Home About us Contact
|
Home About us Contact | ||
|
|
||
Melanocytes
Kinds of Melanocytes Terms modified by Melanocytes Selected AbstractsAutologous Cultured Melanocytes in Vitiligo TreatmentDERMATOLOGIC SURGERY, Issue 9 2007RAFAL CZAJKOWSKI MD BACKGROUND Surgical treatment of vitiligo is indicated when lesions are localized in poorly responding areas. OBJECTIVES The objectives were: (1) to establish the melanocyte culture obtained from the epidermis of vitiligo patients for future treatment; (2) to estimate the influence of selected factors on the formation of suction blisters and the results of culture; and (3) to compare the results of treatment of vitiliginous macules localized in the dorsum of the hands and lower limbs by transplantation of cultured autologous melanocytes plus psoralen and ultraviolet A (PUVA) therapy (CMP), suction blister transplantation plus PUVA therapy (SBP), cryotherapy plus PUVA-therapy (CP), and only PUVA therapy (OP). METHODS Forty patients were qualified for the study. The roofs of the suction blisters were used as a melanocyte source for culture establishment or were directly transplanted. RESULTS The CMP procedure was successfully performed on only 10 of 20 patients because of the difficulties in cell culture establishment. The SBP method was carried out on all 20 patients. A total lack of effectiveness was found in CP and OP methods. CONCLUSIONS The effectiveness of culture depends on time of suction blister forming, phototype, and previous PUVA therapy. This study demonstrated the advantage of the SBP over the CMP method. [source] From Melanocytes to Melanoma: The Progression to MalignancyDERMATOLOGIC SURGERY, Issue 6 2006WILLIAM P. COLEMAN III MD No abstract is available for this article. [source] Iris as a recipient tissue for pigment cells: Organized in vivo differentiation of melanocytes and pigmented epithelium derived from embryonic stem cells in vitroDEVELOPMENTAL DYNAMICS, Issue 9 2008Hitomi Aoki Abstract Regenerative transplantation of embryonic stem (ES) cell-derived melanocytes into adult tissues, especially skin that includes hair follicles or the hair follicle itself, generally not possible, whereas that of ES cell-derived pigmented epithelium was reported previously. We investigated the in vivo differentiation of these two pigment cell types derived from ES cells after their transfer into the iris. Melanocytes derived from ES cells efficiently integrated into the iris and expanded to fill the stromal layer of the iris, like those prepared from neonatal skin. Transplanted pigmented epithelium from either ES cells or the neonatal eye was also found to be integrated into the iris. Both types of these regenerated pigment cells showed the correct morphology. Regenerated pigment epithelium expressed its functional marker. Functional blocking of signals required for melanocyte development abolished the differentiation of transplanted melanocytes. These results indicate successful in vivo regenerative transfer of pigment cells induced from ES cells in vitro. Developmental Dynamics 237:2394,2404, 2008. © 2008 Wiley-Liss, Inc. [source] ,-MSH and cAMP signalling in normal human melanocytesEXPERIMENTAL DERMATOLOGY, Issue 9 2004R. Buscà Melanocytes are neural crest-derived skin cells specialized in the synthesis of melanin pigments responsible, in human, for skin and hair colour. The pro-opiomelanocortin peptide, ,-MSH is a strong melanogenic agent secreted by keratinocytes following UV radiation. ,-MSH through the binding to the MC1R and activation of the cyclic AMP pathway plays a pivotal role in melanocyte differentiation and in the regulation of skin pigmentation. During the last few years, we have elucidated the molecular events linking the cAMP pathway to melanogenesis upregulation. This cascade involves the activation of protein kinase A and CREB transcription factor, leading to the upregulation of the expression of microphthalmia-associated transcription factor (MITF). MITF binds and activates the melanogenic gene promoters thereby increasing their expression, which results in an increased melanin synthesis. Beyond this simplified scheme, other intracellular signalling pathways are regulated by cAMP and participate to the regulation of melanocyte differentiation. Indeed, cAMP inhibits the phosphatidyl inositol 3-kinase pathway, leading to the inhibition of AKT and to the activation of GSK3,. This kinase phosphorylates MITF and allows its binding to the target sequence. Such pathways are involved in the upregulation of melanogenesis. ,-MSH and cAMP signalling also regulate melanocyte dendricity, and melanosome transport through the inhibition of the Rho GTPase cascade that function downstream the PI3 kinase. It should be also mentioned that cAMP activates the ERK pathway through a melanocyte-specific pathway involving Ras and B-Raf. The activation of ERK and RSK1 leads to the phosphorylation of MITF and target MITF to the proteasome degradation pathway. Interestingly, several proteins involved in melanocyte differentiation by ,-MSH (MC1R, PI3K, B-Raf and MITF) have also been implicated in the development of melanoma, suggesting that the cAMP pathway could influence melanocyte transformation. [source] Modulations of nerve growth factor and Bcl-2 in ultraviolet-irradiated human epidermisJOURNAL OF CUTANEOUS PATHOLOGY, Issue 6 2003Catherine M. Stefanato Background:, Ultraviolet (UV) irradiation to the skin causes apoptosis of keratinocytes. Melanocytes are more resistant to UV-induced apoptosis, due, in part, to high levels of antiapoptotic proteins such as Bcl-2. In vitro studies have shown that nerve growth factor (NGF), a neurotrophic polypeptide, is produced by keratinocytes and exerts a protective role for melanocytes by upregulating Bcl-2. The purpose of this study was to determine NGF and Bcl-2 modulations in UV-irradiated human skin. Methods:, Nine volunteers were irradiated with two minimal erythema doses using solar-simulated UV irradiation. Seventy-two hours post irradiation, skin biopsies were obtained from irradiated and sun-protected skin. The skin specimens were stained with anti-tyrosinase-related protein-1 monoclonal antibody IgG2a (Mel-5), anti-Bcl-2 (monoclonal antibody IgG-kappa), and with anti-NGF (polyclonal antibody IgG). Results:, NGF staining was identified within the cytoplasm of epidermal melanocytes, similar to the staining observed for TRP-1 and Bcl-2. While no significant difference in the number of TRP-1- and Bcl-2-positive melanocytes was observed between irradiated and non-irradiated skin within 72 h, the number of NGF-positive melanocytes decreased significantly, 72 h after UV irradiation (p < 0.024). NGF was also identified within keratinocytes, and while non-irradiated skin exhibited cytoplasmic NGF staining throughout the epidermis, NGF staining was reduced in the lower epidermal layers after UV irradiation. Conclusions:, This is the first in vivo study showing NGF to be present in melanocytes, as well as showing modulations of NGF and Bcl-2 in melanocytes, following solar-simulated UV irradiation. [source] The hair follicle melanocytes in vitiligo in relation to disease durationJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 8 2009T S Anbar Abstract Background and aims, Vitiligo is an acquired pigmentary disorder of skin and hair. Active melanocytes in hair follicles can be detected by DOPA and immunohistochemical staining, while amelanotic melanocytes can only be detected by the latter. None of the studies on hair melanocytes in vitiligo discussed the effect of disease duration on these melanocytes. Here, we study the presence of melanotic and amelanotic melanocytes in vitiligo hair follicles and statistically correlating their presence with the disease duration. Methods, This study was conducted on 30 patients with vitiligo and 10 normal volunteers. Three biopsies were taken from each patient: two from black and white hairs from vitiliginous areas and the third from apparently normal skin of the same patients. Sections were stained by DOPA reaction and NKI/beteb then examined for the presence of melanocytes. The presence of melanocytes and the disease duration were correlated statistically using the t -test. Results, Active melanocytes were detected in black hairs of 6.7% of vitiligo patients and in 100% of apparently normal skin of the same patients and controls. On examining black hairs of the 28 vitiligo patients with negative DOPA reaction, 19 of them (67.9%) showed positive NKI/beteb stain. Disease duration was inversely correlated with the melanocytes' presence within hair follicles. Melanocytes were absent from 100% of white hairs. Conclusions, The melanotic melanocytes were the first target of the disease process followed by the amelanotic melanocytes. Since the disappearance of the latter was inversely correlated with the disease duration, early treatment in vitiligo is advised. Conflicts of interest None declared. [source] Molecular Responses to Stress Induced in Normal Human Caucasian Melanocytes in Culture by Exposure to Simulated Solar UV,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Laurent Marrot ABSTRACT Melanocytes play a central role in the response of skin to sunlight exposure. They are directly involved in UV-induced pigmentation as a defense mechanism. However, their alteration can lead to melanoma, a process where the role of sun overexposure is highly probable. The transformation process whereby UV damage may result in melanoma initiation is poorly understood, especially in terms of UV-induced genotoxicity in pigmented cells, where melanin can act either as a sunscreen or as a photosensitizer. The aim of this study was to analyze the behavior of melanocytes from fair skin under irradiation mimicking environmental sunlight in terms of spectral power distribution. To do this, normal human Caucasian melanocytes in culture were exposed to simulated solar UV (SSUV, 300,400 nm). Even at relatively high doses (until 20 min exposure, corresponding to 12 kJ/m2 UV-B and 110 kJ/m2 UV-A), cell death was limited, as shown by cell viability and low occurrence of apoptosis (caspase-3 activation). Moreover, p53 accumulation was three times lower in melanocytes than in unpigmented cells such as fibroblasts after SSUV exposure. However, an important fraction of melanocyte population was arrested in G2-M phase, and this correlated well with a high induction level of the gene GADD45, 4 h after exposure. Among the genes involved in DNA repair, gene XPC was the most inducible because its expression increased more than two-fold 15 h after a 20 min exposure, whereas expression of P48 was only slightly increased. In addition, an early induction of Heme Oxygenase 1 (HO1) gene, a typical response to oxidative stress, was also observed for the first time in melanocytes. Interestingly, this induction remained significant when melanocytes were exposed to UV-A radiation only (320,400 nm), and stimulation of melanogenesis before irradiation further increased HO1 induction. These results were obtained with normal human cells after exposure to SSUV radiation, which mimicked natural sunlight. They provide new data related to gene expression and suggest that melanin in light skin could contribute to sunlight-induced genotoxicity and maybe to melanocyte transformation. [source] Melanin Offers Protection Against Induction of Cyclobutane Pyrimidine Dimers and 6,4 Photoproducts by UVB in Cultured Human Melanocytes,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2001Nico P. M. Smit ABSTRACT The goal of this investigation was to correlate the melanin content in human pigmentary cells with the generation of UVB-induced photoproducts and to examine the relationship between the melanin content and the removal of the photoproducts. Cultured melanocytes from light-skinned individuals synthesized less melanin and produced more cyclobutane pyrimidine dimers and 6,4 photoproducts upon UVB exposure than did melanocytes from black skin. Tyrosine-stimulated melanogenesis provided protection against DNA damage in both cell types. In another set of pigmented cell lines a ratio between eumelanin and pheomelanin was determined. The assessment of association between DNA damage induction and the quantity and quality of melanin revealed that eumelanin concentration correlated better with DNA protection than pheomelanin. Skin type,I and skin type,VI melanocytes, congenital nevus (CN)-derived cells and skin type,II melanocytes from a multiple-melanoma patient were grown in media with low or high l -tyrosine concentration. The cells were irradiated with 200 J/m2 UVB, and the levels of the photoproducts were determined immediately and after 6 and 24 h. Once again the induction of the photoproducts was mitigated by increased melanogenesis, and it was inversely correlated with the skin type. No significant differences were found for the removal of photoproducts in the cultures of skin types I and VI and CN cells. No indications of a delay in the removal of photoproducts in the melanocytes from the multiple-melanoma patient were found either. [source] The PTEN,AKT3 signaling cascade as a therapeutic target in melanomaPIGMENT CELL & MELANOMA RESEARCH, Issue 4 2009SubbaRao V. Madhunapantula Summary Melanocytes undergo extensive genetic changes during transformation into aggressive melanomas. These changes deregulate genes whose aberrant activity promotes the development of this disease. The phosphoinositide-3-kinase (PI3K) and mitogen-activated protein (MAP) kinase pathways are two key signaling cascades that have been found to play prominent roles in melanoma development. These pathways relay extra-cellular signals via an ordered series of consecutive phosphorylation events from cell surface throughout the cytoplasm and nucleus regulating diverse cellular processes including proliferation, survival, invasion and angiogenesis. It is generally accepted that therapeutic agents would need to target these two pathways to be an effective therapy for the long-term treatment of advanced-stage melanoma patients. This review provides an overview of the PI3 kinase pathway focusing specifically on two members of the pathway, called PTEN and Akt3, which play important roles in melanoma development. Mechanisms leading to deregulation of these two proteins and therapeutic implications of targeting this signaling cascade to treat melanoma are detailed in this review. [source] The location of heart melanocytes is specified and the level of pigmentation in the heart may correlate with coat colorPIGMENT CELL & MELANOMA RESEARCH, Issue 4 2008Ichiro Yajima Summary Melanocytes are mainly found in the skin and more rarely in other parts of the body, including the heart. We analyzed the localization of heart melanocytes and their levels of pigmentation in a series of mutant mice presenting different numbers of melanocytes and pigmentation in the skin. We found that melanocytes were localized in the valves (mitral, tricuspid, and aortic) and septa (ventricular and atrial). Moreover, the numbers of melanocytes in the heart appears to reflect that of the skin. Mice having a high or low level of pigmented cells and/or melanin in valves and septa have similar lifespan. In this respect, melanocytes found in the valves and septa of the heart are probably not essential in a healthy and non-stressful environment. [source] Uveal Melanocytes Produce Matrix Metalloproteinases-2 and -9 In VitroPIGMENT CELL & MELANOMA RESEARCH, Issue 6 2004Shu-Chen Chu The purpose of the present study was to investigate the expression of matrix metalloproteinase (MMP)-2 and MMP-9 by cultured human uveal melanocytes, and to test the effects of 12- O -tetradecanoyl-phorbol-13-acetate on the expression of these MMPs. Gelatin zymography of conditioned culture medium from four cultures of human uveal melanocytes (two cultures of iridal melanocytes and two cultures of choroidal melanocytes) detected MMP-2 (72 kDa) and a relatively small amount of MMP-9 (92 kDa), both in the latent form. RT-PCR analysis revealed the MMP-2 mRNA and MMP-9 mRNA in cultured uveal melanocytes. Addition of 12- O -tetradecanoyl-phorbol-13-acetate (10 ng/ml) to the culture medium caused an increase of production of MMP-2 and MMP-9 by cultured uveal melanocytes, and also stimulated the transcription of MMP-2 and MMP-9 of these cells. [source] Morphology of Cultured Human Epidermal Melanocytes Observed by Atomic Force MicroscopyPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2004Ru-zhi Zhang The objective of this study was to image the surface structure of cultured human epidermal melanocytes using atomic force microscopy (AFM). Epidermis obtained from human foreskins was treated with 0.5% dispase. Cell suspensions of the epidermis were prepared and seeded in six-well plates, in which sheets of mica had been placed. Samples for AFM were fixed on mica and scanning AFM images were captured by contacting and tapping modes operated under normal atmospheric pressure and temperature. Human epidermal melanocytes exhibited rounded, oval, triangular or quadrangular perikarya from which eight to 10 thick dendrites arose. These dendrites first bifurcated near the soma and then divided profusely into daughter branches, which spread out in all directions. We observed string-like long thin projections, growth cones and shorter thicker projections, which arose from the dendritic shafts, in which groups of melanosomes were arrayed. In addition to such structures, the most striking feature was the presence of filopodia arising from the melanocyte dendrite tips and the melanocyte cell body, many of which contained melanosomes. The termini of dendrites formed unbranched terminal protrusions (approximately 1500,2000 nm wide) consisting of two to three melanosomes wrapped in an arc, with their filopodia extending outwards. The tips of these structures also appeared to be squeezed and finally pinched off by the melanocyte to form a pouch filled with numerous melanosomes. We conclude that secondary and tertiary branches and subordinate branches might take part in transferring melanosomes into keratinocytes in addition to the transfer through the tips of the dendritic shafts. The melanin granules were expelled by exocytosis. [source] Quercetin Enhances Melanogenesis By Increasing the Activity and Synthesis of Tyrosinase in Human Melanoma Cells and in Normal Human MelanocytesPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2004Hidetaka Nagata Quercetin (3,3,,4,,5,7-pentahydroxyflavone) is a diphenyl propanoid widely distributed in edible plants. In this study, we examined the effect of quercetin on melanogenesis in human HMVII melanoma cells and in normal human epidermal melanocytes (NHEM) in the absence of ultraviolet radiation. Upon the addition of quercetin to the culture medium, the melanin content in melanoma cells (HMVII) increased remarkably in time- and dose-dependent manners. In addition, quercetin induced melanogenesis in cultured NHEM. As compared with controls, melanin content was increased about sevenfold by treatment with 20 ,M (HMVII) or 1 ,M (NHEM) quercetin for 7 d. Tyrosinase activity was also increased, to 61.8-fold higher than the control. The expression of tyrosinase protein was slightly increased by the addition of quercetin. However, quercetin did not affect the expression of tyrosinase mRNA. Tyrosinase activation by quercetin was blocked by actinomycin-D or by cycloheximide demonstrating that its actions in stimulating melanogenesis may involve both transcriptional and translational events. Tyrosinase activity was increased dramatically whereas the level of melanogenic inhibitor was remarkably decreased following quercetin treatment. Taken together, these results demonstrate that in human melanoma cells and in NHEM, quercetin stimulates melanogenesis by increasing tyrosinase activity and decreasing other factors such as melanogenic inhibitors. [source] Effects of Melanogenesis-Inducing Nitric Oxide and Histamine on the Production of Eumelanin and Pheomelanin in Cultured Human MelanocytesPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2003Michael W. Lassalle Melanin pigments produced in human melanocytes are classified into two categories; black coloured eumelanin and reddish-yellow pheomelanin. Stimulation of melanocytes with ,-melanocyte-stimulating hormone (,-MSH), one of several melanogenic factors, has been reported to enhance eumelanogenesis to a greater degree than pheomelanogenesis, which contributes to hyperpigmentation in skin. Nitric oxide (NO) and histamine are also melanogenesis-stimulating factors that are released from cells surrounding melanocytes following ultraviolet (UV) irradiation. In this study, the effects of NO and histamine on the ratio of eumelanin and pheomelanin were examined in human melanocytes, and then compared with that of ,-MSH. The amounts of eumelanin and pheomelanin were quantified using high-performance liquid chromatography analysis after oxidation and hydrolysis of melanin. Melanogenesis was induced by the addition of ,-MSH, NO, or histamine to melanocytes. The amount of eumelanin production significantly increased with independent stimulation by these melanogenic factors, especially histamine, while that of pheomelanin significantly increased with ,-MSH and NO, but only slightly with histamine. As a result, the ratio of eumelanin and pheomelanin increased significantly with the addition of NO or histamine. These results suggest that NO and histamine, as in the case of ,-MSH, may contribute to UV-induced hyperpigmentation by enhancing eumelanogenesis. [source] Keratinocytes Control the Pheo/Eumelanin Ratio in Cultured Normal Human MelanocytesPIGMENT CELL & MELANOMA RESEARCH, Issue 6 2002Christine Duval The pheo/eumelanin ratio of cultured normal human melanocytes is distinct from the ratio observed for the same cells in vivo where they are in close contact with keratinocytes. To study the possible involvement of keratinocytes in the control of melanogenesis, we compared quantitatively and qualitatively the melanin production in melanocyte mono-cultures, in melanocyte,keratinocyte co-cultures and in pigmented reconstructed epidermis. Pheomelanin and eumelanin contents were assessed by high-performance liquid chromatography with electrochemical and fluorometric detection of their specific degradation products and revealed striking differences in the presence of keratinocytes. In the absence of keratinocytes (melanocyte mono-cultures), we observed a very limited eumelanin production and a very high pheomelanin synthesis. The pheo/eumelanin ratio in mono-cultures could be slightly influenced by changing the composition of the culture medium, however, the very strong imbalance in favor of pheomelanin remained unchanged. An induction of eumelanin synthesis accompanied by an important reduction of pheomelanin formation was only observed in the presence of keratinocytes. The pheo/eumelanin ratio in melanocyte mono-culture dropped from 1043 down to about 25 in the presence of keratinocytes (co-cultures). The same observations were made when the melanocytes were integrated into a reconstructed human epidermis. Interestingly, under co-culture conditions resulting in only a partial contact between melanocytes and keratinocytes, the reduction of the pheo/eumelanin ratio were less pronounced. From these results we conclude that keratinocytes play an important role in the melanin production, affecting the melanogenic pathways. [source] Cellular and Hormonal Regulation of Pigmentation in Human Ocular MelanocytesPIGMENT CELL & MELANOMA RESEARCH, Issue 4 2001Linda C. Smith-Thomas The purpose of this study was to examine some of the factors that may be relevant to regulating pigmentation in the human eye, specifically whether choroidal and iridial melanocytes are sensitive to regulation by epithelial and stromal cells and ,-melanocyte stimulating hormone (,-MSH). Human choroidal and iridial melanocytes were established in culture and co-cultured with epithelial cells and stromal cells derived both from skin and from eye in order to determine their influence on choroidal and iridial melanocyte dopa oxidase activity. In all cases, co-culture of melanocytes with either epithelial cells or fibroblasts led to an increase in dopa oxidase activity during 5 days of co-culture. The extent of the increase ranged from 60% (non-significant) to as much as 185% when both fibroblasts and keratinocytes were present. The optimal ratio of fibroblasts to melanocytes was 1:10 (for dermal fibroblasts) or 1:2 (for iridial fibroblasts) and 1:1 for all epithelial cells to melanocytes. Both choroidal (three out of three cultures) and iridial (two out of three cultures) melanocytes showed increases in dopa oxidase activity to ,-MSH when cultured in Green's media but the same cells cultured in MCDB153 were unresponsive to ,-MSH. These in vitro studies suggest that ocular melanocytes have the capacity to be influenced by adjacent epithelial and stromal cells with respect to pigmentation. [source] Inhibition of Melanosome Transfer from Melanocytes to Keratinocytes by Lectins and Neoglycoproteins in an In Vitro Model SystemPIGMENT CELL & MELANOMA RESEARCH, Issue 3 2001Ljiljana Minwalla We propose that some of the critical molecules involved in the transfer of melanosomes from melanocytes to keratinocytes include plasma membrane lectins and their glycoconjugates. To investigate this mechanism, co-cultures of human melanocytes and keratinocytes derived from neonatal foreskins were established. The process of melanosome transfer was assessed by two experimental procedures. The first involved labeling melanocyte cultures with the fluorochrome CFDA. Labeled melanocytes were subsequently co-cultured with keratinocytes, and the transfer of fluorochrome assessed visually by confocal microscopy and quantitatively by flow cytometry. The second investigative approach involved co-culturing melanocytes with keratinocytes, and processing the co-cultures after 3 days for electron microscopy to quantitate the numbers of melanosomes in keratinocytes. Results from these experimental approaches indicate significant transfer of dye or melanosomes from melanocytes to keratinocytes that increased with time of co-culturing. Using these model systems, we subsequently tested a battery of lectins and neoglycoproteins for their effect in melanosome transfer. Addition of these selected molecules to co-cultures inhibited transfer of fluorochrome by approximately 15,44% as assessed by flow cytometry, and of melanosomes by 67,93% as assessed by electron microscopy. Therefore, our results suggest the roles of selected lectins and glycoproteins in melanosome transfer to keratinocytes in the skin. [source] Differential expression of nitric oxide synthases in human scalp epidermal and hair follicle pigmentary units: implications for regulation of melanogenesisBRITISH JOURNAL OF DERMATOLOGY, Issue 2 2005H.M. Sowden Summary Background, Nitric oxide (NO) is a ubiquitous gaseous lipophilic molecule generated from the conversion of l -arginine to l -citrulline by the NO synthases (NOSs). Ultraviolet radiation (UVR)-induced NO production appears to stimulate epidermal melanogenesis. However, given their relative protection from UVR, it is unclear whether NO plays a similar role in hair bulb melanocytes. Objectives, We aimed to identify the expression profiles of the NOS isoforms endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) and of phosphorylated eNOS and nitrotyrosine within the epidermal and follicular melanin units of normal human haired scalp during the hair growth cycle. Methods, This study employed single and double immunohistochemical and immunofluorescence staining techniques using haired scalp from 10 healthy individuals (six women and four men). Results, Melanocytes in the basal layer of the epidermis expressed eNOS, nNOS and nitrotyrosine. By contrast, melanogenically active melanocytes of the anagen hair bulb were wholly negative for these markers. However, other follicular melanocytes not actively involved in pigment production, including undifferentiated melanocytes located in the outer root sheath and melanocytes surviving the apoptosis-driven hair follicle (HF) regression during catagen/telogen, expressed eNOS, nNOS and nitrotyrosine. While iNOS was only weakly expressed in the basal layer of the human epidermis, it was highly expressed in keratinocytes of the inner root sheath (IRS), where it colocalized with trichohyalin, a differentiation-associated protein of the IRS that requires enzyme-catalysed conversion of arginine to citrulline. Conclusions, The NOS isoforms and nitrotyrosine are differentially expressed in different cutaneous melanocyte subpopulations. Results of this study suggest a possible role for eNOS, nNOS, iNOS and nitrotyrosine in melanocyte biology, particularly with respect to melanogenesis and melanocyte survival during HF regression. Another example of possible NO involvement in HF biology is the postsynthetic modification of trichohyalin in differentiating keratinocytes of the IRS. These results suggest that NO may influence several aspects of HF biology. [source] Tyrosine phosphate in melanoma progressionBRITISH JOURNAL OF DERMATOLOGY, Issue 2 2003L. Mcardle Summary Background Cellular tyrosine phosphorylation is regulated by two large families of enzymes. Protein tyrosine kinases (PTK) mediate addition, and protein tyrosine phosphatases (PTP), removal of phosphate from protein substrates. PTKs are oncogenes and PTPs have been hypothesized to function as tumour suppressor genes. Objectives To determine changes in tyrosine phosphate and PTP activity that occur during melanoma progression. Methods Immunohistochemistry was used to study phosphotyrosine in melanocytic lesions. In addition, PTP activity of normal melanocytes and melanoma cell lines was measured using an enzyme-linked immunosorbent assay-based system. Results Melanocytes in normal skin and most (67%) benign naevi were not immunostained. Neither were early malignant lesions (80% of malignant melanoma in situ and radial growth phase melanomas) stained. However, most advanced melanomas (100% of vertical growth phase, and 90% of metastatic melanomas) were immunoreactive. When total PTP enzyme activity was assayed in normal melanocytes and malignant melanoma cell lines, there was a significant increase in activity associated with melanoma progression. Conclusions Taken together, the data suggest increased phosphotyrosine signalling occurs during melanoma progression at the stage when cells first become competent for metastasis. [source] Cell Shape Normalization, Dendrite Orientation, and Melanin Production of Normal and Genetically Altered (Haploinsufficient NF1)-Melanocytes by Microstructured Substrate InteractionsCHEMPHYSCHEM, Issue 1 2004Simon Jungbauer Abstract Little is known about how functional regulation failure in genetically altered cells is influenced by topographical confinement of cells, a situation often present in tissues in vivo. We used cultured melanocytes derived from human skin samples as a model system for such investigations. Normal melanocytes have a very well defined shape consisting of a cell body and two dendrites arranged 180° relative to each other. In contrast, neurofibromin 1-melanocytes (NF1-melanocytes) have up to a 50,% reduction of neurofibromin 1, which results in an altered morphology that can be easily measured. NF1-melanocytes deviate from the defined structure of normal melanocytes by forming more than two dendrites per cell. We show that morphology consequences of genetically altered melanocytes can be canceled if cells interact with substrates microstructured by stripes that apply mechanophysical signals in the form of physical topography. The strength of the mechanophysical signal was varied systematically by increasing the height of the microstructures. Melanocytes respond to surface topographical features that are larger than 50 nm and have lateral confinements smaller 4 ,m. The response of normal and NF1-melanocytes to different topographies was analyzed quantitatively by determining density distributions for the number of dendrites per cell, the angles between dendrites, and the orientation imprinted in the substrate. The synthesis of melanin, a pigment produced by melanocytes, differs in the case of genetically altered NF1- and normal melanocytes. In both cases, the interaction with microstripes enhanced melanin production significantly. This enhanced melanin production is speculated to be caused by the mechanical stabilization of the dendrites by substrate guidance. [source] Treatment of Vitiligo on Difficult-to-Treat Sites Using Autologous Noncultured Cellular GraftingDERMATOLOGIC SURGERY, Issue 1 2009SANJEEV V. MULEKAR MD BACKGROUND Because of the limitations of medical treatment, various surgical therapies have been developed and are being accepted to treat vitiligo. However, certain areas such as the fingers and toes, palms and soles, lips, eyelids, nipples and areolas, elbows and knees, and genitals are considered difficult-to-treat areas. OBJECTIVE To evaluate data pertaining to individual sites considered to be difficult to treat and highlight that noncultured melanocyte,keratinocyte transplantation (MKT) does not require any special precautions to treat these anatomical sites. METHODS AND MATERIALS Forty patients (13 male and 27 female) with bilateral vitiligo and nine (4 male and 5 female) with unilateral vitiligo were treated using noncultured MKT, for "difficult-to-treat" sites at the National Center for Vitiligo and Psoriasis, Riyadh, Saudi Arabia, and were analyzed for response according to region. Repigmentation was graded as excellent with 95% to 100% pigmentation, good with 65% to 94%, fair with 25% to 64%, and poor with 0% to 24% of the treated area. RESULTS For bilateral vitiligo, more than 50% of patients treated for difficult sites showed more than 65% repigmentation of the treated areas. For unilateral vitiligo, all of the patients except for two treated for the eyelids showed more than 65% repigmentation of the treated area. CONCLUSIONS The concept of a "difficult-to-treat site" is a relative term and depends upon the technique used. The noncultured MKT does not require any special precautions to treat these anatomical sites. This review may help physicians to change the concept of "difficult-to-treat site." [source] Exposure to the polychlorinated biphenyl mixture Aroclor® 1254 alters melanocyte and tail muscle morphology in developing Xenopus laevis tadpolesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2003Marla A. Fisher Abstract Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that have damaging effects on both ecosystem and human health. Numerous studies have shown that exposure to PCBs can alter growth and development of aquatic organisms, including frogs. In this report, developing Xenopus laevis tadpoles were exposed to the PCB mixture Aroclor® 1254. Tadpoles were exposed from 5 through 9 d postfertilization to either 0, 1, 10, 50, or 100 ppm Aroclor 1254. Exposure to an acute, high concentration of Aroclor 1254 (10, 50, and 100 ppm) caused statistically significant reductions in survival and body size. In addition, tadpoles exposed to these higher concentrations showed histological abnormalities, including aberrant tail tip, myotomal, and melanocyte morphologies. Described adverse health effects associated with PCB exposure of developing frogs will serve as useful health endpoints in ongoing and future molecular-based studies that correlate health effects with changes in gene expression. [source] Effective inhibition of melanosome transfer to keratinocytes by lectins and niacinamide is reversibleEXPERIMENTAL DERMATOLOGY, Issue 7 2005Amanda Greatens Abstract:, Skin pigmentation results in part from the transfer of melanized melanosomes synthesized by melanocytes to neighboring keratinocytes. Plasma membrane lectins and their glycoconjugates expressed by these epidermal cells are critical molecules involved in this transfer process. In addition, the derivative of vitamin B3, niacinamide, can inhibit melanosome transfer and induce skin lightening. We investigated the effects of these molecules on the viability of melanocytes and keratinocytes and on the reversibility of melanosome-transfer inhibition induced by these agents using an in vitro melanocyte,keratinocyte coculture model system. While lectins and neoglycoproteins could induce apoptosis in a dose-dependent manner to melanocytes or keratinocytes in monoculture, similar dosages of the lectins, as opposed to neoglycoproteins, did not induce apoptosis to either cell type when treated in coculture. The dosages of lectins and niacinamide not affecting cell viability produced an inhibitory effect on melanosome transfer, when used either alone or together in cocultures of melanocytes,keratinocytes. Cocultures treated with lectins or niacinamide resumed normal melanosome transfer in 3 days after removal of the inhibitor, while cocultures treated with a combination of lectins and niacinamide demonstrated a lag in this recovery. Subsequently, we assessed the effect of niacinamide on facial hyperpigmented spots using a vehicle-controlled, split-faced design human clinical trial. Topical application of niacinamide resulted in a dose-dependent and reversible reduction in hyperpigmented lesions. These results suggest that lectins and niacinamide at concentrations that do not affect cell viability are reversible inhibitors of melanosome transfer. [source] Skin-lightening products revisitedINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2003L. Petit Synopsis Skin colour typology depends on the amount and location of its chromophores. Among them, eumelanins derived from 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI), and phaeomelanins are of utmost importance. These biomolecules result from the multi-step enzymatic and non-enzymatic conversion of tyrosine into melanins. Pigmentation disorders are multiple and depend on alterations in the density in active melanocytes, and on specific abnormalities of any of the complex melanogenesis mechanisms. This review presents some of the main skin-lightening agents with respect to their mechanisms of action and side-effects. Some of the novel compounds may lead to new perspectives in the fields of dermatology and cosmetology. The methods commonly used to assess efficacy of skin-lightening products rely on in vitro models including cell-free enzymatic assays, melanocyte cultures and reconstructed epidermis bioassays. Animal models have little relevance. By contrast, human testing with the support of instrumental evaluations is the most informative. Résumé La couleur de la peau et la typologie dépendant de la quantité et de la localization de ses chromophores. Parmi ceux-ci, les eumélanines dérivées des 5.6-dihydroxyindole-2-carboxylic acide (DHICA) et 5.6-dihydroxyindole (DHI) et les phaeomélanines sont de la plus grande importance. Ces biomolécules résultent de la conversion enzymatique et non enzymatiques en plusieurs étapes de la tyrosine en mélanines. Les troubles de la pigmentation sont multiples et dépendent d'altérations dans la densité de mélanocytes actifs et d'anomalies spécifiques touchant l'un ou l'autre étape du processus complexe de la mélanogenèse. Cette revue présente quelques agents dépigmentants en considérant leurs mécnaismes d'action et leurs effets secondaires. Certains des nouveaux composés ouvrent de nouvelles perspectives dans les domaines de la dermatologie et de la cosmétologie. Les méthodes visant àévaluer l'efficacité de produits dépigmentants font appel à des modèles in vitro incluant des bioessais enzymatiques, des cultures de mélnaocytes et l'épiderme reconstruit. Les modèles animaux sont peu pertinants. En revanche, els tests sur volontaires humains s'appuyant sur des évaluations instrumentales sont les plus informatives. [source] Fifteen-year quest for microphthalmia-associated transcription factor target genesPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2010Yann Cheli Summary Microphthalmia-associated transcription factor (MITF) was initially shown to play a key role in melanocyte differentiation through the direct transcriptional control of TYROSINASE, TYRP1 and DCT genes, encoding the three enzymes involved in melanin synthesis or melanogenesis. Sixteen years after the first description of MITF, more than 40 direct MITF target genes have been described. They play a key role in melanocyte, osteoclast and mast cell specific functions. Furthermore, several MITF target genes, e.g. BCL2, CDK2, CDKN1A, CDKN2A, MET and HIF1A, link MITF to general cellular processes such as growth or survival. In this review, we provide an overview of the MITF-regulated genes. We pay special attention to the MITF target genes in melanocytes and raise questions about target specificity. [source] The discovery of the human melanocytePIGMENT CELL & MELANOMA RESEARCH, Issue 3 2006Wiete Westerhof Summary Around 2200 bc the first written description of a human pigmentation disorder, most likely vitiligo, was recorded, and from that moment the history of research into human pigmentation can be traced. For the following 4000 yr, the origins of human skin colour remained an enigma that was to generate a multitude of misconceptions. Even after European physicians began to dissect and compare dark and light coloured skin to reveal its underlying anatomy, the origins of skin and hair pigmentation were a matter of frequently erroneous speculation. The true source of human pigmentation was only finally revealed with the discovery of the melanocyte in the 19th century. Once tyrosinase was identified to be the key enzyme in pigment formation, attention focused on elucidating the chemical structure of melanin, an enterprise that remains incomplete. The developmental origins of the melanocyte were described from 1940 to 1960, and the concept of the epidermal melanin unit was introduced together with a description of the ultrastructure of the melanosome and melanosome transfer. With these advances came the realization that different skin types exhibit distinct differences at the histological level that relate to varying amounts of eumelanin and pheomelanin produced by the melanocytes. The foundation established over the past 4000 yr is the basis for all current research into this fascinating cell type. [source] Morphology of Cultured Human Epidermal Melanocytes Observed by Atomic Force MicroscopyPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2004Ru-zhi Zhang The objective of this study was to image the surface structure of cultured human epidermal melanocytes using atomic force microscopy (AFM). Epidermis obtained from human foreskins was treated with 0.5% dispase. Cell suspensions of the epidermis were prepared and seeded in six-well plates, in which sheets of mica had been placed. Samples for AFM were fixed on mica and scanning AFM images were captured by contacting and tapping modes operated under normal atmospheric pressure and temperature. Human epidermal melanocytes exhibited rounded, oval, triangular or quadrangular perikarya from which eight to 10 thick dendrites arose. These dendrites first bifurcated near the soma and then divided profusely into daughter branches, which spread out in all directions. We observed string-like long thin projections, growth cones and shorter thicker projections, which arose from the dendritic shafts, in which groups of melanosomes were arrayed. In addition to such structures, the most striking feature was the presence of filopodia arising from the melanocyte dendrite tips and the melanocyte cell body, many of which contained melanosomes. The termini of dendrites formed unbranched terminal protrusions (approximately 1500,2000 nm wide) consisting of two to three melanosomes wrapped in an arc, with their filopodia extending outwards. The tips of these structures also appeared to be squeezed and finally pinched off by the melanocyte to form a pouch filled with numerous melanosomes. We conclude that secondary and tertiary branches and subordinate branches might take part in transferring melanosomes into keratinocytes in addition to the transfer through the tips of the dendritic shafts. The melanin granules were expelled by exocytosis. [source] Keratinocytes Control the Pheo/Eumelanin Ratio in Cultured Normal Human MelanocytesPIGMENT CELL & MELANOMA RESEARCH, Issue 6 2002Christine Duval The pheo/eumelanin ratio of cultured normal human melanocytes is distinct from the ratio observed for the same cells in vivo where they are in close contact with keratinocytes. To study the possible involvement of keratinocytes in the control of melanogenesis, we compared quantitatively and qualitatively the melanin production in melanocyte mono-cultures, in melanocyte,keratinocyte co-cultures and in pigmented reconstructed epidermis. Pheomelanin and eumelanin contents were assessed by high-performance liquid chromatography with electrochemical and fluorometric detection of their specific degradation products and revealed striking differences in the presence of keratinocytes. In the absence of keratinocytes (melanocyte mono-cultures), we observed a very limited eumelanin production and a very high pheomelanin synthesis. The pheo/eumelanin ratio in mono-cultures could be slightly influenced by changing the composition of the culture medium, however, the very strong imbalance in favor of pheomelanin remained unchanged. An induction of eumelanin synthesis accompanied by an important reduction of pheomelanin formation was only observed in the presence of keratinocytes. The pheo/eumelanin ratio in melanocyte mono-culture dropped from 1043 down to about 25 in the presence of keratinocytes (co-cultures). The same observations were made when the melanocytes were integrated into a reconstructed human epidermis. Interestingly, under co-culture conditions resulting in only a partial contact between melanocytes and keratinocytes, the reduction of the pheo/eumelanin ratio were less pronounced. From these results we conclude that keratinocytes play an important role in the melanin production, affecting the melanogenic pathways. [source] Production of Melanocyte-Specific Antibodies to Human Melanosomal Proteins: Expression Patterns in Normal Human Skin and in Cutaneous Pigmented LesionsPIGMENT CELL & MELANOMA RESEARCH, Issue 4 2001Victoria Virador Multiple factors affect skin pigmentation, including those that regulate melanocyte and/or keratinocyte function. Such factors, particularly those that operate at the level of the melanosome, are relatively well characterized in mice, but the expression and function of structural and enzymatic proteins in melanocytes in human skin are not as well known. Some years ago, we generated peptide-specific antibodies to murine melanosomal proteins that proved to be instrumental in elucidating melanocyte development and differentiation in mice, but cross-reactivity of those antibodies with the corresponding human proteins often was weak or absent. In an effort to characterize the roles of melanosomal proteins in human skin pigmentation, and to understand the underlying mechanism(s) of abnormal skin pigmentation, we have now generated polyclonal antibodies against the human melanocyte-specific markers, tyrosinase, tyrosinase-related protein 1 (TYRP1), Dopachrome tautomerase (DCT) and Pmel17 (SILV, also known as GP100). We used these antibodies to determine the distribution and function of melanosomal proteins in normal human skin (adult and newborn) and in various cutaneous pigmented lesions, such as intradermal nevi, lentigo simplex, solar lentigines and malignant melanomas. We also examined cytokeratin expression in these same samples to assess keratinocyte distribution and function. Immunohistochemical staining reveals distinct patterns of melanocyte distribution and function in normal skin and in various types of cutaneous pigmented lesions. Those differences in the expression patterns of melanocyte markers provide important clues to the roles of melanocytes in normal and in disrupted skin pigmentation. [source] Plasticity of Cadherin,Catenin Expression in the Melanocyte LineagePIGMENT CELL & MELANOMA RESEARCH, Issue 4 2000ALICE JOUNEAU Cadherins are calcium-dependent cell adhesion receptors with strong morphoregulatory functions. To mediate functional adhesion, cadherins must interact with actin cytoskeleton. Catenins are cytoplasmic proteins that mediate the interactions between cadherins and the cytoskeleton. In addition to their role in cell,cell adhesion, catenins also participate in signaling pathways that regulate cell growth and differentiation. Cadherins and catenins appear to be involved in melanocyte development and transformation. Here, we investigated the function of cadherin,catenin complexes in the normal development and transformation of melanocytes by studying the patterns of expression of the cell,cell adhesion molecules, E-, N- and P-cadherin, and the expression of their cytoplasmic partners, ,-, ,- and ,-catenin, during murine development. Similar analyses were performed in vitro using murine melanoblast, melanocyte, and melanoma cell lines in the presence and absence of keratinocytes, the cells with which melanocytes interact in vivo. Overall, the results suggest that the expression of cadherins and catenins is very plastic and depends on their environment as well as the transformation status of the cells. This plasticity is important in fundamental cellular mechanisms associated with normal and pathological ontogenesis, as well as with tumorigenesis. [source] | ||||||||||||||||