Skin Model Research Articles

In situ MgO nanoparticle-doped Janus electrospun dressing against bacterial invasion and immune imbalance for irregular wound healing.

Owing to the unpredictable size of wounds and irregular edges formed by trauma, nanofibers' highly customizable and adherent in situ deposition can contribute to intervention in the healing process. However, electrospinning is limited by the constraints of conventional polymeric materials despite its potential for anti-inflammatory and antimicrobial properties. Here, inspired by the Janus structure and biochemistry of nanometal ions, we developed an in situ sprayed electrospinning method to overcome bacterial infections and immune imbalances during wound healing. The bilayer fiber scaffold has a hydrophobic outer layer composed of polycaprolactone (PCL) and a hydrophilic inner layer composed of gelatin, poly(L-lactic acid) (PLLA), and magnesium oxide nanoparticles, constituting the PCL/PLLA-gelatin-MgO (PPGM) electrospun scaffold. This electrospun scaffold blocked the colonization and growth of bacteria and remained stable on the wound for continuous anti-inflammatory properties to promote wound healing. Furthermore, PPGM electrospinning modulated collagen deposition and the inflammatory microenvironment in the full-thickness skin model, significantly accelerating vascularization and epithelialization progression. This personalized Janus electrospun scaffold has excellent potential as a new type of wound dressing for first aid and wound healthcare.

On Skin Model Describability using Laplace-Beltrami Operator for Geometrical Product Specification and Verification

The skin model serves as a foundational concept defined in ISO standards on Geometrical Product Specifications and verification (ISO GPS), facilitating the consideration of geometric variations on the surfaces of mechanical products. However, the lack of a solid scientific foundation and practical operational applications has become a barrier for skin model concept to keep up with the development of standardized feature operations. A previous investigation was devoted to a scientific approach to defining and interpreting the skin model for ISO GPS, grounded in the structure of solids and set theory. In this paper, the use of the Laplace-Beltrami Operator (LBO) is explored as a mathematical operation to enhance the computational representations of the skin model. The describability of skin model is achieved by applying LBO in both continuous and discrete cases. Geometric filter banks, established through LBO, are employed for skin model to identify defects at various scales of observation. An application of LBO is demonstrated through a case study to highlight the use of established geometric filter banks for skin model. Further discussions show that the spectral analysis of a surface using LBO enables the characterization of skin model, contributing to the current and future standardization of geometrical product specification and verification. Finally, conclusion and future works are highlighted.

Advancing skin model development: A focus on a self-assembled, induced pluripotent stem cell-derived, xeno-free approach

The demand for skin models as alternatives to animal testing has grown due to ethical concerns and the need for accurate substance evaluation. These alternatives, known as New Approach Methodologies (NAMs), are increasingly used for regulatory decisions. Current skin models from primary human cells often rely on bovine collagen, raising ethical issues. This study explores self-assembled skin models (SASM) as a new method, utilizing hair follicle-derived keratinocytes reprogrammed into induced pluripotent stem cells (iPSC) and differentiated into fibroblasts and keratinocytes. The model relies on the ability of fibroblasts to secrete collagen to produce a xeno-free dermal layer and on the differentiation of keratinocytes to create a functional epidermal layer. These layers exhibited confirmed metabolic activity and the capability to withstand test substances. The successful development of SASM underscores the significance of accurate alternatives in dermatological research, providing an ethical and reliable option for substance evaluation and regulatory testing.

Based on In Vitro and 3D Epidermal Skin Model: The Efficacy of Bletilla Striata Extract for Skin Care

Introduction: Bletilla Striata (Thunb. ex A. Murray) Rchb. f.) Is a native herb of the orchidaceae family. Modern pharmacological activity studies have shown that Bletilla striata mainly has pharmacological activities such as promoting blood circulation and hemostasis, promoting wound healing anticancer, anti-tumor disease-resistant pathogenic microorganisms, protecting mucosa, anti-ulcer, whitening and anti-oxygen, anti-aging, and immune regulation, which have been widely recognized and applied. Research on the efficacy of plant extracts mainly adopts in vitro testing methods, such as cell experiment and 3D skin model experiment. Objective: To evaluate the soothing effect of Bletilla striata extracton UVB-stimulated keratinocytes (HaCaT) and its barrier repair efficacy in Skinovo-Epi skin model. Methods: The soothing and barrier repairing effects of Bletilla striata extract were studied in vitro. The cytotoxicity of the sample was measured by MTT assay, and cytotoxicity to keratinocytes was evaluated by cell survival rate. The soothing effect was evaluated by detecting changes in inflammatory cytokines (IL-6, IL-1β, IL-8, TNF-α) secreted by UVB-stimulated keratinocytes with the sample treatment. Barrier repair efficacy was assessed in a Skinovo-Epi skin model by measuring changes in FLG (Filaggrin) and LOR (Loricrin) protein levels after topical application of the sample. Results: The sample showed low cytotoxicity on keratinocytes. The sample significantly reduced UVB-stimulated secretion of inflammatory cytokines in keratinocytes. Topical application of the sample increased FLG and LOR protein levels in the Skinovo-Epi skin model. Conclusions:Bletilla striata extract exhibits soothing and barrier repair activities in vitro. Bletilla striata extract reduces UVB-stimulated inflammation in keratinocytes and improves skin barrier function. The data provide novel experimental evidence supporting the innovative application of Bletilla striata for skin disorders. Bletilla striata has potential as a therapeutic herb for sensitive and damaged skin conditions.

Histological and functional characterization of 3D human skin models mimicking the inflammatory skin diseases psoriasis and atopic dermatitis.

Three-dimensional (3D) human skin equivalents have emerged as valuable tools in skin research, replacing animal experimentation and precluding the need for patient biopsies. In this study, we advanced 3D skin equivalents to model the inflammatory skin diseases atopic dermatitis and psoriasis by cytokine stimulation, and were successful in integrating TH1 T cells into skin models to develop an immunocompetent 3D psoriasis model. We performed in-depth histological and functional characterization of 3D skin equivalents and validated them in terms of tissue architecture, pathological changes, expression of antimicrobial peptides and Staphylococcus aureus colonization using 3D reconstruction by multiphoton microscopy and phenotyping by highly multiplexed 'co-detection by indexing' (CODEX) microscopy. We show that our skin equivalents have a structural architecture with a well-developed dermis and epidermis, thus resembling human skin. In addition, the skin models of atopic dermatitis and psoriasis show several phenotypic features of inflammatory skin disease, including disturbed epidermal differentiation and alterations in the expression of epidermal barrier genes and antimicrobial peptides, and can be reliably used to test novel treatment strategies. Therefore, these 3D equivalents will be a valuable tool in experimental dermatological research.

Glutamic-acid grafted hyaluronic acid inhibits inflammatory factors via fibroblast and skin model tests.

Excessive inflammation may cause tissue damage and disrupt the function of the skin barrier. Hyaluronic acid (HA), an endogenous component, was found to regulate multiple inflammatory factors for skin health. This work aims to further enhance its efficacy by grafting amino acid onto its molecule. Glutamic acid (Glu) was selected as the ligand to react with low-molecular-weight HA. Fibroblast tests and a 3D skin model were used to investigate the anti-inflammation efficacy of HA-Glu. For IL-1α, IL-6 and TNF-α, the grafted compound presents stronger inhibition ability versus native HA. Moreover, HA-Glu could promote the repair of damaged skin by improving the compactness of the stratum corneum and increasing the thickness of the living cell layer. The application of HA-Glu compound in skin care formulas would be effective to alleviate inflammation-induced skin symptoms and skin aging.

A microneedle transdermal patch loaded with iron(ii) nanoparticles for non-invasive sustained delivery to combat anemia

A new innovative Iron Microneedles Patch for treatment of anemia was tested in vitro on two skin models. It shows steady release of Iron (FeSO4⋅7H2O) nanoparticles over 12 days, with a controlled burst release of 10% to 30% and near-linear kinetics.

Regulation of the immune microenvironment by pioglitazone-loaded polylactic glycolic acid nanosphere composite scaffolds to promote vascularization and bone regeneration

Osteogenesis is caused by multiple factors, and the inflammatory response, osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), regeneration of blood vessels, and other factors must be considered in bone tissue engineering. To effectively repair bone defect, it is important to decrease excessive inflammation, enhance the differentiation of mesenchymal stem cells into osteoblasts, and stimulate angiogenesis. Herein, nano-attapulgite (ATP), polyvinyl alcohol (PVA), and gelatin (GEL) scaffolds were produced using 3D printing technology and pioglitazone (PIO)-containing polylactic acid–glycolic acid (PLGA) nanospheres were added. In both in vitro and in vivo studies, material scaffolds with PIO-loaded polylactic acid–glycolic acid nanospheres could reduce the inflammatory response by encouraging macrophage polarization from M1 to M2 and promoting the osteogenic differentiation of BMSCs by activating the BMP2/Smad/RUNX2 signal pathway to repair bone defects. The vascularization of human umbilical vein endothelial cells (HUVECs) through the PI3K/AKT/HIF1-/VEGF pathway was also encouraged. In vivo research using PIO-containing PLGA nanospheres revealed massive collagen deposition in skin models. These findings indicate a potentially effective scaffold for bone healing, when PLGA nanospheres—which contain the drug PIO—are combined with ATP/PVA/GEL scaffolds.

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies.

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

Modeling of solar UV-induced photodamage on the hair follicles in human skin organoids

Solar ultraviolet (sUV) exposure is known to cause skin damage. However, the pathological mechanisms of sUV on hair follicles have not been extensively explored. Here, we established a model of sUV-exposed skin and its appendages using human induced pluripotent stem cell-derived skin organoids with planar morphology containing hair follicles. Our model closely recapitulated several symptoms of photodamage, including skin barrier disruption, extracellular matrix degradation, and inflammatory response. Specifically, sUV induced structural damage and catagenic transition in hair follicles. As a potential therapeutic agent for hair follicles, we applied exosomes isolated from human umbilical cord blood-derived mesenchymal stem cells to sUV-exposed organoids. As a result, exosomes effectively alleviated inflammatory responses by inhibiting NF-κB activation, thereby suppressing structural damage and promoting hair follicle regeneration. Ultimately, our model provided a valuable platform to mimic skin diseases, particularly those involving hair follicles, and to evaluate the efficacy and underlying mechanisms of potential therapeutics.

Homogenous and multilayer electromagnetics models for estimating skin reflectance

<span>Reflectance measurements of human skin are widely limited over the millimeter wave (MMW) band in literature. This is due to the cost and technical difficulties of the experimental setup. This paper proposes homogenous and multilayer skin models for estimating the reflectance of the forearm and palm of the hand skin over the MMW band 30-100 GHz. The simulation results demonstrate that the differences in reflectance between the homogenous and multilayer models of forearm skin are limited to 0.014, indicating that the thin stratum corneum (SC) layer in the multilayer skin models has a minimal impact on the interaction with MMW of the forearm skin. However, in the palm of hand skin, there is a substantial difference in reflectance calculations between the homogenous and the multilayer skin models in the range of 0.099 to 0.143. These differences are attributed to the presence of a thick SC layer in the palm of the hand. Thus, the simulation results suggested that two-layer should be used for the palm of hand skin as it better captures the reflectance characteristics of this region. The importance of having those models are in calculating the skin reflectance that can be used for the non-invasive diagnosis of skin conditions.</span>

Injectable and biodegradable collagen-chitosan microspheres for enhanced skin regeneration.

Skin aging is influenced by both external environmental factors and intrinsic biological mechanisms. Traditional microsphere implants aim to rejuvenate aging skin through collagen regeneration, yet their non-biodegradability and risk of granuloma formation often limit their effectiveness. In this study, we developed novel, injectable, highly bioactive, and degradable collagen-chitosan double-crosslinked composite microspheres for skin rejuvenation. The microspheres demonstrated excellent injectability, requiring an injection force of only 0.9 N, and significant biodegradability, effectively degraded in solutions containing phosphate buffer, type I collagenase, and pepsin. In addition, the microspheres exhibited excellent biocompatibility and bioactivity, significantly promoting the proliferation, adhesion, and migration of human foreskin fibroblast-1 (HFF-1) cells. In a photoaged mouse skin model, the implantation of microspheres significantly enhanced dermal density and skin elasticity while reducing transepidermal water loss. Importantly, the implant promoted the regeneration of collagen fibers. This study suggests that collagen-chitosan double-crosslinked composite microspheres hold significant potential for skin rejuvenation treatments.

Peptide Cy RL-QN15 accelerates hair regeneration in diabetic mice by binding to the Frizzled-7 receptor.

Individuals with diabetes frequently face serious challenges, including delayed wound healing and increased risk of infection. Notably, the regeneration of hair follicles plays a crucial role in accelerating diabetic skin damage repair, reducing the risk of infection, and enhancing overall skin health. Research has predominantly emphasized the re-epithelialization of diabetic wounds, with a paucity of in-depth studies on hair follicle regeneration. In the current study, we explored the effects of a bioactive amphibian-derived peptide, Cy RL-QN15, on promoting hair regeneration in a diabetic skin model. In vivo experiments demonstrated that local treatment with Cy RL-QN15 not only accelerated wound healing of scalded skin on the backs of diabetic Kunming (KM) mice but also improved growth of damaged hair follicles. Additionally, back-shaved diabetic C57BL/6 mice showed a significant increase in the growth of newly formed hair after 28 days of continuous Cy RL-QN15 treatment. Further analysis indicated that the hair-regenerating effects of Cy RL-QN15 were closely associated with the proliferation and migration of hair follicle stem cells (HFSCs). Cy RL-QN15 enhanced intracellular β-catenin expression by binding to the Frizzled-7 receptor on the surface of HFSCs. The up-regulation in β-catenin modulated the levels of downstream proteins, such as c-MYC, Cyclin D1, and Lef1, ultimately inducing hair regeneration. This study not only reveals the robust effects of the bioactive peptide Cy RL-QN15 in hair follicle regeneration but also provides novel avenues for the development of more targeted and effective therapeutics for diabetic wound healing in the future.

Three-Dimensional Cultured Human Dermal Papilla Cells in HGC-Coated Environments Enhance Hair Regeneration and Artificial Skin Integration

The rapid development of biomimetic materials in the field of regenerative medicine has made it possible to mimic natural cellular environments and allow in vitro systems to replace in vivo systems. In particular, the emergence of hexanoyl glycol chitosan (HGC) is playing an important role the development of 3-dimensional (3D) cell culture and tissue engineering. We employed HGC-coated dishes to cultivate human hair follicle dermal papilla (HDP) cells in 3D spheroids, assessing their ability to form hair-like structures. The study also tested the effect of minoxidil on these spheroids and explored their integration into artificial skin models. HDP cell spheroids successfully formed hair-like structures within the 3D culture. Minoxidil treatment showed enhanced hair growth in spheroids cocultured with keratinocytes. In addition, transplantation of these spheroids into artificial skin led to the formation of functional papilla structures, suggesting a closer mimicry of human skin. Hair-like structure formation and successful integration into artificial skin models pave the way for innovative approaches in hair loss treatment research, cosmetic, and pharmaceutical evaluations and skin restoration therapies.

Adaptive Weighted Vector Means Optimization for Healthy and Malignant Skin Modeling at Microwave Frequencies Using Clinical Data

Adaptive Weighted Vector Means Optimization for Healthy and Malignant Skin Modeling at Microwave Frequencies Using Clinical Data

Experimenting with Pig-based Skin Model for Burns. Testing of Mean Literature Findings.

Introduction: Animal models that closely mimic human burn wound healing processes are essential for developing effective burn wound treatments. Pigs are useful animal models for studying burn wound healing. From their extensive literature review, Andrews and Cuttle (2017) reported mean temperature and exposure time values. This study was done to provide initial burn depth for another experiment comparing two burn wound treatments. The secondary goal was to validate a systematic review on porcine burn model standardization. Material and Methods: Six four-week-old Large White x Landrace gilts were housed in a closed structure for 10 days to acclimatize. The procedures were performed under general anesthesia. A round 2.5 cm copper plate welded to an aluminum rod with a wooden handle caused the injuries. The burning device was used to reach a contact temperature of 110 C on the pig's skin. The objective was to create a superficial partial thickness (SPT) burn for 10 seconds (Group 10s) and a deep partial thickness (DPT) burn for 20 seconds (Group 20s) using a plate heated at 110ºC. No stabilizer or pressure controller was used. Wounds were conclusively dressed and harvested 24 hours later. The usual hematoxylin-eosin protocol was used to cut and stain 4-micron sections. Results: A significant difference (p 0.01) was observed in dermis involvement, with a mean of 85.61 % (95% CI= 80.62 to 90.61) for group 10s and 123.71% (95% CI= 114.91 to 132.50) for group 20s. An exposure time of 20 seconds increased dermis depth-related total collagen denaturation by almost 50% compared to 10 seconds. Conclusions: In conclusion, our experiment produced DPT burns in 10 seconds and FT burns in 20 seconds without a pressure application device.

Efficient Generation of CRISPR/Cas9-Mediated Knockout Human Primary Keratinocytes by Electroporation.

Due to their full differentiation capacity in vitro, the culture of human primary keratinocytes (HPKs) represents a physiological model for answering basic biological and dermatological research questions, including those related to skin diseases and the investigation of treatment options. When modified with the CRISPR/Cas9 gene editing approach and cultivated in organotypic 3D epidermal equivalents (EEs), these human cells have the potential to replace established mouse models. However, even when cultivated on feeder cells, HPKs have only a low proliferation capacity in 2D culture, limiting their application potential. This is particularly true for CRISPR/Cas9-modified HPKs, whose generation commonly requires selection of targeted cells, negatively affecting their lifespan. Here, we describe a robust protocol for the rapid, simple, and efficient generation of single- and multi-gene CRISPR/Cas9 knockout HPKs by electroporation of ribonucleoprotein (RNP) complexes, which comprise one or multiple guide RNAs (gRNAs) and Cas9 protein. Unlike DNA transfection or virus-based targeting strategies, electroporation of RNPs represents a targeting approach that minimizes immunological and toxic side effects. Using efficient gRNAs results in the generation of HPKs with a high yield of knockout cells, allowing for their immediate use in experiments without requiring the laborious process of selecting targeted cells or maintaining a feeder cell culture. Furthermore, the use of RNPs and their delivery via electroporation minimizes off-target and other unspecific effects, preventing unintended genomic alterations. Most importantly, CRISPR/Cas9 knockout HPKs generated with this protocol have the ability to form a fully differentiated epidermis in 3D, thus facilitating the understanding of specific protein functions in a highly physiological human skin model. Alternatively, this approach proves valuable for generating models of mono- or polygenic skin diseases via knockouts, providing insights into the underlying molecular mechanisms and facilitating the development of novel therapeutic approaches.

Spatially Averaged Epithelial/Absorbed Power Density for Nonplanar Skin Models Exposed to Antenna at 10–90 GHz

Spatially Averaged Epithelial/Absorbed Power Density for Nonplanar Skin Models Exposed to Antenna at 10–90 GHz

Anisotropic rough surfaces representation in geometrical deviations modeling for tolerance analysis

Accurate modeling of geometrical deviations is the premise and critical step for tolerance analysis. Traditional tolerance modeling methods usually simplify deviations to variations in degrees of freedom. Although this facilitates the uniform representation and accumulative calculation, it is not possible to consider the effects of real topography over mating interfaces on tolerance analysis in high-precision scenarios. In this regard, this paper proposed a tolerance modeling method for representing anisotropic rough surfaces information under the framework of Skin Model Shapes. Specifically, the spatial information on rough surfaces is represented by autocorrelation functions. A set of nonlinear equations are constructed according to given autocorrelation functions and then solved to obtain the desired surface topography. In case studies simulated rough surfaces with different input parameters are illustrated and the consistency of this method is verified. The proposed method provides an accurate and practical way to represent anisotropic rough surfaces for tolerance modeling and analysis.

Mechanical and chemical itch regulated by neuropeptide Y-Y1 signaling.

Itch is a somatosensory sensation to remove potential harmful stimulation with a scratching desire, which could be divided into mechanical and chemical itch according to diverse stimuli, such as wool fiber and insect biting. It has been reported that neuropeptide Y (NPY) neurons, a population of spinal inhibitory interneurons, could gate the transmission of mechanical itch, with no effect on chemical itch. In our study, we verified that chemogenetic activation of NPY neurons could inhibit the mechanical itch as well as the chemical itch, which also attenuated the alloknesis phenomenon in the chronic dry skin model. Afterwards, intrathecal administration of NPY1R agonist, [Leu31, Pro34]-NPY (LP-NPY), showed the similar inhibition effect on mechanical itch, chemical itch and alloknesis as chemo-activation of NPY neurons. Whereas, intrathecal administration of NPY1R antagonist BIBO 3304 enhanced mechanical itch and reversed the alloknesis phenomenon inhibited by LP-NPY treatment. Moreover, selectively knocking down NPY1R by intrathecal injection of Npy1r siRNA enhanced mechanical and chemical itch behavior as well. These results indicate that NPY neurons in spinal cord regulate mechanical and chemical itch, and alloknesis in dry skin model through NPY1 receptors.