Epidermal changes in active vitiligo

Mitochondria-Melanocyte cellular interactions: An emerging mechanism of vitiligo pathogenesis

Mitochondria has emerged as a potential modulator of melanocyte function other than just meeting its cellular ATP demands. Mitochondrial DNA defects are now an established cause of maternal inheritance diseases. Recent cellular studies have highlighted the mitochondrial interaction with other cellular organelles that lead to disease conditions such as in Duchenne muscular dystrophy, where defective mitochondria was found in melanocytes of these patients. Vitiligo, a depigmentory ailment of the skin, is another such disorder whose pathogenesis is now found to be associated with mitochondria. The complete absence of melanocytes at the lesioned site in vitiligo is a fact; however, the precise mechanism of this destruction is still undefined. In this review we have tried to discuss and link the emerging facts of mitochondrial function or its inter- and intra-organellar communications in vitiligo pathogenesis. Mitochondrial close association with melanosomes, molecular involvement in melanocyte-keratinocyte communication and melanocyte survival are new paradigm of melanogenesis that could ultimately account for vitiligo. This definitely adds the new dimensions to our understanding of vitiligo, its management and designing of future mitochondrial targeted therapy for vitiligo.

Alterations of the pigmentation system in the aging process

Human skin aging is a natural phenomenon that results from continuous exposure to intrinsic (time, genetic factors, hormones) as well as extrinsic factors (UV exposure, pollution, tobacco). In areas that are frequently exposed to the sun, photoaging blends with the process of intrinsic aging, resulting in an increased senescent cells number and consequently accelerating the aging process. The severity of photodamage depends on constitutional factors, including skin phototype (skin color, tanning capacity), intensity, and duration of sunlight/UV exposure. Aging affects nearly every aspect of cutaneous biology, including pigmentation. Clinically, the phenotype of age pigmented skin has a mottled, uneven color, primarily due to age spots, with or without hypopigmentation. Uneven pigmentation might be attributed to the hyperactivation of melanocytes, altered distribution of pigment, and turnover. In addition to direct damage to pigment-producing cells, photodamage alters the physiological crosstalk between keratinocytes, fibroblasts, endothelial cells, and melanocytes responsible for natural pigmentation homeostasis. Interestingly, age-independent diffuse expression of senescence-associated markers in the dermal and epidermal compartment is also associated with vitiligo, suggesting that premature senescence plays an important role in the pathology.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

Vitamin D receptor gene polymorphism, serum 25-hydroxyvitamin D levels, and risk of vitiligo: A meta-analysis

OBJECTIVES

To explore the relationship among the vitamin D receptor (VDR) gene polymorphisms, serum 25-hydroxyvitamin D levels, and vitiligo.

METHODS

Databases including PubMed, Cochrane Library, Ovid, Web of Science, CNKI, SinoMed, and Wanfang Data were systematically searched. The association was assessed using odds ratios (ORs), standard mean difference (SMD), and 95% confidence intervals (CIs). The statistical tests were performed using Review Manager 5.3.3.

RESULTS

We identified a total of 17 studies. The relationship between VDR gene polymorphisms (BsmI, ApaI, TaqI, and FokI), serum 25 (OH)D levels, and incidence of vitiligo was investigated. The results of this meta-analysis showed that the dominant genetic model (CC+AC vs AA, P = .007, OR = 1.41, 95% CI = 1.10-1.80), recessive genetic model (CC vs AC+AA, P = .01, OR = 4.10, 95% CI = 1.36-12.35), and allelic contrast model (C vs A, P = .005, OR = 1.87, 95% CI = 1.21-2.90) of VDR Apal locus increased the risk of vitiligo, and BsmI, TaqI, and FokI loci and the risk of vitiligo have no obvious correlation. Serum 25 (OH)D deficiency was positively associated with the incidence of vitiligo (P < .0001, SMD = -0.94, 95% CI = -1.39, -0.48).

CONCLUSION

This meta-analysis revealed that VDR Apal polymorphism increased the susceptibility risk of vitiligo, and there is a positive correlation between serum 25 (OH)D deficiency and the incidence of vitiligo.

Mapping architectural and transcriptional alterations in non-lesional and lesional epidermis in vitiligo

In vitiligo, chronic loss of melanocytes and consequent absence of melanin from the epidermis presents a challenge for long-term tissue maintenance. The stable vitiligo patches are known to attain an irreversible depigmented state. However, the molecular and cellular processes resulting in this remodeled tissue homeostasis is unclear. To investigate the complex interplay of inductive signals and cell intrinsic factors that support the new acquired state, we compared the matched lesional and non-lesional epidermis obtained from stable non-segmental vitiligo subjects. Hierarchical clustering of genome-wide expression of transcripts surprisingly segregated lesional and non-lesional samples in two distinct clades, despite the apparent heterogeneity in the lesions of different vitiligo subjects. Pathway enrichment showed the expected downregulation of melanogenic pathway and a significant downregulation of cornification and keratinocyte differentiation processes. These perturbations could indeed be recapitulated in the lesional epidermal tissue, including blunting of rete-ridges, thickening of stratum corneum and increase in the size of corneocytes. In addition, we identify marked increase in the putrescine levels due to the elevated expression of spermine/spermidine acetyl transferase. Our study provides insights into the intrinsic self-renewing ability of damaged lesional tissue to restore epidermal functionality in vitiligo.

Biomarkers of disease activity in vitiligo: A systematic review

The pathophysiology of vitiligo is complex although recent research has discovered several markers which are linked to vitiligo and associated with disease activity. Besides providing insights into the driving mechanisms of vitiligo, these findings could reveal potential biomarkers. Activity markers can be used to monitor disease activity in clinical trials and may also be useful in daily practice. The aim of this systematic review was to document which factors have been associated with vitiligo activity in skin and blood. A second goal was to determine how well these factors are validated in terms of sensitivity and specificity as biomarkers to determine vitiligo activity. Both in skin (n=43) as in blood (n=66) an adequate number of studies fulfilled the predefined inclusion criteria. These studies used diverse methods and investigated a broad range of plausible biomarkers. Unfortunately, sensitivity and specificity analyses were scarce. In skin, simple histopathology with or without supplemental CD4 and CD8 stainings can still be considered as the gold standard, although more recently chemokine (C-X-C motif) ligand (CXCL) 9 and NLRP1 have demonstrated a good and possibly even better association with progressive disease. Regarding circulating biomarkers, cytokines (IL-1β, IL-17, IFN-γ, TGF-β), autoantibodies, oxidative stress markers, immune cells (Tregs), soluble CDs (sCD25, sCD27) and chemokines (CXCL9, CXCL10) are still competing. However, the two latter may be preferable as both chemokines and soluble CDs are easy to measure and the available studies display promising results. A large multicenter study could make more definitive statements regarding their sensitivity and specificity.

Possible patterns of epidermal melanocyte disappearance in nonsegmental vitiligo: a clinicopathological study

BACKGROUND

The depigmentation of vitiligo results in a progressive and chronic melanocyte loss with rare melanocytes occasionally remaining in the epidermis or the hair follicle reservoirs. Destruction by immune infiltrates in close contact with melanocytes within microvesicles and/or detachment of melanocytes followed by their transepidermal elimination should be regarded as possible mechanisms of chronic loss of pigment cells.

OBJECTIVES

To assess the frequency of these two histological findings and to establish a direct correlation with clinical features.

METHODS

This was a prospective observational study that took place over 1 year. Each patient received a standardized evaluation that included daylight and Wood's lamp examinations, pictures, biopsies performed on the marginal area, and histological and immunohistological studies. A second examination to assess the activity of the lesions was performed 1 year after inclusion in the study. Clinical changes associated with microvesicles were compared with those associated with detached melanocytes from the basal layer.

RESULTS

This study included 50 patients. The histological findings were classified as inflammatory with isolated microvesicles (29 cases), noninflammatory with only detached melanocytes from the basal layer (12 cases) and a combination of coexisting microvesicles and detached melanocytes (six cases). Correlations were obtained between the histological findings and clinical features (aspect and activity of the lesions) and E-cadherin expression.

CONCLUSIONS

Our data suggest the existence of two patterns of melanocyte disappearance in nonsegmental vitiligo.

Segmental and generalized vitiligo: both forms demonstrate inflammatory histopathological features and clinical mosaicism

BACKGROUND

Segmental vitiligo (SV) and generalized vitiligo (GV) are perceived to evolve by different mechanisms, the former with unspecified neural mechanisms and the latter by melanocyte specific autoimmune mechanisms. However, the two diverse mechanisms are difficult to reconcile in cases of "mixed vitiligo". To test the possibility of a common pathogenesis, we reviewed clinical and histopathological features of SV and GV.

MATERIALS AND METHODS

As part of an ongoing histopathological study on vitiligo and vitiligo like lesions, over a 10 year period from 2002 to 2011, biopsies were taken routinely from evolving or recently evolved lesions. 50 cases of SV with quasi-dermatomal distribution and 154 cases of GV were identified and the clinical and histopathological features were compared.

RESULTS

Mild clinical inflammation was recorded in 33 of 154 GV cases but, none among 50 SV had such features. In addition to bilateral symmetrical involvement, mirror image lesions with unusual segmentation were observed in nine cases of GV. SV with a few bilateral lesions (4) and GV with quasi-dermatomal lesions (3), i.e., mixed vitiligo, were included in their corresponding groups for analytical purposes. Focal lichenoid inflammation of varying degrees around epidermal/adnexal melanocytes was identified as a common feature in evolving lesions of both SV (78%) and GV (70%).

CONCLUSIONS

SV and GV demonstrated a similar inflammatory histopathological spectrum. "Segmentation/mosaicism", identified for the first time in GV is another unifying factor. Cutaneous mosaicism harboring fragile melanocyte populations, which are susceptible to external as well as auto-inflammatory mechanisms, is an attractive hypothesis to pursue in the causation of vitiligo.

Stability in Vitiligo: Is there a Perfect Way to Predict it?

Stability is a hard-to-define concept in the setting of vitiligo, but is nonetheless extremely crucial to the planning of treatment regimens and also in prognosticating for the patient. There are several ways to judge stability in vitiligo, which include clinical features and, recently, many biochemical, cytological and ultrastructural correlates of the same. These recent advances help in not only in prognosticating individual patients but also in elucidating some of the mechanisms for the pathogenesis of vitiligo, including melanocytorrhagy and oxidative damage to melanocytes.

Immunolocalization of tenascin-C in vitiligo

The disappearance of melanocytes because of defective adhesion is one of the accepted theories to explain vitiligo. Tenascin-C is a large, extracellular matrix glycoprotein that is thought to inhibit adhesion of melanocytes to fibronectin. The current study aimed to evaluate the pattern of tenascin-C expression in vitiligenous skin compared with normal pigmented skin by means of immunohistochemistry. The study was carried out on skin biopsies from lesional and perilesional skin of 30 patients with vitiligo and on normal skin of 10 healthy volunteers. Several histopathologic changes were observed in vitiliginous skin such as keratinocyte vacuolization, a thickened basement membrane, and dermal inflammatory changes. Tenascin-C was expressed in keratinocytes of the basal epidermal layer of normal skin biopsies at a mild intensity but it did not stain the dermis, whereas vitiligenous skin showed tenascin-C expression in most cases (93.3% ), in the papillary dermis, epidermis, and in both. Diffuse epidermal expression of tenascin-C correlated with more loss of pigment and continuous staining of tenascin-C in the papillary dermis correlated with progressive forms of vitiligo. Intense tenascin-C expression was associated with a more progressive course of the disease assessed by the vitiligo disease activity score. From this study, tenascin-C is highly expressed in the dermis, epidermis, and both of vitiligo as a secondary event for the disease. Keratinocyte is a source of tenascin-C in vitiligo, and diffuse epidermal expression of tenascin-C may induce more loss of melanocytes and melanin pigment. Dermal expression of tenascin-C in the vitiligenous lesion may be linked to the disease more than epidermal expression, because this pattern is only seen in a vitiligenous lesion and it is completely absent in normal and perilesional skin.

Revised classification/nomenclature of vitiligo and related issues: the Vitiligo Global Issues Consensus Conference

During the 2011 International Pigment Cell Conference (IPCC), the Vitiligo European Taskforce (VETF) convened a consensus conference on issues of global importance for vitiligo clinical research. As suggested by an international panel of experts, the conference focused on four topics: classification and nomenclature; definition of stable disease; definition of Koebner's phenomenon (KP); and 'autoimmune vitiligo'. These topics were discussed in seven working groups representing different geographical regions. A consensus emerged that segmental vitiligo be classified separately from all other forms of vitiligo and that the term 'vitiligo' be used as an umbrella term for all non-segmental forms of vitiligo, including 'mixed vitiligo' in which segmental and non-segmental vitiligo are combined and which is considered a subgroup of vitiligo. Further, the conference recommends that disease stability be best assessed based on the stability of individual lesions rather than the overall stability of the disease as the latter is difficult to define precisely and reliably. The conference also endorsed the classification of KP for vitiligo as proposed by the VETF (history based, clinical observation based, or experimentally induced). Lastly, the conference agreed that 'autoimmune vitiligo' should not be used as a separate classification as published evidence indicates that the pathophysiology of all forms of vitiligo likely involves autoimmune or inflammatory mechanisms.

Childhood vitiligo in China: clinical profiles and immunological findings in 620 cases

BACKGROUND

Childhood vitiligo is a common pediatric skin disorder. The pathogenesis of vitiligo is unclear, and immunological dysfunction may play an important role.

OBJECTIVES

This prospective study aimed to profile childhood vitiligo and to discuss its correlation with immunological dysfunction.

METHODS

All of the 620 enrolled patients were aged younger than 14 years, and were assessed with a standard questionnaire. The levels of immunoglobulins, complement, and T-lymphocyte subsets were measured in 270 of these 620 patients.

RESULTS

Of the 620 children, 302 (48.71%) were boys and 318 (51.29%) were girls, with an average disease onset age of 7.57 years. The average duration was 13.45 months. 453 (73.06%) children had head and neck involvement and 160 (25.81%) children had segmental vitiligo. 84 (13.55%) children had a family history. There was a correlation between the disease and seasons. The onset or progression usually occurred in summer and spring. Halo nevus was seen in both segmental and non-segmental vitiligo. Precipitating factors such as stress appeared more commonly in segmental vitiligo. As to the immunological findings, in segmental vitiligo, the levels of C3 and C4 were lower in the active relative to the quiescent stage (p < 0.05); and in non-segmental vitiligo, the percentages of CD3+ and CD4+ lymphocytes and the CD4+/CD8+ ratio were lower in the active relative to the quiescent stage (p < 0.01).

CONCLUSIONS

Childhood vitiligo has its own clinical features. The different types of vitiligo have different characteristics. There is immunological dysfunction in children with vitiligo. Dysfunction of humoral immunity may play a role in the progression of segmental vitiligo, while non-segmental vitiligo is more related to cellular immunity.

Vitiligo, reactive oxygen species and T-cells

The acquired depigmenting disorder of vitiligo affects an estimated 1% of the world population and constitutes one of the commonest dermatoses. Although essentially asymptomatic, the psychosocial impact of vitiligo can be severe. The cause of vitiligo remains enigmatic, hampering efforts at successful therapy. The underlying pathogenesis of the pigment loss has, however, been clarified to some extent in recent years, offering the prospect of effective treatment, accurate prognosis and rational preventative strategies. Vitiligo occurs when functioning melanocytes disappear from the epidermis. A single dominant pathway is unlikely to account for all cases of melanocyte loss in vitiligo; rather, it is the result of complex interactions of biochemical, environmental and immunological events, in a permissive genetic milieu. ROS (reactive oxygen species) and H2O2 in excess can damage biological processes, and this situation has been documented in active vitiligo skin. Tyrosinase activity is impaired by excess H2O2 through oxidation of methionine residues in this key melanogenic enzyme. Mechanisms for repairing this oxidant damage are also damaged by H2O2, compounding the effect. Numerous proteins and peptides, in addition to tyrosinase, are similarly affected. It is possible that oxidant stress is the principal cause of vitiligo. However, there is also ample evidence of immunological phenomena in vitiligo, particularly in established chronic and progressive disease. Both innate and adaptive arms of the immune system are involved, with a dominant role for T-cells. Sensitized CD8+ T-cells are targeted to melanocyte differentiation antigens and destroy melanocytes either as the primary event in vitiligo or as a secondary promotive consequence. There is speculation on the interplay, if any, between ROS and the immune system in the pathogenesis of vitiligo. The present review focuses on the scientific evidence linking alterations in ROS and/or T-cells to vitiligo.

Autoimmune destruction of skin melanocytes by perilesional T cells from vitiligo patients

In vitiligo, cytotoxic T cells infiltrating the perilesional margin are suspected to be involved in the pathogenesis of the disease. However, it remains to be elucidated whether these T cells are a cause or a consequence of the depigmentation process. T cells we obtained from perilesional skin biopsies, were significantly enriched for melanocyte antigen recognition, compared with healthy skin-infiltrating T cells, and were reactive to melanocyte antigen-specific stimulation. Using a skin explant model, we were able to dissect the in situ activities of perilesional T cells in the effector phase of depigmentation. We show that these T cells could infiltrate autologous normally pigmented skin explants and efficiently kill melanocytes within this microenvironment. Interestingly, melanocyte apoptosis was accompanied by suprabasal keratinocyte apoptosis. Perilesional T cells did, however, not induce apoptosis in lesional skin, which is devoid of melanocytes, indicating the melanocyte-specific cytotoxic activity of these cells. Melanocyte killing correlated to local infiltration of perilesional T cells. Our data show that perilesional cytotoxic T cells eradicate pigment cells, the characteristic hallmark of vitiligo, thereby providing evidence of T cells being able to mediate targeted autoimmune tissue destruction.

Keratinocyte cultures from involved skin in vitiligo patients show an impaired in vitro behaviour

Vitiligo depigmentation is considered a consequence of either melanocyte disappearance or loss of functioning melanocytes in the involved areas. However, it has been reported that keratinocytes in involved vitiligo skin are damaged too. Based on this evidence, we evaluated the in vitro behaviour, in life span cultures, of involved and uninvolved vitiligo keratinocytes and their expression of proliferation, differentiation and senescence markers. An additional purpose was to investigate whether vitiligo keratinocytes from depigmented skin are able to sustain survival and growth of normal melanocytes (when added in co-culture experiments), as normal human keratinocytes manage to do. Our results demonstrate that almost all involved vitiligo keratinocytes have a shorter life span in vitro than the uninvolved cells and all of them do not maintain melanocytes in culture in a physiological ratio. Modification of proliferation and senescence marker expression also occurs. Indeed, we detected low initial expression levels of the senescence marker p16 in involved vitiligo keratinocytes, despite their shorter in vitro life span, and increased expression of proliferating cell nuclear antigen and p53. This preliminary analysis of a small number of in vitro cultured vitiligo keratinocytes suggests an impaired senescence process in lesional vitiligo keratinocytes and attempts to regulate it.

Inflammatory Changes in Vitiligo

Frequent failure of early studies to demonstrate inflammatory changes in vitiligo led many investigators to consider the disease as noninflammatory. However, others found an inflammatory element in vitiliginous lesions. In this study we tried to verify that assumption. Twenty-five patients (10 males and 15 females) with common vitiligo and 11 normal healthy individuals were included. Histopathologic studies were carried out using epon-embedded sections stained with modified toluidine blue stain. Comparisons of the results of histopathologic examination of the stained specimens of vitiliginous lesions (both stage I and II), marginal areas, and uninvolved normal skin of vitiligo patients with normal healthy control were performed. Focal spongiosis was observed in 48% of the specimens of vitiligo patients and largely limited to the marginal areas and stage I vitiligo lesions. Epidermal mononuclear cell infiltration was seen in 80% of both the marginal areas and stage I vitiligo specimens. The number of these cells was significantly higher than that in stage II lesions and uninvolved skin. Many of the epidermotropic lymphocytes were grouped together, forming clusters resembling Pautrier microabscesses. The extent of epidermal mononuclear cell invasion did not always parallel the density of the subjacent dermal infiltrate. Vitiligo is an inflammatory disease, and the epidermal lymphocytic infiltration is most likely the primary immunologic event.

Eumelanin and phaeomelanin contents of depigmented and repigmented skin in vitiligo patients

BACKGROUND

There are two chemically distinct types of melanin: the red-yellow phaeomelanin and the brown-black eumelanin. Both types of melanin have been detected in human hair, epidermis and cultured melanocytes.

OBJECTIVES

In a preliminary study, to quantify levels of both eumelanin and phaeomelanin in depigmented as well as repigmented patches of vitiligo following psoralen plus ultraviolet A (PUVA) therapy.

METHODS

We enrolled five patients with vitiligo for this study. We took biopsies from depigmented as well as repigmented lesions after PUVA therapy. The eumelanin and phaeomelanin contents of the skin biopsies were quantified by high-performance liquid chromatography.

RESULTS

The mean concentrations in depigmented lesions were 229.4 ng per piece for phaeomelanin and 572 ng per piece for eumelanin (mean phaeomelanin/eumelanin ratio 0.36). In repigmented lesions, the mean concentration of phaeomelanin was 74.8 ng per piece and that of eumelanin was 1657.6 ng per piece (mean phaeomelanin/eumelanin ratio 0.049).

CONCLUSIONS

Depigmented lesions showed both types of melanin, and contained a substantial amount of phaeomelanin, whereas repigmented lesions after PUVA showed predominantly eumelanin. We detected melanin in depigmented lesions of vitiligo of 5 years duration, suggesting that some residual melanocytes are still active in depigmented lesions.

Evidence for an autoimmune pathogenesis of vitiligo

Vitiligo is a depigmenting disorder characterized by the development of white patches in various distributions, which are due to the loss of melanocytes from the epidermis. A variety of arguments from clinical observations to research findings in human and animal models support the hypothesis of autoimmunity and are reviewed in this article. The association with autoimmune diseases and organ-specific autoantibodies is well known. Various effective treatment options have an immunosuppressive effect. Today the autoimmune pathogenesis of the disease has become a rapidly evolving field of research. Detection of circulating melanocyte antibodies in human and animal models implicates a possible role of humoral immunity. Histological and immunohistochemical studies in perilesional skin suggest the involvement of cellular immunity in vitiligo. Recently, T-cell analyses in peripheral blood further support this hypothesis. Interestingly, new insights in the association of vitiligo and melanoma may help to clarify the role of autoimmunity in the development of vitiligo.

Ultrastructural studies in stable vitiligo

Vitiligo is a disease of melanocytes characterized by achromic lesions in the skin, affecting the epidermis and the pilosebaceous follicle. We performed an ultrastructural analysis of biopsy specimens from four patients with noninflammatory, stable vitiligo of long duration (three had generalized vitiligo and one had segmental vitiligo). The samples were taken from the oldest achromic lesions, and the biopsy sites were far from normal skin. In all cases we noted alterations in keratinocytes, Langerhans cells, and melanocytes. We also found lymphocytes in the epidermis, and these cells and macrophages were noted in the dermis. The basal membrane disappeared at some points, and sometimes it was possible to see dermal cells with processes that engulfed either granular material or vesicles of epidermal origin in such areas. Our studies suggest that even in stable vitiligo, achromia implies intense cytologic activity, probably involving cell-mediated cytotoxicity, and ultrastructural findings resemble those of a lichenoid reaction.

Melanocyte detachment after skin friction in non lesional skin of patients with generalized vitiligo

BACKGROUND

In vitiligo, melanocytes are gradually lost in depigmented macules of the skin. The disappearance of melanocytes has, however, not been clearly observed and consequently the aetiology of the disease (autoimmune, neural, cytotoxic) is still elusive. The starting point of vitiligo macules is frequently determined by local conditions such as wounds and excoriations, but may also follow minor traumas such as pressure or repeated friction. This prominent feature is often neglected.

OBJECTIVES

To clarify the biological consequences of repeated friction on the attachment and survival of melanocytes in non lesional vitiligo skin.

METHODS

Light reproducible skin friction was performed for 4 min on the volar forearm of 18 patients with extensive vitiligo and five controls with normal healthy skin. Biopsies from the test area and control skin were taken at 1, 4, 24 and 48 h following friction. Serial sections were examined with standard light microscopy, transmission electron microscopy, histochemistry and immunohistochemistry (dihydroxyphenylalanine, HMB-45, E-cadherin and an early apoptosis marker, M30 cytoDEATH antibody).

RESULTS

The observation of sections at 1 and 48 h after friction on vitiligo skin and at all time points in controls revealed no changes. In contrast, in vitiligo skin at 4 and 24 h after friction, several melanocytes had undergone detachment and were found in various suprabasal positions, including the stratum spinosum, granular layer, and within and outside the stratum corneum.

CONCLUSIONS

Detachment and transepidermal elimination of melanocytes following minor mechanical trauma in non lesional vitiligo skin is probably the cause of depigmentation occurring in the isomorphic response (Koebner phenomenon). We propose that transepidermal elimination of melanocytes in vitiligo should be regarded as a possible mechanism of chronic loss of pigment cells, perhaps previously damaged by another process.

Melanocytes are not absent in lesional skin of long duration vitiligo

This paper provides evidence that melanocytes are still present in the depigmented epidermis of patients with vitiligo even after stable disease of 25 years' duration. Melanocyte cultures were successfully established from depigmented epidermal suction blister tissue of all 12 randomly selected patients and these cells produced melanin. Even under in vitro conditions, vacuolation of melanocytes was demonstrated in five patients with active disease, which was reversible upon exogenous addition of bovine catalase to the culture medium. Full skin biopsies from 17 patients with vitiligo, obtained from depigmented and normally pigmented areas, confirmed the involvement of melanocytes, keratinocytes, and Langerhans cells in this disorder. In addition, the presence of clustered and single pre-melanosomes in basal and supra-basal keratinocytes of lesional and normal epidermis, as well as the retention of single melanocytes in lesional epidermis, was demonstrated by light and electron microscopy. Upon topical application of a narrow band UVB-activated pseudocatalase, vacuolation, granulation, and dilatation of the endoplasmic reticulum completely recovered, but the ectopic pre-melanosome shedding remained. Taken together, these observations indicate that melanocytes are never completely absent in the depigmented epidermis and that these melanocytes can recover their functionality in vivo and in vitro upon the removal of hydrogen peroxide. Furthermore, this study supports the concept that vitiligo involves the entire epidermal unit in both depigmented and 'normal' pigmented skin.

Clinical and histopathologic characteristics of trichrome vitiligo

BACKGROUND

The term trichrome vitiligo describes lesions that have a tan zone of varying width between normal and totally depigmented skin, which exhibits an intermediate hue. However, the pathogenesis and the histopathologic characteristics of trichrome vitiligo are unknown.

OBJECTIVE

Our purpose was to investigate the clinical and histopathologic characteristics and the pathogenesis of trichrome vitiligo.

METHODS

Four punch biopsy specimens were taken from 21 patients with trichrome vitiligo; they were from vitiliginous skin, light brown skin, perilesional normal skin, and normal skin as far as 5 cm from the nearest vitiligo spot. The sections were stained with hematoxylin-eosin; in selected cases, we performed immunohistochemical staining with S-100 protein and CD1a.

RESULTS

Trichrome vitiligo occurred most frequently on the trunk in active vitiligo vulgaris. Focal vacuolar degeneration of the basal cell layer and mild inflammatory cell infiltration of the epidermis and dermis were more prominent in light brown skin and perilesional normal skin than in vitiliginous skin and normal skin. The number of melanocytes was decreased in light brown skin compared with perilesional normal skin (P <.05) and in vitiliginous skin compared with light brown skin (P <.05); a few melanocytes were observed even in skin affected by trichrome vitiligo. The number of Langerhans cells was increased in the epidermis of light brown skin and perilesional normal skin compared with vitiliginous and normal skin (P <.05). PUVA therapy yielded excellent repigmentation.

CONCLUSION

Trichrome vitiligo is a variant of active vitiligo. The changes of melanocytes, keratinocytes, and Langerhans cells may be involved in the pathogenesis of depigmentation in trichrome vitiligo.

Vitiligo coexistent with nevus depigmentosus

A 45-year-old Korean man had two distinct types of hypopigmented lesions on the forehead and back: vitiligo and nevus depigmentosus (ND). The hypopigmented macules on the forehead were incidentally discovered 15 days previously and responded well to steroid therapy. The hypopigmented macule on the back had been present since birth, was stable in size, and showed no response to steroid therapy. There were no remarkable differences between the two lesions in routine histopathology or Fontana-Masson staining. However, the lesion on the back was shown to contain melanocytes in electron microscopy (EM).

Absence of Merkel cells in lesional skin of vitiligo [corrected]

BACKGROUND

In vitiligo, other than loss of melanocytes and melanin pigment in the lesional skin, keratinocytes are also involved. Human fetal Merkel cells are now generally considered to be derived from the epidermis. To date, no observations on Merkel cells in lesional skin of active vitiligo have been reported.

METHODS

Merkel cells were identified by indirect immunofluorescence microscopy using the monoclonal antibody TROMA 1.

RESULTS

No TROMA 1-positive cells were observed in the vitiliginous skin lesions in any of the specimens examined, whereas normal numbers of these cells were seen in the adjacent pigmented skin.

CONCLUSIONS

This finding suggests that the processes that lead to damage of keratinocytes in vitiligo also involve other keratin-expressing cells such as the Merkel cells.

Generalized vitiligo preceded by a generalized figurate erythematosquamous eruption

The pathogenesis of vitiligo is still unknown. We saw a patient with vitiligo who may support an immunological pathogenesis for this disease. A 77-year-old man developed sharply demarcated, irregularly shaped, figurate, erythematosquamous plaques on most of the areas of his body. Histologically, lymphocytic cells invaded the lower epidermis. The lesions were gradually replaced by vitiliginous macules of the same configuration. Histologically, there were no active melanocytes in the vitiliginous lesions. We believe that the present patient presents an extraordinary example of inflammatory vitiligo and may provide an indication of an immunological pathogenesis for vitiligo.

Focal gaps in the basement membrane of involved and uninvolved skin of vitiligo: are they normal?

It has been suggested that, in vitiligo, the structural abnormalities may not be restricted to melanocytes alone, but also to keratinocytes of involved and uninvolved skin. Focal gaps in the vitiligo epidermal basement membrane have been furthermore interpreted as evidence of extramelanocyte alterations. To understand the occurrence of the gaps we undertook a study to establish which cells are related to them. Immunofluorescence and immunoperoxidase techniques were used to visualize, in involved, uninvolved, and control skin, the basement membrane, melanocytes, and Merkel cells. Double staining was performed with fluorescein-coupled anti-collagen IV antibodies and rhodamin-coupled antibodies against Nicein (GB3), a hemidesmosome component. Propidium iodide staining was used to detect infiltrating lymphocytes. The basement membrane structure was always found to be intact and unaltered. Absence of staining in areas of uninvolved skin was related to the presence of Merkel cells, melanocytes, and infiltrating lymphocytes. Gaps in the epidermal basement membrane are thus due to lack of staining caused by the presence of immigrant cells.

The change of melanocyte cytotoxicity after systemic steroid treatment in vitiligo patients

Although there is evidence of a strong association between antimelanocyte autoantibodies and vitiligo, the etiology of vitiligo is still unclear. To elucidate the biological significance of antimelanocyte autoantibodies in vitiligo, we measured the percent cytotoxicity of melanocyte mediated by autoantibody and complement in normal controls (n = 31) and in the patients with active, progressive vitiligo (n = 37). Significant differences in percent cytotoxicity of melanocyte were seen between the control and vitiligo groups (P = 0.0001). There were no significant differences in the percent cytotoxicity of melanocyte between the patients (n = 24) with more than 1 year duration and those (n = 13) with less than 1 year duration. The change of percent cytotoxicity between pre- and post-treatment groups (n = 29) with systemic steroid showed significant differences (P = 0.0243). These findings support the hypothesis that a decrease in the antibody-mediated cytotoxicity against melanocytes may play a role in the improvement of vitiliginous lesions after systemic steroid treatment.

Cytolytic antibodies to melanocytes in vitiligo

Patients with vitiligo have been found to have circulating antibodies to pigment cells. To evaluate the functional activity of these antibodies, a highly sensitive europium release assay was used to compare complement-mediated cytolysis of human melanocytes by sera of 56 patients with vitiligo (20 with active disease, 25 with inactive disease, 11 with unidentified disease activity) and 47 control individuals. Significant melanocyte lysis was mediated by 32 (57%) of the patients with vitiligo but by only three (6%) of the control sera (p < 0.001), and by 17 (85%) of 20 patients with active vitiligo versus 11 (44%) of 25 patients with inactive disease (p < 0.025). Mean melanocyte lysis by vitiligo sera was 24% versus 6% by control sera (p < 0.0001). A subset of 12 vitiligo sera with high titers of cytolytic antibodies to melanocytes (34% mean cytolysis) reacted minimally (< 2% mean cytolysis) to a panel of control cells that included human and murine melanomas, human fibroblasts, lung carcinoma, and rhabdomyosarcoma. These findings indicate that antibodies present in patients with vitiligo have the functional ability to selectively kill melanocytes and are more common in active disease. These observations support, but do not prove, the hypothesis that vitiligo is an autoimmune disease and that anti-pigment cell antibodies have a role in inducing the disease.

Peripheral blood lymphocyte imbalance in Koreans with active vitiligo

BACKGROUND

An immune-mediated destruction of melanocytes is the most popular current theory of vitiligo. There have been a few published reports on the assessment of lymphocyte population in vitiligo, and they showed mixed results. The purpose of our investigation was to assess peripheral lymphocyte subpopulations in Koreans with actively spreading vitiligo.

METHODS

Fifty patients with actively spreading vitiligo and 30 normal persons were studied for peripheral blood lymphocyte imbalance using flow cytometry. The percentages of total T-lymphocytes, B-lymphocytes, helper T cells, suppressor T cells, and natural killer cells were evaluated with the use of CD3, CD19, CD4, CD8, and CD16 monoclonal antibodies, respectively.

RESULTS

The mean value of helper T cells showed a significant difference between the two groups with the value being 38.2% in patients and 43.5% in control subjects. Seventeen of the 50 patients showed reversed helper/suppressor T cell ratio, whereas only 1 of 30 control subjects showed reversed ratio. There was a statistically significant difference in the mean percentage of helper T cells and suppressor T cells between generalized vitiligo patients and control subjects. The percentage of B cells in patients with recent onset less than 1 year was higher than control subjects and patients with late onset. The mean percentage of natural killer cells was increased significantly in patients with negative autoantibody test.

CONCLUSIONS

The present data show that immunologic abnormalities, both cellular and humoral, are involved in the pathogenesis of vitiligo.

Vitiligo: where do we stand?

Vitiligo is a puzzling disorder characterized by a disappearance of epidermal and/or follicular melanocytes by unknown mechanisms. This very common disorder involving 1-4% of the world population is thus of great importance for the practicing dermatologist. The cellular and molecular mechanisms leading to the destruction of melanocytes in this disorder have not yet been elucidated, making it of major interest for the cell biologist involved in melanocyte research. Recent advances in this field, due largely to the availability of techniques for culturing normal human melanocytes, opened new perspectives in the understanding of vitiligo. Although vitiligo has long been considered a disorder confined to the skin, there is now good evidence that it also involves the extracutaneous compartment of the "melanocyte organ." It is also clear that vitiligo is not only a melanocyte disorder, but that it also involves cells, such as keratinocytes and Langerhans cells, found in the epidermis and follicular epithelium. The three prevailing theories of the pathogenesis of vitiligo are the immune hypothesis, the neural hypothesis, and the self-destruct hypothesis. New hypotheses suggest that vitiligo may be due to (1) a deficiency in an unidentified melanocyte growth factor, (2) an intrinsic defect of the structure and function of the rough endoplasmic reticulum in vitiligo melanocytes, (3) abnormalities in a putative melatonin receptor on melanocytes and (4) a breakdown in free radical defense in the epidermis. None of these hypotheses has been demonstrated, and according to the available data, it is likely that the loss of epidermal and follicular melanocytes in vitiligo may be the result of several different pathogenetic mechanisms.