Action of staphylococcal exfoliative toxins on epidermal cell cultures and organotypic skin.

In the staphylococcal scalded skin syndrome, spontaneous intraepithelial cleavages are due to the exfoliative toxins A or B (ETA or ETB). Until now, these toxins have been studied either on epidermis or on organotypic skin cultures. In the present study, we compare the effects of these toxins on human keratinocyte cell cultures to those on human and mouse organotypic skin cultures. With concentrations of ETA or ETB of 1 mg/ml for 3 hours, spontaneous intraepithelial cleavages were noted in both cell and organotypic cultures. Keratinocyte cell cultures were as sensitive as organotypic skin cultures to these toxins. Since keratohyaline granules may represent a possible binding site for ETA or ETB, we tried to correlate the expression of keratohyaline granules with the appearance of intraepithelial clefts due to the toxins. However, when cultured in liquid medium, epithelia were not differentiated enough to allow the detection of the binding site of ETA-ETB.     

Immunostimulatory activity of murine keratinocyte‐derived exosomes

It has long been known that keratinocytes influence cutaneous immunity through secretion of soluble factors. Exosomes, small membrane vesicles of endocytotic origin, have been implicated in intercellular communication processes such as the transfer of tumor cell antigens and the activation of recipient dendritic cells (DC). However, little is known about immunomodulatory functions of keratinocyte‐derived exosomes. To address this question, we analysed exosome secretion of the murine keratinocyte cell line MPEK under steady state as well as inflammatory conditions (+/? IFNγ). These exosomes were readily taken up by bone marrow‐derived DC (BMDC) in vitro resulting in a matured phenotype, as evidenced by increased CD40 expression as well as by the production of large amounts of IL‐6, IL‐10 and IL‐12. When the transfer of antigen‐specific information through exosomes was investigated, it was found that keratinocytes took up antigen (ovalbumin) and transferred it to their exosomes. However, these antigen‐harbouring exosomes failed to induce antigen‐specific T cell responses via BMDC. Together, this novel biological function suggests that keratinocytes are able to direct unspecific immune processes but do not elicit specific immune responses.     

Characterization of pigmented dermo‐epidermal skin substitutes in a long‐term in vivo assay

In our laboratory, we have been using human pigmented dermo‐epidermal skin substitutes for short‐term experiments since several years. Little is known, however, about the long‐term biology of such constructs after transplantation. We constructed human, melanocyte‐containing dermo‐epidermal skin substitutes of different (light and dark) pigmentation types and studied them in a long‐term animal experiment. Developmental and maturational stages of the epidermal and dermal compartment as well as signs of homoeostasis were analysed 15 weeks after transplantation. Keratinocytes, melanocytes and fibroblasts from human skin biopsies were isolated and assembled into dermo‐epidermal skin substitutes. These were transplanted onto immuno‐incompetent rats and investigated 15 weeks after transplantation. Chromameter evaluation showed a consistent skin colour between 3 and 4 months after transplantation. Melanocytes resided in the epidermal basal layer in physiological numbers and melanin accumulated in keratinocytes in a supranuclear position. Skin substitutes showed a mature epidermis in a homoeostatic state and the presence of dermal components such as Fibrillin and Tropoelastin suggested advanced maturation. Overall, pigmented dermo‐epidermal skin substitutes show a promising development towards achieving near‐normal skin characteristics and epidermal and dermal tissue homoeostasis. In particular, melanocytes function correctly over several months whilst remaining in a physiological, epidermal position and yield a pigmentation resembling original donor skin colour.     

Effects of a ceramide‐containing water‐in‐oil ointment on skin barrier function and allergen penetration in an IL‐31 treated 3D model of the disrupted skin barrier

Atopic dermatitis (AD) is a chronically relapsing, pruritic inflammation of the skin with dryness and disturbed skin barrier function. Recently, we established that IL‐31 treatment of human 3D skin models resulted in a disrupted skin barrier phenotype resembling AD. In this model, we found that IL‐31 interferes with the differentiation of keratinocytes and inhibits the expression of terminal differentiation markers. In the present study, we investigated the effects of a ceramide‐containing water‐in‐oil skin care ointment on the physical skin barrier structure and function in disrupted skin barrier models, generated either by using primary normal human epidermal keratinocytes (NHEK) or HaCaT cells. We observed that the physical skin barrier of the models recovered after daily topical treatment with the ceramide‐containing ointment. Topical application of the ointment prevented downregulation of filaggrin and disorganization of other differentiation markers, such as keratin 10 and β4‐integrin, as demonstrated by immunohistological analysis. The expression of Ki67 was also upregulated in response to the ointment. Furthermore, functional studies revealed that local application of the ointment diminished the increased uptake of fluorescently labelled recombinant allergens of timothy grass (phl p1) in our model. In conclusion, our data revealed that topical application of a ceramide‐containing skin care ointment reduced IL‐31 induced impairments of the physical skin barrier and skin barrier function in an in vitro model of the disrupted skin barrier. This standardized model can be utilized in the future to monitor ex vivo effects of various topical therapies on skin morphology, physiology, and gene expression.     

Effects of tacrolimus on an organotypic raft‐culture model mimicking oral mucosa

Background. Tacrolimus ointment has shown efficacy in treating T‐cell‐mediated inflammatory oral mucosal diseases, including lichen planus. However, the safety of topical tacrolimus has been questioned, based on its possible association with malignant transformation. Aim. To evaluate the safety aspects of tacrolimus in a three‐dimensional in vitro model of oral mucosa containing both multilayered epithelium and connective tissue (raft culture). Methods. Raft cultures mimicking oral mucosa were topically exposed to tacrolimus, and the effects on cell proliferation and adhesion, epidermal growth factor receptors (EGFR, ERBB2, ERBB3, ERBB4), and apoptosis were evaluated with immunohistochemistry and terminal dUTP nick‐end labelling, respectively. Results. The epithelium of the cultures was found to be slightly thinner, but no changes in cell proliferation or adhesion, apoptosis, or expression of epidermal growth factor receptors were detected. Conclusions. Our results suggest that short‐term topical tacrolimus exposure of in vitro constructed oral mucosa does not induce changes in a number of factors known to be involved in malignant transformation.     

Topical hesperidin prevents glucocorticoid‐induced abnormalities in epidermal barrier function in murine skin

Systemic and topical glucocorticoids (GC) can cause significant adverse effects not only on the dermis, but also on epidermal structure and function. In epidermis, a striking GC‐induced alteration in permeability barrier function occurs that can be attributed to an inhibition of epidermal mitogenesis, differentiation and lipid production. As prior studies in normal hairless mice demonstrated that topical applications of a flavonoid ingredient found in citrus, hesperidin, improve epidermal barrier function by stimulating epidermal proliferation and differentiation, we assessed here whether its topical applications could prevent GC‐induced changes in epidermal function in murine skin and the basis for such effects. When hairless mice were co‐treated topically with GC and 2% hesperidin twice‐daily for 9 days, hesperidin co‐applications prevented the expected GC‐induced impairments of epidermal permeability barrier homoeostasis and stratum corneum (SC) acidification. These preventive effects could be attributed to a significant increase in filaggrin expression, enhanced epidermal β‐glucocerebrosidase activity and accelerated lamellar bilayer maturation, the last two likely attributable to a hesperidin‐induced reduction in stratum corneum pH. Furthermore, co‐applications of hesperidin with GC largely prevented the expected GC‐induced inhibition of epidermal proliferation. Finally, topical hesperidin increased epidermal glutathione reductase mRNA expression, which could counteract multiple functional negative effects of GC on epidermis. Together, these results show that topical hesperidin prevents GC‐induced epidermal side effects by divergent mechanisms.     

自体表皮细胞混悬液移植治疗皮肤慢性溃疡临床观察

目的评估自体表皮细胞混悬液移植治疗皮肤慢性溃疡的疗效。方法 20例皮肤慢性溃疡患者,以1:1比例分为自体表皮细胞混悬液移植组(试验组)和常规外科换药组(对照组)。观察溃疡在两组的平均愈合时间。结果对照组与试验组创面的平均愈合时间分别为(0.177±0.114)cm2/d和(0.375±0.238)cm2/d,差异有统计学意义(P=0.029)。结论自体表皮细胞混悬液移植是治疗皮肤慢性溃疡的一种有效方法。     

Optimization of murine keratinocyte culture for the production of graftable epidermal sheets.

The aim of the present study was to optimize murine epidermal cell cultures in order to obtain graftable sheets. Newborn (1-3 days old) Balb/c mice skin were used to optimize culture media and plating cell concentration, then epidermal sheet production, and grafting. Epidermal cells were plated at various concentrations in different culture media containing low (0.1 mM) or high (greater than 1 mM) Ca2+ levels. After a 3 day culture at the 10(4) cells/cm2 plating cell concentration, the percentage of differentiated cells was more than 80% in the high Ca2+ culture medium and less than 50% with bulky cells in the low Ca2+ culture medium. Under these conditions confluence was not obtained. At the 10(5) cells/cm2 seeding inoculum, the percentage of confluence increased to 95-100% during the first 72 h of culture in both high and low Ca2+ culture media. Three-day-old culture showed stratified multilayer epidermal sheets in the high calcium medium, and monolayer epidermal sheets were present in the low calcium medium after seeding keratinocytes in fibronectin precoated flasks. Seven days after plating, post confluent cultures were composed of a high percentage of differentiated cells (90%) with an increase in shedding cells in the medium. Considering the above morphological observations, sheets obtained with 10(5) cells/cm2 in MCDB-153 (A), DME-HAM (B) or GMEM (C) media after 3 days in culture were grafted. Twenty days after grafting, histological analysis of biopsies showed an epidermal structure and organization comparable to normal murine epidermis without hair follicles. Epidermal transplants showed a complete basement membrane, hemidesmosomes, and tonofilament bundles. Sheets obtained after seven day culture in all media showed lower coverage of the wound bed. These studies point out the importance of the plating cell and Ca2+ concentrations, and the culture time for murine keratinocyte confluence and differentiation to obtain graftable epidermal sheets.     

Microbiological analysis of epidermal growth factor receptor inhibitor therapy‐associated paronychia

Background Paronychia is a well‐known, but difficult to treat cutaneous toxicity associated with epidermal growth factor receptor (EGFR) inhibitor therapy. Although bacterial and fungal infections as well as mechanical trauma may play a role as co‐pathogens, there is no good basis for an empirical antimicrobial chemotherapy in these patients. Materials and methods We retrospectively analysed the microbiological results and resistance analysis of 42 cases of EGFR inhibitor‐associated paronychia induced by cetuximab. Results We identified 20 different species, among these 72% Gram‐positive bacteria, 23% Gram‐negative bacteria and 5%Candida species. About half of the microbes identified may be considered as residential bacterial flora of the skin, but isolation of microbes from paronychia may indicate a pathogenic relevance for this type of reaction. Eight of our patients were treated with oral antibiotics, whereas two patients received oral antimycotic therapy. All other cases of paronychia were controlled using topical antiseptic, antibiotic and antimycotic agents. Conclusion Empirical oral antibiotic treatment may be performed with oral cephalosporines, ciprofloxacin, levofloxacin or moxifloxacin, as these antimicrobials have high in vitro activity against the majority of the isolated microorganisms and reach high concentrations in the relevant tissue.     

Low environmental humidity induces synthesis and release of cortisol in an epidermal organotypic culture system

Dry environmental conditions induce a variety of skin pathologies and a recent report indicating that cortisol synthesis in epidermis was increased during wound healing led us to hypothesize that environmental dryness might induce increased cortisol secretion in epidermis. Therefore, we incubated a skin equivalent model under dry (relative humidity: less than 10%) and humid (relative humidity: approximately 100%) conditions for 48 hours and evaluated cortisol secretion and mRNA levels of cortisol‐synthesizing enzyme (steroid 11β‐hydroxylase, CYP11B1) and IL‐1β. Cortisol secretion was increased threefold, and CYP11B1 and IL‐1β mRNAs were increased 38‐fold and sixfold, respectively, in the dry condition versus the humid condition. Occlusion with a water‐impermeable plastic membrane partially blocked the increases in cortisol secretion and CYP11B1 and IL‐1β mRNA expression in the dry condition. Thus, environmental dryness might induce increased cortisol secretion in epidermis of diseased skin characterized by epidermal barrier dysfunction, potentially influencing mental state and systemic physiology.     

Morphogenesis of dermal-epidermal junction in a model of reconstructed skin: beneficial effects of vitamin C

In skin, cohesion between the dermis and the epidermis is ensured by the dermal-epidermal junction which is also required for control of epidermal growth and differentiation. Here we showed that addition of vitamin C optimized the formation of the dermal-epidermal junction in an in vitro human reconstructed skin model leading to a structure closer to that of normal human skin. Compared with controls, vitamin C treatment led to a better organization of basal keratinocytes, an increase in fibroblast number and a faster formation of the dermal-epidermal junction. Vitamin C also accelerated deposition of several basement membrane proteins, like type IV and VII collagens, nidogen, laminin 10/11, procollagens I and III, tenascin C and fibrillin-1 at the dermal-epidermal junction. The mechanism of action of vitamin C was investigated by quantitative polymerase chain reaction in fibroblasts and keratinocytes respectively. Vitamin C effects passed in part through an increase in col I alpha1, col III alpha1 and fibrillin-1 mRNA levels. Effects on the other markers appeared to happen at the translational and/or post-translational level, as illustrated for tenascin C, col IV alpha2 and col VII alpha1 mRNA levels which were reduced by vitamin C in both cell types.     

Real‐time three‐dimensional imaging of epidermal splitting and removal by high‐definition optical coherence tomography

While real‐time 3‐D evaluation of human skin constructs is needed, only 2‐D non‐invasive imaging techniques are available. The aim of this paper is to evaluate the potential of high‐definition optical coherence tomography (HD‐OCT) for real‐time 3‐D assessment of the epidermal splitting and decellularization. Human skin samples were incubated with four different agents: Dispase II, NaCl 1 M, sodium dodecyl sulphate (SDS) and Triton X‐100. Epidermal splitting, dermo‐epidermal junction, acellularity and 3‐D architecture of dermal matrices were evaluated by High‐definition optical coherence tomography before and after incubation. Real‐time 3‐D HD‐OCT assessment was compared with 2‐D en face assessment by reflectance confocal microscopy (RCM). (Immuno) histopathology was used as control. HD‐OCT imaging allowed real‐time 3‐D visualization of the impact of selected agents on epidermal splitting, dermo‐epidermal junction, dermal architecture, vascular spaces and cellularity. RCM has a better resolution (1 μm) than HD‐OCT (3 μm), permitting differentiation of different collagen fibres, but HD‐OCT imaging has deeper penetration (570 μm) than RCM imaging (200 μm). Dispase II and NaCl treatments were found to be equally efficient in the removal of the epidermis from human split‐thickness skin allografts. However, a different epidermal splitting level at the dermo‐epidermal junction could be observed and confirmed by immunolabelling of collagen type IV and type VII. Epidermal splitting occurred at the level of the lamina densa with dispase II and above the lamina densa (in the lamina lucida) with NaCl. The 3‐D architecture of dermal papillae and dermis was more affected by Dispase II on HD‐OCT which corresponded with histopathologic (orcein staining) fragmentation of elastic fibres. With SDS treatment, the epidermal removal was incomplete as remnants of the epidermal basal cell layer remained attached to the basement membrane on the dermis. With Triton X‐100 treatment, the epidermis was not removed. In conclusion, HD‐OCT imaging permits real‐time 3‐D visualization of the impact of selected agents on human skin allografts.     

Specific binding of Clostridium perfringens enterotoxin fragment to Claudin‐b and modulation of zebrafish epidermal barrier

Claudins (Cldn) are the major components of tight junctions (TJs) sealing the paracellular cleft in tissue barriers of various organs. Zebrafish Cldnb, the homolog of mammalian Cldn4, is expressed at epithelial cell–cell contacts and is important for regulating epidermal permeability. The bacterial toxin Clostridium perfringens enterotoxin (CPE) has been shown to bind to a subset of mammalian Cldns. In this study, we used the Cldn‐binding C‐terminal domain of CPE (194–319 amino acids, cCPE_194–319) to investigate its functional role in modulating zebrafish larval epidermal barriers. In vitro analyses show that cCPE_194–319 removed Cldn4 from epithelial cells and disrupted the monolayer tightness, which could be rescued by the removal of cCPE_194–319. Incubation of zebrafish larvae with cCPE_194–319 removed Cldnb specifically from the epidermal cell membrane. Dye diffusion analysis with 4‐kDa fluorescent dextran indicated that the permeability of the epidermal barrier increased due to cCPE_194–319 incubation. Electron microscopic investigation revealed reversible loss of TJ integrity by Cldnb removal. Collectively, these results suggest that cCPE_194–319 could be used as a Cldnb modulator to transiently open the epidermal barrier in zebrafish. In addition, zebrafish might be used as an in vivo system to investigate the capability of cCPE to enhance drug delivery across tissue barriers.     

SPINK5 knockdown in organotypic human skin culture as a model system for Netherton syndrome: effect of genetic inhibition of serine proteases kallikrein 5 and kallikrein 7

Netherton syndrome (NS; OMIM 256500) is a genetic skin disease resulting from defects in the serine protease inhibitor Kazal‐type 5 (SPINK5) gene, which encodes the protease inhibitor lympho‐epithelial Kazal type inhibitor (LEKTI). We established a SPINK5 knockdown skin model by transfecting SPINK5 small interfering RNA (siRNA) into normal human epidermal keratinocytes, which were used together with fibroblast‐populated collagen gels to generate organotypic skin cultures. This model recapitulates some of the NS skin morphology: thicker, parakeratotic stratum corneum frequently detached from the underlying epidermis and loss of corneodesmosomes. As enhanced serine protease activity has been implicated in the disease pathogenesis, we investigated the impact of the kallikreins KLK5 [stratum corneum trypsin‐like enzyme (SCTE)] and KLK7 [stratum corneum chymotrypsin‐like enzyme (SCCE)] on the SPINK5 knockdown phenotype by generating double knockdowns in the organotypic model. Knockdown of KLK5 or KLK7 partially ameliorated the epidermal architecture: increased epidermal thickness and expression of desmocollin 1 (DSC1), desmoglein 1 (DSG1) and (pro)filaggrin. Thus, inhibition of serine proteases KLK5 and KLK7 could be therapeutically beneficial in NS.