• Biomolecules & Therapeutics
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• v.27 no.6
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• pp.553-561
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• 2019

Rab25, a member of the Rab11 small GTPase family, is central to achieving cellular polarity in epithelial tissues. Rab25 is highly expressed in epithelial cells of various tissues including breast, vagina, cervix, the gastrointestinal tract, and skin. Rab25 plays key roles in tumorigenesis, mainly by regulating epithelial differentiation and proliferation. However, its role in skin physiology is relatively unknown. In this study, we demonstrated that Rab25 knock-out (KO) mice show a skin barrier dysfunction with high trans-epidermal water loss and low cutaneous hydration. To examine this observation, we investigated the histology and epidermal differentiation markers of the skin in Rab25 KO mice. Rab25 KO increased cell proliferation at the basal layer of epidermis, whereas the supra-basal layer remained unaffected. Ceramide, which is a critical lipid component for skin barrier function, was not altered by Rab25 KO in its distribution or amount, as determined by immunohistochemistry. Notably, levels of epidermal differentiation markers, including loricrin, involucrin, and keratins (5, 14, 1, and 10) increased prominently in Rab25 KO mice. In line with this, depletion of Rab25 with single hairpin RNA increased the expression of differentiation markers in a human keratinocyte cell line, HaCaT. Transcriptomic analysis of the skin revealed increased expression of genes associated with skin development, epidermal development, and keratinocyte differentiation in Rab25 KO mice. Collectively, these results suggested that Rab25 is involved in the regulation of epidermal differentiation and proliferation.

• Journal of Microbiology and Biotechnology
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• v.32 no.2
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• pp.238-247
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• 2022

Since the skin covers most surfaces of the body, it is susceptible to damage, which can be fatal depending on the degree of injury to the skin because it defends against external attack and protects internal structures. Various types of artificial skin are being studied for transplantation to repair damaged skin, and recently, the production of replaceable skin using three-dimensional (3D) bioprinting technology has also been investigated. In this study, skin tissue was produced using a 3D bioprinter with human skin cell lines and cells extracted from mouse skin, and the printing conditions were optimized. Gelatin was used as a bioink, and fibrinogen and alginate were used for tissue hardening after printing. Printed skin tissue maintained a survival rate of 90% or more when cultured for 14 days. Culture conditions were established using 8 mM calcium chloride treatment and the skin tissue was exposed to air to optimize epidermal cell differentiation. The skin tissue was cultured for 14 days after differentiation induction by this optimized culture method, and immunofluorescent staining was performed using epidermal cell differentiation markers to investigate whether the epidermal cells had differentiated. After differentiation, loricrin, which is normally found in terminally differentiated epidermal cells, was observed in the cells at the tip of the epidermal layer, and cytokeratin 14 was expressed in the lower cells of the epidermis layer. Collectively, this study may provide optimized conditions for bioprinting and keratinization for three-dimensional skin production.

• Biomolecules & Therapeutics
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• v.23 no.6
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• pp.525-530
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• 2015

Ceramide is the most abundant lipid in the epidermis and plays a critical role in maintaining epidermal barrier function. Overall ceramide content in keratinocyte increases in parallel with differentiation, which is initiated by supplementation of calcium and/or vitamin C. However, the role of metabolic enzymes responsible for ceramide generation in response to vitamin C is still unclear. Here, we investigated whether vitamin C alters epidermal ceramide content by regulating the expression and/or activity of its metabolic enzymes. When human keratinocytes were grown in 1.2 mM calcium with vitamin C ($50{\mu}g/ml$) for 11 days, bulk ceramide content significantly increased in conjunction with terminal differentiation of keratinocytes as compared to vehicle controls (1.2 mM calcium alone). Synthesis of the ceramide fractions was enhanced by increased de novo ceramide synthesis pathway via serine palmitoyltransferase and ceramide synthase activations. Moreover, sphingosine-1-phosphate (S1P) hydrolysis pathway by action of S1P phosphatase was also stimulated by vitamin C supplementation, contributing, in part, to enhanced ceramide production. However, activity of sphingomyelinase, a hydrolase enzyme that converts sphingomyelin to ceramide, remained unaltered. Taken together, we demonstrate that vitamin C stimulates ceramide production in keratinocytes by modulating ceramide metabolicrelated enzymes, and as a result, could improve overall epidermal barrier function.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.20 no.4
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• pp.334-340
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• 1998

Stimulatory effects of epidermal growth factor (EGF) and transforming growth $factor-{\alpha}$($TGF-{\alpha}$) on the growth of squamous cancer cell lines established from human oral cancer tissue with moderate differentiation were studied in vitro. After culturing in serum-free media for 24 hours, growth factors-EGF only, $TGF-{\alpha}$ only and EGF, $TGF-{\alpha}$ together-were added to the media and numbers of cells were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and compared with the control at 96, 144 hours. Each of EGF and $TGF-{\alpha}$ showed statistically significant stimulatory effects on the growth of cells respectively. Dose-dependent relationship of the stimulatory effects were not clearly demonstrated. The effects of EGF were higher than those of $TGF-{\alpha}$ and combinative administration showed higher effects than those of single uses. In conclusion, EGF may play an important and major role in differentiation and growth of human oral squamous cancer cells. $TGF-{\alpha}$, produced from cells activated by EGF, also can stimulate the cell growth and could be an alternative ligand for EGF receptor.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.335-338
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• 1996

We attempted to reconstruct basement membrane (BM) in between the epidermal compartment and dermal compartment in the artificial skin preparation and examine its effect on the skin architecture as well as on the epidermal differentiation. Laminin, one of the component of BM, stimulate the migration of the basal cells but type IV collagen which is a major component of the mechanical network of BM did not stimulate epidermal migration. However laminin in the presence of type IV collagen at a 1:1 molar ratio did not stimulate epidermal migration but provide nice demarcation between epidermis and dermis. This mixture of laminin and type IV collagen enhanced epidermal differentiation in the artificial skin based on the morphological observation as well as biochemical criteria. The epidermal acquirement of migratory ability on the laminin-rich substrate suggest that this type of unbalance in the expression of the components of BM may prevail in the area of healing tissue and the invasive transition of the tumor. The result in this study provide the technical improvement in the artificial skin preparation and further application of this technique for the reconstruction of other bio-artificial organ.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.32 no.1 s.55
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• pp.17-22
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• 2006

Phosphatidyiserine (PS) is a phospholipid which plays the structural role in membranes and serves as a cofactor of signaling enzymes for diverse cellular functions. In this study, we observed that topical treatment with PS significantly decreased trans-epidermal water loss (TEWL) induced by tape-stripping in hairless mice. Also, ceramides in epidermis were increased in PS-treated group compared to vehicle-treated one in vivo. the amounts of non-hydroxyl ceramide (NHCER) (1.4 fold) and glucosylceramide (glucosylCER) (1.6 fold), in the skin of hairless mice, were increased by topical treament with PS. Also, we demonstrated that PS stimulated keratinocyte differentiation. We observed that PS treatment morphologically altered normal human keratinocyte (NHK) from the proliferating phase to the differentiating one, suggesting that PS stimulated epidermal differentiation in NHK. We also showed that the expressions of the specific markers for epidermal differentiation, involucrin (INV) (3.5 fold up) and transglutaminase 1 (TG'ase 1) (3 fold up), were significantly increased by PS treatment, compared to untreated control in vitro. In addition, topical treatment with PS resulted in a progressive increase in INV and loricrin protein levels in vivo. In conclusion, we provide the first evidence for the physiological activities of PS in skin, and we suggest that PS strengthen the epidermal permeability harrier by stimulation of keratinocyte differentiation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.1
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• pp.1-8
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• 2008

Epidermis is one of the most dynamic organs in the human body. Multiple layers of keratinocytes in the epidermis continuously undergo proliferation, differentiation, and desquamation cycles, which is the bases of maintaining the epidermal homeostasis. Epidermal homeostasis eventually leads to establish and maintain permeability barrier homeostasis, the most important function of the epidermis. The permeability barrier is located in the stratum corneum. Tightly coordinated regulations are required for the sustained normal barrier function. Extensive studies have established that several nuclear hormone liposensors, including peroxisome proliferator-activated receptor a PPARa, PPARb/d, PPARg and LXRs are expressed in keratinocyte. Activation of PPARs and LXRs could provide a mechanism to coordinate the formation of the corneocytes and extracellular lipid membranes that constitute the stratum corneum. Topical application of PPAR/LXR ligands to murine skin results in the increased expression of keratinocyte differentiation-related proteins, such as involucrin, loricrin, profilaggrin, and trans-glutaminase 1, which would stimulate cornified envelope formation. In conclusion, topical application of ligands or activators of PPAR/LXR as an epidermotherapy would be a promising option to deal dry skin conditions such as atopy.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.29 no.2 s.43
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• pp.105-130
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• 2003

Human skin equivalents, also designated as cultured skin substitute (Boyce and Warden, 2002) or organotypic co-cultures (Maas-Szabowski et al., 1999, 2000, 2003), are three-dimensional systems that are engineered by seeding fibroblasts into a three-dimensional dermal matrix. Such a dermal equivalent is then subsequently seeded with human keratinocytes. After cell attachment, the culture is kept first under submerged condition to allow keratinocyte proliferation. Thereafter, the culture is lifted the air-liquid interface (A/L) to expose the epidermal compartment to the air, and to further induce keratinocyte differentiation. During the air-exposure, nutrients from the medium will diffuse through the underlying dermal substrate towards the epidermal compartment and support keratinocyte proliferation and differentiation. Under these conditions, a HSE is formed that shows high similarity with the native tissue from which it was derived (Figure 1) (Bell et at., 1981; Boyce et al., 1988; Ponec et al., 1997;El Ghalbzouri et al.., 2002).

• Toxicological Research
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• v.7 no.2
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• pp.209-229
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• 1991

In the epidermis of skin, a fine balance exists between proliferating progenitor cells and terminally differentiating cells. We examined the effects of TGF-betas and retinoic acid (RA) on controlling this balance in normal human epidermal keratinocytes cultured under conditions where most morphological and biochemical features of epidermis in vivo are retained. Our results revealed marked and pleiotropic effects of both TGF-beta and RA on kerationcytes. In contrast to retinoids, TGF-betas acted on mitotically active basal cells to retard cell proliferation.

• Korean Journal of Food Science and Technology
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• v.40 no.6
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• pp.686-690
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• 2008

Recent research has shown that curcumin has beneficial effects in a variety of skin diseases, including scleroderma, psoriasis, and skin cancer. In this study, we assessed the effects of curcumin on epidermal permeability barrier function in vivo and in vitro. In order to evaluate the effects of curcumin on epidermal permeability barrier function in vivo, hairless rats were exposed to UVB irradiation, and curcumin was administered orally at a dosage of 150 mg/kg per day for 8 weeks. Transepidermal water loss (TEWL) and epidermal thickness were measured at the end of the experiment. The expression of filaggrin, a marker of keratinocyte differentiation, and serine palmitoyltransferase (SPT), a marker of the formation of the stratum corneum lipid barrier, in human HaCat keratinocytes were analyzed. The in vivo results showed that an 8 week administration of curcumin markedly prevented the UVB-induced increase in TEWL. The UV-induced increase in epidermal thickness was also reduced significantly by curcumin treatment. The in vitro results demonstrated the concentration-dependent effects of curcumin on the expression of both filaggrin and SPT in HaCat cells, reflecting the notion that curcumin can induce epidermal keratinocyte differentiation and can improve the recovery of skin barrier functions. These results show that curcumin is a promising candidate for the improvement of epidermal permeability barrier function.