Melanocyte mitogens induce both melanocyte chemokinesis and chemotaxis

Vitiligo: Mechanisms of Pathogenesis and Treatment

Vitiligo is an autoimmune disease of the skin that targets pigment-producing melanocytes and results in patches of depigmentation that are visible as white spots. Recent research studies have yielded a strong mechanistic understanding of this disease. Autoreactive cytotoxic CD8+ T cells engage melanocytes and promote disease progression through the local production of IFN-γ, and IFN-γ-induced chemokines are then secreted from surrounding keratinocytes to further recruit T cells to the skin through a positive-feedback loop. Both topical and systemic treatments that block IFN-γ signaling can effectively reverse vitiligo in humans; however, disease relapse is common after stopping treatments. Autoreactive resident memory T cells are responsible for relapse, and new treatment strategies focus on eliminating these cells to promote long-lasting benefit. Here, we discuss basic, translational, and clinical research studies that provide insight into the pathogenesis of vitiligo, and how this insight has been utilized to create new targeted treatment strategies.

The enigma and challenges of vitiligo pathophysiology and treatment

Vitiligo is the most common acquired pigmentary disorder, which afflicts 0.5%-1% of the world population, and is characterized by depigmented skin patches resulting from melanocyte loss. Vitiligo has a complex etiology and varies in its manifestations, progression, and response to treatment. It presents as an autoimmune disease, evidenced by circulating melanocyte-specific antibodies, and association with other autoimmune diseases. However, autoimmunity may be secondary to the high oxidative stress in vitiligo skin and to intrinsic defects in melanocytes and their microenvironment, which contribute to aberrant stress response, neo-antigenicity, and susceptibility of melanocytes to immune attack and apoptosis. There is also a genetic predisposition to vitiligo, which sensitizes melanocytes to environmental agents, such as phenolic compounds. Currently, there are different treatment modalities for re-pigmenting vitiligo skin. However, when repigmentation is achieved, the major challenge is maintaining the pigmentation, which is lost in 40% of cases. In this review, we present an overview of the clinical aspects of vitiligo, its pathophysiology, the intrinsic defects in melanocytes and their microenvironment, and treatment strategies. Based on lessons from the biology of human melanocytes, we present our perspective of how repigmentation of vitiligo skin can be achieved and sustained.

Self-Generated Gradients Yield Exceptionally Robust Steering Cues

Chemotaxis is a widespread mechanism that allows migrating cells to steer to where they are needed. Attractant gradients may be imposed by external sources, or self-generated, when cells create their own steep local gradients by breaking down a prevalent, broadly distributed attractant. Here we show that chemotaxis works far more robustly toward self-generated gradients. Cells can only respond efficiently to a restricted range of attractant concentrations; if attractants are too dilute, their gradients are too shallow for cells to sense, but if they are too high, all receptors become saturated and cells cannot perceive spatial differences. Self-generated gradients are robust because cells maintain the attractant at optimal concentrations. A wave can recruit varying numbers of steered cells, and cells can take time to break down attractant before starting to migrate. Self-generated gradients can therefore operate over a greater range of attractant concentrations, larger distances, and longer times than imposed gradients. The robustness is further enhanced at low cell numbers if attractants also act as mitogens, and at high attractant concentrations if the enzymes that break down attractants are themselves induced by constant attractant levels.

Inhibitory effects of extracellular superoxide dismutase on ultraviolet B-induced melanogenesis in murine skin and melanocytes

AIMS

Several anti-melanogenic molecules have been developed or identified, but their uses are limited due to either adverse effects or instability during the treatment. We aimed to evaluate the effects of extracellular superoxide dismutase (SOD3), a powerful antioxidant, as a candidate anti-melanogenic molecule.

MAIN METHODS

UVB-induced reactive oxygen species (ROS) production and proliferation in melan-a cells was evaluated by 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate staining and bromodeoxyuridine incorporation assay, respectively. Quantitative real-time polymerase chain reaction and western blot were performed to detect the melanogenesis-related gene expression and downstream signaling. Anti-melanogenic effects of SOD3 were also evaluated using SOD3 transgenic mice under UVB exposure in-vivo condition.

KEY FINDINGS

SOD3 inhibited UVB-induced proliferation, ROS production and melanogenesis in melanocytes. Measurement of melanin content and tyrosinase activity assays showed that SOD3 significantly inhibited melanin synthesis. Moreover, these suppressive effects of SOD3 were dependent on the endothelin-1 (ET-1)/endothelin B receptor, protein kinase C, melanocortin 1 receptor/protein kinase A, Wnt7a/β-catenin, and mitogen-activated protein kinase pathways, with concomitant downregulation of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related proteins 1, dopachrome tautomerse. Interestingly, SOD3 was found to inhibit transforming growth factor-beta 1 (TGF-β1) to inactivate the ET-1 signaling pathway, and finally prevents the production of melanin.

SIGNIFICANCE

Our results provide novel insights into the role of SOD3 in melanocyte homeostasis and its uses as a potential biomedicine to treat hyperpigmentary conditions of the skin.

Clinicopathologic features and pathogenesis of melanocytic colonization in atypical meningioma

Only two prior cases of benign dendritic melanocytes colonizing a meningioma have been reported. We add a third case, describe clinicopathologic features shared by the three, and elucidate the risk factors for this very rare phenomenon. A 29 year-old Hispanic woman presented with headache and hydrocephalus. MRI showed a lobulated enhancing pineal region mass measuring 41 mm in greatest dimension. Subtotal resection of the mass demonstrated an atypical meningioma, WHO grade II, and the patient subsequently underwent radiotherapy. She presented 4 years later with diplopia, and MRI showed an enhancing extra-axial mass measuring 47 mm in greatest dimension and centered on the tentorial incisura. Subtotal resection showed a brain-invasive atypical meningioma with melanocytic colonization. The previous two cases in the literature were atypical meningiomas, one of which was also brain invasive. Atypical meningiomas may be at particular risk for melanocytic colonization as they upregulate molecules known to be chemoattractants for melanocytes. We detected c-Kit expression in a minority of the melanocytes as well as stem cell factor and basic fibroblast growth factor in the meningioma cells, suggesting that mechanisms implicated in normal melanocyte migration may be involved. In some cases, brain invasion with disruption of the leptomeningeal barrier may also facilitate migration from the subarachnoid space into the tumor. Whether there is low-level proliferation of the dendritic melanocytes is unclear. Given that all three patients were non-Caucasian, meningiomas in persons and/or brain regions with increased dendritic melanocytes may predispose to colonization. The age range spanned from 6 years old to 70 years old. All three patients were female. The role of gender and estrogen in the pathogenesis of this entity remains to be clarified. Whether melanocytic colonization may also occur in the more common Grade I meningiomas awaits identification of additional cases.

Paracrine regulation of melanocyte genomic stability: a focus on nucleotide excision repair

UV radiation is a major environmental risk factor for the development of melanoma by causing DNA damage and mutations. Resistance to UV damage is largely determined by the capacity of melanocytes to respond to UV injury by repairing mutagenic photolesions. The nucleotide excision repair (NER) pathway is the major mechanism by which cells correct UV photodamage. This multistep process involves the basic steps of damage recognition, isolation, localized strand unwinding, assembly of a repair complex, excision of the damage-containing strand 3' and 5' to the photolesion, synthesis of a sequence-appropriate replacement strand, and finally ligation to restore continuity of genomic DNA. In melanocytes, the efficiency of NER is regulated by several hormonal pathways including the melanocortin and endothelin signaling pathways. Elucidating molecular mechanisms by which melanocyte DNA repair is regulated offers the possibility of developing novel melanoma-preventive strategies to reduce UV mutagenesis, especially in UV-sensitive melanoma-prone individuals.

Trends in Regenerative Medicine: Repigmentation in Vitiligo Through Melanocyte Stem Cell Mobilization

Vitiligo is the most frequent human pigmentary disorder, characterized by progressive autoimmune destruction of mature epidermal melanocytes. Of the current treatments offering partial and temporary relief, ultraviolet (UV) light is the most effective, coordinating an intricate network of keratinocyte and melanocyte factors that control numerous cellular and molecular signaling pathways. This UV-activated process is a classic example of regenerative medicine, inducing functional melanocyte stem cell populations in the hair follicle to divide, migrate, and differentiate into mature melanocytes that regenerate the epidermis through a complex process involving melanocytes and other cell lineages in the skin. Using an in-depth correlative analysis of multiple experimental and clinical data sets, we generated a modern molecular research platform that can be used as a working model for further research of vitiligo repigmentation. Our analysis emphasizes the active participation of defined molecular pathways that regulate the balance between stemness and differentiation states of melanocytes and keratinocytes: p53 and its downstream effectors controlling melanogenesis; Wnt/β-catenin with proliferative, migratory, and differentiation roles in different pigmentation systems; integrins, cadherins, tetraspanins, and metalloproteinases, with promigratory effects on melanocytes; TGF-β and its effector PAX3, which control differentiation. Our long-term goal is to design pharmacological compounds that can specifically activate melanocyte precursors in the hair follicle in order to obtain faster, better, and durable repigmentation.

A Unifying Concept of Uveal Pigment Cell Distribution and Dissemination Based on an Animal Model: Insights into Ocular Melanogenesis

Pigmented cells are derived from neural crest cells, which migrate along the peripheral nerve sheets into their specific final region. During their migration, cells progressively acquire pigment-producing capabilities, maturation, and the shape of melanocytes. These insights, along with specific clinical characteristics of melanocytic nevi, have led to new concepts of cutaneous, periocular, and iris nevogenesis. To further elucidate the specific ocular embryogenic melanoblast distribution and dissemination - that could explain the distinct distribution of uveal melanocytic neoplasms - we investigated the ocular pigmentation of dogs affected by a specific mutation called Merle, which results in either pigment- (wild type) or non-pigment- (mutated type) producing cells. Based on our observations, we propose a unifying concept of uveal pigment cell distribution and dissemination, which postulates melanoblast migration and maturation following the trigeminal V1 branch and, later, their entrance into the eye along the ciliary nerves and their finest iris branches. Our concept provides an explanation not only for the specific distribution of ocular melanocytic lesions, including uveal and iris nevi, but also for the different locations depending on the metastatic potential of the ocular melanoma. Though speculative, the higher metastatic potential of posterior uveal melanomas compared to iris melanomas may be related to a less differentiated stage in the maturation of migrating melanocytes in the posterior segment compared to the anterior segment of the eye. However, there is a need of further studies focusing on cell differentiation markers of melanocytes at different locations in the eye.

Cross-sectional analysis of the dermoscopic patterns and structures of melanocytic naevi on the back and legs of adolescents

BACKGROUND

Junctional (flat) naevi predominate on the extremities, whereas dermal (raised) naevi are found primarily on the head, neck and trunk. Few studies have investigated the anatomical site prevalence of melanocytic naevi categorized using dermoscopy.

OBJECTIVES

To identify the prevalence of dermoscopic patterns and structures of naevi from the back and legs of adolescents.

METHODS

Dermoscopic images of acquired melanocytic naevi were obtained from the back and legs of students from a population-based cohort in Framingham, Massachusetts. Naevi were classified into reticular, globular, homogeneous or complex dermoscopic patterns. Multinomial logistic regression modelling assessed the associations between dermoscopic pattern and anatomical location.

RESULTS

In total 509 participants (mean age 14 years) contributed 2320 back naevi and 637 leg naevi. Compared with homogeneous naevi, globular and complex naevi were more commonly observed on the back than the legs [odds ratio (OR) 29·39, 95% confidence interval (CI) 9·53-90·65, P < 0·001 and OR 6·8, 95% CI 2·7-17·14, P < 0·001, respectively], whereas reticular lesions were less likely to be observed on the back than on the legs (OR 0·67, 95% CI 0·54-0·84, P = 0·001). Naevi containing any globules were more prevalent on the back than on the legs (25% vs. 3·6%, P < 0·001). Naevi containing any network were more prevalent on the legs than on the back (56% vs. 40·6%, P < 0·001).

CONCLUSIONS

These findings add to a robust body of literature suggesting that dermoscopically defined globular and reticular naevi represent biologically distinct naevus subsets that differ in histopathological growth pattern, age- and anatomical-site-related prevalence, molecular phenotype and aetiological pathways.

Gliadin Induces Neutrophil Migration via Engagement of the Formyl Peptide Receptor, FPR1

Background

Gliadin, the immunogenic component within gluten and trigger of celiac disease, is known to induce the production of Interleukin-8, a potent neutrophil-activating and chemoattractant chemokine. We sought to study the involvement of neutrophils in the early immunological changes following gliadin exposure.

Methods

Utilizing immunofluorescence microscopy and flow cytometry, the redistribution of major tight junction protein, Zonula occludens (ZO)-1, and neutrophil recruitment were assessed in duodenal tissues of gliadin-gavaged C57BL/6 wild-type and Lys-GFP reporter mice, respectively. Intravital microscopy with Lys-GFP mice allowed monitoring of neutrophil recruitment in response to luminal gliadin exposure in real time. In vitro chemotaxis assays were used to study murine and human neutrophil chemotaxis to gliadin, synthetic alpha-gliadin peptides and the neutrophil chemoattractant, fMet-Leu-Phe, in the presence or absence of a specific inhibitor of the fMet-Leu-Phe receptor-1 (FPR1), cyclosporine H. An irrelevant protein, zein, served as a control.

Results

Redistribution of ZO-1 and an influx of CD11b⁺Lys6G⁺ cells in the lamina propria of the small intestine were observed upon oral gavage of gliadin. In vivo intravital microscopy revealed a slowing down of GFP⁺ cells within the vessels and influx in the mucosal tissue within 2 hours after challenge. In vitro chemotaxis assays showed that gliadin strongly induced neutrophil migration, similar to fMet-Leu-Phe. We identified thirteen synthetic gliadin peptide motifs that induced cell migration. Blocking of FPR1 completely abrogated the fMet-Leu-Phe-, gliadin- and synthetic peptide-induced migration.

Conclusions

Gliadin possesses neutrophil chemoattractant properties similar to the classical neutrophil chemoattractant, fMet-Leu-Phe, and likewise uses FPR1 in the process.

Skin as a living coloring book: how epithelial cells create patterns of pigmentation

The pigmentation of mammalian skin and hair develops through the interaction of two basic cell types - pigment donors and recipients. The pigment donors are melanocytes, which produce and distribute melanin through specialized structures. The pigment recipients are epithelial cells, which acquire melanin and put it to use, collectively yielding the pigmentation visible to the eye. This review will focus on the pigment recipients, the historically less understood cell type. These end-users of pigment are now known to exert a specialized control over the patterning of pigmentation, as they identify themselves as melanocyte targets, recruit pigment donors, and stimulate the transfer of melanin. As such, this review will discuss the evidence that the skin is like a coloring book: the pigment recipients create a 'picture,' a blueprint for pigmentation, which is colorless initially but outlines where pigment should be placed. Melanocytes then melanize the recipients and 'color in' the picture.

Melanocyte migration is influenced by E-cadherin-dependent adhesion of keratinocytes in both two- and three-dimensional in vitro wound models

During wound healing, melanocytes are required to migrate into the wounded area that is still in the process of re-construction. The role and behaviour of melanocytes during this process is poorly understood, that is, whether melanocyte migration into the wound is keratinocyte-dependent or not. This paper attempts, through the use of both two- and three-dimensional in vitro models, to understand the role and behaviour of melanocytes during the process of wound healing. In addition, it sheds light on whether keratinocytes influence/contribute toward melanocyte migration and ultimately wound healing. Scratch assays were performed to analyse migration and Western blot analyses measured cellular E-cadherin expression. Immunohistochemistry was used to analyse the in vivo 3D wound healing effect. Scratch assays performed on co-cultures of melanocytes and keratinocytes demonstrated that melanocytes actively migrated, with the use of their dendrites, into the scratch ahead of the proliferating keratinocyte sheet. Migration of the melanocyte into the wound bed was accompanied by loss of attachment to keratinocytes at the wound front with concomitant downregulation of E-cadherin expression as observed through immunocytochemistry. This result suggests that, in vitro, melanocyte migration occurs independently of keratinocytes but that the migration is influenced by keratinocyte E-cadherin expression. We now demonstrate that melanocyte migration during re-pigmentation is an active process, and suggest that targeting of mechanisms involved in active melanocyte migration (e.g. the melanocyte dendrite) may enhance the re-pigmentation process.

Vitiligo: characterization of melanocytes in repigmented skin after punch grafting

BACKGROUND

Punch grafting is a surgical technique mainly applied in therapy-resistant, stable and circumscribed vitiligo.

OBJECTIVE

(i) To characterize in detail the features of the repigmented skin among punch grafts; and (ii) to correlate the ex vivo results with clinical data and punch grafting outcome.

METHODS

We evaluated by immunohistochemistry and image analysis the expression of a panel of specific melanocyte markers including HMB45, MITF, c-kit, MART-1 and TRP1, the proliferation marker Ki67 and the cell-cell adhesion molecule E-cadherin in tissue samples collected from nine patients after punch grafting.

RESULTS

Cells positive for MITF, c-kit, MART-1 and TRP1 were detected in the repigmented skin of all biopsies, whereas no reactivity was observed for HMB45. Melanocytes were identified along the entire length of the sections, and their mature state was assessed by the immuno-reactivity for the differentiation marker MART-1, the absence of cells positively stained for Ki67 and by the co-expression of c-kit and TRP1, a marker of a differentiated and pigmented state. Clinically, smaller punch grafts aimed at repigmenting lesional areas on the face gave the faster clinical results with no side-effects. Patients subjected to bigger punch grafts on the knee exhibited a longer repigmentation time and presented cobble stoning.

CONCLUSION

Our results suggest that the repigmentation observed in the areas between the grafts is due to the activation of the melanocytes located in the donor sites. These cells start to horizontally migrate towards the lesional skin thanks to successively the enlargement of intercellular spaces in relation to a decrease of E-cadherin reactivity and the up-modulation of pro-melanogenic mediators. Production and transfer of melanin in the surrounding keratinocytes and their persistence were assessed by the reactivity for MITF, c-kit, MART-1 and TRP1 but not for the pre-melanosome marker (HMB45).

One-stage nipple and breast reconstruction following areola-sparing mastectomy

BACKGROUND

Skin-sparing mastectomy with immediate breast reconstruction is increasingly becoming a proven surgical option for early-stage breast cancer patients. Areola-sparing mastectomy (ASM) has also recently become a popular procedure. The purpose of this article is to investigate the reconstructive and aesthetic issues experienced with one-stage nipple and breast reconstruction using ASM.

METHODS

Among the patients who underwent mastectomy between March 2008 and March 2010, 5 women with a low probability of nipple-areolar complex malignant involvement underwent ASM and immediate breast reconstruction with simultaneous nipple reconstruction using the modified C-V flap. The cosmetic outcomes of this series were reviewed by plastic surgeons and patient self-assessment and satisfaction were assessed via telephone interview.

RESULTS

During the average 11-month follow-up period, there were no cases of cancer recurrence, the aesthetic outcomes were graded as excellent to very good, and all of the patients were satisfied. Two patients developed a gutter-like depression around the reconstructed nipple, and one patient developed skin erosion in a small area of the areola, which healed with conservative dressing. The other complications, such as necrosis of the skin flap or areola, seroma, hematoma, or fat necrosis did not occur.

CONCLUSIONS

Since one-stage nipple and breast reconstruction following ASM is an oncologically safe, cost-effective, and aesthetically satisfactory procedure, it is a good surgical option for early breast cancer patients.

Endothelin-1 is a transcriptional target of p53 in epidermal keratinocytes and regulates ultraviolet-induced melanocyte homeostasis

Keratinocytes contribute to melanocyte activity by influencing their microenvironment, in part, through secretion of paracrine factors. Here, we discovered that p53 directly regulates Edn1 expression in epidermal keratinocytes and controls UV-induced melanocyte homeostasis. Selective ablation of endothelin-1 (EDN1) in murine epidermis (EDN1(ep-/-) ) does not alter melanocyte homeostasis in newborn skin but decreases dermal melanocytes in adult skin. Results showed that keratinocytic EDN1 in a non-cell autonomous manner controls melanocyte proliferation, migration, DNA damage, and apoptosis after ultraviolet B (UVB) irradiation. Expression of other keratinocyte-derived paracrine factors did not compensate for the loss of EDN1. Topical treatment with EDN1 receptor (EDNRB) antagonist BQ788 abrogated UV-induced melanocyte activation and recapitulated the phenotype seen in EDN1(ep-/-) mice. Altogether, the present studies establish an essential role of EDN1 in epidermal keratinocytes to mediate UV-induced melanocyte homeostasis in vivo.

Narrow-band UVB irradiation stimulates the migration and functional development of vitiligo-IgG antibodies-treated pigment cells

BACKGROUND

The pathogenesis of vitiligo remains unclear. Most authorities favoured the autoimmune cause for the strong associations of vitiligo with multiple autoimmune diseases and the presence of autoantibodies in vitiligo patients. Narrow-band UVB (NBUVB) irradiation has been considered to be an effective treatment for vitiligo with simple treatment procedure and decreased accumulated ultraviolet exposure doses.

OBJECTIVES

The aim this study was to investigate the effects of NBUVB irradiation on normal IgG antibodies (N-IgG) or vitiligo IgG antibodies (V-IgG)-treated NCCmelan5 cells in terms of proliferation, migration and melanin formation.

METHODS

Cultured NCCmelan5 cells were treated with (i) NBUVB irradiation alone, (ii) N-IgG or V-IgG alone, and (iii) combination of N-IgG or V-IgG with NBUVB irradiation. The proliferation of NCCmelan5 cells were evaluated using BrdU incorporation assay. Western blotting was used to determine the expressions of phosphorylated p125(FAK) (pp125(FAK)) and tyrosinase in NCCmelan5 cells. The locomotion of NCCmelan5 cells was assessed using time-lapse assay and in vitro wound scratch assay.

RESULTS

Neither N-IgG nor V-IgG significantly affected the proliferation of NCCmelan5 cells. The migration, melanin formation and tyrosinase expression in NCCmelan5 cells were decreased by V-IgG. NBUVB irradiation increased the proliferation of V-IgG treated NCCmelan5 cells. In addition, NBUVB irradiation enhanced the mobility of V-IgG-treated NCCmelan5 cells via upregulation of pp125(FAK). The melanogenesis and tyrosinase expression in V-IgG-treated NCCmelan5 cells were promoted using NBUVB irradiation.

CONCLUSIONS

Our study demonstrated that the deleterious effects of V-IgG in the pathogenesis of vitiligo might be overcome by NBUVB irradiation.

Aesthetic and technical refinements in latissimus dorsi implant breast reconstruction: a 15-year experience

BACKGROUND

The latissimus dorsi myocutaneous flap and implant breast reconstruction procedure has undergone many refinements over its lifetime. In fact, the authors have made many aesthetic and technical refinements to their own approach to breast reconstruction.

OBJECTIVES

The authors review the historical progression of latissimus flap and breast reconstruction techniques and compare these to their own 15-year experience.

METHODS

A retrospective chart review was conducted for all latissimus and implant breast reconstructions performed by the senior author (MAC) from July 1994 to June 2009, for a total of 52 procedures in 31 patients. Surgical and oncological data, complications, and outcomes data were recorded.

RESULTS

The mean age of the patients at time of surgery was 47.6 years. Average mastectomy weight was 283 grams and average final implant volume was 364 cc. Average follow-up was three years, four months. Of the 52 total procedures, 34.6% were immediate breast reconstructions utilizing skin-sparing mastectomy (SSM); 13.5% of the reconstructed breasts also had preservation of the areola (areolar-sparing mastectomy [ASM]). The most common complication was donor site seroma (40.4%). Aesthetic and surgical refinements identified over the time period included the adoption of SSM and ASM techniques, immediate nipple reconstruction, the placement of an adjustable saline implant to allow for postoperative size adjustment, and implant placement in the prepectoral position. The overall latissimus dorsi implant reconstruction success rate was 94.2% (49/52).

CONCLUSIONS

The data demonstrated a successful outcome for latissimus dorsi and implant breast reconstruction for patients with a low or normal body mass index and a small (A to C cup) breast size. The aesthetic outcome of latissimus dorsi breast reconstruction has been improved over the past 15 years by the adoption of SSM and ASM techniques. Immediate nipple reconstruction and the placement of an adjustable saline implant potentially render this procedure a true single-stage reconstruction. Prepectoral implant position provides good aesthetics while preserving the subpectoral space for future management of capsular contracture if required.

Low-energy helium-neon laser induces melanocyte proliferation via interaction with type IV collagen: visible light as a therapeutic option for vitiligo

BACKGROUND

The treatment of vitiligo remains a challenge for clinical dermatologists. We have previously shown that the helium-neon laser (He-Ne laser, 632.8 nm) is a therapeutic option for treatment of this depigmentary disorder.

OBJECTIVES

Addressing the intricate interactions between melanocytes, the most important cellular component in the repigmentation scheme of vitiligo, and their innate extracellular matrix collagen type IV, the current study aimed to elucidate the effects of the He-Ne laser on melanocytes.

METHODS

Cultured melanocytes were irradiated with the He-Ne laser. Relevant biological parameters including cell attachment, locomotion and growth were evaluated. In addition, the potentially involved molecular pathways were also determined.

RESULTS

Our results show that in addition to suppressing mobility but increasing attachment to type IV collagen, the He-Ne laser stimulates melanocyte proliferation through enhanced alpha2beta1 integrin expression. The expression of phosphorylated cyclic-AMP response element binding protein (CREB), an important regulator of melanocyte growth, was also upregulated by He-Ne laser treatment. Using a specific mitochondrial uncoupling agent [carbonyl cyanide m-chlorophenyl-hydrazone (CCCP)], the proliferative effect of the He-Ne laser on melanocytes was abolished and suppression of melanocyte growth was noted.

CONCLUSIONS

In summary, we have demonstrated that the He-Ne laser imparts a growth stimulatory effect on functional melanocytes via mitochondria-related pathways and proposed that other minor pathways including DNA damage may also be inflicted by laser treatment on irradiated cells. More importantly, we have completed the repigmentation scheme of vitiligo brought about by He-Ne laser light in vitro and provided a solid theoretical basis regarding how the He-Ne laser induces recovery of vitiligo in vivo.

Vitiligo and the melanocyte reservoir

Repigmentation of vitiligo depends on available melanocytes from three possible sources: from the hair follicle unit which is the main provider of pigment cells, from the border of vitiligo lesions, and from unaffected melanocytes within depigmented areas; pigment cells at these locations originate a perifollicular, border spreading and a diffuse repigmentation pattern. In order for repigmentation to take place under stimulation with diverse therapies, melanocytes should be present in appropriate numbers. Melanocyte tissue stem cells located in the niche at the bulge region of the hair follicle are the most important sources for providing immature pigment cells that undergo terminal differentiation and originate repigmentation, but cytokines, UVR and other molecules acting in melanogenesis with adequate regulation mechanisms contribute to successful recovery in vitiligo. The presence of keratinocyte stem cells in the interfollicular epidermis raises the question on the possibility of melanocyte stem cells in a similar location and the development of future strategies for therapeutic purposes.

Human hair pigmentation--biological aspects

Skin and hair colour contribute significantly to our overall visual appearance and to social/sexual communication. Despite their shared origins in the embryologic neural crest, the hair follicle and epidermal pigmentary units occupy distinct, although open, cutaneous compartments. They can be distinguished principally on the basis of the former's stringent coupling to the hair growth cycle compared with the latter's continuous melanogenesis. The biosynthesis of melanin and its subsequent transfer from melanocyte to hair bulb keratinocytes depend on the availability of melanin precursors and on a raft of signal transduction pathways that are both highly complex and commonly redundant. These signalling pathways can be both dependent and independent of receptors, act through auto-, para- or intracrine mechanisms and can be modified by hormonal signals. Despite many shared features, follicular melanocytes appear to be more sensitive than epidermal melanocytes to ageing influences. This can be seen most dramatically in hair greying/canities and this is likely to reflect significant differences in the epidermal and follicular microenvironments. The hair follicle pigmentary unit may also serve as an important environmental sensor, whereby hair pigment contributes to the rapid excretion of heavy metals, chemicals and toxins from the body by their selective binding to melanin; rendering the hair fibre a useful barometer of exposures. The recent availability of advanced cell culture methodologies for isolated hair follicle melanocytes and for intact anagen hair follicle organ culture should provide the research tools necessary to elucidate the regulatory mechanisms of hair follicle pigmentation. In the longer term, it may be feasible to develop hair colour modifiers of a biological nature to accompany those based on chemicals.

Dedicated epithelial recipient cells determine pigmentation patterns

Mammals generate external coloration via dedicated pigment-producing cells but arrange pigment into patterns through mechanisms largely unknown. Here, using mice as models, we show that patterns ultimately emanate from dedicated pigment-receiving cells. These pigment recipients are epithelial cells that recruit melanocytes to their position in the skin and induce the transfer of melanin. We identify Foxn1 (a transcription factor) as an activator of this "pigment recipient phenotype" and Fgf2 (a growth factor and Foxn1 target) as a signal released by recipients. When Foxn1 - and thus dedicated recipients - are redistributed in the skin, new patterns of pigmentation develop, suggesting a mechanism for the evolution of coloration. We conclude that recipients provide a cutaneous template or blueprint that instructs melanocytes where to place pigment. As Foxn1 and Fgf2 also modulate epithelial growth and differentiation, the Foxn1 pathway should serve as a nexus coordinating cell division, differentiation, and pigmentation.

Effects of psoralen plus ultraviolet A irradiation on cultured epidermal cells in vitro and patients with vitiligo in vivo

BACKGROUND

Both psoralen plus ultraviolet (UV) A (PUVA) and narrowband UVB (NB-UVB) irradiation are effective treatments for vitiligo vulgaris. However, the mechanisms of PUVA and NB-UVB in repigmentation are not thoroughly clarified. Our previous results showed that NB-UVB irradiation directly promotes melanocyte (MC) migration and stimulates MC proliferation via keratinocytes (KCs).

OBJECTIVES

In the present study, we used NB-UVB as a reference for comparison to investigate the immediate effects of PUVA on MC proliferation and migration.

METHODS

Cultured MCs and KCs were treated with PUVA or irradiated with NB-UVB. The direct impact of PUVA treatment on MCs was assessed in terms of its effect on MC proliferation and migration. The indirect effect of PUVA treatment and NB-UVB irradiation on MC proliferation via KCs was also investigated. The activities of matrix metalloproteinase (MMP)-2 and MMP-9, known for their influence on cell migration, were evaluated in the PUVA-treated MC and KC supernatants. The concentrations of MC mitogens/growth factors in the PUVA-treated KC supernatants were also determined. In addition, the serum levels of MC mitogens/growth factors in healthy controls, in patients with active vitiligo and in patients with repigmenting vitiligo after PUVA treatment were determined to elucidate the mechanisms of how PUVA induces vitiligo repigmentation in vivo.

RESULTS

Our results demonstrated that PUVA treatment did not significantly stimulate the release of MC mitogens/growth factors from KCs. The migration of MCs was also not enhanced after PUVA treatment. The expression of MMP-2 activity in supernatants derived from PUVA-treated MCs was significantly increased as compared with the control group. However, neither MMP-2 nor MMP-9 activity in KC supernatants was stimulated by PUVA treatment. In contrast to NB-UVB, immediate effects of PUVA on MC proliferation and migration were not observed in this study. Sera from patients with repigmenting vitiligo after PUVA treatment contained higher levels of basic fibroblast growth factor, stem cell factor and hepatocyte growth factor as compared with healthy controls and patients with active vitiligo.

CONCLUSIONS

Our results indicate that in addition to immune suppression, PUVA treatment creates a favourable milieu for promoting the growth of MCs in patients with vitiligo instead of directly stimulating the regrowth of MCs. Based on our results, we propose that in the active stage of vitiligo, PUVA treatment is the therapy of choice to slow down the destruction of MCs and to create a favourable environment for MCs to survive. In the stable stage of vitiligo, NB-UVB irradiation should be used to stimulate the proliferation and migration of MCs directly.

Interaction between stem cell factor and endothelin-1: effects on melanogenesis in human skin xenografts

The two paracrine melanogenic cytokines, stem cell factor (SCF) and endothelin-1 (ET-1), have been demonstrated to play pivotal roles in skin pigmentation including UVB-induced pigmentation and senile lentigo. However, little is known regarding their interactive effect on skin pigmentation. In order to investigate their roles in vivo, facultative pigmentation of human skin xenografts on severe combined immunodeficient (SCID) mice was assessed. After 1 week of acclimation in a pathogen-free barrier, dermatomed fresh cadaveric skin was surgically grafted onto the back of the mice and allowed to heal for 5-6 weeks prior to cytokine administration. Intradermal injections of SCF at 0.7 or 2.0 microg significantly increased skin pigmentation when compared to vehicle control. Despite the lack of a dose-dependent pigmentation response following ET-1 administration, the combination of 0.2 microg SCF and 0.1 microg ET-1 demonstrated a statistically significant increase in tyrosinase gene expression substantiated by the enhancement of melanin content and skin pigmentation compared to treatment with SCF alone or ET-1 alone. These findings establish an in vivo interaction between SCF and ET-1 with regard to their capacity to effect an increase in skin pigmentation.

Endothelin-1 is significantly elevated in plasma of patients with vitiligo treated with psoralen plus ultraviolet A

BACKGROUND

Recent evidence suggests that systemic psoralen plus ultraviolet A (PUVA) therapy may have a stimulatory effect on melanocytes, not only locally but also systemically. Aim. We aimed to assess endothelin-1 (ET-1), a potent melanocyte mitogen, in plasma of PUVA-treated paients with vitiligo.

METHODS

ET-1 was sequentially assessed (using ELISA) in patients with nonsegmental vitiligo treated with PUVA (n = 20), at 8, 16 and 24 h following the PUVA session. Evaluations took place at 0, 1 and 3 months of therapy. Patients with psoriasis (n = 15) treated identically and healthy subjects not receiving any therapy (n = 15) served as controls. Vitiligo Area Scoring Index (VASI) and Psoriasis Area Severity Index (PASI) scores were simultaneously evaluated.

RESULTS

ET-1 was significantly lower in vitiligo than in psoriasis at month 0 (8.2 +/- 3.6 vs. 13.7 +/- 5.4 pg/mL; P = 0.03) and it was significantly higher in both than in healthy controls at all time points of the PUVA sessions (P < 0.001). In vitiligo, it significantly increased at month 3 at 8 (8.2 +/- 3.6 vs. 10.8 +/- 2.7 pg/mL; P = 0.02) and 16 h (8.2 +/- 3.6 vs. 11.5 +/- 3.9 pg/mL; P < 0.01), whereas in psoriasis, it significantly decreased at month 3 at 8 (13.7 +/- 5.4 vs. 3.5 +/- 0.4 pg/mL; P < 0.01) and 16 h (13.7 +/- 5.4 vs. 6.3 +/- 4 pg/mL; P = 0.01). In contrast to psoriasis, sequential values of vitiligo revealed insignificant variance (P > 0.05). VASI score significantly decreased at month 3 (19 +/- 9.6 vs. 11.9 +/- 7.3; P < 0.01), whereas PASI score significantly decreased at months 1 (38.2 +/- 16.1 vs. 13.8 +/- 3; P < 0.05) and 3 (38.2 +/- 16.1 vs. 7 +/- 2.6; P = 0.03). There was a significant indirect correlation of ET-1 with VASI score (P < 0.01) and a significant direct correlation with PASI score (P < 0.01).

CONCLUSION

Systemic PUVA therapy in vitiligo may have a generalized mitogenic effect on melanocytes through the release of ET-1 into the circulation.

Low-energy helium-neon laser induces locomotion of the immature melanoblasts and promotes melanogenesis of the more differentiated melanoblasts: recapitulation of vitiligo repigmentation in vitro

Helium-neon laser (He-Ne Laser, 632.8 nm) is a low-energy laser that has therapeutic efficacy on various clinical conditions. Our previous study has demonstrated efficacy of He-Ne laser on vitiligo, a disease characterized by skin depigmentation. To regain skin tone on vitiligo lesions, the process began by the migration of the immature melanoblasts (MBs) to the epidermis, which was followed by their functional development to produce melanin. In this study, we investigated the physiologic effects of He-Ne laser irradiation on two MB cell lines: the immature NCCmelb4 and the more differentiated NCCmelan5. The intricate interactions between MBs with their innate extracelluar matrix, fibronectin, were also addressed. Our results showed that He-Ne laser irradiation enhanced NCCmelb4 mobility via enhanced phosphorylated focal adhesion kinase expression and promoted melanogenesis in NCCmelan5. In addition, He-Ne laser decreased the affinity between NCCmelb4 and fibronectin, whereas the attachment of NCCmelan5 to fibronectin increased. The alpha5beta1 integrin expression on NCCmelb4 cells was enhanced by He-Ne laser. In conclusion, we have demonstrated that He-Ne laser induced different physiologic changes on MBs at different maturation stages and recapitulated the early events during vitiligo repigmentation process brought upon by He-Ne laser in vitro.

Surgical approaches for stable vitiligo

BACKGROUND

Vitiligo therapy is difficult. Depending on its clinical presentation, unilateral or bilateral vitiligo lesions respond well with different repigmentation rates, according to age, affected anatomic area, extension of lesions, time at onset, timing of depigmentation spread, and other associated factors. When stable and refractory to medical treatment, vitiligo lesions may be treated by implanting pigment cells on depigmented areas.

OBJECTIVE

To describe the main events of depigmentation and the fundamentals of surgical techniques for repigmenting vitiligo by implanting noncultured cellular or tissue grafts, in vitro cultured epidermis-bearing pigment cells, or melanocyte suspensions.

METHODS

A description of the available techniques for repigmentation of vitiligo is done, emphasizing the most important details of each procedure to obtain the best repigmentation and minimize side effects.

RESULTS

With most of these techniques, adequate repigmentation is obtained, although there are limitations when applying some methods to clinical practice.

CONCLUSIONS

Restoration of pigmentation may be accomplished with all available surgical procedures in most anatomic locations, but they are of little value for acral areas. Unilateral vitiligo responds well in a high proportion of patients, and bilateral disease may also respond when stable. Appropriate patient selection is important to achieve the best results.

Contact guidance in human dermal fibroblasts is modulated by population pressure

Morphogenesis is underpinned by orientated cell division, motility and growth. The substratum for migrating cells in vivo comprises either extracellular matrix or the surfaces of adjacent cells and both are believed to inform the dynamic behaviour of adherent cells through contact guidance. Collisions between migrating cells in vitro can induce the phenomena of contact inhibition of locomotion and division, suggesting that their sensitivity to substratum-derived cues may also be influenced by population density. In the present study dermal fibroblasts, which are known to be motile in culture and are fundamental to the organization of the extracellular matrix, were used to examine the influence of population pressure on the ability of substratum topography to induce contact guidance. The findings suggest that sensitivity to substratum-derived morphogenetic guidance cues, as revealed by alignment of cells to microtopography, is modulated by population pressure.

FK506 promotes melanocyte and melanoblast growth and creates a favourable milieu for cell migration via keratinocytes: possible mechanisms of how tacrolimus ointment induces repigmentation in patients with vitiligo

BACKGROUND

Vitiligo is an acquired pigmentary disorder characterized by depigmentation of skin and hair. As the pathogenesis of this disease is still obscure, the treatment of vitiligo has generally been unsatisfactory and often disappointing. Topical tacrolimus (FK506) ointment has recently been added to the armamentarium against this pigmentary disorder. Despite its clinical efficacy, the underlying mechanisms of how topical tacrolimus induces repigmentation in vitiligo have rarely been investigated. As tacrolimus ointment is applied directly to the skin, its impact on keratinocytes (KCs) requires thorough investigation.

OBJECTIVES

To investigate the effects of FK506 on melanocyte (MC) and melanoblast (MB) growth via KCs.

METHODS

Cultured MCs and MBs were treated with supernatant of KC cultures conditioned with various concentrations of FK506. The impact of supernatant on MCs and MBs was assessed in terms of its effect on MC/MB proliferation, melanin formation and cell migration. The activities of matrix metalloproteinase (MMP)-2 and MMP-9, known for their influence on cell migration, were evaluated. The concentrations of MC/MB growth factors in the KC supernatant were also determined.

RESULTS

Results demonstrated that proliferation of both MCs and MBs was significantly enhanced by FK506-treated KC supernatant. In addition, the concentration of stem cell factor in KC supernatant increased dose-dependently with FK506 treatment. The supernatant from FK506-treated KC culture showed a significant increase in MMP-9 activity.

CONCLUSIONS

Our study provides in vitro evidence demonstrating that direct interaction between FK506 and KCs creates a favourable milieu for MC growth and migration. Furthermore, our findings provide a possible mechanism explaining how tacrolimus ointment induces repigmentation in patients with vitiligo.

Vitiligo: analysis of grafting versus curettage alone, using melanocyte morphology and reverse transcriptase polymerase chain reaction for tyrosinase mRNA

CONTEXT AND OBJECTIVE

Recent studies have indicated that vitiligo areas contain inactive or dormant melanocytes. Melanin synthesis is related to tyrosinase presence and indicative of active metabolic state. The aim of this study was to compare repigmentation, epidermal melanocyte distribution and tyrosinase mRNA detection through reverse transcriptase polymerase chain reaction, in tissue samples of vitiligo, before and after curettage, with or without subsequent autologous skin graft using a new method.

DESIGN AND SETTING

Prospective, in the Department of Dermatology, Faculdade de Medicina do ABC, Santo André.

METHODS

Two vitiligo areas were curetted. One subsequently received grafted normal sacral autologous skin, whereas the other had no further treatment. The curetted areas were examined after 30 days, to evaluate the degree of repigmentation. The melanocyte percentages and tyrosinase mRNA presence in normal skin and vitiligo areas, before and after curettage and grafting, were compared.

RESULTS

Complete repigmentation was seen in all grafted areas, whereas non-grafted curetted vitiligo presented partial repigmentation. The melanocyte percentage in grafted areas was greater than in non-treated vitiligo skin (p = 0.01) and skin with curettage alone (p = 0.015). Tyrosinase mRNA was negative in 93.75% of non-treated vitiligo areas. After treatment (curettage alone or curettage and grafting), all lesions became positive for tyrosinase mRNA.

CONCLUSION

Metabolically inactive or dormant melanocytes are probably present within vitiligo areas, and may be activated by exogenous or endogenous stimuli.

Narrow-band ultraviolet-B stimulates proliferation and migration of cultured melanocytes

Narrow-band ultraviolet-B (UVB) radiation is an effective treatment for vitiligo vulgaris. However, the mechanisms of narrow-band UVB in inducing repigmentation of vitiligo lesions are not thoroughly clarified. The purpose of our study was to investigate the effects of narrow-band UVB irradiation on melanocyte proliferation and migration in vitro. Our results showed that the cell counts as well as [3H]thymidine uptake of melanocytes were significantly enhanced by narrow-band UVB-irradiated keratinocyte supernatants. In these supernatants, a significant increase in basic fibroblast growth factor (bFGF) and in endothelin-1 (ET-1) release was observed. bFGF is a natural mitogen for melanocytes, whereas ET-1 can stimulate DNA synthesis in melanocytes. This stimulatory effect of melanocyte proliferation by supernatants derived from narrow-band UVB-irradiated keratinocytes was significantly reduced by a selective endothelin-B (ET-B) receptor antagonist (BQ788), suggesting an essential role of ET-1 on melanocyte proliferation. Our results of time-lapse microphotography revealed a stimulatory effect of narrow-band UVB irradiation on melanocyte migration. Focal adhesion kinase (FAK) plays a pivotal role in cell migration. Phosphorylated FAK (p125(FAK)) expression on melanocyte was enhanced by narrow-band UVB irradiation. In this study, narrow-band UVB irradiation stimulated a significant increase in matrix metalloproteinase-2 (MMP-2) activity in melanocyte supernatants. Narrow-band UVB-irradiation-induced migration of melanocytes was significantly annihilated by the addition of p125(FAK) inhibitor (herbimycin-A) or MMP-2 inhibitor (GM6001). These results suggest that p125(FAK) and MMP-2 activity play important roles in narrow-band UVB-induced migration of melanocytes. Our results provide a theoretical basis for the effectiveness of narrow-band UVB irradiation in treating vitiligo.

Isolation and culture of amelanotic melanocytes from human hair follicles

We report a method to establish amelanotic melanocytes (AMMC) in culture and we investigate the effects of various components in the culture medium. Normal human scalp from cadaver donors was transected 1 mm below the epidermis, and hair follicles in the remaining dermis were isolated by a two-step enzyme treatment. The individual hair follicles were washed exhaustively and suspensions of hair follicle cells were prepared and cultured in Eagle's minimum essential medium supplemented with 12-o-tetradecanoyl-phorbol-13-acetate (TPA), cholera toxin and keratinocyte serum-free medium (K-SFM). Geneticin was used to eliminate contaminating fibroblasts. Proliferation of AMMC was observed after addition of TPA and K-SFM including bovine pituitary extract (BPE) into the culture medium. Cell type was determined by staining with monoclonal antibodies, NKI/beteb and HMB-45, which recognize premelanosomal and melanosomal antigens, respectively. The AMMC were also examined using transmission electron microscopy. Treatment with geneticin eliminates the majority of fibroblasts and does not impair the growth of keratinocytes or AMMC. After contaminating fibroblasts and keratinocytes were removed, two distinct cell morphologies remained: (1) large, dendritic and deeply pigmented cells, which did not proliferate and which disappeared by the third passage, and (2) small bipolar cells, which initially were unpigmented and proliferated very rapidly. We observed that TPA at various concentrations stimulated the proliferation of the cells, and at high concentrations could induce the formation of multiple dendrites. K-SFM including BPE accelerated the proliferation of the cells in a dose-dependent manner. After passage 3, almost all cells expressed premelanosomal and melanosomal antigens, recognized by NKI/beteb and HMB-45, respectively. Active mitochondria, abundant rough endoplasmic reticulum, Golgi complexes, ribosomes and melannosomes (predominantly in stages I, II or III with some at stage IV in some AMMC) were observed ultrastructurally in the cytoplasm of the cultured cells.

Satellite repigmentation after punch grafting

Punch grafting is an established treatment modality for management of localized, nonprogressive vitiligo resistant to conventional therapies.(1) In our set up, punch grafting is routinely carried out in focal vitiligo, segmental vitiligo and even in few cases of generalized vitiligo, especially when it is a serious cosmetic problem.(2) However, the procedure is adopted only when the disease is stable for a sufficient period. All patients are routinely kept on psoralen tablets and ultraviolet light exposure from sunlight (PUVA sol therapy) after 2-3 weeks of punch grafting. Interestingly, follow up of such patients revealed conspicuous repigmentation in surrounding ungrafted patches in four of the patients (out of 55 follow-up cases). Herein, this phenomenon has been aptly termed satellite repigmentation (SR). To the best of our knowledge, no other report documenting SR after punch grafting exists in the medical literature. We report the observations of these four patients.

Helium-neon laser irradiation stimulates migration and proliferation in melanocytes and induces repigmentation in segmental-type vitiligo

Low-energy helium-neon lasers (632.8 nm) have been employed in a variety of clinical treatments including vitiligo management. Light-mediated reaction to low-energy laser irradiation is referred to as biostimulation rather than a thermal effect. This study sought to determine the theoretical basis and clinical evidence for the effectiveness of helium-neon lasers in treating vitiligo. Cultured keratinocytes and fibroblasts were irradiated with 0.5-1.5 J per cm2 helium-neon laser radiation. The effects of the helium-neon laser on melanocyte growth and proliferation were investigated. The results of this in vitro study revealed a significant increase in basic fibroblast growth factor release from both keratinocytes and fibroblasts and a significant increase in nerve growth factor release from keratinocytes. Medium from helium-neon laser irradiated keratinocytes stimulated [3H]thymidine uptake and proliferation of cultured melanocytes. Furthermore, melanocyte migration was enhanced either directly by helium-neon laser irradiation or indirectly by the medium derived from helium-neon laser treated keratinocytes. Thirty patients with segmental-type vitiligo on the head and/or neck were enrolled in this study. Helium-neon laser light was administered locally at 3.0 J per cm2 with point stimulation once or twice weekly. The percentage of repigmented area was used for clinical evaluation of effectiveness. After an average of 16 treatment sessions, initial repigmentation was noticed. Marked repigmentation (>50%) was observed in 60% of patients with successive treatments. Basic fibroblast growth factor is a putative melanocyte growth factor, whereas nerve growth factor is a paracrine factor for melanocyte survival in the skin. Both nerve growth factor and basic fibroblast growth factor stimulate melanocyte migration. It is reasonable to propose that helium-neon laser irradiation clearly stimulates melanocyte migration and proliferation and mitogen release for melanocyte growth and may also rescue damaged melanocytes, therefore providing a microenvironment for inducing repigmentation in vitiligo.

A human placental extract: in vivo and in vitro assessments of its melanocyte growth and pigment-inducing activities

BACKGROUND

The authenticity of various prototype human placental extracts with biological activity, such as that inducing vitiligo repigmentation, is under serious criticism, mainly due to a lack of demonstration at the cellular level. Considering the present worldwide scenario with regard to the occurrence and treatment of vitiligo, a thorough scientific exploration of such extracts should be undertaken.

METHOD

One such prototype placental preparation was prepared, and was evaluated with regard to its melanogenic action in C57BL/6J mice in vivo and its mitogenic and melanogenic activity on B16F10 mouse melanoma cells and normal human melanocytes in vitro. The extract was applied topically to mice with age-induced prolonged telogenic phase of hair growth (grey body coat hair). Standard 3H-thymidine incorporation and spectrophotometric methods were followed to illustrate mitogenic and melanogenic effects at the cellular level.

RESULTS

The resurgence of blue skin, followed by shiny black hair, at the regions of application of the extract demonstrated the reversal of the age-induced prolonged telogenic phase of hair growth to the anagenic phase after topical application of the extract on C57BL/6J mice. Further support was obtained from histology where, at the extract-treated sites, the development of new melanogenic centers and hair follicles was observed. During in vitro studies, the vehicle-free extract constituents stimulated both mitogenesis and melanogenesis of B16F10 mouse melanoma cells in a concentration-dependent manner. The cell morphology and extent of melanogenesis also showed significant changes. In addition, two known melanocyte activity-modulating peptides, endothelin-1 (ET-1) and adrenocorticotropic hormone (ACTH), were determined in the extract, chiefly in the total lipid fraction, indicating their effective cutaneous permeation.

CONCLUSIONS

The extract was found to be a potent mitogen in the in vitro condition and a potent melanogen in both the in vitro and in vivo situations. This strongly suggests its therapeutic potential for the repigmentation of vitiligo patches.

Changes in the motility of B16F10 melanoma cells induced by alterations in resting calcium influx

Alterations in the extracellular Ca(2+) or K(+) concentration had significant influences on the motility of B16F10 melanoma cells measured in the absence of exogenous integrins using a conventional Boyden chamber assay. At normal K(+) concentrations, motility increased slightly when the concentration of Ca(2+) was increased 10-fold. At normal Ca(2+) concentrations, motility increased by 290% when the extracellular K(+) concentration was reduced 10-fold (from control of 5.4 mM to 0.54 mM), and increased to 250% of control levels when the K(+) concentration was increased between 30 and 54 mM, but was relatively uninfluenced at K(+) concentrations between 5 and 30 mM. Simultaneous application of low concentrations (20 microM) of GdCl(3) completely prevented the effects of low and high K(+) on motility. Exposure to Gd(3+) or Tb(3+) also produced a flattening of the cells and enhanced cell attachment. Although the steady state intracellular Ca(2+) concentration was not significantly influenced by the K(+) concentration, the resting permeability to divalent cations, determined from Mn(2+) quench rates in fura-loaded cells, was significantly increased by a reduction in the K(+) concentration. These results indicate that resting Ca(2+) influx is critical to the movement of B16F10 melanoma cells, and demonstrate that lanthanides, which block resting Ca(2+) influx pathways, are potent antimotility agents.

Cultured human dermal papilla cells secrete a chemotactic factor for melanocytes

Large numbers of pigmented melanocytes are located in human hair follicles, predominantly around the dermal papillae, and the number of melanocytes and the melanogenic activity of the hair follicles are closely related to the hair cycle. We found that cultured human dermal papilla cells secreted a melanocyte chemoattractant into the medium. Skin fibroblasts also showed weak chemoattraction of melanocytes, while skin keratinocytes and melanocytes did not. Since this chemotactic activity was heat-and protease-sensitive and was present in the relatively high molecular weight fraction (130-200 kDa), it may be due to extracellular matrix (ECM) that proteins secreted from the cultured dermal papilla cells. This chemotactic signal between dermal papillae and melanocytes may control the localization and migration of hair melanocytes in vivo.

Review: ligands for receptor tyrosine kinases expressed in the skin as environmental factors for melanocyte development

Skin is the major tissue where melanocytes develop, and skin keratinocytes provide the necessary micro-environment for melanocyte survival, proliferation, differentiation, and migration. In this paper, we will discuss the ligands for receptor tyrosine kinases produced as environmental cues to support melanocyte development in the skin.