Human Skin Physiology Research Articles

Vitamin C and its derivatives in maintaining the good skin condition

Vitamin C is one of the most important and necessary nutrient for human health, which has great potential as cosmeceutic, which protects health and the skin good condition. Thru the collagen biosynthesis stimulation it affects to the physiology of human skin, participating in the hydroxylation process of proline and lysine, and participates in tissue reconstruction while wound healing. Deficiency of vitamin C causes irregularities in the blood vessels functioning, epidermis and dermis. Is an effective antioxidant neutralizing free radicals, prevents inflammatory and carcinogenic processes. The epidermis and dermis are most exposed to free radicals from the external environment and from the inside of the body. In inflammatory diseases of the skin, such as atopic dermatitis, psoriasis, in the proper skin the levels of vitamin C are reduced. Therefore, delivering it to the skin using cosmetic preparations is important not only for cosmetic, but also health effect. The problem associated with the introduction of vitamin C in cosmetics is its limited penetration through the stratum corneum. Current studies are focused on searching for stable compounds of ascorbic acid and new media, which will allow for better way of delivery of ascorbic acid to the dermis in the future.

Human relevance of in vivo and in vitro skin irritation tests for hazard classification of pesticides

Background: Test methods to inform hazard characterization and labeling of pesticides to protect human health are typically conducted using laboratory animals, and for skin irritation/corrosion the rabbit Draize test is currently required by many regulatory agencies. Although the Draize test is generally regarded to provide protective classifications for human health, new approach methodologies (NAMs) have been developed that offer more human relevant models that circumvent the uncertainty associated with species differences that exist between rabbits and humans. Despite wide applicability and use of these test methods across a broad range of chemicals, they have not been widely adopted for testing pesticides and pesticidal formulations. One of the barriers to adoption of these methods in this sector is low concordance with results from the Draize rabbit test, particularly for chemicals within the mild to moderate irritation spectrum. Methods: This review compares and contrasts the extent to which available models used in skin irritation testing mimic the anatomy and physiology of human skin, and how each aligns with the known key events leading to chemically-induced adverse skin irritation and corrosion. Doing so fully characterizes the human relevance of each method. Results: As alternatives to the rabbit Draize test, several protocols using ex vivo, in chemico, and in vitro skin models are available as internationally harmonized test guidelines. These methods rely on a variety of models of human skin, including excised rodent skin, synthetic biochemical models of barrier function, cell culture systems, and reconstructed human tissue models. We find these models exhibit biological and mechanistic relevance aligned with human skin irritation responses. Further, recent retrospective analyses have shown that the reproducibility of the Draize test is less than 50% for mild and moderate responses, with many of the replicate predictions spanning more than one category (e.g., a moderate response reported in one study followed by a non-irritant response reported in another study). Conclusions: Based on this comparative evaluation, we recommend top-down and bottom-up testing strategies that use the most human relevant in vitro test methods for skin irritation and corrosion classification of pesticides and pesticide formulations. To further discriminate among mild and non-irritant formulations, optimization of a cytokine release protocol and subsequent analyses of reference formulation test results is recommended.

Oral supplementation of vegan collagen biomimetic has beneficial effects on human skin physiology: A double-blind, placebo-controlled study

BackgroundVegan collagen is an innovative plant-based collagen biomimetic that contains a variety of plant extracts, including asiaticoside, ginsenoside, and through fermented amino acids, which stimulates the natural process for type I collagen synthesis. MethodsIn this study, using vegan collagen (Corpowell BV, Schilde, Belgium) to explore the skin beautifying effects in the human body. 90 subjects were recruited and divided into a placebo group (n = 30), a vegan collagen group (n = 30), and a fish collagen group (n = 30). Subjects were informed to consume 1 sachet of the sample daily for 8 weeks. Skin conditions were measured at week 0, week 4 and week 8. ResultsThe results showed that vegan collagen significantly increased collagen density and elasticity by 4.7% and 5.1% and decreased wrinkles, texture, and pores by 27.5%, 20.1%, and 12.3% compared to the placebo group. In addition, the hydration and lightness were increased by 4.3% and 2.3% compared to the placebo group. ConclusionVegan collagen has the potential to improve skin collagen density, elasticity, texture, wrinkles, pores, hydration, and lightness.

In Vitro and Ex Vivo Models for Screening Topical Anti-Inflammatory Drugs

Skin inflammation occurs as an immune response to various stimuli such as ultraviolet light, irritants, or any type of skin barrier injury. Finding safe and effective drugs to combat skin inflammation remains a research challenge. Ethical and legal considerations in animal testing encourage the development of in vitro and ex vivo models for the detection of skin inflammation. This report presents an updated review of non-animal study models available for screening drugs with anti-inflammatory potential. It includes a description of the basic methods used to inhibit protein denaturation and red blood cell membrane stability. Three in vitro inhibition assay methods for enzymes relevant to the skin inflammatory process are then described. The development of cell culture models is described: relatively simple and easy-to-produce two-dimensional (2D) skin cell cultures that allow assessment of response to a given stimulus, three-dimensional (3D) cell cultures that better mimic human skin physiology by more accurately replicating mechanical and chemical signals, and vascularized 3D skin models with dynamic perfusion and microfluidic devices known as skin on a chip. Finally, ex vivo skin models are presented that could more accurately represent human skin in terms of structure, cell signaling mechanisms, and absorption effects. Although the current development of models without the use of animals is promising, improvements and refinements are needed to make the models more suitable as screening platforms for topical anti-inflammatory drugs.

Correlation between Blood Flow and Various Physiological Parameters in Human Skin

Blood flow is an important parameter of the human organism and skin physiology. It correlates with skin temperature, penetration of active substances through the skin, delivery of antioxidants and development of disease symptoms, especially during inflammatory processes. Dr. Alexander Vasilyevich Priezzhev played a major role in the investigation of blood circulation, cell aggregation and disease correlation, as well as in the development of an aggregometer to determine the rheology of human blood flow. The following article provides an overview of the work performed at the Charité – Universitätsmedizin Berlin, Department of Dermatology and Allergology, Center of Experimental and Applied Cutaneous Physiology, partly in cooperation with Dr. Priezzhev, on the correlation of blood flow and various physiological parameters in human and animal skin in vivo.

228 Analysis of the effect of media conditioned by human sensory neurons subjected to oxidative stress on human epidermis

Oxidative stress (OS) is a deleterious process involved in premature aging and in several inflammatory dermatosis (atopic dermatitis, psoriasis…). Beyond cutaneous cells, OS can also have adverse effects on free nerve endings innervating epidermis and that play a crucial role in cutaneous homeostasis. Little is known about the consequence of OS on these neurons and then, on skin. The aim of this study was to assess the effects of OS (H2O2) on sensory neurons derived from human induced pluripotent stem cells (iPSC) on human skin physiology (Reconstructed Human Epidermis, RHE) by using conditioned supernatants (CS).

223 Canonical and Dominant Negative Peroxisome Proliferator-Activated Receptor γ Isoforms are Differentially Expressed in Human Skin and Skin Appendages

Peroxisome proliferator-activated receptors (PPARs), which exert multiple key signaling functions in human skin physiology and pathology, exist in various isoforms. These include canonical (cPPARγ1-4) and dominant negative isoforms (dnPPARγ: γORF4 (γ1-3ORF4), truncated PPARG (PPARγtr) and PPARγΔ5. Yet their exact expression patterns in human skin remain unclear. Therefore, we have localized and quantified PPARγ isoforms in skin biopsies from healthy donors by qRT-PCR or in situ hybridization (for cPPARG).

743 Hair follicles can “taste”: Stevioside stimulation of the bitter taste receptor, TAS2R4, inhibits human hair growth ex vivo

Besides taste buds, many other tissues express taste receptors (TR), where they exert various, often ill-explored non-gustatory functions, e.g. in immunity and metabolism. These evolutionary ancient functions of human TRs can be optimally interrogated in human skin, whose keratinocytes express selected TRs, and its dominant appendage, the hair follicle (HF). However, the role of TRs in human skin physiology is unknown. Therefore, we have asked whether TRs are expressed in human scalp HFs and if their specific stimulation or silencing affects hair growth. Here, we show that human scalp HF keratinocytes prominently and hair cycle-dependently express the bitter taste receptor, TAS2R4 (mRNA, protein). When TAS2R4 was stimulated in organ-cultured anagen scalp HFs by the sweet-tasting steviol-glycoside TAS2R4 agonist, rebaudioside A (Reb A), this significantly inhibited hair matrix keratinocyte proliferation and induced premature catagen development ex vivo. These RebA effects could be reversed by TAS2R4 knockdown ex vivo. Mechanistically, these HF effects are mainly caused by TAS2R4-mediated enhanced expression/ secretion of the key catagen-promoting growth factor, TGFβ2, since TGFß-neutralization counteracted RebA-induced catagen induction and since RNAseq analysis showed upregulation of TGFß-related signaling pathways. Thus, we introduce here TRs as important, ancestral chemosensory regulators of human skin physiology, human (mini-)organ remodeling (=HF cycling), and growth factor production (TGFß). We also identify a novel, drug-free, “gustatory” strategy for the therapeutic inhibition of unwanted hair growth (hirsutism, hypertrichosis) with a natural sweetener.

842 Novel human skin organ culture models for the identification and characterization of anti-aging actives ex vivo

Research of chronological (intrinsic) aging in human skin and the development of potent anti-aging and rejuvenating agents are impeded by the limited availability of clinically relevant models. As current cell culture approaches cannot satisfactorily recapitulate normal human skin physiology and aging, even under 3D conditions, human full-thickness skin organ culture (hSOC) remains an excellent, but under-used alternative for pre-clinical aging research and the testing of candidate senolytics. Here, we present three distinct, complementary novel hSOC approaches to interrogating intrinsic, UV-free human skin aging.

Cymbopogon citratus (DC.) Stapf essential oil: Unraveling potential benefits on human skin

The essential oil of Cymbopogon citratus (DC.) Stapf is widely used for the production of fragrances, cosmetics, and detergents. However, there is no information on the effects of formulations containing C. citratus essential oil (EOCC) on human skin. This study aimed to evaluate the effects of formulation containing EOCC on human skin physiology. The study involved participants of both sexes (n=12). Two areas (3 cm x 3 cm) were drawn on both forearms. One randomly chosen area was treated for 14 days, 2 times/day with polyacrylic acid gel containing 5% EOCC and the other was used as a control for the same time period. Transepidermal water loss (TEWL), hydration, epidermal lipids, and biomechanics were measured (D0 and D14). High resolution Sonography images were also obtained. Results revealed a significant decrease in TEWL, a significant increase in hydration, firmness and elasticity, and a decrease in lipids, in the areas treated with EOCC. Sonography showed an increase in echogenicity of the epidermis after applying the formulation indicating that the essential oil penetrates only the most superficial layers of the skin. Results also suggest that formulations containing EOCC are safe for topical application and can improve and protect human skin. Keywords: Cymbopogon citratus; essential oil; citral; lemongrass

Fabrication of Human Skin Equivalents Using Decellularized Extracellular Matrix.

There is a growing demand for in vitro models of human tissues that recapitulate the complex structures and functions found in vivo, and the biomaterials that support these physiologically relevant models are essential underpinning technologies. Here, we present an optimized protocol for generating human skin equivalents (HSEs) using a dermal matrix isolated from decellularized porcine skin. The decellularized extracellular matrix (dECM) contains a complex mixture of fibrillar collagens and matrisomal proteins that mimic native skin and can be produced in large quantities. The procedure for decellularization, digestion, and solubilization of the dECM is described in detail. In addition, we provide instructions for how to construct a three‐dimensional HSE model using the dECM as the dermal support matrix for human keratinocytes and dermal fibroblasts. Recent studies from our laboratory have shown that HSEs generated using porcine dECM display improved epidermal differentiation and stratification compared to existing protocols using type I collagen gels. Thus, dECM‐based biomaterials are a useful tool for replicating human skin physiology in vitro and developing advanced human skin models for therapeutic discovery and testing. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Preparation of decellularized extracellular matrix from porcine skin Basic Protocol 2: Generation of human skin equivalents

Impact of microstructure on cell behavior and tissue mechanics in collagen and dermal decellularized extra-cellular matrices

Skin models are used for many applications such as research and development or grafting. Unfortunately, most lack a proper microenvironment producing poor mechanical properties and inaccurate extra-cellular matrix composition and organization. In this report we focused on mechanical properties, extra-cellular matrix organization and cell interactions in human skin samples reconstructed with pure collagen or dermal decellularized extra-cellular matrices (S-dECM) and compared them to native human skin. We found that Full-thickness S-dECM samples presented stiffness two times higher than collagen gel and similar to ex vivo human skin, and proved for the first time that keratinocytes also impact dermal mechanical properties. This was correlated with larger fibers in S-dECM matrices compared to collagen samples and with a differential expression of F-actin, vinculin and tenascin C between S-dECM and collagen samples. This is clear proof of the microenvironment's impact on cell behaviors and mechanical properties. Statement of significanceIn vitro skin models have been used for a long time for clinical applications or in vitro knowledge and evaluation studies. However, most lack a proper microenvironment producing a poor combination of mechanical properties and appropriate biological outcomes, partly due to inaccurate extra-cellular matrix (ECM) composition and organization. This can lead to limited predictivity and weakness of skin substitutes after grafting. This study shows, for the first time, the importance of a complex and rich microenvironment on cell behaviors, matrix macro- and micro-organization and mechanical properties. The increased composition and organization complexity of dermal skin decellularized extra-cellular matrix populated with differentiated cells produces in vitro skin models closer to native human skin physiology.

Growth Hormone and the Human Hair Follicle.

Ever since the discoveries that human hair follicles (HFs) display the functional peripheral equivalent of the hypothalamic-pituitary-adrenal axis, exhibit elements of the hypothalamic-pituitary-thyroid axis, and even generate melatonin and prolactin, human hair research has proven to be a treasure chest for the exploration of neurohormone functions. However, growth hormone (GH), one of the dominant neurohormones of human neuroendocrine physiology, remains to be fully explored in this context. This is interesting since it has long been appreciated clinically that excessive GH serum levels induce distinct human skin pathology. Acromegaly, or GH excess, is associated with hypertrichosis, excessive androgen-independent growth of body hair, and hirsutism in females, while dysfunctional GH receptor-mediated signaling (Laron syndrome) is associated with alopecia and prominent HF defects. The outer root sheath keratinocytes have recently been shown to express functional GH receptors. Furthermore, and contrary to its name, recombinant human GH is known to inhibit female human scalp HFs’ growth ex vivo, likely via stimulating the expression of the catagen-inducing growth factor, TGF-β2. These limited available data encourage one to systematically explore the largely uncharted role of GH in human HF biology to uncover nonclassical functions of this core neurohormone in human skin physiology.

A Novel Xenograft Model Demonstrates Human Fibroblast Behavior During Skin Wound Repair and Fibrosis.

Objective: Xenografts of human skin in immunodeficient mice provide a means of assessing human skin physiology and its response to wounding. Approach: We describe a novel xenograft model using full-thickness human neonatal foreskin to examine human skin wound repair. Full-thickness 8 mm human neonatal foreskin biopsies were sutured into the dorsum of NOD scid gamma (NSG; NOD.Cg-Prkdc scidIl2rgtm1Wjl/SzJ) pups as subcutaneous grafts. At postnatal day 21 the subcutaneous grafts were exposed to cutaneous grafts. Following maturation of 2 months, xenografts were then wounded with 5 mm linear incisions and monitored until postwound day (PWD) 14 to study skin repair and fibrosis. To explore whether our model can be used to test the efficacy of topical therapies, wounded xenografts were injected with antifibrotic fibroblast growth factor 2 (FGF2) for the first four consecutive PWDs. Xenografts were harvested for analysis by histology and fluorescence-activated cell sorting (FACS). Results: Xenografts were successfully engrafted with evidence of mouse-human anastomoses and resembled native neonatal foreskin at the gross and microscopic level. Wounded xenografted skin scarred with human collagen and an expansion of CD26-positive human fibroblasts. Collagen scar was quantitated by neural network analysis, which revealed distinct clustering of collagen fiber networks from unwounded skin and wounded skin at PWD7 and PWD14. Collagen fiber networks within FGF2-treated wounds at PWD14 resembled those in untreated wounded xenografts at PWD7, suggesting that FGF2 treatment at time of wounding can reduce fibrosis. Innovation and Conclusion: This novel xenograft model can be used to investigate acute fibrosis, fibroblast heterogeneity, and the efficacy of antifibrotic agents during wound repair in human skin.

Effects of Oral Supplementation of TrichovitalsTM on Human Skin, Hair and Nail Physiology

In this study, Microcore’s oral supplements of TrichovitalsTM contains Collagen type (I,III,V,X), elastin, ellagic acid, Sabbery b glucogallin, Biotin, Curcumin C3 reduct ODN and Murraya koenigii. ESM ingestion is associated with significant impact on hair thickness, reduction in hair breakage and improvement in hair growth. This study leads to evaluate the impacts of a nutritional intervention as compared to control group (without oral supplements intake) on the appearances of hair, skin, and nails in healthy middle-aged adults. Two pilot studies were run to assess TrichovitalsTM on skin parameter. 1. Self-assessment questionnaire intended to perform an assessment on skin, hair, and nail health after 12 weeks of treatment for a group of 25 female volunteers 2. Evaluated the efficacy of TrichovitalsTM effect of 5-week treatment on hydration of skin by corneometry, on elasticity with the cutometer, and on pigmentation with themexameteron for a group of 7 female volunteers, Microscopic studies of hair strength and nail growth. In study 1-Participants were predominantly satisfied with the effects obtained on general face (100% volunteers satisfied) and (94% volunteers satisfied) body skin condition and skin properties (100% volunteers satisfied) with facial skin softness, 95% ith facial skin hydration, 63% of facial skin brightness and 89% with body skin hydration and significant effects on hair damages (100% volunteers satisfied), hair falls (95% volunteers satisfied) and hair growth (96% volunteers satisfied) and nail appearance (80% volunteers satisfied) and improvement in brittle nails. In this open-label 5 weeks study, Oral Microcore’s TrichovitalsTM ingestion was associated with a significant improvement in skin appearance such as increase skin hydration and skin elasticity, reduces skin pigmentation after 5 weeks treatment and facial skin tone, with significant impact on hair thickness, reduces split ends, hair loss, hair breakage and improvement in hair growth after 5 weeks treatment, increase of 80% nail growth rate and a decrease of 42% brittle nails after 6 weeks. Microcore’s TrichovitalsTM achieved significant change improvement in skin, hair and nail appearance (thickness/density) than control group (without oral supplements intake) by week 12 of the study. From the result analysis, Microcore’s TrichovitalsTM is deemed to be one of the most effective anti-aging products in cosmetic sector and overall physical appearance. Oral supplementation of 500mg/day of Microcore’s TrichovitalsTM for 12 weeks is associated with significant improvement in the appearance of facial skin, hair and nail. Increases in skin hydration and skin elasticity with reduced pigmentation on skin were observed after 5 weeks treatment, which is a very important marker for skin aging. Also significant impact on hair thickness reduces split ends, hair loss, hair breakage and improvement in hair growth and healthy development of nails after 5 weeks treatment.

Effects of Oral Supplementation of Muttaijow complexTM on Human Skin, Hair and Nail Physiology

In this study, Microcore’s oral supplements of Muttaijow ComplexTM obtained from the egg shell that contains naturally occurring collagen Type (I, V, X), Elastin (Desmosine and isodesmosine), Hyaluronic acid, Glucosamine, Chondroitin, Glycosaminoglycans or Muco-polysaccharides, Membrane bound protein molecules, and Calcium are used in a group of volunteers. This study leads to evaluate the impacts of a nutritional intervention as compared to control group (without oral supplements intake) on the appearances of hair, skin, and nails in healthy middle-aged adults. Two pilot studies were run to assess Muttaijow ComplexTM on skin parameter. 1. Self-assessment questionnaire intended to perform an assessment on skin, hair, and nail health after 12 weeks of treatment for a group of 25 female volunteers 2. Evaluated the efficacy of Muttaijow ComplexTM effect of 5-week treatment on hydration of skin by corneometry, on elasticity with the cutometer, and on pigmentation with themexameteron for a group of 7 female volunteers, Microscopic studies of hair strength and nail growth. In study 1-Participants were predominantly satisfied with the effects obtained on general face (100% volunteers satisfied) and body (94% volunteers satisfied) skin condition and skin properties (100% volunteers satisfied with facial skin softness, 95% with facial skin hydration, 83% of facial skin brightness and 89% with body skin hydration) and partly with effects on hair (65-70%volunteers satisfied) and nail appearance (70% volunteers satisfied) and improvement in brittle nails. In this open-label 5 weeks study, Oral Microcore’s Muttaijow ComplexTM ingestion was associated with a significant improvement in skin appearance such as increase skin hydration and skin elasticity, reduces skin pigmentation after 5 weeks treatment and facial skin tone, with significant impact on hair thickness, reduces split ends, hair loss, hair breakage and improvement in hair growth after 5 weeks treatment, increase of 12% nail growth rate and a decrease of 42% brittle nails after 6 weeks. Microcore’s Muttaijow ComplexTM achieved significant change improvement in skin, hair and nail appearance (thickness/density) than control group (without oral supplements intake) by week 12 of the study. From the result analysis, Microcore’s Muttaijow ComplexTM is deemed to be one of the most effective anti-aging products in cosmetic sector and overall physical appearance. Oral supplementation of 500mg/day of Microcore’s Muttaijow ComplexTM for 12 weeks is associated with significant improvement in the appearance of facial skin, hair and nail. Increases in skin hydration and skin elasticity with reduced pigmentation on skin were observed after 5 weeks treatment, which is a very important marker for skin aging. Also, significant impact on hair thickness, reduces split ends, hair loss, hair breakage and improvement in hair growth and healthy development of nails after 5 weeks treatment.

Effect of Sodium Lauryl Sulfate (SLS) Applied as a Patch on Human Skin Physiology and Its Microbiota

In this study, we assessed the change in skin microbiota composition, relative abundance, and diversity with skin physiology disruption induced by SLS patch. Healthy women declaring to have a reactive skin were submitted to a 0.5% aqueous sodium lauryl sulfate solution application under occlusive patch condition for 24 h. Skin properties were characterized by tewametry, corneometry, and colorimetry and bacterial diversity was assessed by 16S rRNA sequencing. Analysis before and one day after SLS patch removal revealed an increase of skin redness and a decrease of stratum corneum hydration and skin barrier function. The relative abundance of taxa containing potential pathogens increase (Firmicutes: Staphylococcaceae; Proteobacteria: Enterobacteriaceae, Pantoea) while some of the most occurring Actinobacteria with valuable skin protection and repair capacities decreased (Micrococcus, Kocuria, and Corynebacterium). We observed an impaired skin barrier function and dehydration induced by SLS patch disturb the subtle balance of skin microbiota towards skin bacterial community dysbiosis. This study provides new insights on the skin bacterial composition and skin physiology simultaneously impaired by a SLS patch.

Ustekinumab pharmacokinetics after subcutaneous administration in swine model.

BackgroundDue to multiple similarities in the structure and physiology of human and pig skin, the pig model is extremely useful for biological drug testing after subcutaneous administration. Knowledge of the differences between subcutaneous injection sites could have a significant impact on the absorption phase and pharmacokinetic profiles of biological drugs.ObjectivesThis study aimed to analyze the impact of administration site on pharmacokinetics and selected biochemical and hematological parameters after a single subcutaneous administration of ustekinumab in pigs. Drug concentrations in blood plasma were analyzed by enzyme-linked immunosorbent assay. Pharmacokinetic analyses were performed based on raw data using Phoenix WinNonlin 8.1 software and ThothPro v 4.1.MethodsThe study included 12 healthy, female, large white piglets. Each group received a single dose of ustekinumab given as a 1 mg/kg subcutaneous injection into the internal part of the inguinal fold or the external part of the inguinal fold.ResultsThe differences in absorption rate between the internal and external parts of the inguinal fold were not significant. However, the time of maximal concentration, clearance, area under the curve calculated between zero and mean residence time and mean residence time between groups were substantially different (p > 0.05). The relative bioavailability after administration of ustekinumab into the external part of the inguinal fold was 40.36% lower than after administration of ustekinumab into the internal part of the inguinal fold.ConclusionsHealthy breeding pigs are a relevant model to study the pharmacokinetic profile of subcutaneously administered ustekinumab.

Влияние модуляции активности p53 на взаимодействие членов семейства p53 в процессе дифференцировки кератиноцитов линии HaСaT

HaCaT cell line is a widely used model for studying normal human keratinocytes. However, mutations of TP53 gene are typical for this cell line, which have a substantial impact on functions of the encoded protein. The features of this regulatory circuit should be considered when using HaСaT cells for assessment of human skin physiology and pathology in vitro. The study was aimed to assess the features of differentiation realization in HaCaT cells with modulated activity of p53 protein. The expression of p53 was reduced by knockdown of TP53 gene by shRNA (by 2.2 times, p < 0.05), and the elevated concentration of the p53 active forms was achieved via exposure of cells to Nutlin-3a, the MDM2 inhibitor and the major negative regulator of p53. It has been found that regulation of at least three differentiation markers, СASP14, IVL (expression increase by 3.9 and 3.7 times respectively in the p53-knockdown cells, p < 0.05) and TGM1 (twofold expression decrease in the p53-knockdown cells, and 1.7-fold expression increase under exposure to Nutlin-3a, p < 0.05) in HaCaT cells is p53-mediated. The positive correlation has been revealed for expression of TGM1 and p53 that might be realized indirectly via ΔNp63 expression alteration. At the same time, modulation of p53 does not result in significant alterations in expression of cytokeratins.

Vitamin C\u2013squalene bioconjugate promotes epidermal thickening and collagen production in human skin

Vitamin C (Vit C) benefits to human skin physiology notably by stimulating the biosynthesis of collagen. The main cutaneous collagens are types I and III, which are less synthesized with aging. Vit C is one of the main promotors of collagen formation but it poorly bypasses the epidermis stratum corneum barrier. To address this challenge, we developed a lipophilic version of Vit C for improving skin diffusion and delivery. Vit C was covalently conjugated to squalene (SQ), a natural lipid of the skin, forming a novel Vit C–SQ derivative suitable for cream formulation. Its biological activity was investigated on human whole skin explants in an ex vivo model, through histology and protein and gene expression analyses. Results were compared to Vit C coupled to the reference lipophilic compound palmitic acid, (Vit C–Palmitate). It was observed that Vit C–SQ significantly increased epidermal thickness and preferentially favored collagen III production in human skin after application for 10 days. It also promoted glycosaminoglycans production in a higher extent comparatively to Vit C–Palmitate and free Vit C. Microdissection of the explants to separate dermis and epidermis allowed to measure higher transcriptional effects either in epidermis or in dermis. Among the formulations studied, the strongest effects were observed with Vit C–SQ.