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Seborrheic keratosis (SK) is a common benign tumour, often associated with hyperpigmentation. To investigate the mechanism of melanin accumulation in SK, we have conducted comprehensive gene expression and histological analyses. We obtained five pairs of skin samples, including non‐lesional and SK samples, from the backs of three male Japanese participants aged 40–59 years. To examine melanocytes and keratinocytes in SK, three pairs of skin samples were separated by laser capture microdissection into the basal layer and the other layer in the epidermis. We performed a comprehensive gene expression analysis to identify differentially expressed genes between non‐lesional and SK skin, followed by gene ontology and pathway analysis. We found abnormal morphogenesis and cell proliferation in the basal layer, along with increased immune response and impaired cell differentiation and metabolism in the other layer of SK. We focused on cell proliferation and differentiation, as these are directly associated with melanin accumulation. Immunohistochemical analyses of Ki67, keratin 10, and keratin 14 demonstrated the decreases in the proliferation and early differentiation of the epidermis. Contrarily, no significant changes were observed in terminal differentiation markers, filaggrin and loricrin. Although the number of melanocytes was higher in SK than in non‐lesional skin, melanogenic activity showed no difference. These results indicated that melanin accumulation in SK is caused by delayed melanin excretion due to reduced turnover around the basal and spinous layers of the epidermis and melanin production due to an increased number of melanocytes. Our findings provide new insights for therapeutic approaches in SK. [ABSTRACT FROM AUTHOR]

Background: It is well known that solar radiation accelerates skin photoaging. To evaluate subclinical photodamage in the skin especially from the early phase of ultraviolet (UV)‐induced damage, we have focused on ultraweak photon emission (UPE), also called biophotons. Our previous study reported that the amount of long‐lasting UPE induced by UV, predominantly from lipid peroxidation, is a valuable indicator to assess cutaneous photodamage even at a suberythemal dose, although it was only applied to evaluate acute UV damage. The aim of this study was to further investigate whether long‐lasting UPE could also be a useful marker to assess subclinical chronic sun damage in the course of skin photoaging. Materials and Methods: Forty‐three Japanese females in their 20s were recruited and were divided into two groups according to their history of sun exposure based on a questionnaire (high‐ and low‐sun‐exposure groups). Several skin properties on the cheek and outer forearm were measured in addition to UV‐induced UPE. Results: Among the skin properties measured, water content, average skin roughness, and the lateral packing of lipids in the stratum corneum were significantly deteriorated in the high‐sun‐exposure group as were changes in some skin photoaging scores such as pigmented spots and wrinkles. In addition, those skin properties were correlated with the UPE signals, suggesting the possible impact of oxidative stress on chronic skin damage. Conclusion: Subtle oxidative stress detected by long‐lasting UPE may contribute to subclinical cutaneous damage at the beginning phase of chronic sun exposure, which potentially enhances skin photoaging over a lifetime. [ABSTRACT FROM AUTHOR]

Tight junction (TJ) dysfunction in the stratum granulosum leads to aberrant barrier function of the stratum corneum (SC) in the epidermis. However, it is unclear whether TJs are perturbed in atopic dermatitis (AD), a representative aberrant SC-related skin disease, and whether some factors related to AD pathogenesis induce TJ dysfunction. To address these issues, we investigated the alterations of TJs in AD skin and the effects of Th2 and Th17 cytokines on TJs in a skin-equivalent model. The levels of TJ proteins were determined in the epidermis of nonlesional and lesional skin sites of AD. Western blot and immunohistochemical analyses revealed that the levels of zonula occludens 1 were decreased in the nonlesional sites of AD, and the levels of zonula occludens 1 and claudin-1 were decreased in the lesional sites relative to the levels in skin from healthy subjects. Next, we examined the effects of interleukin (IL)-4, tumor necrosis factor-α, IL-17, and IL-22 on the TJ barrier in a skin-equivalent model. Only IL-17 impaired the TJ barrier. Furthermore, we observed a defect in filaggrin monomer degradation in the IL-17–treated skin model. Thus, TJs are dysfunctional in AD, at least partly, due to the effect of IL-17, which may result in an aberrant SC barrier. [ABSTRACT FROM AUTHOR]

Highlights: [•] Expression of full-length KIAA1199 is essential for HA depolymerizing activity. [•] The cleavage of N-terminal 30 amino acids occurs in functionally matured KIAA1199. [•] The deletion of the N-terminal portion results in altered localization of KIAA1199. [•] The N-terminal 30 amino acids of KIAA1199 are indeed the cleavable signal sequence. [Copyright &y& Elsevier]

Abstract: Background: Hyaluronan (HA) plays a role in keratinocyte proliferation and differentiation, and have shown different biological activities depending on its molecular mass. While many studies have shown changes in the amount of HA after UVB irradiation, molecular mass change remains to be elucidated. Objective: To investigate the change in the molecular mass of HA after UVB irradiation in mouse epidermis. Methods: The mice were irradiated with a single dose of UVB (0.15J/cm2). The amount of HA was examined using HABP sandwich assay. The molecular mass distribution was estimated by Sephacryl S-1000 chromatography. Has and Hyal mRNA expressions were detected by real-time PCR. Results: On day 2 after UVB irradiation, both the amount of HA and the up-regulation of Has3 mRNA expression reached their maximum. The average HA molecular mass was about 1000kDa, a level similar to that of the non-irradiated epidermis. On day 3, the average HA molecular mass drastically decreased to 100kDa, while Hyal1, Hyal2, and Hyal3 mRNA expressions slightly increased. The amount of HA, however, remained high. On days 4 and 5, the amount of HA gradually decreased, but the molecular mass of HA remained low. A drastic reduction of the HA molecular mass after UVB irradiation was confirmed. Conclusion: UVB irradiation elicits remarkable changes in the molecular mass of HA, as well as amount. These qualitative and quantitative changes of HA might play an important role in UVB-induced cell proliferation and differentiation. Further study will be required to resolve the mechanism of HA degradation in the epidermis. [Copyright &y& Elsevier]