Chronic ultraviolet radiation modulates epidermal differentiation as it up-regulates transglutaminase 1 and its substrates

BACKGROUND: Ultraviolet radiation (UVR) stimulates cellular mitosis, which leads to epidermal hyperplasia. On the basis of hypothesis that chronic UVR may modulate differentiation as well as epidermal hyperplasia, we evaluated the modulation of markers of epidermal differentiation, such as transglutaminase 1 (TGase 1), filaggrin and loricrin, by chronic UVR in vivo. METHODS: Total TGase activities assay or in situ TGase activities were measured in human and mouse skin. TGase 1 expression was identified by immunohistochemical staining in human skin. In the human, the pre-auricular skin of face was used for samples of chronic UVR, and the post-auricular skin was selected as non-UVR control. The changes of filaggrin and loricrin were identified by western immunoblots. RESULTS: In human and mouse epidermis, chronic UVR induced the increase of in situ TGase activities or total TGase activities as it up-regulated TGase 1 expression in the epidermis. As the substrates of TGase 1, chronic UVR induced the up-regulation of filaggrin and loricrin in mouse epidermis as well. At the same time, chronic UVR induced the marked epidermal hyperplasia in human and mouse skin. CONCLUSION: Chronic UVR stimulates epidermal differentiation as it up-regulates TGase 1 and its substrates. The modified epidermal differentiation is balanced with epidermal hyperplasia, leading to the maintenance of epidermal homeostasis in the UV-irradiated epidermis.     

Heparanase activation induces epidermal hyperplasia,angiogenesis, lymphangiogenesis and wrinkles

Please cite this paper as: Heparanase activation induces epidermal hyperplasia, angiogenesis, lymphangiogenesis and wrinkles. Experimental Dermatology 2010; 19 : 965–972. Abstract: To clarify the difference between cutaneous responses to single and repeated barrier disruption, changes of epidermal gene expression were examined by using RT‐PCR. In repeatedly barrier‐disrupted skin, heparanase was specifically up‐regulated in epidermis. In addition, there was a marked decrease in heparan sulfate (HS) chains of perlecan in basement membrane at the dermal–epidermal junction (DEJ) compared with singly disrupted skin. HS chains form a reservoir for heparan sulfate‐binding growth factors. In repeatedly barrier‐disrupted skin, expression of vascular endothelial growth factor‐A (VEGF‐A), an angiogenic factor, was induced in epidermis, whereas thrombospondin‐1 (TSP‐1), an angiogenesis inhibitor, was down‐regulated, and concomitantly blood vessels were elongated and enlarged in dermis. Expression of VEGF‐C, a lymphangiogenesis factor, was augmented in epidermis of repeatedly barrier‐disrupted skin, concomitantly with an increase in the number and size of lymphatic vessels. Topical application of a synthetic heparanase inhibitor, 1‐[4‐(1H‐benzoimidazol‐2‐yl)phenyl]‐3‐[4‐(1H‐benzoimidazol‐2‐yl)phenyl]urea, to skin after barrier disruption significantly suppressed wrinkle formation, degradation of HS chains in the basement membrane, epidermal hyperplasia and the changes of blood and lymphatic vessels. These results suggest that chronic barrier disruption activates heparanase and induces gene expression changes, leading to increased growth factor interaction between epidermis and dermis, and facilitating various cutaneous changes, including wrinkle formation.     

Key role of heparan sulfate chains in assembly of anchoring complex at the dermal-epidermal junction

Epidermal basement membrane forms anchoring complex composed of hemidesmosomes, anchoring filaments, lamina densa and anchoring fibrils to link epidermis to dermis. However, the anchoring complex is rarely formed in skin equivalent models, probably because of degradation of extracellular matrix (ECM) proteins and heparan sulfate chains by matrix metalloproteinases (MMPs) and heparanase, respectively. To explore the roles of ECM proteins and heparan sulfate in anchoring complex assembly, we used specific inhibitors of MMPs and heparanase, and the formation of anchoring complex was analysed in terms of polarized deposition of collagen VII, BP180 and β4 integrin at the dermal-epidermal junction (DEJ) by means of immunohistochemistry and transmission electron microscopy (TEM). The deposition of collagen VII was polarized to the basal side by the addition of MMP inhibitor, and the staining intensity was increased by combined treatment with MMP inhibitor and heparanase inhibitor, which enhanced anchoring fibril formation as observed by TEM. BP180 was polarized to the basal side by heparanase inhibitor, which protects HS chains, but not by MMP inhibitor. MMP inhibitor improved the polarization of β4 integrin. Hemidesmosomes were formed in the presence of each inhibitor, as observed by TEM, and formation was greatly enhanced by the combined treatment. These findings suggest that heparan sulfate chains, in addition to ECM proteins at the DEJ, play an important role in the assembly of anchoring complex, especially hemidesmosomes and anchoring fibrils.     

Hyperpigmentation in human solar lentigo is promoted by heparanase-induced loss of heparan sulfate chains at the dermal-epidermal junction

Background

Skin pigmentation induced by ultraviolet B radiation is caused in part by inflammation mediated by cytokines secreted from keratinocytes and fibroblasts in the irradiated area. Heparanase is also activated in the irradiated skin, and this leads to loss of heparan sulfate at the dermal-epidermal junction (DEJ), resulting in uncontrolled diffusion of heparan sulfate-binding cytokines through the DEJ. However, it is not clear whether heparanase-induced loss of heparan sulfate at the DEJ is involved in the pigmentation process in sun-exposed skin.

Objective

We examined the role of heparan sulfate in the pigmentation process of human pigmented skin and in pigmented skin-equivalent model.

Methods

Heparan sulfate and blood vessels in human pigmented skin, solar lentigo, and non-pigmented skin were evaluated by means of immunohistochemistry. Pigmented skin equivalent models were cultured with or without heparanase inhibitor and the pigmentation levels were compared.

Results

In solar lentigo, heparan sulfate was hardly observed, presumably due to the increase of heparanase at the DEJ, in spite of the deposition of core protein of perlecan (also known as heparan sulfate proteoglycan). The number of blood vessels was significantly increased in solar lentigo. In the pigmented skin equivalent model, heparanase inhibitor increased the staining intensity of heparan sulfate at the DEJ and markedly reduced melanogenesis in the epidermis.

Conclusions

Our results indicate that heparanase-induced loss of heparan sulfate at the DEJ is involved in the pigmentation process of human skin. Consequently, heparanase inhibitors can be expected to exert a protective effect against ultraviolet exposure-induced skin pigmentation.     

Plasmin induces degradation and dysfunction of laminin 332 (laminin 5) and impaired assembly of basement membrane at the dermal-epidermal junction

Background The epidermal basement membrane (BM), located at the dermal–epidermal junction (DEJ), plays important roles not only in adhesion between epidermis and dermis, but also in controlling skin functions. In sun‐exposed skin, the BM becomes disrupted and multilayered. In order to explore the impairment of BM assembly, we have used a skin‐equivalent (SE) as a model of BM damage and previously clarified the involvement of matrix metalloproteinases (MMPs) in impairment of BM assembly. Objectives In this work, we examined the role of urokinase‐type plasminogen activator (uPA) and plasmin in impairment of BM assembly at the DEJ by using the SE, as ultraviolet irradiation to the skin increases uPA as well as MMPs. Methods SEs were used as a model of formation and damage of BM. Human uPA was detected by enzyme‐linked immunosorbent assay and zymography, and gelatinases such as MMP‐2 and MMP‐9 were detected by zymography. Human plasminogen was added at 0·06 μmol L^?1 (about 3% of plasma level) to increase plasmin to a pathological level. N‐terminal peptide sequence analysis of plasmin‐treated laminin 332 was carried out to identify α3, β3 and γ2 chains of laminin 332 and their cleavage sites of each chain. Plasmin‐treated laminin 332 was analysed in keratinocyte adhesion activity and binding to type VII collagen. Results Human uPA was detected in addition to MMP‐2 and MMP‐9, in conditioned medium of SE. Although the BM was well organized in the presence of an MMP inhibitor alone, the activated plasmin disorganized the BM even in the presence of the inhibitor. The impairment of BM assembly made the epidermis thinner as compared with that of a control cultured in the presence of MMP inhibitor, indicating that the BM affects the polarity and differentiation of the epidermis. The addition of aprotinin, a serine proteinase inhibitor, and tranexamic acid, a uPA‐plasmin inhibitor, inhibited the plasmin‐induced impairment of BM assembly and facilitated BM reorganization, thereby improving the epidermal structure. N‐terminal peptide sequence analysis of plasmin‐treated laminin 332 revealed the removal of a 5‐ or 10‐kDa fragment, including the cell adhesion region, from the G3 domain of the α3 chain, and the LN domain, which binds to the noncollagenous 1 domain in type VII collagen, from the β3 chain. Plasmin‐treated laminin 332 showed lower keratinocyte adhesion activity and reduced binding to type VII collagen. Conclusions These results suggest that uPA and plasmin are involved in the impairment of BM assembly and epidermal differentiation, and that these effects arise at least partly through direct degradation of laminin 332.     

1‐(2‐Hydroxyethyl)‐2‐imidazolidinone,a heparanase and matrix metalloproteinase inhibitor,improves epidermal basement membrane structure and epidermal barrier function

Daily exposure to sunlight is known to affect the structure and function of the epidermal basement membrane (BM), as well as epidermal differentiation and epidermal barrier function. The aim of this study is to clarify whether the inhibition of BM‐degrading enzymes such as heparanase and matrix metalloproteinase 9 (MMP‐9) can improve the epidermal barrier function of facial skin, which is exposed to the sun on a daily basis. 1‐(2‐hydroxyethyl)‐2‐imidazolidinone (HEI) was synthesized as an inhibitor of both heparanase and MMP‐9. HEI inhibited not only the BM damage at the DEJ but also epidermal proliferation, differentiation, water contents and transepidermal water loss abnormalities resulting from ultraviolet B (UVB). This was determined in this study by the use of UVB‐induced human cultured skins as compared with the control without HEI. Moreover, topical application of HEI improved epidermal barrier function by increasing water content and decreasing transepidermal water loss in daily sun‐exposed facial skin as compared with non‐treated skins. These results suggest that the inhibition of both heparanase and MMP‐9 is an effective way to care for regularly sun‐exposed facial skin by protecting the BM from damage.     

Regulatory role for the profilaggrin N-terminal domain in epidermal homeostasis

It is well known that profilaggrin, after its release from keratohyalin granules through dephosphorylation, becomes enzymatically processed into individual filaggrin monomers. The roles for filaggrin monomers in aggregating keratin filaments, as a component of the cornified cell envelope, and as a source of natural moisturizing factor are well established. A specific N-terminal fragment, called the PF-AB domain, becomes proteolytically released as well, but much less is known about its functional role in epidermal development. Here, the functional role of profilaggrin N-terminal (PF-N) domain was addressed by overexpressing three overlapping fragments from a lentiviral expression vector in the epidermis of living skin equivalents. The PF-N domain expression impaired the epidermal development through reducing keratinocyte proliferation and impairing differentiation. The expression of well-known differentiation markers profilaggrin, loricrin, and keratin 10 was considerably downregulated in PF-N domain overexpressing-skin equivalents. The activation of caspase 14 was also substantially affected. In contrast, total silencing of profilaggrin expression, obtained with a lentiviral miR vector, resulted in a hyperproliferative epidermis. We propose a hypothesis that profilaggrin AB domain provides a key feedback mechanism that controls epidermal homeostasis.     

Expression of loricrin in skin disorders.

Loricrin, the major component of the cornified envelope, is normally expressed in the granular layer of epidermis during the last steps of keratinocyte differentiation. Using an antiloricrin antiserum (A8-73), an increased expression of this envelope precursor was found in some disorders of hyperorthokeratosis (ichthyosiform erythroderma; lichen ruber), but not in others (keratodermia ichthyosis vulgaris). In disorders accompanied by parakeratosis, a sign of incomplete differentiation (psoriasis, prurigo nodularis) loricrin was not detected, whereas the tissue expressed filaggrin. Treatment of normal skin with retinoic acid, increasing epidermal thickness in some subjects, led to an increased expression of loricrin. Loricrin might be a useful indicator of the extent of terminal epidermal differentiation in skin disorders.     

表皮蛋白质及板层小体对激素依赖性皮炎皮肤屏障变化的影响

目的 探讨表皮蛋白质、板层小体的变化对激素依赖性皮炎皮肤屏障变化的影响。 方法 无创性皮肤测试比较60例激素依赖性皮炎患者与40例正常人,皮肤经表皮水分流失（TEWL）的差异,13例患者及10例正常人配合皮损取材,行HE染色观察皮损组织病理学变化。免疫组化观察患者表皮K6、K10、K14、K15、兜甲蛋白、丝聚合蛋白、内披蛋白的变化。电镜观察板层小体密度的变化。结果 与正常人比较,患者TEWL增加,差异有统计学意义（P < 0.05）,显示皮肤屏障功能受损。患者皮损的组织病理学为非特异性炎症表现,根据临床特点,各类皮损的组织病理学表现存在一定差异。免疫组化示患者表皮K10、K14、丝聚合蛋白、兜甲蛋白、内披蛋白的表达均减少,K15出现异常表达,差异均有统计学意义（P < 0.05）,显示表皮增殖、分化受抑制,CE结构受损;电镜下颗粒层内板层小体数量减少,密度降低。结论 与正常人皮肤比较,激素依赖性皮炎患者皮肤屏障结构受到破坏,恢复皮肤屏障对治疗激素依赖性皮炎具有重要意义。     

Peroxisome-proliferator-activated receptor (PPAR)-gamma activation stimulates keratinocyte differentiation

Previous studies demonstrated that peroxisome-proliferator-activated receptor (PPAR)-alpha or PPAR-delta activation stimulates keratinocyte differentiation, is anti-inflammatory, and improves barrier homeostasis. Here we demonstrate that treatment of cultured human keratinocytes with ciglitazone, a PPAR-gamma activator, increases involucrin and transglutaminase 1 mRNA levels. Moreover, topical treatment of hairless mice with ciglitazone or troglitazone increases loricrin, involucrin, and filaggrin expression without altering epidermal morphology. These results indicate that PPAR-gamma activation stimulates keratinocyte differentiation. Additionally, PPAR-gamma activators accelerated barrier recovery following acute disruption by either tape stripping or acetone treatment, indicating an improvement in permeability barrier homeostasis. Treatment with PPAR-gamma activators also reduced the cutaneous inflammatory response that is induced by phorbol 12-myristate-13-acetate, a model of irritant contact dermatitis and oxazolone, a model of allergic contact dermatitis. To determine whether the effects of PPAR-gamma activators are mediated by PPAR-gamma, we next examined animals deficient in PPAR-gamma. Mice with a deficiency of PPAR-gamma specifically localized to the epidermis did not display any cutaneous abnormalites on inspection, but on light microscopy there was a modest increase in epidermal thickness associated with an increase in proliferating cell nuclear antigen (PCNA) staining. Key functions of the skin including permeability barrier homeostasis, stratum corneum surface pH, and water-holding capacity, and response to inflammatory stimuli were not altered in PPAR-gamma-deficient epidermis. Although PPAR-gamma activators stimulated loricrin and filaggrin expression in wild-type animals, however, in PPAR-gamma-deficient mice no effect was observed indicating that the stimulation of differentiation by PPAR-gamma activators is mediated by PPAR-gamma. In contrast, PPAR-gamma activators inhibited inflammation in both PPAR-gamma-deficient and wild-type mouse skin, indicating that the inhibition of cutaneous inflammation by these PPAR-gamma activators does not require PPAR-gamma in keratinocytes. These observations suggest that thiazolidindiones and perhaps other PPAR-gamma activators maybe useful in the treatment of cutaneous disorders.     

Improvement of the dermal epidermal junction in human reconstructed skin by a new c-xylopyranoside derivative

Skin aging entails drastic changes in the extracellular dermal matrix (ECM) and dermal-epidermal junction (DEJ). These biological alterations are reflected in the clinical signs of aged skin. A new C-xylopyranoside derivative, C-beta-D-xylopyranoside-2-hydroxy-propane (C-Xyloside) has been shown to induce neo-synthesis of matrix proteins such as glycosaminoglycans and heparan sulfate proteoglycans. The aim of this study was to assess the effects of C-Xyloside on markers of the dermal epidermal junction. Basement membrane components, collagen IV, collagen VII and laminin 5 as well as sub-epidermal dermal markers, pro-collagen I and fibrillin 1 were analysed using immunohistochemistry in a reconstructed skin model, including a dermal equivalent populated with living fibroblasts. Levels of mRNA of collagen VII alpha1 and collagen IV alpha1 were evaluated in dermal fibroblasts using RT-PCR. The results showed that C-Xyloside significantly induced a higher deposition of basement membrane and DEJ proteins in the reconstructed skin model and increased collagen VII gene expression. These findings indicate that, in addition to stimulating glycosaminoglycan and heparan sulfate proteoglycan expression, C-Xyloside improves the morphogenesis of the whole DEJ, and strongly suggests beneficial effects in aged skin from restoring DEJ integrity.     

Induction of selected lipid metabolic enzymes and differentiation-linked structural proteins by air exposure in fetal rat skin explants

The epidermal permeability barrier of premature infants matures rapidly following birth. Previous studies suggest that air exposure could contribute to this acceleration, because: (i) development of a structurally and functionally mature barrier accelerates when fetal rat skin explants are incubated at an air-medium interface, and (ii) occlusion with a water-impermeable membrane prevents this acceleration. To investigate further the effects of air exposure on epidermal barrier ontogenesis, we compared the activities of several key enzymes of lipid metabolism and gene expression of protein markers of epidermal differentiation in fetal rat skin explants grown immersed versus air exposed. The rate-limiting enzymes of cholesterol (HMG CoA reductase) and ceramide (serine palmitoyl transferase) synthesis were not affected. In contrast, the normal developmental increases in activities of glucosylceramide synthase and cholesterol sulfotransferase, responsible for the synthesis of glucosylceramides and cholesterol sulfate, respectively, were accelerated further by air exposure. Additionally, two enzymes required for the final stages of barrier maturation and essential for normal stratum corneum function, beta-glucocerebrosidase, which converts glucosylceramide to ceramide, and steroid sulfatase, which desulfates cholesterol sulfate, also increased with air exposure. Furthermore, filaggrin and loricrin mRNA levels, and filaggrin, loricrin, and involucrin protein levels all increased with air exposure. Finally, occlusion with a water-impermeable membrane prevented both the air-exposure-induced increase in lipid enzyme activity, and the expression of loricrin, filaggrin, and involucrin. Thus, air exposure stimulates selected lipid metabolic enzymes and the gene expression of key structural proteins in fetal epidermis, providing a biochemical basis for air-induced acceleration of permeability barrier maturation in premature infants.     

Loss of normal profilaggrin and filaggrin in flaky tail (ft/ft) mice: an animal model for the filaggrin-deficient skin disease ichthyosis vulgaris

Flaky tail (gene symbol ft) is an autosomal recessive mutation in mice that results in a dry, flaky skin, and annular tail and paw constrictions in the neonatal period. Previous studies demonstrated that the ft mutation maps to the central region of mouse chromosome 3, in the vicinity of the epidermal differentiation complex, a gene locus that includes many nonkeratin genes expressed in epidermis. In this study we report a detailed characterization of the flaky tail mouse. Affected homozygous ft/ft mice exhibit large, disorganized scales on tail and paw skin, marked attenuation of the epidermal granular layer, mild acanthosis, and orthokeratotic hyperkeratosis. Biochemical analysis demonstrated that ft/ft mice lacked normal high molecular profilaggrin (approximately 500 kDa), and instead expressed a lower molecular weight form of profilaggrin (220 kDa) that is not proteolytically processed to profilaggrin intermediates or filaggrin. Mutant mice lacked the large, irregular F-type keratohyalin granules that contain profilaggrin, and filaggrin was absent from the cornified layers of ft/ft epidermis. The expression of epidermal keratins was unchanged, whereas the cornified envelope proteins involucrin and loricrin were increased in ft/ft epidermis. Cultured ft/ft keratinocytes also synthesized reduced amounts of profilaggrin mRNA and protein, demonstrating that the defect in profilaggrin expression is intrinsic to epidermal cells. These findings demonstrate that flaky tail mice express an abnormal profilaggrin polypeptide that does not form normal keratohyalin F-granules and is not proteolytically processed to filaggrin. We propose that the absence of filaggrin, and in particular the hygroscopic, filaggrin-derived amino acids that are thought to function in epidermal hydration, underlies the dry, scaly skin characteristic of ft/ft mice. This animal model provides a tool for understanding the role of filaggrin in normal epidermal function and may provide insight into the molecular basis of the filaggrin-deficient human skin disorder ichthyosis vulgaris. J Invest Dermatol 115:1072-1081 2000     

Activators of PPARs and LXR decrease the adverse effects of exogenous glucocorticoids on the epidermis

Abstract:  While glucocorticoids (GC) exert beneficial effects (anti-inflammatory), they also have adverse effects on the epidermis including decreased epidermal differentiation, decreased keratinocyte proliferation, and decreased cutaneous permeability barrier homeostasis. Thus, the purpose of this study was to develop strategies to prevent these GC toxicities using simultaneous topical treatments in clobetasol-treated mice. While a triple-lipid mixture of stratum corneum lipids (ceramide, free fatty acid and cholesterol) was previously shown to reverse the GC-induced abnormality in cutaneous barrier function [ J Invest Dermatol , 120 (2003) 456], this lipid mixture did not prevent the GC-induced abnormalities in either keratinocyte proliferation or differentiation. As activators of PPARα, β/δ, γ and LXR, regulate keratinocyte proliferation and differentiation and improve permeability barrier homeostasis, we next assessed the effects of these activators during concurrent GC treatment. Co-application of either ciglitazone (PPARγ activator), clofibrate (PPARα activator) or 22R (OH) cholesterol (LXR activator) with clobetasol prevented the decrease in involucrin, filaggrin and loricrin expression. By contrast, a PPARβ/δ activator (GW501516) normalized only the expression of involucrin and filaggrin but not loricrin. Moreover, topical application of PPARα, β/δ or LXR activators partially prevented the decrease in keratinocyte proliferation in GC-treated murine skin, as measured using PCNA, while no effect was seen after co-treatment with PPARγ activators. Finally, PPARγ and PPARβ/δ activators but not PPARα and LXR activators improved permeability barrier homeostasis in GC-treated mice. Together, these studies demonstrate that PPAR and LXR activators can prevent several of the adverse effects of topical GC on the epidermis.     

Interaction of the profilaggrin N-terminal domain with loricrin in human cultured keratinocytes and epidermis

The relationship between the two coexpressed differentiation markers, profilaggrin and loricrin, is not clear right now. In this study, we explored the interaction of profilaggrin N-terminal domain (PND) with loricrin in keratinocytes and epidermis. Confocal immunofluorescence microscopic analysis of human epidermis showed that PND colocalized with loricrin. Loricrin nucleofected into HaCaT cells colocalized with PND in the nucleus and cytoplasm. The PND localizes to both the nucleus and cytoplasm of epidermal granular layer cells. Nucleofected PND also colocalized with keratin 10 (K10) in the nucleus and cytoplasm. Immunoelectron microscopic analysis of human epidermis confirmed the findings in nucleofected keratinocytes. Yeast two-hybrid assays showed that the B domain of human and mouse PND interacted with loricrin. The glutathione S-transferase (GST) pull-down analysis using recombinant GST-PND revealed that PND interacted with loricrin and K10. Knockdown of PND in an organotypic skin culture model caused loss of filaggrin expression and a reduction in both the size and number of keratohyalin granules, as well as markedly reduced expression of loricrin. Considering that expression of PND is closely linked to keratinocyte terminal differentiation, we conclude that PND interacts with loricrin and K10 in vivo and that these interactions are likely to be relevant for cornified envelope assembly and subsequent epidermal barrier formation.     

Gene expression profiles of three different models of reconstructed human epidermis and classical cultures of keratinocytes using cDNA arrays

The gene expression profiles of three different models of reconstructed human epidermis were analyzed in a comparative study using cDNA array technology. The study also included normal human subconfluent keratinocytes cultured on plastic. Arrays were custom-made and comprised 504 known genes related to cutaneous biology. The gene expression profiles of the three reconstructed epidermis models shared 86% similarity; only 22 of the 504 examined genes showed a different expression level. A comparison of the 3D models with keratinocyte cultures on plastic dishes revealed a set of six genes with a considerably higher expression in the 3D models. These genes were keratin 1, corneodesmosin, filaggrin, loricrin, calmodulin-like skin protein and caspase 14, all related to keratinocyte terminal differentiation. The reported data may contribute to a better understanding and characterization of reconstructed epidermal models and may also serve as established references for investigations related to epidermal differentiation and proliferation.     

A novel antigen of the dermal-epidermal junction defined by an anti-CD1b monoclonal antibody (NU-T2)

NU-T2 is a mouse monoclonal IgG1 antibody to the CD1b molecule, (cross-)reacting with an antigen of the dermal-epidermal junction (NU-T2 DEJ AG). Further immunohistochemical characterization of the NU-T2 DEJ AG showed it to display unique properties that differentiate it from other known antigens of the dermal-epidermal junction. Indeed, the NU-T2 DEJ AG is primate-specific and present only in epithelial basement membranes. In normal human skin it is expressed within the lowermost lamina lucida of the dermal-epidermal junction but not in the deep part of epidermal appendages nor in the deep part of epidermal appendages nor in the basement membrane of dermal vessels, smooth muscles or nerves. In diseases with intraepidermal or intradermal cleavage, NU-T2 reactivity was observed at the floor of the blister. In various skin specimens with a cleavage through the lamina lucida (NaCl — or dispase-split skin, bullous pemphigoid, junctional epidermolysis bullosa), NU-T2 immunoreactivity seemed reduced, being localized at the dermal side of the cleavage. These results suggest that the antigen recognized by NU-T2 is a novel component of the lamina lucida of the dermal-epidermal junction, that seems to be important for dermal-epidermal adhesion.This work was presented at the XIXth Annual Meeting of the Society for Cutaneous Ultrastructure Research held in Lyon, France, 17–19 September 1992 in honour of Prof. J. Thivolet     

Importance of the dermal-epidermal junction and recent advances

The zone of human skin between the epidermis and dermis is called the dermal-epidermal junction (DEJ). The importance of the DEJ is outlined and three new areas of research involving the DEJ are reviewed: the intracellular pool of bullous pemphigoid antigen, the interactions between fibronectin and keratinocytes and the epidermolysis bullosa acquisita antigen.     

Effect of C-xyloside on morphogenesis of the dermal epidermal junction in aged female skin. An ultrastuctural pilot study

A placebo-controlled randomized pilot study was performed on five postmenopausal women aged from 60 to 75 years. The women applied 320?mg (2?mg/cm(2))?of either placebo or 10% C-β-D-xylopyranoside-2-hydroxy-propane (C-xyloside) cream to each outer forearm twice daily for 3?months. At the end of the treatment, skin biopsies were collected from application areas on both forearms. Transmission electron microscope examinations revealed skin ultrastructural changes at the dermal epidermal junction (DEJ) after 10% C-xyloside application for 3 months. The morphological appearance of the DEJ showed strong improvements, with more homogeneous and regular lamina densa in the C-xyloside-treated compared to the placebo treated skin areas. The number of zones showing basement membrane re-duplication was indeed strikingly reduced on C-xyloside-treated skin. These ultrastructural results were further confirmed by a statistically significant increase in the expression levels of α6-integrin the and laminin-332, as estimated by immunohistochemistry. Altogether, these data suggest that topical C-xyloside application in vivo may be efficient in inducing a better dermal-epidermal cohesion when such a junction is deficient, as is the case in photo-aged or chronologically aged skin. Moreover, a statistically significant increase in CD44 expression was noted in the epidermis of C-xyloside-treated compared to the placebo treated skin areas.