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Epidermal Differentiation (epidermal + differentiation)
Selected AbstractsDifferentiation of the epidermis of scutes in embryos and juveniles of the tortoise Testudo hermanni with emphasis on beta-keratinizationACTA ZOOLOGICA, Issue 3 2005L. Alibardi Abstract The sequence of differentiation of the epidermis of scutes during embryogenesis in the tortoise Testudo hermanni was studied using autoradiography, electron microscopy and immunocytochemistry. The study was mainly conducted on the epidermis of the carapace, plastron and nail. Epidermal differentiation resembles that described for other reptiles, and the embryonic epidermis is composed of numerous cell layers. In the early stages of differentiation of the carapacial ridge, cytoplasmic blebs of epidermal cells are in direct contact with the extracellular matrix and mesenchymal cells. The influence of the dermis on the formation of the beta-layer is discussed. The dermis becomes rich in collagen bundles at later stages of development. The embryonic epidermis is formed by a flat periderm and four to six layers of subperidermal cells, storing 40,70-nm-thick coarse filaments that may represent interkeratin or matrix material. Beta-keratin is associated with the coarse filaments, suggesting that the protein may be polymerized on their surface. The presence of beta-keratin in embryonic epidermis suggests that this keratin might have been produced at the beginning of chelonian evolution. The embryonic epidermis of the scutes is lost around hatching and leaves underneath the definitive corneous beta-layer. Beneath the embryonic epidermis, cells that accumulate typical large bundles of beta-keratin appear at stage 23 and at hatching a compact beta-layer is present. The differentiation of these cells shows the progressive replacement of alpha-keratin bundles with bundles immunolabelled for beta-keratin. The nucleus is degraded and electron-dense nuclear material mixes with beta-keratin. In general, changes in tortoise skin when approaching terrestrial life resemble those of other reptiles. Lepidosaurian reptiles form an embryonic shedding layer and crocodilians have a thin embryonic epidermis that is rapidly lost near hacthing. Chelonians have a thicker embryonic epidermis that accumulates beta-keratin, a protein later used to make a thick corneous layer. [source] Epidermal differentiation in embryos of the tuatara Sphenodon punctatus (Reptilia, Sphenodontidae) in comparison with the epidermis of other reptilesJOURNAL OF ANATOMY, Issue 1 2007L. Alibardi Abstract Studying the epidermis in primitive reptiles can provide clues regarding evolution of the epidermis during land adaptation in vertebrates. With this aim, the development of the skin of the relatively primitive reptile Sphenodon punctatus in representative embryonic stages was studied by light and electron microscopy and compared with that of other reptiles previously studied. The dermis organizes into a superficial and deep portion when the epidermis starts to form the first layers. At embryonic stages comparable with those of lizards, only one layer of the inner periderm is formed beneath the outer periderm. This also occurs in lizards and snakes so far studied. The outer and inner periderm form the embryonic epidermis and accumulate thick, coarse filaments (25,30 nm thick) and sparse alpha-keratin filaments as in other reptiles. Beneath the embryonic epidermis an oberhautchen and beta-cells form small horny tips that represent overlapping borders along the margin of beta-cells that overlap other beta-cells (in a tile-like arrangement). The tips resemble those of agamine lizards but at a small scale, forming a lamellate-spinulated pattern as previously described in adult epidermis. The embryonic epidermis matures by the dispersion of coarse filaments among keratin at the end of embryonic development and is shed around hatching. The presence of these matrix organelles in the embryonic epidermis of this primitive reptile further indicates that amniote epidermis acquired interkeratin matrix proteins early for land adaptation. Unlike the condition in lizards and snakes, a shedding complex is not formed in the epidermis of embryonic S. punctatus that is like that of the adult. Therefore, as in chelonians and crocodilians, the epidermis of S. punctatus also represents an initial stage that preceded the evolution of the shedding complex for moulting. [source] Cx31 and Cx43 double-deficient mice reveal independent functions in murine placental and skin developmentDEVELOPMENTAL DYNAMICS, Issue 3 2005Mark Kibschull Abstract The overlapping expression of gap junctional connexins in tissues has indicated that the channels may compensate for each other. During development, Cx31 and Cx43 are coexpressed in preimplantation embryos, in the spongiotrophoblast of the placenta and in the epidermis. This study shows that Cx31/Cx43 double-deficient mice exhibit the known phenotypes of the single-knockout strains but no combined effects. Thus, Cx43, coexpressed with Cx31 at midgestation in the spongiotrophoblast of the placenta, cannot be responsible for a partial rescue of the lethal Cx31 knockout phenotype, as assumed before (Plum et al. [ 2001] Dev Biol 231:334,337). It follows that both connexins have unique functions in placental development. Despite an altered expression of other epidermal connexin mRNAs, epidermal differentiation and physiology was unaltered by the absence of Cx31 and Cx43. Therefore, in epidermal and preimplantation development, gap junctional communication can probably be compensated by other isoforms coexpressed with Cx31 and Cx43. Developmental Dynamics 233:853,863, 2005. © 2005 Wiley-Liss, Inc. [source] Expression of the human Cathepsin L inhibitor hurpin in mice: skin alterations and increased carcinogenesisEXPERIMENTAL DERMATOLOGY, Issue 9 2007Markus Walz Abstract:, The serine protease inhibitor (serpin) hurpin (serpin B13) is a cross class-specific inhibitor of the cysteine protease Cathepsin (Cat) L. Cat L is involved in lysosomal protein degradation, hair follicle morphogenesis, epidermal differentiation and epitope generation of antigens. Hurpin is a 44 kDa protein which is expressed predominantly in epidermal cells. In psoriatic skin samples, hurpin was strongly overexpressed when compared with normal skin. Keratinocytes overexpressing hurpin showed increased resistance towards UVB-induced apoptosis. To further analyse the functional importance of this inhibitor, we have generated transgenic mice with deregulated Cat L activity by expressing human hurpin in addition to the endogenous mouse inhibitor. The three independent transgenic lines generated were characterized by identical effects excluding insertional phenotypes. Macroscopically, mice expressing human hurpin are characterized by abnormal abdominal fur. The number of apoptotic cells and caspase-3 positive cells was reduced after UV-irradiation in transgenic animals compared with wild-type mice. Interestingly, after chemical carcinogenesis, transgenic mice showed an increased susceptibility to develop skin cancer. Array analysis of gene expression revealed distinct differences between wild-type and hurpin-transgenic mice. Among others, differentially expressed genes are related to antigen presentation and angiogenesis. These results suggest an important role of Cat L regulation by hurpin which might be of clinical relevance in human skin diseases. [source] Stimulation of keratinocyte differentiation , a new role for the vanilloid receptor subtype 1 (VR1/TRPV1)?EXPERIMENTAL DERMATOLOGY, Issue 2 2005Sonja Ständer Vanilloids and endogenous cannabinoids mediate their actions via the vanilloid receptor subtype 1 (VR1/TRPV1), a non-selective cation channel, which is widely distributed in the central and peripheral nervous system. Only recently, VR1 has been shown to be expressed in keratinocytes in vitro and in vivo. However, a precise description of VR1 localization in epithelial cells was missing. To determine this, we investigated VR1-immunoreactivity as well as mRNA and protein expression in a series of biopsies from normal, diseased, and capsaicin-treated human skin. VR1 was found in epidermal keratinocytes, the inner root sheet and the infundibulum of hair follicles, differentiated sebocytes, sweat gland ducts, and the secretory portion of eccrine sweat glands upon immunohistochemistry, RT-PCR and Western blot analysis. Interestingly, in diseased skin such as prurigo nodularis, psoriasis vulgaris, and atopic dermatitis, VR1 expression in keratinocytes correlated with the degree of epidermal differentiation. Enhanced VR1 immunoreactivity and protein content was found in prurigo nodularis in which epidermal keratinocytes are highly differentiated. Under effective capsaicin therapy of prurigo nodularis, the epidermis thinned and the distribution pattern of VR1 on epidermal keratinocytes normalized. In psoriasis vulgaris, a disease with disturbed epidermal differentiation, less intense immunostaining for VR1 was observed. This could be confirmed by western blot analysis showing less VR1 protein amount in comparison to prurigo nodularis although histologically both showed a thickened epidermis. In atopic dermatitis, which is characterized by a moderate epidermal hyperplasia only and regular differentiated keratinocytes, VR1 immunoreactivity was unchanged in comparison to normal skin. These findings suggest that VR1 may contribute to regular differentiation of keratinocytes. VR1 activation opens non-selective cation channels with high permeability to calcium, a ion that is crucially important for the synthesis of cornification proteins such as involucrin, fillagrin and loricrin. The role of VR1 in other epithelial cells of appendage structures remains to be determined. In summary, VR1 is widely distributed in the skin suggesting a central role for this receptor not only in nociception but also maturation and function of epithelial cells. [source] Erythrokeratodermia variabilis (EKV) , eine Störung der epidermalen Expression von Gap-Junction-ProteinenJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 5 2005Erythrokeratodermia variabilis (EKV), a disorder due to altered epidermal expression of gap junction proteins Connexin,31; Connexin,43; Erythrokeratodermia variabilis; Gap Junctions Zusammenfassung Die Erythrokeratodermia variabilis (EKV) ist eine seltene autosomal-dominant vererbte Genodermatose mit einer epidermalen Verhornungsstörung. Das klinische Bild der EKV wird von zwei Morphen geprägt: transiente, schnell wandernde Erytheme und persistierende braune Hyperkeratosen. Vor kurzem wurde der zugrunde liegende Gendefekt der EKV auf dem kurzen Arm von Chromosom,1 lokalisiert, der für das Gap-Junction-Protein Connexin,31 kodiert. Wir stellen einen 48jährigen Patienten vor, bei dem seit dem dreißigsten Lebensjahr großflächige, scharf begrenzte, randständig schuppende Erytheme an den Extremitäten, Gesäß und Rumpf auftreten. Histologisch fand sich eine orthokeratotische Hyperkeratose mit fokaler Parakeratose bei Akanthose der Epidermis. Immunhistochemisch konnte eine vermindert Expression des Gap-Junction-Proteins Connexin,31 sowie vermehrte Expression von Connexin,43 dargestellt werden. Ultrastrukturell zeigten sich erweiterte Interzellularräume in der oberen Epidermis mit unauffälligen Desmosomen, Adherensjunktionen und regulären Gap Junctions. In der Epidermis wird u. a. die Zellproliferation und -differenzierung über die Gap Junctions reguliert. Die Mutation im Connexin,31 wird daher als ursächlich für das klinische Bild der EKV angesehen. Die Überexpression von Connexin,43, die hier erstmals beschrieben wird, entsteht möglicherweise reaktiv als Folge der CX31-Mutation und kompensiert vorübergehend den Defekt. Summary Erythrokeratodermia variabilis (EKV) is a rare autosomal dominant genodermatosis with disturbed epidermal differentiation. Its clinical picture varies from transient, fast moving erythema to persistent brown hyperkeratoses. The gene defect in EKV was recently located on the short arm of chromosome,1 encoding the gap junction protein connexin,31. We report on a 48-year-old patient with sharply circumscribed, scaling erythema on the extremities, buttocks and trunk starting since 30,years of age. Histological investigation showed orthokeratotic hyperkeratosis with focal parakeratosis overlying an acanthotic epidermis. Immunohistochemistry revealed a decreased expression of the gap junction protein connexin,31 as well as increased expression of connexin,43. At the ultrastructural level, widened intercellular spaces in the upper epidermis were present with regular desmosomes, adherens junctions and gap junctions. Epidermal cell proliferation and differentiation are regulated by gap junctions. The mutation in connexin,31 is regarded therefore as causal for the clinical picture of the EKV. The unique up-regulation of connexin,43 may occur as a consequence of the Cx31 mutation and temporarily compensate for this defect. [source] Gene expression profiling of porokeratosisJOURNAL OF CUTANEOUS PATHOLOGY, Issue 11 2008Zheng-Hua Zhang Background:, Porokeratosis (PK) represents a heterogeneous group of disorders of keratinization and has a wide variety of clinical manifestations. PK may exhibit similarities with psoriasis at both clinical and molecular levels. The genetic basis and pathogenesis for PK remain elusive. Methods:, We studied the transcriptional profiles of three pairwise lesional and uninvolved skin biopsies from patients with different subtypes of PK using the Illumina® BeadArrayÔ platform. Results:, A total of 37 upregulated genes were identified in our study, including wound-induced keratins, S100 calcium-binding protein genes involved in epidermal differentiation, as well as genes involved in mediating intercellular communication and the immune response. To our knowledge, this is the first study that characterizes the immune profile of PK lesions. Conclusions:, Here, we report that keratinocytes (KCs)-harboring lesions have activated and overexpressed wound-induced keratin genes, which appear to be coregulated with other genes involved in mediating epidermal differentiation, intercellular communication and immunity. This study, from the perspective of gene profiling, supports that gene misregulation in PK mimics that of psoriasis. Our data indicate that the genes implicated in the T-cell-mediated immune response pathway and activation of KCs play a key role in the pathogenesis of PK. [source] Topical paricalcitol (19-nor-1,,25-dihydroxyvitamin D2) is a novel, safe and effective treatment for plaque psoriasis: a pilot studyBRITISH JOURNAL OF DERMATOLOGY, Issue 1 2004C. Durakovic Summary Background, There continues to be a need to develop new pharmacological approaches for treating psoriasis. Topical active vitamin D compounds have proven to be both safe and effective for treating psoriasis. Paricalcitol (19-nor-1,,25-dihydroxyvitamin D2) is a novel vitamin D analogue which has been developed for the prevention of secondary hyperparathyroidism in patients with chronic renal failure. Objectives, To investigate the efficacy and safety of 12 weeks' therapy with a once-daily application of paricalcitol ointment (15 ,g g,1) in comparison with placebo ointment. Methods, This pilot double-blinded self-controlled study was initiated in 11 patients with moderate plaque psoriasis. To characterize the biological effects further and to evaluate the efficacy of topical paricalcitol treatment in psoriasis, we have analysed immunohistochemically the expression of one of the markers for epidermal differentiation (transglutaminase K) in paricalcitol-treated skin as compared with placebo treatment. Results, Treatment with paricalcitol was superior to placebo treatment beginning at week 1. The global severity score for erythema, plaque elevation and scaling was improved significantly more by paricalcitol ointment than by placebo (P < 0·001). Similar results were obtained for assessments of scaling, erythema and plaque elevation. No symptoms of local skin irritation were noted. Laboratory parameters including serum calcium, phosphorus, parathyroid hormone and urinary calcium/creatinine ratio did not reveal any changes of clinical relevance during treatment. The immunoreactivity of transglutaminase K changed after 12 weeks of paricalcitol treatment almost completely to the pattern characteristic for nonlesional psoriatic skin. Conclusions, Once-daily application of paricalcitol ointment was safe and effective for the treatment of plaque psoriasis. [source] Ultraviolet B induces hyperproliferation and modification of epidermal differentiation in normal human skin grafted on to nude miceBRITISH JOURNAL OF DERMATOLOGY, Issue 4 2004S. Del Bino Summary Background For ethical and technical reasons, the in vivo biological effects of ultraviolet (UV) radiation on skin are difficult to study in human volunteers. The use of human skin grafted on to nude mice may circumvent this difficulty. Objectives To investigate the effects of a single moderate UVB exposure on human skin grafted on to nude mice. Methods Modifications of epidermal differentiation markers and patterns of keratin expression were assessed from 24 h to 14 days after a physiological UVB irradiation characterized by the induction of sunburn cells. Results During the first 48 h postexposure, involucrin, loricrin, transglutaminase type I, filaggrin and keratin K2e expression were altered together with the formation of abnormal horny layers. Constitutive keratin K14 was increased while keratin K10 expression was delayed. Newly synthesized keratins K6, K16, K17 and K19 were induced in parallel with an increase in the epidermal proliferation rate. A progressive normalization of both keratinocyte proliferation and differentiation took place during the following days, reaching completion within 2 weeks. Conclusions Exposure of human skin to a UVB dose corresponding to a mild sunburn reaction induces epidermal hyperproliferation and alterations of several constitutive differentiation markers, as well as a drastic modification in the pattern of epidermal keratins. Although these modifications were shown to be progressively reversed in a single exposure model, the data also suggest that subsequent UV exposures occurring during the recovery period may lead to potentially deleterious long-term consequences, such as photoageing and photocarcinogenesis. Grafted human skin appeared to be an attractive and promising model for investigating the biological consequences of UVB radiation in vivo. [source] A multiparameter flow cytometric analysis of the effect of bexarotene on the epidermis of the psoriatic lesionBRITISH JOURNAL OF DERMATOLOGY, Issue 3 2003M.E.J. Franssen Summary Background A new retinoid, bexarotene (Targretin®), was recently investigated in a large multicentre trial for its efficacy and safety in psoriasis. Bexarotene is a novel retinoid X receptor (RXR)-selective ligand. Objectives The aim was to study the effect of bexarotene in psoriasis by analysing markers for epidermal differentiation, proliferation and inflammation in epidermal single cell suspensions from lesions of patients with psoriasis treated with various doses of bexarotene. Methods Thirty-four patients with moderate to severe plaque psoriasis participated in this study and were assigned in sequence to four different dose regimens: 0·5, 1, 2 and 3 mg kg,1 once daily. Before and after 12 weeks of bexarotene treatment, punch biopsies were taken from lesional skin from which epidermal single cell suspensions were prepared using an optimized thermolysin protocol. A sum of scores was determined for each biopsy site, based on a four-point scale for erythema, induration and desquamation. An improved multiparameter flow cytometric assay was used that enabled simultaneous assessment of epidermal proliferation, various aspects of differentiation and epidermal inflammation. The following variables were measured simultaneously: relative DNA content, relative cell size, keratin (K) 10, K6 and vimentin expression. Results The psoriasis area and severity index (PASI) and sum of scores for the individual psoriatic lesion each showed a statistically significant decrease of 28% after 12 weeks of bexarotene treatment (P < 0·001). However, no significant dose,response effect was found. The total percentage of K10+ cells showed a significant increase of 43% (P < 0·01). The total population of K6 expressing cells did not show significant changes. Regarding the subpopulations of K6 single, K10 single and K6 and 10 co-expressing cells, a significant increase of 77% was seen in the K10+ K6, cells (P < 0·05), a significant decrease of 33% in K10, K6+ cells (P < 0·01), and no significant changes in the remaining population of K10+ K6+ cells. After 12 weeks of treatment with bexarotene no significant changes in epidermal proliferation and inflammation were shown. Conclusions The present study indicates a direct effect of RXR activation by bexarotene on the transition of proliferation-associated keratinization into normal keratinization. Although no direct effect of bexarotene on DNA content in the total K10, cells was shown, further studies on subpopulations within the germinative layer such as stem cells and transit amplifying cells might be worthwhile. [source] |