at the published works shows that study parameters such as the type of skin model, skin sections analyzed, employed controls, or even the extraction methodologies differ to a great extent among the studies, producing either unreliable results or precluding comparisons altogether. Hence, the present study proposes to review different skin models and methods for quantitative and qualitative analysis of follicular penetration of nano-entrapped drugs and their influence on the obtained results, as a way of providing more coherent study protocols for the intended application.

Comparison of structural characteristics and molecular markers of rabbit skin, pig skin, and reconstructed human epidermis for an ex vivo human skin model

The Organization for Economic Co-operation and Development approved a reconstructed human epidermis (RHE) model for in vitro skin irritation and corrosion tests as an alternative to animal testing for cosmetics, which has been banned in the European Union since 2013. However, RHE models have several limitations, such as high manufacturing costs, a loose skin barrier, and inability to simulate all cellular and non-cellular components of the human epidermis. Therefore, new alternative skin models are needed. Ex vivo skin models have been suggested as promising tools. Here, we investigated the structural similarities in the epidermis of pig and rabbit skin, a commercial RHE model (Keraskin), and human skin. To compare the structural similarity, the thickness of each epidermal layer was compared using molecular markers. Among the candidate human skin surrogates, the epidermal thickness of the pig skin was the most similar to that of human skin, followed by rabbit skin and Keraskin. Keraskin showed thicker cornified and granular layers than human skin, while rabbit skin displayed thinner layers. Moreover, the proliferation indices of Keraskin and rabbit skin were higher than those of human skin, whereas the proliferation index of the pig skin was similar to that of human skin. Some or none of the human skin barrier proteins FLG, CLDN1, and CDH1 were expressed in pig and rabbit skin, whereas all human proteins were expressed in Keraskin. Collectively, we propose ex vivo pig skin as the most suitable model for skin irritation testing because of its similarity to human skin.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-023-00185-1.

Exploring the potential of Halomonas levan and its derivatives as active ingredients in cosmeceutical and skin regenerating formulations

Demand on natural products that contain biological ingredients mimicking growth factors and cytokines made natural polysaccharides popular in pharmaceutical and cosmetic industries. Levan is the β-(2-6) linked, nontoxic, biocompatible, water-soluble, film former fructan polymer that has diverse applications in pharmacy and cosmeceutical industries with its moisturizing, whitening, anti-irritant, anti-aging and slimming activities. Driven by the limited reports on few structurally similar levan polymers, this study presents the first systematic investigation on the effects of structurally different extremophilic Halomonas levan polysaccharides on human skin epidermis cells. In-vitro experiments with microbially produced linear Halomonas levan (HL), its hydrolyzed, (hHL) and sulfonated (ShHL) derivatives as well as enzymatically produced branched levan (EL) revealed increased keratinocyte and fibroblast proliferation (113-118 %), improved skin barrier function through induced expressions of involucrin (2.0 and 6.43 fold changes for HL and EL) and filaggrin (1.74 and 3.89 fold changes for hHL and ShHL) genes and increased type I collagen (2.63 for ShHL) and hyaluronan synthase 3 (1.41 for HL) gene expressions together with fast wound healing ability within 24 h (100 %, HL) on 2D wound models clearly showed that HL and its derivatives have high potential to be used as natural active ingredients in cosmeceutical and skin regenerating formulations.

A Wall Fragment of Cutibacterium acnes Preserves Junctional Integrity Altered by Staphylococcus aureus in an Ex Vivo Porcine Skin Model

(1) Background alteration of the skin microbiota, dysbiosis, causes skin barrier impairment resulting in disease development. Staphylococcus aureus, the main pathogen associated with dysbiosis, secretes several virulence factors, including α-toxin that damages tight junctions and compromises the integrity of the skin barrier. The use of members of the resident microbiota to restore the skin barrier, bacteriotherapy, represents a safe treatment for skin conditions among innovative options. The aim of this study is the evaluation of a wall fragment derived from a patented strain of Cutibacterium acnes DSM28251 (c40) alone and conjugated to a mucopolysaccharide carrier (HAc40) in counteracting S. aureus pathogenic action on two tight junction proteins (Claudin-1 and ZO-1) in an ex vivo porcine skin infection model. Methods: skin biopsies were infected with live S. aureus strains ATCC29213 and DSM20491. Tissue was pre-incubated or co-incubated with c40 and HAc40. (3) Results: c40 and HAc40 prevent and counteract Claudin-1 and Zo-1 damage (4) Conclusions: c40 and the functional ingredient HAc40 represent a potential non-pharmacological treatment of skin diseases associated with cutaneous dysbiosis of S. aureus. These findings offer numerous avenues for new research.

Multilamellar ceramide core-structured microvehicles with substantial skin barrier function recovery

This study introduces a multilamellar ceramide core-structured microvehicle platform for substantial skin barrier function recovery. Our approach essentially focused on fabricating bacterial cellulose nanofiber (BCNF)-enveloped ceramide-rich lipid microparticles (CerMPs) by solidifying BCNF-armored oil-in-water Pickering emulsions. The oil drops consisted of Ceramide NP (a phytosphingosine backbone N-acylated with a saturated stearic acid) and fatty alcohols (FAs) with a designated stoichiometry. The thin BCNF shell layer completely blocked the growth of ceramide molecular crystals from the CerMPs for a long time. The CerMP cores displayed a multilamellar structure wherein the interlayer distance and lateral packing could be manipulated using FAs with different alkyl chain lengths. The CerMPs remarkably lowered the trans-epidermal water loss while restoring the structural integrity of the epidermis in damaged skin. The results obtained herein highlight that the CerMP system provides a practical methodology for developing various types of skin-friendly formulations that can strengthen the skin barrier function.

Characterization and modeling of the in-plane collagen fiber distribution in the porcine dermis

The structural arrangement of collagen fibers in the plane of the dermis layer plays a critical role in accurately predicting the mechanical behavior of skin tissues. This paper combines a histological analysis with statistical modeling to characterize and model the in-plane collagen fiber distribution in the porcine dermis. The histology data reveals that the fiber distribution in the plane of the porcine dermis is non-symmetric. The histology data forms the basis of our model, which employs a combination of two π-periodic von-Mises distribution density functions to create a non-symmetric distribution. We demonstrate that a non-symmetric in-plane fiber distribution is a significant improvement over a symmetric distribution.

A new iron supplement: The chelate of pig skin collagen peptide and Fe2+ can treat iron-deficiency anemia by modulating intestinal flora

Introduction

Iron deficiency anemia (IDA) is one of the most common nutritional diseases encountered all over the world. Nowadays, oral iron supplementation is still the mainstay of IDA treatment.

Methods

In this study, a new iron nutritional supplement named pig skin collagen peptides ferrous chelates (PSCP-Fe) was prepared, and its structure was characterized by the scanning electron microscopy, sykam amino acid analyzer and Fourier transform infrared spectroscopy (FTIR). The anti-IDA activity of PSCP-Fe was evaluated in low-Fe²⁺ diet-induced IDA in rats. 16S amplicon sequencing technology was then used to reveal the mechanism of PSCP-Fe against IDA.

Results

The results of amino acid analysis and FTIR showed that aspartic acid (Asp), arginine (Arg), histidine (His), glutamic acid (Glu), cystine (Cys), and lysine (Lys) residued in PSCP chelated readily with Fe²⁺ through their functional groups. PSCP-Fe treated reversed the hematology-related indexes, such as red blood cells (RBC), hemoglobin (HGB), hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentrate (MCHC), serum ferritin (SF), serum hepcidin (HEPC) and serum transferrin receptor (TFR). And its regulatory action was better than that of FeSO₄. Moreover, PSCP-Fe alleviated the hepatocyte apoptosis and necrosis, Fe²⁺ loss, and injury in IDA rats. In addition, PSCP-Fe could significantly retrace the disturbed profile of gut microbiota in IDA rats (p < 0.05) and significantly up-regulated the relative abundances of nine bacterial genus, including Lactobacillus, Alloprevotella, unclassified_of_Oscillospiraceae, and NK4A214_group (p < 0.05). It could also downgrade the relative abundances of Subdoligranulum and Coriobacteriaceae_UCG-002 (p < 0.05). The results of Spearman's correlation analysis and distance-based redundancy analysis (db-RDA) revealed that Subdoligranulum and Christensenellaceae_R-7_group may be potential microbial markers for effective PSCP-Fe action in the treatment of IDA.

Discussion

Overall, our results elucidate the interactions between gut bacteria and related cytokines and reveal the mechanisms underlying the anti-IDA effect of PSCP-Fe. They will thus provide a theoretical foundation for PSCP-Fe as a new iron nutritional supplement.

Biopolymer Nano-Network for Antimicrobial Peptide Protection and Local Delivery

Antimicrobial resistance (AMR) develops when bacteria no longer respond to conventional antimicrobial treatment. The limited treatment options for resistant infections result in a significantly increased medical burden. Antimicrobial peptides offer advantages for treatment of resistant infections, including broad-spectrum activity and lower risk of resistance development. However, sensitivity to proteolytic cleavage often limits their clinical application. Here, a moldable and biodegradable colloidal nano-network is presented that protects bioactive peptides from enzymatic degradation and delivers them locally. An antimicrobial peptide, PA-13, is encapsulated electrostatically into positively and negatively charged nanoparticles made of chitosan and dextran sulfate without requiring chemical modification. Mixing and concentration of oppositely charged particles form a nano-network with the rheological properties of a cream or injectable hydrogel. After exposure to proteolytic enzymes, the formed nano-network loaded with PA-13 eliminates Pseudomonas aeruginosa during in vitro culture and in an ex vivo porcine skin model while the unencapsulated PA-13 shows no antibacterial effect. This demonstrates the ability of the nano-network to protect the antimicrobial peptide in an enzyme-challenged environment, such as a wound bed. Overall, the nano-network presents a useful platform for antimicrobial peptide protection and delivery without impacting peptide bioactivity.

Effect of Cosmetics Use on the In Vitro Skin Absorption of a Biocide, 1,2-Benzisothiazolin-3-one

1,2-Benzisothiazolin-3-one (BIT) is a commonly used organic biocide containing an isothiazolone ring. However, it may have adverse effects on human health and its risk needs to be properly evaluated. Dermal exposure is the main route of BIT exposure, and co-exposed substances may affect its absorption. The dermal permeation profile of BIT has not been well-studied. This study aimed to investigate the dermal permeation profiles of BIT with or without cosmetic use. Dermal permeation profiles of BIT were investigated after infinite- (100 μg/cm²), or a finite-dose (10 μg/cm²) application with or without cosmetics using a minipig skin and Strat-M^®, an artificial membrane. A cream, lotion, and essence (namely, face serum) were pre-treated as representative cosmetics on minipig skin for 30 min, with BIT treatment afterward. After the treatment, BIT left on the skin surface was collected by cotton swabbing, BIT in the stratum corneum, by sequential tape stripping, and BIT retained in the remaining skin was extracted after cutting the skin into pieces before LC-MS/MS analysis. When an infinite dose was applied, permeation coefficients (K_p, cm/h) for minipig skin and Strat-M^® were 2.63 × 10⁻³ and 19.94 × 10⁻³, respectively, reflecting that skin permeation was seven to eight times higher in Strat-M^® than in the minipig skin. BIT, in the presence of cosmetics, rapidly permeated the skin, while the amount in the stratum corneum and skin deposit was reduced. We performed a risk assessment of dermally applied BIT in the absence or presence of cosmetics by calculating the skin absorption rate at 10 h based on the toxicological data from several references. The risk level was higher in the presence of essence as compared to lotion, which was higher than cream, which was higher than the control (non-treated). However, all of the margins of safety values obtained were greater than 100, suggesting that BIT is safe for use in dermally exposed consumer products. We believe that this research contributes to a greater understanding of the risk assessment of isothiazolinone biocides.

Importance of the pig as a human biomedical model

[Figure: see text].

Skin Epidermis and Barrier Function

The skin epidermis is the outermost epithelial tissue that protects the body from the external environment [...].