A melanocyte-keratinocyte coculture model to assess regulators of pigmentation in vitro

The Impact of Antioxidants on Vitiligo and Melasma: A Scoping Review and Meta-Analysis

Reactive oxygen species (ROS) generated during melanogenesis make melanocytes particularly vulnerable to oxidative stress, influencing their survival and melanin synthesis. Oxidative stress, significantly present in vitiligo and recently also detected in melasma, triggers inflammatory cascades and melanogenesis, making antioxidants a promising therapeutic avenue. A systematic search was conducted on Embase and Pubmed to study the efficacy of antioxidants for treating vitiligo and/or melasma. Meta-analysis was performed to assess the difference in Melasma Severity Index (MASI) scores between baseline and follow-up. Various antioxidants like polypodium leucotomos, ginkgo biloba, catalase/superoxide dismutase, and vitamin E have potential in vitiligo. For melasma, vitamin C, silymarin, and niacinamide were among those showing promise in reducing pigmentation, with vitamin C displaying significant effects in meta-analysis. Different antioxidants improve both vitiligo and melasma, with an increased minimal erythema dose (MED) following UV exposure being significant for vitiligo and tyrosinase inhibition being crucial for melasma. However, the efficacy of individual antioxidants varies, and their exact mechanisms, especially in stimulating melanocyte proliferation and anti-inflammatory pathways, require further investigation to understand better and optimize their use.

Characterization and screening of anti-melanogenesis and anti-photoaging activity of different enzyme-assisted polysaccharide extracts from Portulaca oleracea L

BACKGROUND

The flavonoids and polysaccharides in Portulaca oleracea L. (PO) have significant antibacterial and antioxidant effects, which can inhibit common bacteria and remove free radicals in the body. However, there was little research on the use of PO to alleviate hyperpigmentation and photoaging damage.

PURPOSE

This study was to investigate the anti-photoaging and whitening activity mechanism of polysaccharide of PO (POP) in vitro and in vivo.

METHOD

In this study, 16 fractions obtained by four enzyme-assisted extraction from PO and their scavenging capabilities against 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radicals were evaluated. Among these fractions, a polysaccharide fraction (VPOP3) showed the strongest biological activity. VPOP3 was characterized by Fourier-transform infrared spectroscopy, molecular weight (MW), and monosaccharide composition analysis, and the protective effect of VPOP3 on photoaging and hyperpigmentation was researched.

RESULTS

VPOP3 is a low-MW acidic heteropolysaccharide with MW mainly distributed around 0.71KDa, arabinose as its main monosaccharide component. VPOP3 reliably reduced the reactive oxygen species levels in cells and zebrafish and the level of lipid peroxidation in zebrafish. In addition, VPOP3 inhibited UVB-induced apoptotic body formation and apoptosis by downregulating caspase-3 and Bax and upregulating Bcl-2 in mitochondrion-mediated signaling pathways. On the other hand, VPOP3 at high concentrations significantly downregulated the expression of microphthalmia-associated transcription factor, tyrosinase (TYR), and TYR-related protein-1 and TYR-related protein-2 in the melanogenic signaling pathway to achieve a whitening effect.

CONCLUSION

The above results showed that VPOP3 has superior activities of anti-photoaging and anti-melanogenesis and can be utilized as a safe resource in the manufacture of cosmetics.

The Combination of Niacinamide, Vitamin C, and PDRN Mitigates Melanogenesis by Modulating Nicotinamide Nucleotide Transhydrogenase

Nicotinamide nucleotide transhydrogenase (NNT) is involved in decreasing melanogenesis through tyrosinase degradation induced by cellular redox changes. Nicotinamide is a component of coenzymes, such as NAD+, NADH, NADP+, and NADPH, and its levels are modulated by NNT. Vitamin C and polydeoxyribonucleotide (PDRN) are also known to decrease skin pigmentation. We evaluated whether a mixture of nicotinamide, vitamin C, and PDRN (NVP-mix) decreased melanogenesis by modulating mitochondrial oxidative stress and NNT expression in UV-B-irradiated animals and in an in vitro model of melanocytes treated with conditioned media (CM) from UV-B-irradiated keratinocytes. The expression of NNT, GSH/GSSG, and NADPH/NADP+ in UV-B-irradiated animal skin was significantly decreased by UV-B radiation but increased by NVP-mix treatment. The expression of NNT, GSH/GSSG, and NADPH/NADP+ ratios decreased in melanocytes after CM treatment, although they increased after NVP-mix administration. In NNT-silenced melanocytes, the GSH/GSSG and NADPH/NADP+ ratios were further decreased by CM compared with normal melanocytes. NVP-mix decreased melanogenesis signals, such as MC1R, MITF, TYRP1, and TYRP2, and decreased melanosome transfer-related signals, such as RAB32 and RAB27A, in UV-B-irradiated animal skin. NVP-mix also decreased MC1R, MITF, TYRP1, TYRP2, RAB32, and RAB27A in melanocytes treated with CM from UV-irradiated keratinocytes. The expression of MC1R and MITF in melanocytes after CM treatment was unchanged by NNT silencing. However, the expression of TYRP1, TYRP2, RAB32, and RAB27A increased in NNT-silenced melanocytes after CM treatment. NVP-mix also decreased tyrosinase activity and melanin content in UV-B-irradiated animal skin and CM-treated melanocytes. In conclusion, NVP-mix decreased mitochondrial oxidative stress by increasing NNT expression and decreased melanogenesis by decreasing MC1R/MITF, tyrosinase, TYRP1, and TYRP2.

A Mixture of Topical Forms of Polydeoxyribonucleotide, Vitamin C, and Niacinamide Attenuated Skin Pigmentation and Increased Skin Elasticity by Modulating Nuclear Factor Erythroid 2-like 2

It is well-known that increased oxidative stress caused by ultraviolet B (UV-B) radiation induces melanogenesis and activates metalloproteinases (MMPs), which degrade collagen and elastin fibers, leading to decreased skin elasticity. Various antioxidant agents, such as vitamin C and niacinamide, have been evaluated for use as treatments for photoaging or skin pigmentation. In this study, we evaluated the ability of a topical liquid formula of polydeoxyribonucleotide (PDRN), vitamin C, and niacinamide (PVN) delivered via a microneedling therapy system (MTS) to attenuate photoaging and pigmentation by increasing nuclear factor erythroid 2-like 2 (NRF2)/heme oxygenase-1 (HO-1) and decreasing MMP expression in a UV-B-radiated animal model. The effects of the PVN were compared with those of individual PDRN and hydroquinone (HQ) compounds. The expression of NRF2/HO-1 significantly increased in response to HQ, PDRN, and PVN in UV-B-radiated animal skin. The activity of nicotinamide adenine dinucleotide phosphate hydrogen oxidase decreased in response to HQ, PDRN, and PVN, and the superoxide dismutase activity increased. The expression of tumor protein p53 and microphthalmia-associated transcription factor and tyrosinase activity decreased in response to HQ, PDRN, and PVN, and this decrease was accompanied by decreased melanin content in the skin. The expression of nuclear factor kappa-light-chain enhancer of activated B cells and MMP2/3/9 decreased in response to HQ, PDRN, and PVN in UV-B-radiated skin. However, the expression of collagen type I α1 chain and the amount of collagen fibers that were evaluated by Masson's trichrome staining increased in response to HQ, PDRN, and PVN. The contents of elastin fibers, fibrillin 1/2 and fibulin 5 increased in response to HQ, PDRN, and PVN. In conclusion, PVN delivered via MTS led to decreased melanogenesis and destruction of collagen and elastin fibers by MMPs, and, thus, PVN decreased skin pigmentation and increased skin elasticity.

Potential of Biofermentative Unsulfated Chondroitin and Hyaluronic Acid in Dermal Repair

Chondroitin obtained through biotechnological processes (BC) shares similarities with both chondroitin sulfate (CS), due to the dimeric repetitive unit, and hyaluronic acid (HA), as it is unsulfated. In the framework of this experimental research, formulations containing BC with an average molecular size of about 35 KDa and high molecular weight HA (HHA) were characterized with respect to their rheological behavior, stability to enzymatic hydrolysis and they were evaluated in different skin damage models. The rheological characterization of the HHA/BC formulation revealed a G’ of 92 ± 3 Pa and a G″ of 116 ± 5 Pa and supported an easy injectability even at a concentration of 40 mg/mL. HA/BC preserved the HHA fraction better than HHA alone. BTH was active on BC alone only at high concentration. Assays on scratched keratinocytes (HaCaT) monolayers showed that all the glycosaminoglycan formulations accelerated cell migration, with HA/BC fastening healing 2-fold compared to the control. In addition, in 2D HaCaT cultures, as well as in a 3D skin tissue model HHA/BC efficiently modulated mRNA and protein levels of different types of collagens and elastin remarking a functional tissue physiology. Finally, immortalized human fibroblasts were challenged with TNF-α to obtain an in vitro model of inflammation. Upon HHA/BC addition, secreted IL-6 level was lower and efficient ECM biosynthesis was re-established. Finally, co-cultures of HaCaT and melanocytes were established, showing the ability of HHA/BC to modulate melanin release, suggesting a possible effect of this specific formulation on the reduction of stretch marks. Overall, besides demonstrating the safety of BC, the present study highlights the potential beneficial effect of HHA/BC formulation in different damage dermal models.

Pro-pigmentary action of 5-fluorouracil through the stimulated secretion of CXCL12 by dermal fibroblasts

Background:

There is growing evidence that 5-fluorouracil (5-FU) combined with therapeutic trauma can effectively induce skin repigmentation in vitiligo patients who are unresponsive to conventional treatments. Previous studies have mainly focused on identifying the antimitotic activity of 5-FU for the treatment of skin cancer, but few studies have investigated its extra-genotoxic actions favoring melanocyte recruitment.

Methods:

We utilized the full thickness excisional skin wound model in Dct-LacZ transgenic mice to dynamically assess the migration of melanocytes in the margins of wounds treated with or without 5-FU. The in-situ expression of CXCL12 was examined in the wound beds using immunofluorescence staining. Quantitative real-time polymerase chain reaction and Western blotting analyses were performed to detect the expression levels of CXCL12 mRNA and protein in primary mouse dermal fibroblasts treated with or without 5-FU. Transwell assays and fluorescein isothiocyanate (FITC)-phalloidin staining were used to observe cell migration and filamentous actin (F-actin) changes of melan-a murine melanocytes.

Results:

Whole mount and cryosection X-gal staining showed that the cell numbers of LacZ-positive melanocytes were much higher in the margins of dorsal and tail skin wounds treated with 5-FU compared with the controls. Meanwhile, CXCL12 immunostaining was significantly increased in the dermal compartment of wounds treated with 5-FU (control vs. 5-FU, 22.47 ± 8.85 vs. 44.69 ± 5.97, P < 0.05). Moreover, 5-FU significantly upregulated the expression levels of CXCL12 mRNA (control vs. 5-FU, 1.00 ± 0.08 vs. 1.54 ± 0.06, P < 0.05) and protein (control vs. 5-FU, 1.00 ± 0.06 vs. 2.93 ± 0.10, P < 0.05) in cultured fibroblasts. Inhibition of the CXCL12/CXCR4 axis suppressed melanocyte migration in vitro using a CXCL12 small interfering RNA (siRNA) or a CXCR4 antagonist (AMD3100).

Conclusion:

5-FU possesses a pro-pigmentary activity through activation of the CXCL12/CXCR4 axis to drive the chemotactic migration of melanocytes.

K Locus Effects in Gray Wolves: Experimental Assessment of TLR3 Signaling and the Gene Expression Response to Canine Distemper Virus

In North American gray wolves, black coat color is dominantly inherited via a 3 base pair coding deletion in the canine beta defensin 3 (CBD103) gene. This 3 base pair deletion, called the KB allele, was introduced through hybridization with dogs and subsequently underwent a selective sweep that increased its frequency in wild wolves. Despite apparent positive selection, KBB wolves have lower fitness than wolves with the KyB genotype, even though the 2 genotypes show no observable differences in black coat color. Thus, the KB allele is thought to have pleiotropic effects on as-yet unknown phenotypes. Given the role of skin-expressed CBD103 in innate immunity, we hypothesized that the KB allele influences the keratinocyte gene expression response to TLR3 pathway stimulation and/or infection by canine distemper virus (CDV). To test this hypothesis, we developed a panel of primary epidermal keratinocyte cell cultures from 24 wild North American gray wolves of both Kyy and KyB genotypes. In addition, we generated an immortalized Kyy line and used CRISPR/Cas9 editing to produce a KyB line on the same genetic background. We assessed the transcriptome-wide responses of wolf keratinocytes to the TLR3 agonist polyinosinic:polycytidylic acid (polyI:C), and to live CDV. K locus genotype did not predict the transcriptional response to either challenge, suggesting that variation in the gene expression response does not explain pleiotropic effects of the KB allele on fitness. This study supports the feasibility of using cell culture methods to investigate the phenotypic effects of naturally occurring genetic variation in wild mammals.

Mechanistic Basis and Clinical Evidence for the Applications of Nicotinamide (Niacinamide) to Control Skin Aging and Pigmentation

Vitamin B3 (nicotinic acid, niacin) deficiency causes the systemic disease pellagra, which leads to dermatitis, diarrhea, dementia, and possibly death depending on its severity and duration. Vitamin B3 is used in the synthesis of the NAD+ family of coenzymes, contributing to cellular energy metabolism and defense systems. Although nicotinamide (niacinamide) is primarily used as a nutritional supplement for vitamin B3, its pharmaceutical and cosmeceutical uses have been extensively explored. In this review, we discuss the biological activities and cosmeceutical properties of nicotinamide in consideration of its metabolic pathways. Supplementation of nicotinamide restores cellular NAD+ pool and mitochondrial energetics, attenuates oxidative stress and inflammatory response, enhances extracellular matrix and skin barrier, and inhibits the pigmentation process in the skin. Topical treatment of nicotinamide, alone or in combination with other active ingredients, reduces the progression of skin aging and hyperpigmentation in clinical trials. Topically applied nicotinamide is well tolerated by the skin. Currently, there is no convincing evidence that nicotinamide has specific molecular targets for controlling skin aging and pigmentation. This substance is presumed to contribute to maintaining skin homeostasis by regulating the redox status of cells along with various metabolites produced from it. Thus, it is suggested that nicotinamide will be useful as a cosmeceutical ingredient to attenuate skin aging and hyperpigmentation, especially in the elderly or patients with reduced NAD+ pool in the skin due to internal or external stressors.

3D skin models in domestic animals

The skin is a passive and active barrier which protects the body from the environment. Its health is essential for the accomplishment of this role. Since several decades, the skin has aroused a strong interest in various fields (for e.g. cell biology, medicine, toxicology, cosmetology, and pharmacology). In contrast to other organs, 3D models were mostly and directly elaborated in humans due to its architectural simplicity and easy accessibility. The development of these models benefited from the societal pressure to reduce animal experiments. In this review, we first describe human and mouse skin structure and the major differences with other mammals and birds. Next, we describe the different 3D human skin models and their main applications. Finally, we review the available models for domestic animals and discuss the current and potential applications.

Anti-Melanogenesis Effects of Lotus Seedpod In Vitro and In Vivo

Melanogenesis has many important physiological functions. However, abnormal melanin production causes various pigmentation disorders. Melanin synthesis is stimulated by α-melanocyte stimulating hormone (α-MSH) and ultraviolet (UV) irradiation. Lotus seedpod extract (LSE) has been reported as possessing antioxidative, anti-aging, and anticancer activities. The present study examined the effect of LSE on melanogenesis and the involved signaling pathways in vitro and in vivo. Results showed that non-cytotoxic doses of LSE and its main component epigallocatechin (EGC) reduced both tyrosinase activity and melanin production in the α-MSH-induced melanoma cells. Western blotting data revealed that LSE and EGC inhibited expressions of tyrosinase and tyrosinase-related protein 1 (TRP-1). Phosphorylation of p38 and protein kinase A (PKA) stimulated by α-MSH was efficiently blocked by LSE treatment. Furthermore, LSE suppressed the nuclear level of cAMP-response element binding protein (CREB) and disturbed the activation of melanocyte inducing transcription factor (MITF) in the α-MSH-stimulated B16F0 cells. The in vivo study revealed that LSE inhibited melanin production in the ear skin of C57BL/6 mice after exposure to UVB. These findings suggested that the anti-melanogenesis of LSE involved both PKA and p38 signaling pathways. LSE is a potent novo natural depigmenting agent for cosmetics or pharmaceutical applications.

A 2D and 3D melanogenesis model with human primary cells induced by tyrosine

Research on melanogenesis, its regulation in health and disease, and the discovery of new molecules with pigmenting and depigmenting activities use different models. Here we standardize a protocol based on previous ones using primary human melanocytes and keratinocytes in co-cultures, in which melanogenesis was induced under mild conditions by the addition of tyrosine plus ammonium chloride (NH₄Cl). The expression of MITF, TYR, TYRP1, and Melan-A as well as melanin content were measured. Furthermore, we extended this study to a reconstructed 3D model. Pigmentation was visually observable and melanosomes were identified by Fontana-Masson staining by the addition of tyrosine plus NH₄Cl during the stratification phase. The 2D and 3D protocols proposed here circumvent limitations of previous models, using human primary cells and mild conditions for melanogenesis. These protocols offer a viable, robust, simple, and animal-free investigational option for human skin pigmentation studies and screening tests for new compounds that modulate pigmentation.

Human Melanocyte-Derived Spheroids: A Precise Test System for Drug Screening and a Multicellular Unit for Tissue Engineering

Pigmentation is the result of melanin synthesis, which takes place in melanocytes, and its further distribution. A dysregulation in melanocytes' functionality can result in the loss of pigmentation, the appearance of pigment spots and melanoma development. Tissue engineering and the screening of new skin-lightening drugs require the development of simple and reproducible in vitro models with maintained functional activity. The aim of the study was to obtain and characterize spheroids from normal human melanocytes as a three-dimensional multicellular structure and as a test system for skin-lightening drug screening. Melanocytes are known to lose their ability to synthesize melanin in monolayer culture. When transferred under non-adhesive conditions in agarose multi-well plates, melanocytes aggregated and formed spheroids. As a result, the amount of melanin elevated almost two times within seven days. MelanoDerm™ (MatTek) skin equivalents were used as a comparison system. Cells in spheroids expressed transcription factors that regulate melanogenesis: MITF and Sox10, the marker of developed melanosomes-gp100, as well as tyrosinase (TYR)-the melanogenesis enzyme and melanocortin receptor 1 (MC1R)-the main receptor regulating melanin synthesis. Expression was maintained during 3D culturing. Thus, it can be stated that spheroids maintain melanocytes' functional activity compared to that in the multi-layered MelanoDerm™ skin equivalents. Culturing both spheroids and MelanoDerm™ for seven days in the presence of the skin-lightening agent fucoxanthin resulted in a more significant lowering of melanin levels in spheroids. Significant down-regulation of gp100, MITF, and Sox10 transcription factors, as well as 10-fold down-regulation of TYR expression, was observed in spheroids by day 7 in the presence of fucoxanthin, thus inhibiting the maturation of melanosomes and the synthesis of melanin. MelanoDerm™ samples were characterized by significant down-regulation of only MITF, Sox10 indicating that spheroids formed a more sensitive system allowed for quantitative assays. Collectively, these data illustrate that normal melanocytes can assemble themselves into spheroids-the viable structures that are able to accumulate melanin and maintain the initial functional activity of melanocytes. These spheroids can be used as a more affordable and easy-to-use test system than commercial skin equivalents for drug screening.

PD-L1 produced by HaCaT cells under polyinosinic-polycytidylic acid stimulation inhibits melanin production by B16F10 cells

Skin forms a physical barrier that protects the body against outside agents. The deepest layer of the skin, the stratum basale, contains two cell types: agent-sensing keratinocytes, and melanin-producing melanocytes. Keratinocytes can sense both harmless commensal organisms and harmful pathogens via Toll-like receptors (TLRs), and keratinocytes subsequently drive immune responses. Activation of TLR3 is required for barrier repair because it stimulates essential genes, including tight junction genes, and inflammatory cytokines. Within the basal layer of the skin, resident melanocytes use their dendritic processes to connect with approximately 30–40 neighboring keratinocytes. Most studies have focused on the transfer of melanin-synthesizing melanosomes from melanocytes to keratinocytes, but the potential regulation of melanogenesis by soluble factor(s) produced by keratinocytes remains to be explored. Studying such regulation in vivo is challenging because of the keratinocyte:melanocyte ratio in the epidermis and the location of the cells within the skin. Therefore, in this study, we investigated whether keratinocytes affected melanocyte melanogenesis in vitro under normal or inflammatory conditions. We found that polyinosinic-polycytidylic acid [poly(I:C)] stimulation induced PD-L1 secretion from HaCaT cells and that poly(I:C)-induced PD-L1 inhibited melanin production by B16F10 cells. These data provide key evidence that keratinocytes can alter melanocyte melanogenesis via the production of soluble factors under inflammatory conditions.

Natural skin-whitening compounds for the treatment of melanogenesis (Review)

Melanogenesis is the process for the production of melanin, which is the primary cause of human skin pigmentation. Skin-whitening agents are commercially available for those who wish to have a lighter skin complexions. To date, although numerous natural compounds have been proposed to alleviate hyperpigmentation, insufficient attention has been focused on potential natural skin-whitening agents and their mechanism of action from the perspective of compound classification. In the present article, the synthetic process of melanogenesis and associated core signaling pathways are summarized. An overview of the list of natural skin-lightening agents, along with their compound classifications, is also presented, where their efficacy based on their respective mechanisms of action on melanogenesis is discussed.

Ca2+ transients in melanocyte dendrites and dendritic spine-like structures evoked by cell-to-cell signaling

Melanocytes are the neural crest-derived pigment-producing cells of the skin that possess dendrites. Yet little is known about how melanocyte dendrites receive and process information from neighboring cells. Here, using a co-culture system to interrogate the interaction between melanocyte dendrites and keratinocytes, we show that signals from neighboring keratinocytes trigger local compartmentalized Ca2+ transients within the melanocyte dendrites. The localized dendritic Ca2+ transients could be triggered by two keratinocyte-secreted factors, endothelin and acetylcholine, which acted via specific melanocyte receptors. Furthermore, compartmentalized Ca2+ transients were also generated on discrete dendritic spine-like structures on the melanocytes. These spines were also present in intact human skin. Our findings provide insights into how melanocyte dendrites communicate with neighboring cells and offer a new model system for studying compartmentalized signaling in dendritic structures.

Inhibition of melanin synthesis and melanosome transfer by chitosan biomaterials

Decreasing skin pigmentation is desirable for various medical or cosmetic conditions. Although numerous pharmaceutical agents are currently available, their depigmentation effects are still not satisfactory. In this study, we investigated the effects of chitosan, a natural marine product, on melanin synthesis and melanosome transfer. Treating B16F10 melanoma cells caused the inhibitory effect of chitosan on melanogenesis to be more prominent under α-melanocyte-stimulating hormone (α-MSH) stimulation. Chitosan samples of different molecular weights inhibited melanogenesis to a comparable extent, whereas increasing the deacetylation of chitosan enhanced its depigmentation effects. Chitosan was found to effectively reduce basal or α-MSH-stimulated melanogenesis by suppressing the expression of melanogenic-related proteins (microphthalmia transcription factor, tyrosinase, and tyrosinase-related protein-1 and protein-2) as well as inhibiting tyrosinase activity. Moreover, the inhibitory effect of chitosan on melanogenesis in human melanocytes was confirmed. A transwell coculture system using permeable inserts was designed to allow the contact of human melanocytes and human HaCaT keratinocytes through the tiny holes on the membrane. When chitosan was added to this melanocyte-keratinocyte coculture system, we observed decreased melanosome release from melanocytes. Reduced melanosome uptake by keratinocytes was also observed, and was probably mediated by inhibiting protease-activated receptor 2 expression. Many skin-whitening agents can modulate the process of melanogenesis, but few have been shown to inhibit the melanosome transfer and uptake process. We demonstrated that chitosan exhibits a robust effect on depigmentation by inhibiting melanogenesis as well as melanosome transfer and uptake. Therefore, chitosan represents a potential therapeutic agent for hyperpigmentation disorders.

Intramelanocytic Acidification Plays a Role in the Antimelanogenic and Antioxidative Properties of Vitamin C and Its Derivatives

Although vitamin C (VC, L-ascorbic acid) has been widely used as a skin lightening agent for a long time, the mechanism by which it inhibits melanogenesis remains poorly understood. It is well-documented that the intramelanocytic pH is an important factor in regulating tyrosinase function and melanosome maturation. The activity of tyrosinase, the rate-limiting enzyme required for melanin synthesis, is generally minimal in an acidic environment. Given that VC is an acidic compound, we might speculate that the intracellular acidification of melanocytes induced by VC likely reduces melanin content through the suppression of tyrosinase activity. The results of this study reveal that treatment of melanocytes with VC or its derivatives, magnesium ascorbyl phosphate (MAP) and 3-O-ethyl-L-ascorbic acid (AAE), resulted in significant decreases in the tyrosinase activity and melanin content and in the levels of intracellular reactive oxygen species (ROS), indicating that VC and its derivatives possess antimelanogenic and antioxidative activities. Western blotting analysis indicated that VC, MAP, and AAE exert their antimelanogenic activity by inhibiting the tyrosinase activity rather than by downregulating the expression of melanogenic proteins such as tyrosinase, premelanosome protein 17 (Pmel17) and microphthalmia-associated transcription factor (MITF). Further, we found that the reduced tyrosinase activity of melanocytes treated with VC or its derivatives could be reactivated following intracellular neutralization induced by ammonium chloride (NH₄Cl) or concanamycin A (Con A). Finally, we examined the expression of sodium-dependent VC transporter-2 (SVCT-2) using western blotting and qPCR, which revealed that there was a significant increase in the expression of SVCT-2 in melanocytes following treatment with VC. VC-mediated intracellular acidification was neutralized by phloretin (a putative SVCT-2 inhibitor) in a dose-dependent manner. Taken together, these data show that VC and its derivatives suppress tyrosinase activity through cytoplasmic acidification that potentially results from enhanced VC transmembrane transport via the VC transporter SVCT-2.

Melanocyte Chitosan/Gelatin Composite Fabrication with Human Outer Root Sheath-Derived Cells to Produce Pigment

The hair follicle serves as a melanocyte reservoir for both hair and skin pigmentation. Melanocyte stem cells (MelSCs) and melanocyte progenitors reside in the bulge/sub-bulge region of the lower permanent portion of the hair follicle and play a vital role for repigmentation in vitiligo. It would be beneficial to isolate MelSCs in order to further study their function in pigmentary disorders; however, due to the lack of specific molecular surface markers, this has not yet been successfully accomplished in human hair follicles (HuHF). One potential method for MelSCs isolation is the “side population” technique, which is frequently used to isolate hematopoietic and tumor stem cells. In the present study, we decided to isolate HuHF MelSCs using “side population” to investigate their melanotic function. By analyzing mRNA expression of TYR, SOX10, and MITF, melanosome structure, and immunofluorescence with melanocyte-specific markers, we revealed that the SP-fraction contained MelSCs with an admixture of differentiated melanocytes. Furthermore, our in vivo studies indicated that differentiated SP-fraction cells, when fabricated into a cell-chitosan/gelatin composite, could transiently repopulate immunologically compromised mice skin to regain pigmentation. In summary, the SP technique is capable of isolating HuHF MelSCs that can potentially be used to repopulate skin for pigmentation.

UV-B-activated B16 melanoma cells or HaCaT keratinocytes accelerate signaling pathways associated with melanogenesis via ANGPTL 2 induction, an activity antagonized by Chrysanthemum extract

Sunburn causes inflammation, which increases melanin production in skin and causes hyperpigmentation. Angiopoietin-like protein (ANGPTL) 2 is an inflammatory mediator induced in sun-exposed skin areas. However, whether ANGPTL2 functions in melanin production remains unclear. To assess this possibility, we overexpressed Angptl2 in the melanoma line B16 and in the keratinocyte line HaCaT. Relative to controls, Angptl2-expressing B16 cells produced higher melanin levels via tyrosinase induction. Accordingly, Angptl2-expressing HaCaT cells secreted relatively high levels of both endothelin-1 (ET-1) and α-melanocyte-stimulating hormone (α-MSH). Moreover, treatment with an extract from Chrysanthemum indicum × Erigeron annuus (CE) suppressed ANGPTL2 expression and repressed tyrosinase induction in melanocytes and of α-MSH and ET-1 in keratinocytes. Our data suggest that ANGPTL2 expression in keratinocytes and melanin-producing cells accelerates pigment production and that treatment of skin with a CE extract could prevent melanin accumulation.

Quantitative analysis of melanin content in a three-dimensional melanoma cell culture

Reliable measurement of the amount of melanin produced by melanocytes is essential to study various skin disorders and to evaluate the efficacy of candidate reagents for such disorders or for whitening purposes. Conventional melanin quantification methods are based on absorption spectroscopy, which measures the melanin from lysed cells grown on two-dimensional (2D) surfaces. The 2D culture environment is intrinsically different from in vivo systems though, and therefore cells often lose their original phenotypes. Melanocytes in particular lose their ability to synthesize melanin, thereby requiring melanogenesis stimulators such as alpha-melanocyte stimulating hormone (α-MSH) to promote melanin synthesis. In this study, we compared melanin synthesis in B16 murine melanoma cells grown in 2D and three-dimensional culture environments. B16 cells instantly formed an aggregate in a hanging-drop culture, and synthesized melanin efficiently without treatment of α-MSH. We were able to measure the melanin secreted from a single melanocyte aggregate, indicating that our method enables non-invasive long-term monitoring of melanin synthesis and secretion in a high-throughput format. We successfully tested the developed platform by quantifying the depigmenting effects of arbutin and kojic acid.

A preliminary study of growth characteristics of melanocytes co-cultured with keratinocytes in vitro

To clarify the characteristic growth of melanocytes (MCs) and Keratinocytes (KCs) in vitro and discuss the mechanism of culturing autologous melanocytes in the treatment of vitiligo. Epidermis cells derived from normal skin tissues were isolated and cultured in vitro. Melanocytes in DOPA staining were observed. The expression level of markers in MCs was detected by qRT-PCR and the percentage of MCs and KCs were detected by flow cytometry. Cells derived from normal skin tissues mainly included KCs, MCs, and fibroblasts. There were significant differences between the percentage of KC, MC, fibroblasts (P < 0.05), and the expression of Microphthalmia-associated transcription factor (P < 0.05) and Tyrosinase-related protein-2 (P < 0.05) in the second, 10th, 20th, and 30th day. Significant differences were also found between the average numbers of MC stained by DOPA (P < 0.05) and the average percentage of MCs in the 10th, 20th, and 30th Day (P < 0.05). But there were no significant differences between the average percentage of KCs in the 10th, 20th, and 30th Day (P > 0.05) detected by flow cytometry. The number of MCs co-cultured with KCs in vitro reached the maximum in the 20th Day and this co-cultured model may contribute to the growth of MCs which could be used in the treatment of vitiligo.

Induction of retinal-dependent calcium influx in human melanocytes by UVA or UVB radiation contributes to the stimulation of melanosome transfer

OBJECTIVES

The transfer of melanosomes from melanocytes to neighbouring keratinocytes is critical to protect the skin from the deleterious effects of ultraviolet A (UVA) and ultraviolet B (UVB) irradiation; however, the initial factor(s) that stimulates melanosome transfer remains unclear. In this study, we investigated the induction of retinal-dependent calcium (Ca²⁺ ) influx in melanocytes (MCs) by UVA or UVB irradiation and the effect of transient receptor potential cation channel subfamily M member 1 (TRPM1) (melastatin1)-related Ca²⁺ influx on melanosome transfer.

MATERIALS AND METHODS

Primary human epidermal MCs were exposed to physiological doses of UVB or UVA light and loaded with a calcium indicator Fluo-4 dye. The change of intracellular calcium of MCs was monitored using a two-photon confocal fluorescence microscopy. MCs were co-cultured with human epidermal keratinocytes (KCs) in the absence or presence of voriconazole (a TRPM1 blocker) or calcium chelators. MCs were also transfected with TRPM1 siRNA for silencing the expression of TRPM1 gene. The melanosome transfer in the co-cultured cells was quantitatively analysed using flow cytometry and was further confirmed by immunofluorescent double-staining. The protein levels and distributions of TRPM1, OPN3 and OPN5 in MCs were measured by Western blotting or immunofluorescent staining.

RESULTS

The retinal-dependent Ca²⁺ influx of UVA-exposed melanocytes differed greatly from that of UVB-exposed melanocytes in the timing-phase. The protein expression of TRPM1 in mono- and co-cultured MCs was dose-dependently up-regulated by UVA and UVB. TRPM1 siRNA-mediated knockdown and the blockage of TRPM1 channel using a putative antagonist (voriconazole) significantly inhibited melanosome transfer in co-cultures following UVA or UVB exposure.

CONCLUSIONS

The distinct time-phases of Ca²⁺ influx in MCs induced by UVA or UVB contribute to the consecutive stimulation of melanosome transfer, thereby providing a potent photoprotection against harmful UV radiation.

Label-free and non-invasive discrimination of HaCaT and melanoma cells in a co-culture model by hyperspectral confocal reflectance microscopy

A novel hyperspectral confocal microscopy method to separate different cell populations in a co-culture model is presented here. The described methodological and instrumental approach allows discrimination of different cell types using a non-invasive, label free method with good accuracy with a single cell resolution. In particular, melanoma cells are discriminated from HaCaT cells by hyperspectral confocal imaging, principal component analysis and optical frequencies signing, as confirmed by fluorescence labelling cross check. The identification seems to be quite robust to be insensitive to the cellular shape within the studied samples, enabling to separate cells according to their cytotype down to a single cell sensitivity. Set of hyperspectral images of melanoma-keratinocytes co-culture model (left), score plot of principal component analysis and spectral analysis of principal components coefficients (center), label-free spectral identification of cell populations (right).

The design, synthesis and biological evaluation of pro-EGCG derivatives as novel anti-vitiligo agents

A series of prodrugs of EGCG derivatives were designed, synthesized, and the protective effect on melanocytes against H₂O₂-induced cell damage were extensively evaluated, demonstrating the potential application value of them in anti-vitiligo treatment.

Endothelial Cells Promote Pigmentation through Endothelin Receptor B Activation

Findings of increased vascularization in melasma lesions and hyperpigmentation in acquired bilateral telangiectatic macules suggested a link between pigmentation and vascularization. Using high-magnification digital epiluminescence dermatoscopy, laser confocal microscopy, and histological examination, we showed that benign vascular lesions of the skin have restricted but significant hyperpigmentation compared with the surrounding skin. We then studied the role of microvascular endothelial cells in regulating skin pigmentation using an in vitro co-culture model using endothelial cells and melanocytes. These experiments showed that endothelin 1 released by microvascular endothelial cells induces increased melanogenesis signaling, characterized by microphthalmia-associated transcription factor phosphorylation, and increased tyrosinase and dopachrome tautomerase levels. Immunostaining for endothelin 1 in vascular lesions confirmed the increased expression on the basal layer of the epidermis above small vessels compared with perilesional skin. Endothelin acts through the activation of endothelin receptor B and the mitogen-activated protein kinase, extracellular signal-regulated kinase (ERK)1/2, and p38, to induce melanogenesis. Finally, culturing of reconstructed skin with microvascular endothelial cells led to increased skin pigmentation that could be prevented by inhibiting EDNRB. Taken together these results demonstrated the role of underlying microvascularization in skin pigmentation, a finding that could open new fields of research for regulating physiological pigmentation and for treating pigmentation disorders such as melasma.

Angiotensin II stimulates melanogenesis via the protein kinase C pathway

Melanogenesis is a physiological process that results in the synthesis of melanin pigments, which serve a crucial function in hyperpigmentation. The aim of the present study was to determine the effects of angiotensin II (Ang II) on melanogenesis and to elucidate the molecular events of Ang II-induced melanogenesis. Experiments were performed on human melanocytes to elucidate the pigmenting effect of Ang II and the underlying mechanisms. The elements involved in melanogenesis, including melanin content, tyrosinase (TYR) activity, and microphthalmia-associated transcription factor (MITF) and TYR expression at the mRNA and protein levels were evaluated. Melanin content and TYR activity increased in response to Ang II treatment in a concentration-dependent manner. MITF and TYR mRNA and protein expression levels were increased significantly in response to Ang II in a concentration-dependent manner. The Ang II-induced increase in melanin synthesis was reduced significantly in response to co-treatment with Ro-32-0432, a protein kinase C (PKC) inhibitor, whereas co-treatment with H-89, a PKA inhibitor, did not attenuate the Ang II-induced increase in melanin levels. These results suggest that PKC is required for Ang II-induced pigmentation in human melanocytes and that the mechanism involves the PKC pathway and MITF upregulation.

rhCSF3 accelerates the proliferation of human melanocytes in culture through binding CSF3R and the expression of CSF3R transcripts

Melanogenic paracrine and autocrine cytokine networks have recently been discovered in vitro between melanocytes and other types of skin cells. Granulocyte colony-stimulating factor receptor (CSF3R) controls the survival, proliferation and differentiation of many kinds of cells, including neutrophils. To understand the function of CSF3R and recombinant human granulocyte colony-stimulating factor (rhCSF3) on melanocyte proliferation, this study compared the expression of CSF3R and the effects of rhCSF3 in primary human melanocytes, neutrophils and HEL 92.1.7 cells. The results show that CSF3R is localized in the cytoplasm and on cell membranes of melanocytes and neutrophils. The percentage of CSF3R(+) melanocytes was higher than CSF3R(+) HEL 92.1.7 cells, but was lower than CSF3R(+) neutrophils. Both CSF3R mRNA and CSF3R protein levels in melanocytes were higher than in HEL 92.1.7 cells, but were lower than in neutrophils. Treatment with rhCSF3 increased the proliferation of human melanocytes, but not their tyrosinase activity. Transcripts of CSF3R in human melanocytes, M14, A375 melanoma and A431 squamous cell carcinoma cells were also detected. Expression of the CSF3R V3 transcript was lower in melanocytes than in M14, A375 melanoma and A431 squamous cell carcinoma cells. In conclusion, rhCSF3 can promote melanocyte proliferation through CSF3R without affecting tyrosinase activity.

Superoxide dismutase 1 inhibits alpha-melanocyte stimulating hormone and ultraviolet B-induced melanogenesis in murine skin

Background

Over the last decade, the incidence of ultraviolet B (UVB)-related skin problems has increased. Oxidative stress caused by UVB induces the secretion of melanocyte growth and activating factors from keratinocytes, which results in the formation of cutaneous hyperpigmentation. Therefore, increasing the antioxidant abilities of skin cells is thought to be a beneficial strategy for the development of sunscreen agents. Superoxide dismutase 1 (SOD1) is an antioxidant enzyme that is known to exhibit antioxidant properties.

Objective

The purpose of this study was to investigate the effect of SOD1 on alpha-melanocyte stimulating hormone (α-MSH) and UVB-induced melanogenesis in B16F10 melanoma cells and HRM-2 melanin-possessing hairless mice.

Methods

The inhibitory effect of SOD1 on tyrosinase activity was evaluated in a cell-free system. Additional experiments were performed using B16F10 melanoma cells to demonstrate the effects of SOD1 in vitro, and HRM-2 melanin-possessing hairless mice were used to evaluate the antimelanogenic effects of SOD1 in vivo.

Results

We found that SOD1 inhibited melanin production in a dose-dependent manner without causing cytotoxicity in B16F10 melanoma cells. SOD1 did not inhibit tyrosinase activity under cell-free conditions. The results indicate that SOD1 may reduce pigmentation by an indirect, nonenzymatic mechanism. We also found that SOD1 decreased UVB-induced melanogenesis in HRM-2 melanin-possessing hairless mice, as visualized through hematoxylin and eosin staining and Fontana-Masson staining.

Conclusion

Our results indicate that SOD1 has an inhibitory effect on α-MSH and UVB-induced melanogenesis, indicating that SOD1 may be a promising sunscreen agent.

High-throughput, high-content screening for novel pigmentation regulators using a keratinocyte/melanocyte co-culture system

Skin pigmentation is a complex process including melanogenesis within melanocytes and melanin transfer to the keratinocytes. To develop a comprehensive screening method for novel pigmentation regulators, we used immortalized melanocytes and keratinocytes in co-culture to screen large numbers of compounds. High-throughput screening plates were subjected to digital automated microscopy to quantify the pigmentation via brightfield microscopy. Compounds with pigment suppression were secondarily tested for their effects on expression of microphthalmia transcription factor (MITF) and several pigment regulatory genes, and further validated in terms of non-toxicity to keratinocytes/melanocytes and dose-dependent activity. The results demonstrate a high-throughput, high-content screening approach, which is applicable to the analysis of large chemical libraries using a co-culture system. We identified candidate pigmentation inhibitors from 4000 screened compounds including zoxazolamine, 3-methoxycatechol and alpha-mangostin, which were also shown to modulate expression of MITF and several key pigmentation factors and are worthy of further evaluation for potential translation to clinical use.

Topical treatment of hyperpigmentation disorders

Hyperpigmentation has traditionally been a relatively difficult condition to treat, especially in darker racial ethnic groups. Multiple topical agents available act upon different steps of the pigmentation pathway. We review these topical agents, their mechanisms of action, and their effectiveness as monotherapy and in combination with other compounds. Ultimately, combination therapy is the most efficacious when considering overall depigmentation as well as treatment time required to achieve clinical improvement.

Tyrosinase modulation by five Rwandese herbal medicines traditionally used for skin treatment

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional herbal medicines provide an interesting, largely unexplored source for the development of potential new drugs and skin-care cosmetics. Some herbal extracts are known to be inhibitors of melanin formation, sometimes more potent than the classical inhibitors, hydroquinone/arbutin or kojic acid, and are not associated with melanocytes cytotoxicity or mutagenicity. Such plants are used in traditional medicine in many countries, particularly in Africa, for skin lightening.

AIM OF THE STUDY

To evaluate in vitro the ability of Rwandese medicinal plants, traditionally used for the treatment of skin (discoloration and attenuation of discolored spots), to modulate pigmentation and tyrosinase activity.

MATERIALS AND METHODS

Based on an ethnopharmacological survey, five herbs [Brillantaisia cicatricosa Lindau (Acanthaceae), Chenopodium ugandae (Aellen) Aellen (Chenopodiaceae), Dolichopentas longiflora Oliv. (Rubiaceae), Protea madiensis Oliv. (Proteaceae) and Sesamum angolense Welw. (Pedaliaceae)] were selected. Twenty-seven extracts, obtained by treating the herbs with increasing polarities solvents, were investigated for their effects on cell viability (MTT test) and on pigmentation: inhibition of the enzyme tyrosinase (colorimetry of reaction products, measurement of enzyme activity, TLC-autography; studies on crude cellular extracts obtained from normal melanocytes and on a mushroom tyrosinase) and measurement of melanogenesis by human melanoma cells.

RESULTS

None of the tested plant extracts were cytotoxic on tested human melanoma cell lines, except for Dolichopentas longiflora (IC50 of leaves n-hexane extract, 4μg/ml for MM028 and 4.5μg/ml for MM001; IC50 of roots ethyl acetate extract, 0.8μg/ml for MM028 and 3.9μg/ml for MM001). Almost all extracts inhibited melanogenesis in a melanoma whole cells overall pigmentation assay, a model reflecting the entire cycle of melanogenesis. All the Protea madiensis extracts quite strongly inhibited melanogenesis and, surprisingly, one of the Dolichopentas longiflora leaves extracts was found to increase melanogenesis. These results were confirmed by the modulation of pigmentation reactions by crude cellular extracts obtained from normal melanocytes; interestingly, one of the extracts (Dolichopentas longiflora ethyl acetate extract) is even more active (61% at 500μg/ml) than kojic acid (<3% at 142μg/ml and 68% at 1421μg/ml). In a mushroom tyrosinase inhibition assay, data obtained on some extracts fairly agree with pigmentation inhibition measured on melanocytes proteins as, for example, the methanol extract of Protea madiensis. While a few others extract display discording data, this probably reflects either differences between human and mushroom tyrosinase, interference with melanocytes enzymes at later steps than tyrosinase or the simultaneous presence of compounds with conflicting activities in a given extract.

CONCLUSIONS

Ethnopharmacological data represent an efficient approach to discover active herbs. Some of the selected medicinal plants clearly show potent tyrosinase inhibitions while one extract significantly increases cell pigmentation; one extract contains potent growth melanocytes inhibitors.

Identification of miR-145 as a key regulator of the pigmentary process

The current treatments for hyperpigmentation are often associated with a lack of efficacy and adverse side effects. We hypothesized that microRNA (miRNA)-based treatments may offer an attractive alternative by specifically targeting key genes in melanogenesis. The aim of this study was to identify miRNAs interfering with the pigmentary process and to assess their functional role. miRNA profiling was performed on mouse melanocytes after three consecutive treatments involving forskolin and solar-simulated UV (ssUV) irradiation. Sixteen miRNAs were identified as differentially expressed in treated melan-a cells versus untreated cells. Remarkably, a 15-fold downregulation of miR-145 was detected. Overexpression or downregulation of miR-145 in melan-a cells revealed reduced or increased expression of Sox9, Mitf, Tyr, Trp1, Myo5a, Rab27a, and Fscn1, respectively. Moreover, a luciferase reporter assay demonstrated direct targeting of Myo5a by miR-145 in mouse and human melanocytes. Immunofluorescence tagging of melanosomes in miR-145-transfected human melanocytes displayed perinuclear accumulation of melanosomes with additional hypopigmentation of harvested cell pellets. In conclusion, this study has established an miRNA signature associated with forskolin and ssUV treatment. The significant down- or upregulation of major pigmentation genes, after modulating miR-145 expression, suggests a key role for miR-145 in regulating melanogenesis.

Kojic acid-induced IL-6 production in human keratinocytes plays a role in its anti-melanogenic activity in skin

BACKGROUND

Kojic acid is a fungal metabolite widely used in medicinal and cosmetic formulations as a skin-lightening agent based on its de-pigmenting activity. Although in human clinical studies kojic acid has been shown to be effective in the treatment of hyper-pigmentation disorders such as melasma, the reasons for its apparent lack of anti-melanogenic activity in cultured mammalian melanocytes are unclear.

OBJECTIVES

This study was aimed to elucidate pharmacological mechanisms of the in vivo anti-melanogenic activity of kojic acid in human skin.

METHODS

A primary human melanocyte and keratinocyte co-culture system was used to evaluate whether kojic-acid-induced changes in keratinocytes were associated with anti-melanogenic activities in melanocytes. The cytokine secretion profiles in response to kojic acid were analyzed.

RESULTS

Kojic acid increased interleukin (IL)-6 and IL-8 production in melanocyte/keratinocyte co-cultures; however, IL-6 directly inhibited melanogenesis whereas IL-8 did not. In melanocyte monocultures, kojic acid did not increase IL-6 production whereas in keratinocyte monocultures it significantly up-regulated IL-6 gene and protein expression. Therefore, the up-regulation of IL-6 in melanocyte/keratinocyte co-cultures seems to be originated from kojic acid-induced changes in keratinocytes. Anti-IL-6 antibody treatment antagonized the anti-melanogenic effect of kojic acid on the co-cultures.

CONCLUSIONS

The pharmacological mechanism of kojic acid to explain clinically effective anti-melanogenic activity on hyper-pigmented skin is associated with the kojic acid-induced IL-6 production in keratinocytes. The cross-talk between melanocytes and keratinocytes should be determined in future studies on the pharmacological mechanisms of clinically effective dermatological drugs acting on the epidermis.

In vitro three-dimensional (3D) models in cancer research: an update

Tissues are three-dimensional (3D) entities as is the tumor that arises within them. Though disaggregated cancerous tissues have produced numerous cell lines for basic and applied research, it is generally agreed that these lines are poor models of in vivo phenomena. In this review we focus on in vitro 3D models used in cancer research, particularly their contribution to molecular studies of the early stages of metastasis, angiogenesis, the tumor microenvironment, and cancer stem cells. We present a summary of the various formats used in the field of tissue bioengineering as they apply to mechanistic modeling of cancer stages or processes. In addition we list studies that model specific types of malignancies, highlight drastic differences in results between 3D in vitro models and classical monolayer culturing techniques, and establish the need for standardization of 3D models for meaningful preclinical and therapeutic testing.

Maintenance of immune hyporesponsiveness to melanosomal proteins by DHICA-mediated antioxidation: Possible implications for autoimmune vitiligo

Melanocyte destruction in the skin of vitiligo patients has been considered to be a consequence of an autoimmune response against melanosomal proteins. However, little is known about the molecular mechanisms by which the immune system recognizes these sequestered intracellular self-proteins, which are confined in specialized organelles termed melanosomes, and is provoked into an autoimmune response to melanocytes. Here, we utilize a sucrose density-gradient ultracentrifugation protocol to enrich melanosomal components from dopachrome tautomerase (Dct)-mutant or wild-type melanocytes exposed to a pulse of hydrogen peroxide at a noncytotoxic concentration to evaluate their immunogenicity in mice challenged with the corresponding melanosomal proteins. The results demonstrate that enhanced humoral and cellular immune responses to a challenge with late-stage melanosomal proteins, especially with those derived from Dct-mutant melanocytes, are found in the immunized mice. To elucidate whether a reduced 5,6-dihydroxyindole-2-carboxylic acid (DHICA) content in melanin might cause a loss in antioxidative protection to the proteins, we incubated these melanosomal proteins in vitro with synthetic 5,6-dihydroindole (DHI)-melanin or DHI/DHICA (1:1)-melanin and then used them to immunize mice. T cell proliferation and IgG antibody responsiveness to the challenges were significantly induced by melanosomal proteins treated with DHI-melanin, but not by those treated with DHI/DHICA (1:1)-melanin. Moreover, we observed that melanosomal proteins derived from Dct-mutant melanocytes are subject to oxidative modifications that alter their antigenic configurations to attain an enhanced immunogenicity compared with those derived from wild-type melanocytes. From these results, we conclude that DHICA-mediated antioxidation plays a critical role in the maintenance of immune hyporesponsiveness to melanosomal proteins.

Using human hair follicle-derived keratinocytes and melanocytes for constructing pigmented tissue-engineered skin

BACKGROUND

Traditional tissue-engineered skin does not produce a satisfactory long-term result because it lacks natural skin pigmentation and leads to discolored cosmetically unpleasing skin that only functions to cover the body of patients. Additionally, the cell sources for tissue-engineered skin are generally derived from normal skin, which is often limited in patients with skin defects.

METHODS

In this study, hair follicle melanocytes and keratinocytes were isolated from human scalp. The melanocytes were co-cultured with keratinocytes until the second passage and then purified. Purified melanocytes and keratinocytes were seeded onto the chitosan-gelatin membrane for 1 week to construct pigmented tissue-engineered skin. The pigmented skin equivalent was used to resurface the skin defect in nude mice. Four weeks after grafting, skin biopsies were harvested to take hematoxylin and eosin staining and immunohistochemistry staining of Melan-A and HLA-ABC.

RESULTS

Large quantities of purified melanocytes can be obtained with co-culture method. The hematoxylin and eosin staining of repaired skin biopsy demonstrated that the tissue-engineered skin can repair skin defects successfully. Engineered skin contained pigmentation and stained positive for Melan-A and HLA-ABC, which confirmed the presence of melanocytes and its sources were of human origin.

CONCLUSION

This study demonstrated the possibility of constructing pigmented tissue-engineered skin with human hair follicle-derived keratinocytes and melanocytes, which brings a promising method to make up for the deficiency of traditional tissue-engineered skin and provides an alternative treatment for depigmentation diseases.

HSP70 inducers from Chinese herbs and their effect on melanin production

Skin hyperpigmentation disorders as a result of abnormal melanin production induced by ultraviolet (UV) irradiation are both a clinical and a cosmetic problem. This melanin production is mediated by tyrosinase whose expression is positively regulated by microphthalmia-associated transcription factor (MITF). We recently found that expression of heat shock protein 70 (HSP70) inhibits melanin production. In this study, we searched for HSP70 inducers from Chinese herbs and selected an ethanol extract of Eupatorium lindleyanum (E. lindleyanum). Not only melanin production but also the activity and expression of tyrosinase were significantly suppressed in cells treated with E. lindleyanum extract as well as in HSP70-overexpressing cells. The expression of MITF was clearly suppressed in cells treated with E. lindleyanum extract but not in HSP70-overexpressing cells. These results suggest that E. lindleyanum extract suppresses the expression of tyrosinase and melanin production through both HSP70-dependent and HSP70-independent mechanisms.

Oxidative stress level and tyrosinase activity in vitiligo patients

Background:

Vitiligo is an acquired pigmentary disorder of the skin. Genetic factors, oxidative stress, autoimmunity, and neurochemical agents might be contributing factors for the development of the disease.

Aims:

To evaluate the oxidative stress level and tyrosinase activity in vitiligo patients and to compare them with healthy volunteers.

Materials and Methods:

We used Comet assay to evaluate DNA strand breaks in peripheral blood cells of active vitiligo patients. We then extracted total protein from lesional and nonlesional skin of ten selected patients. Tyrosinase activity was found to play a crucial role in melanogenesis.

Results:

The basal level of systemic oxidative DNA strand breaks in leukocytes increased in vitiligo patients compared to healthy participants. We observed that tyrosinase activity in lesional skin was lower than in nonlesional skin.

Conclusion:

Our finding suggests that increased levels of oxidative stress might impact tyrosinase activity and eumelanin synthesis via anabolism pathway of melanin synthesis. In sum, we observed a negative correlation between levels of systemic oxidative stress and of tyrosinase activity.

[Methods and means for pigmentation and depigmentation. Sense or nonsense?]

Treatment of hyperpigmentation disorders can be a lengthy process. There are several topical treatment options and hydroquinone is the most frequently used. Both combination and monotherapy are employed. These treatment options apply primarily to epidermal hyperpigmentation disorders. Dermal hyperpigmentation disorders cannot yet be effectively managed with currently available therapeutic approaches. Cosmetic disfigurement caused by hypomelanosis, especially vitiligo, can constitute a serious impairment for the patient. So far there is no definitive remedy. Better cosmetic results are generally reported for combination therapies.