The neuropeptide Substance P facilitates the transition from an inflammatory to proliferation phase-associated responses in dermal fibroblasts.

The wound healing process is a product of three successive and overlapping phases of inflammation, proliferation and remodelling. Considerable efforts have been invested in deconstructing the intercellular crosstalk that orchestrates tissue repair, and we investigated the role of neuropeptides released from peripheral neurons upon injury in mediating these interactions. Amongst the most abundant of these neuropeptides secreted by nerves in the skin, is Substance P (SP). Given the role of dermal fibroblasts in coordinating multiple processes in the wound healing program, the effect of SP on human dermal fibroblasts of different ages was evaluated. The use of a substrate that recapitulates the mechanical properties of the in vivo tissue revealed novel effects of SP on dermal fibroblasts, including a block in inflammatory cytokine expression. Moreover, SP can promote expression of some extracellular matrix components and generates signals that regulate angiogenesis. Interestingly, the response of fibroblasts to SP was reduced concomitant with donor age. Altogether, SP acts to inhibit the inflammatory responses and promote proliferation-associated responses in an age-dependent manner in dermal fibroblasts, suggesting a role as a molecular switch between the inflammatory and proliferative phases of the wound healing response.

Anandamide Suppresses Proinflammatory T Cell Responses In Vitro through Type-1 Cannabinoid Receptor-Mediated mTOR Inhibition in Human Keratinocytes.

The endocannabinoid system comprises cannabinoid receptors 1 and 2 (CB1 and CB2), their endogenous ligands, anandamide (AEA) and 2-arachidonoylglycerol, and metabolic enzymes of these ligands. The endocannabinoid system has recently been implicated in the regulation of various pathophysiological processes of the skin that include immune competence and/or tolerance of keratinocytes, the disruption of which might promote the development of skin diseases. Recent evidence showed that CB1 in keratinocytes limits the secretion of proinflammatory chemokines, suggesting that this receptor might also regulate T cell dependent inflammatory diseases of the skin. In this article, we sought to investigate the cytokine profile of IFN-γ-activated keratinocytes, and found that CB1 activation by AEA suppressed production and release of signature TH1- and TH17-polarizing cytokines, IL-12 and IL-23, respectively. We also set up cocultures between a conditioned medium of treated keratinocytes and naive T cells to disclose the molecular details that regulate the activation of highly proinflammatory TH1 and TH17 cells. AEA-treated keratinocytes showed reduced an induction of IFN-γ-producing TH1 and IL-17-producing TH17 cells, and these effects were reverted by pharmacological inhibition of CB1 Further analyses identified mammalian target of rapamycin as a proinflammatory signaling pathway regulated by CB1, able to promote either IL-12 and IL-23 release from keratinocytes or TH1 and TH17 polarization. Taken together, these findings demonstrate that AEA suppresses highly pathogenic T cell subsets through CB1-mediated mammalian target of rapamycin inhibition in human keratinocytes. Thus, it can be speculated that the latter pathway might be beneficial to the physiological function of the skin, and can be targeted toward inflammation-related skin diseases.

A jasmonic acid derivative improves skin healing and induces changes in proteoglycan expression and glycosaminoglycan structure.

BACKGROUND: Jasmonates are plant hormones that exhibit anti-cancer and anti-inflammatory properties and have therefore raised interest for human health applications. The molecular basis of these activities remains poorly understood, although increasing evidence suggests that a variety of mechanisms may be involved. Recently, we have reported that a jasmonate derivative (JAD) displayed anti-aging effects on human skin by inducing extracellular matrix (ECM) remodeling. Based on this observation, we have investigated here the effects of JAD on proteoglycans and glycosaminoglycan (GAG) polysaccharides, which are major cell-surface/ECM components and are involved in a multitude of biological processes. In parallel, we have examined the ability of JAD to promote growth factor activities and improve skin wound healing. METHODS: Proteoglycan expression was analyzed on epidermal primary keratinocytes and reconstituted skin epidermis, using electron/immunofluorescence microscopy, western blotting and flow cytometry. GAG composition was determined by disaccharide analysis. Finally, biological activities of JAD were assessed in cellulo, in FGF-7 induced migration/proliferation assays, as well as in vivo, using a suction blister model performed on 24 healthy volunteers. RESULTS: JAD was found to induce expression of major skin proteoglycans and to induce subtle changes in GAG structure. In parallel, we showed that JAD promoted FGF-7 and improved skin healing by accelerating epithelial repair in vivo. CONCLUSION: This study highlights JAD as a promising compound for investigating GAG structure-function relationships and for applications in skin cosmetic /corrective strategies. GENERAL SIGNIFICANCE: We propose here a novel mechanism, by which jasmonate derivatives may elicit biological activities in mammals.

Sweating the small stuff: Glycoproteins in human sweat and their unexplored potential for microbial adhesion.

There is increasing evidence that secretory fluids such as tears, saliva and milk play an important role in protecting the human body from infection via a washing mechanism involving glycan-mediated adhesion of potential pathogens to secretory glycoproteins. Interaction of sweat with bacteria is well established as the cause of sweat-associated malodor. However, the role of sweat glycoproteins in microbial attachment has received little, if any, research interest in the past. In this review, we demonstrate how recent published studies involving high-throughput proteomic analysis have inadvertently, and fortuitously, exposed an abundance of glycoproteins in sweat, many of which have also been identified in other secretory fluids. We bring together research demonstrating microbial adhesion to these secretory glycoproteins in tears, saliva and milk and suggest a similar role of the sweat glycoproteins in mediating microbial attachment to sweat and/or skin. The contribution of glycan-mediated microbial adhesion to sweat glycoproteins, and the associated impact on sweat derived malodor and pathogenic skin infections are unchartered new research areas that we are beginning to explore.

Chemical organization of the cell wall polysaccharide core of Malassezia restricta.

Malassezia species are ubiquitous residents of human skin and are associated with several diseases such as seborrheic dermatitis, tinea versicolor, folliculitis, atopic dermatitis, and scalp conditions such as dandruff. Host-Malassezia interactions and mechanisms to evade local immune responses remain largely unknown. Malassezia restricta is one of the most predominant yeasts of the healthy human skin, its cell wall has been investigated in this paper. Polysaccharides in the M. restricta cell wall are almost exclusively alkali-insoluble, showing that they play an essential role in the organization and rigidity of the M. restricta cell wall. Fractionation of cell wall polymers and carbohydrate analyses showed that the polysaccharide core of the cell wall of M. restricta contained an average of 5% chitin, 20% chitosan, 5% ß-(1,3)-glucan, and 70% ß-(1,6)-glucan. In contrast to other yeasts, chitin and chitosan are relatively abundant, and ß-(1,3)-glucans constitute a minor cell wall component. The most abundant polymer is ß-(1,6)-glucans, which are large molecules composed of a linear ß-(1,6)-glucan chains with ß-(1,3)-glucosyl side chain with an average of 1 branch point every 3.8 glucose unit. Both ß-glucans are cross-linked, forming a huge alkali-insoluble complex with chitin and chitosan polymers. Data presented here show that M. restricta has a polysaccharide organization very different of all fungal species analyzed to date.

Characterization of the major bacterial-fungal populations colonizing dandruff scalps in Shanghai, China, shows microbial disequilibrium.

Dandruff is a scalp disorder characterized by the formation of flaky white-yellowish scales due to an altered proliferation and differentiation status; a disrupted barrier function; a decrease in the level of hydration and of natural moisturizing factors (NMF) in the scalp, with a persistent and relapsing inflammatory condition. It was recently reported that an imbalance between bacterial and fungal species colonizing the scalp of French volunteers was associated with dandruff condition. The purpose of the present study was to analyze the major bacterial and fungal species present on the scalp surface of Chinese volunteers and to investigate possible region-related variation in the microbiota linked to dandruff condition. The data obtained from the Chinese populations were highly similar to those obtained in France, confirming that dandruff scalps are associated with a higher incidence of Malassezia restricta and Staphylococcal sp. The ratios of Malassezia to Propionibacterium and Propionibacterium to Staphylococcus were also significantly higher in the dandruff volunteers as compared to normal volunteers, suggesting that equilibrium between the major bacterial and fungal taxa found on the normal scalps is perturbed in the dandruff scalps. The main difference between the French and Shanghai subjects was in their Staphylococcal biota. The results obtained in China and in France suggest that targeting one particular Malassezia sp. by antifungals instead of using large spectrum antifungals and rebalancing the dandruff scalp microbiota could be common approach to improve dandruff condition in the two countries.

Activation of toll-like receptors alters the microRNA expression profile of keratinocytes.

Keratinocytes recognize invading pathogens by various receptors, among them Toll-like receptors (TLRs), and provide the first line of defense in skin immunity. The role of microRNAs in this important defense mechanism has not been explored yet. Our aim was to identify microRNAs involved in the innate immune response of keratinocytes. MicroRNA expression profiling revealed that the TLR2 ligand zymosan, the TLR3 ligand poly(I:C) or the TLR5 ligand flagellin significantly altered the microRNA expression in keratinocytes. The regulation of microRNAs was concentration-dependent and it could be neutralized by siRNAs specific for TLR2, TLR3 and TLR5, respectively, confirming the specificity of the TLR response. Interestingly, one microRNA, miR-146a, was strongly induced by all studied TLR ligands, while other microRNAs were regulated in a TLR- or time point-specific manner. These findings suggest an important role for microRNAs in the innate immune response of keratinocytes and provide a basis for further investigations.

A New TGF-ß Mimetic, XEP™-716 Miniprotein™, Exhibiting Regenerative Properties Objectivized by Instrumental Evaluation.

INTRODUCTION: Skin aging, which results from intrinsic and extrinsic factors, is characterized by a rough, uneven and wrinkled appearance of the skin at the macroscopic level. At the microscopic level, aging shows lowered keratinocyte turnover, flattened dermal-epidermal junction and reduced collagen fiber density; however, use of skin biopsies to evaluate characteristic properties of these microscopic changes is too limiting for panelists and rarely used. The development of non-invasive techniques is an opportunity to be considered for such evaluations. Our objective was to demonstrate the rejuvenating effects of XEP™-716 Miniprotein™ on skin, a miniprotein having TGF-ß beta-like properties, in vitro on normal human fibroblasts and at the clinical level. METHODS: In vitro, the skin rejuvenation properties of XEP™-716 Miniprotein™ were studied by quantification of well-known dermal components such as collagen type I, hyaluronic acid and elastin. At the clinical level, we used a non-invasive technique, the confocal laser scanning microscopy (CLSM) system, which enabled non-invasive morphological characterization of skin structures (stratum corneum thickness, viable epidermis, full epidermis, dermal-epidermal junction, papillae, dermal collagen density) and high-frequency ultrasonography to quantify the dermal density and thickness, which are useful parameters for quantifying rejuvenating effects on skin. Lastly, a cutometer was used to assess the skin's biomechanical properties, mainly firmness and elasticity. This monocentric double-blind, split-face, randomized, placebo-controlled clinical trial compared the active ingredient XEP™-716 Miniprotein™ in a vehicle on one hemiface versus vehicle alone on the other (placebo) and enrolled panelists aged 40 to 60 years old. All measurements were carried out on the malar area before and after 28 and 56 days of twice daily application of a cosmetic cream formulation containing either 2.5% or 5% XEP™-716 Miniprotein™. The skin rejuvenating properties were demonstrated by studying dermo-epidermal junction (DEJ) flattening reduction using the measure of two parameters by CLSM: the DEJ length and number of edged papillae. Dermis rejuvenation was assessed by measuring the collagen fiber perimeters (CLSM), dermal density and dermal thickness (ultrasonography). RESULTS: The in vitro results confirmed the ability of XEP™-716 Miniprotein™ to stimulate the key extracellular macromolecules, namely collagen type I, hyaluronic acid and elastin, at a level comparable to that induced by TGF beta growth factor. The clinical data showed that after 28 and 56 days of topical XEP™-716 Miniprotein™ application, there was a statistically significant increase of DEJ length, number of edged papillae and collagen fiber perimeters. At the same time point, the B-scan images of facial skin showed a statistically significant increase of dermal density and thickness. These results reveal that the DEJ became more undulated and tightly attached to the dermis, while the papillary dermis was densified, both traits being typical characteristic of younger skin. Rejuvenation was also confirmed by an improvement of skin firmness and elasticity. CONCLUSION: The in vitro and clinical results presented in this article show that XEP™-716 Miniprotein™ is a potent ingredient to rejuvenate the DEJ and dermis of mature skin.

Endocannabinoids stimulate human melanogenesis via type-1 cannabinoid receptor.

We show that a fully functional endocannabinoid system is present in primary human melanocytes (normal human epidermal melanocyte cells), including anandamide (AEA), 2-arachidonoylglycerol, the respective target receptors (CB(1), CB(2), and TRPV1), and their metabolic enzymes. We also show that at higher concentrations AEA induces normal human epidermal melanocyte apoptosis (∼3-fold over controls at 5 µM) through a TRPV1-mediated pathway that increases DNA fragmentation and p53 expression. However, at lower concentrations, AEA and other CB(1)-binding endocannabinoids dose-dependently stimulate melanin synthesis and enhance tyrosinase gene expression and activity (∼3- and ∼2-fold over controls at 1 µM). This CB(1)-dependent activity was fully abolished by the selective CB(1) antagonist SR141716 or by RNA interference of the receptor. CB(1) signaling engaged p38 and p42/44 mitogen-activated protein kinases, which in turn activated the cyclic AMP response element-binding protein and the microphthalmia-associated transcription factor. Silencing of tyrosinase or microphthalmia-associated transcription factor further demonstrated the involvement of these proteins in AEA-induced melanogenesis. In addition, CB(1) activation did not engage the key regulator of skin pigmentation, cyclic AMP, showing a major difference compared with the regulation of melanogenesis by α-melanocyte-stimulating hormone through melanocortin 1 receptor.

TGFß signaling regulates lipogenesis in human sebaceous glands cells.

BACKGROUND: Sebaceous glands are components of the skin essential for its normal lubrication by the production of sebum. This contributes to skin health and more importantly is crucial for the skin barrier function. A mechanistic understanding of sebaceous gland cells growth and differentiation has lagged behind that for keratinocytes, partly because of a lack of an in vitro model that can be used for experimental manipulation. METHODS: We have developed an in vitro culture model to isolate and grow primary human sebocytes without transformation that display functional characteristics of sebocytes. We used this novel method to probe the effect of Transforming Growth Factor ß (TGFß) signaling on sebocyte differentiation, by examining the expression of genes involved in lipogenesis upon treatment with TGFß1. We also repressed TGFß signaling through knockdown of the TGFß Receptor II to address if the effect of TGFß activation is mediated via canonical Smad signal transduction. RESULTS: We find that activation of the TGFß signaling pathway is necessary and sufficient for maintaining sebocytes in an undifferentiated state. The presence of TGFß ligand triggered decreased expression in genes required for the production of characteristics sebaceous lipids and for sebocyte differentiation such as FADS2 and PPARγ, thereby decreasing lipid accumulation through the TGFß RII-Smad2 dependent pathway. CONCLUSION: TGFß signaling plays an essential role in sebaceous gland regulation by maintaining sebocytes in an undifferentiated state. This data was generated using a novel method for human sebocyte culture, which is likely to prove generally useful in investigations of sebaceous gland growth and differentiation. These findings open a new paradigm in human skin biology with important implications for skin therapies.

PGC-1s shape epidermal physiology by modulating keratinocyte proliferation and terminal differentiation.

Skin plays central roles in systemic physiology, and it undergoes significant functional changes during aging. Members of the peroxisome proliferator-activated receptor-gamma coactivator (PGC-1) family (PGC-1s) are key regulators of the biology of numerous tissues, yet we know very little about their impact on skin functions. Global gene expression profiling and gene silencing in keratinocytes uncovered that PGC-1s control the expression of metabolic genes as well as that of terminal differentiation programs. Glutamine emerged as a key substrate promoting mitochondrial respiration, keratinocyte proliferation, and the expression of PGC-1s and terminal differentiation programs. Importantly, gene silencing of PGC-1s reduced the thickness of a reconstructed living human epidermal equivalent. Exposure of keratinocytes to a salicylic acid derivative potentiated the expression of PGC-1s and terminal differentiation genes and increased mitochondrial respiration. Overall, our results show that the PGC-1s are essential effectors of epidermal physiology, revealing an axis that could be targeted in skin conditions and aging.

Selenium disulfide: a key ingredient to rebalance the scalp microbiome and sebum quality in the management of dandruff.

BACKGROUND: Dandruff is a chronic and relapsing scalp condition characterized by flaky scalp. Environmental and host factors (exposome) may alter the sebaceous gland activity, sebum composition, epidermal barrier function, and scalp microbiome balance, resulting in dandruff. Selenium disulfide (SeS2) improves the clinical signs of dandruff. OBJECTIVES: To investigate the mode of action of SeS2 shampoo during treatment and relapse phases. MATERIALS & METHODS: Two single-center studies assessed dandruff severity, subjective efficacy perception, microbial balance, microbiota diversity and sebum lipids. RESULTS: SeS2 significantly (p≤0.01) reduced scaling and led to a significant decrease of Malassezia and Staphylococcus spp. counts in both lesional and non-lesional areas, compared to the vehicle at D28 returning to baseline levels at D56. Cutibacterium spp. levels were not different between the SeS2 and the vehicle treatment groups but had significantly increased with SeS2 (p<0.001) in the lesional zone at D56. The ratio Malassezia spp./Cutibacterium spp. decreased significantly in lesional zones compared to baseline levels, at both D28 and D35 (p<0.001). The total squalene content significantly increased (p<0.05), whereas peroxided squalene had significantly decreased by almost 50% at D31. The ratio triglycerides/free fatty acids significantly (p<0.0001) increased, almost 5-fold, between D0 and D31. SeS2 shampoo was very well tolerated. CONCLUSION: SeS2 is beneficial in scalp dandruff, even after treatment interruption. It is well tolerated, rebalances the equilibrium between the main bacterial and fungal populations, and improves sebum quality.

Oxidative damage prevention in human skin and sensory neurons by a salicylic acid derivative.

BACKGROUND: Increased protein carbonylation is a hallmark of oxidative stress, protein homeostasis dysregulation and aging in the nervous system and skin. Sensory neurons interact with skin cells and are involved in skin homeostasis. We have previously reported that the 5-octanoyl salicylic acid (C8-SA), a salicylic acid derivative, increased C. elegans lifespan and delayed the accumulation of carbonylated proteins, through the stimulation of autophagy. OBJECTIVES: In this study we aimed to investigate if C8-SA protects human sensory neurons and human skin from extrinsic oxidative stressors as an approach to delay skin aging. METHODS: In vitro reconstituted human epidermis innervated with hiPSc-derived human sensory neurons, as well as ex vivo human organotypic full skin models were used. The fully differentiated sensory neurons were pretreated with C8-SA before oxidative stress induction. Skin explants were maintained in culture and treated topically with C8-SA before the application of urban pollutants. Carbonylated proteins were detected using amino-oxy functionalized fluorophores and quantified. Chaperone mediated autophagy was monitored with LAMP2A immunofluorescence. Inflammation, ROS detoxification and autophagy were assessed by RT-PCR. RESULTS: C8-SA prevented the accumulation of carbonylated proteins, both in human sensory neurons and skin explants. C8-SA stimulated chaperone-mediated autophagy and modulated NRF2 antioxidant response genes, as well as catalase enzymatic activity. CONCLUSIONS: C8-SA acts at two levels to protect skin against oxidative stress: 1) it prevents protein oxidation by stimulating endogenous antioxidant defense and 2) it increases the clearance of oxidized proteins by stimulating chaperone-mediated autophagy. These results suggest that C8-SA maintains skin health in urban polluted environments.

Oligomeric α-Synuclein induces skin degeneration in reconstructed human epidermis.

Aged and photoaged skin exhibit fine wrinkles that are signs of epidermal inflammation and degeneration. It has been shown that healthy elderly skin expresses amyloidogenic proteins, including α-Synuclein, which are known to oligomerize and trigger inflammation and neurodegeneration. However, little is known about their putative role in skin physiology and sensitivity. To unravel this possible role, we investigated the impact of oligomeric α-Synuclein (Oα-Syn) in 2D and 3D keratinocyte human models. Exogenous Oα-Syn caused degeneration of reconstructed human epidermis (RHE) by diminishing proliferation and thickness of the stratum basale. Oα-Syn also increased NF-kB nuclear translocation in keratinocytes and triggered inflammation in the RHE, by increasing expression of interleukin-1ß and tumor necrosis factor-alpha, and the release of tumor necrosis factor-alpha in a time-dependent manner. Dexamethasone and an IL-1ß inhibitor partially diminished RHE degeneration caused by Oα-Syn. These findings suggest that Oα-Syn induces epidermal inflammation and decreases keratinocyte proliferation, and therefore might contribute to epidermal degeneration observed in human skin aging.

Biological evaluation of a new C-xylopyranoside derivative (C-Xyloside) and its role in glycosaminoglycan biosynthesis.

The mechanical properties of skin are determined primarily by the extracellular matrix of the dermis. These mechanical and biological properties change significantly as a function of age. Key components of the extracellular matrix are proteoglycans, which are molecules composed of a core protein and covalently attached glycosaminoglycans. Proteoglycans and their constituent glycosaminoglycans are involved in many biological processes which are important for dermal function, such as proper formation of the collagen network. A recently developed compound, C-xylopyranoside derivative (C-Xyloside), was designed to mimic ß-xylosides, which are known initiators of glycosaminoglycan biosynthesis. C-Xyloside was found, by several criteria, to act like ß-xylosides, such as in the eliciting of an increase in glycosaminoglycan synthesis by human dermal fibroblasts in culture. This increase may lead to the preservation of matrix integrity and thereby contribute to the firmness of skin. Thus, C-Xyloside may be useful in improving the quality of skin.

Vitreoscilla filiformis Extract for Topical Skin Care: A Review.

The term probiotic has been defined by experts as live microorganisms, which when administered in adequate amounts, confer a health benefit on the host. Probiotics are, thus, by definition, live microorganisms, and the viability of probiotics is a prerequisite for certain benefits, such as the release of metabolites at the site or adhesion properties, for example. However, some semi-active or non-replicative bacterial preparations may retain a similar activity to the live forms. On cosmetic, lysates or fractions are generally used. Topically applied Vitreoscilla filiformis extract has shown to have some similar biological activity of probiotics in the gut, for example, regulating immunity by optimisation of regulatory cell function, protecting against infection, and helping skin barrier function for better recovery and resistance. Due to their mode of action and efficacy, V. filiformis extract (lysate including membrane and cytosol) may be considered as non-replicative probiotic fractions, and this review article presents all its properties.

Longitudinal study of the scalp microbiome suggests coconut oil to enrich healthy scalp commensals.

Dandruff is a recurrent chronic scalp disorder, affecting majority of the population worldwide. Recently a metagenomic study of the Indian scalp microbiome described an imperative role of bacterial commensals in providing essential vitamins and amino acids to the scalp. Coconut oil and its formulations are commonly applied on the scalp in several parts of the world to maintain scalp health. Thus, in this study we examined the effect of topical application of coconut oil on the scalp microbiome (bacterial and fungal) at the taxonomic and functional levels and their correlation with scalp physiological parameters. A 16-weeks-long time-course study was performed including 12-weeks of treatment and 4-weeks of relapse phase on a cohort of 140 (70 healthy and 70 dandruff) Indian women, resulting in ~ 900 metagenomic samples. After the treatment phase, an increase in the abundance of Cutibacterium acnes and Malassezia globosa in dandruff scalp was observed, which were negatively correlated to dandruff parameters. At the functional level, an enrichment of healthy scalp-related bacterial pathways, such as biotin metabolism and decrease in the fungal pathogenesis pathways was observed. The study provides novel insights on the effect of coconut oil in maintaining a healthy scalp and in modulating the scalp microbiome.

A perfusable vascularized full-thickness skin model for potential topical and systemic applications.

Vascularization of reconstructed tissues is one of the remaining hurdles to be considered to improve both the functionality and viability of skin grafts and the relevance ofin vitroapplications. Our study, therefore, sought to develop a perfusable vascularized full-thickness skin equivalent that comprises a more complex blood vasculature compared to existing models. We combined molding, auto-assembly and microfluidics techniques in order to create a vascularized skin equivalent representing (a) a differentiated epidermis with a physiological organization and correctly expressing K14, K10, Involucrin, TGM1 and Filaggrin, (b) three perfusable vascular channels with angiogenic sprouts stained with VE-Caderin and Collagen IV, (c) an adjacent microvascular network created via vasculogenesis and connected to the sprouting macrovessels. Histological analysis and immunostaining of CD31, Collagen IV, Perlecan and Laminin proved the integrity of vascular constructs. In order to validate the vascularized skin potential of topical and systemic applications, caffeine and minoxidil, two compounds with different chemical properties, were topically applied to measure skin permeability and benzo[a]pyrene pollutant was systemically applied to evaluate systemic delivery. Our results demonstrated that perfusion of skin reconstructs and the presence of a complex vascular plexus resulted in a more predictive and reliable model to assess respectively topical and systemic applications. This model is therefore aimed at furthering drug discovery and improving clinical translation in dermatology.

Bifidobacterium longum lysate, a new ingredient for reactive skin.

Reactive skin is characterized by marked sensitivity to physical (heat, cold, wind) or chemical (topically applied products) stimuli and by the impairment of the skin barrier's ability to repair itself. Several lines of evidence suggest that beyond their capacity to positively influence the composition of intestinal microbiota, some probiotic bacteria can modulate the immune system both at local and systemic levels, thereby improving immune defense mechanisms and/or down-regulating immune disorders such as allergies and intestinal inflammation. Several recent human clinical trials clearly suggest that probiotic supplementation might be beneficial to the skin. Using a probiotic lysate, Bifidobacterium longum sp. extract (BL), we demonstrated first in vitro, and then in a clinical trial, that this non-replicating bacteria form applied to the skin was able to improve sensitive skin. The effect of BL were evaluated first on two different models. Using ex vivo human skin explant model we found a statistically significant improvement versus placebo in various parameters associated with inflammation such as a decrease in vasodilation, oedema, mast cell degranulation and TNF-alpha release. Moreover, using nerve cell cultures in vitro, we showed that after 6 h of incubation in culture medium (0.3-1%), the probiotic lysate significantly inhibited capsaicin-induced CGRP release by neurones. Then, a topical cream containing the active extract was tested in a randomized, double-blind, placebo-controlled trial. Sixty-six female volunteers with reactive skin were randomly given either the cream with the bacterial extract at 10% (n = 33) or the control cream (n = 33). The volunteers applied the cream to the face, arms and legs twice a day for two months. Skin sensitivity was assessed by stinging test (lactic acid) and skin barrier recovery was evaluated by measuring trans-epidermal water loss following barrier disruption induced by repeated tape-stripping at D1, D29 and D57. The results demonstrated that the volunteers who applied the cream with bacterial extract had a significant decrease in skin sensitivity at the end of the treatment. Moreover, the treatment led to increase skin resistance against physical and chemical aggression compared to the group of volunteers who applied the control cream. Notably, the number of strippings required to disrupt skin barrier function was significantly increased for volunteers treated with the active cream. Clinical and self-assessment scores revealed a significant decrease in skin dryness after 29 days for volunteers treated with the cream containing the 10% bacterial extract. Since in vitro studies demonstrated that, on one hand, isolate sensitive neurones release less CGRP under capsaicin stimulation in the presence of the bacterial extract and, on the other hand, increased skin resistance in volunteers applying the test cream, we speculate that this new ingredient may decrease skin sensitivity by reducing neurone reactivity and neurone accessibility. The results of this studies demonstrate that this specific bacterial extract has a beneficial effect on reactive skin. These findings suggest that new approaches, based on a bacteria lysate, could be developed for the treatment and/or prevention of symptoms related to reactive skin.