From mice to men: An assessment of preclinical model systems for the study of vitiligo.

Vitiligo is an autoimmune skin disease of multiple etiology, for which there is no complete cure. This chronic depigmentation is characterized by epidermal melanocyte loss, and causes disfigurement and significant psychosocial distress. Mouse models have been extensively employed to further our understanding of complex disease mechanisms in vitiligo, as well as to provide a preclinical platform for clinical interventional research on potential treatment strategies in humans. The current mouse models can be categorized into three groups: spontaneous mouse models, induced mouse models, and transgenic mice. Despite their limitations, these models allow us to understand the pathology processes of vitiligo at molecule, cell, tissue, organ, and system levels, and have been used to test prospective drugs. In this review, we comprehensively evaluate existing murine systems of vitiligo and elucidate their respective characteristics, aiming to offer a panorama for researchers to select the appropriate mouse models for their study.

Large-scale functional network connectivity mediates the association between nigral neuromelanin hypopigmentation and motor impairment in Parkinson's disease.

Neuromelanin hypopigmentation within substantia nigra pars compacta (SNc) reflects the loss of pigmented neurons, which in turn contributes to the dysfunction of the nigrostriatal and striato-cortical pathways in Parkinson's disease (PD). Our study aims to investigate the relationships between SN degeneration manifested by neuromelanin reduction, functional connectivity (FC) among large-scale brain networks, and motor impairment in PD. This study included 68 idiopathic PD patients and 32 age-, sex- and education level-matched healthy controls who underwent neuromelanin-sensitive magnetic resonance imaging (MRI), functional MRI, and motor assessments. SN integrity was measured using the subregional contrast-to-noise ratio calculated from neuromelanin-sensitive MRI. Resting-state FC maps were obtained based on the independent component analysis. Subsequently, we performed partial correlation and mediation analyses in SN degeneration, network disruption, and motor impairment for PD patients. We found significantly decreased neuromelanin within SN and widely altered inter-network FCs, mainly involved in the basal ganglia (BG), sensorimotor and frontoparietal networks in PD. In addition, decreased neuromelanin content was negatively correlated with the dorsal sensorimotor network (dSMN)-medial visual network connection (P = 0.012) and dSMN-BG connection (P = 0.004). Importantly, the effect of SN neuromelanin hypopigmentation on motor symptom severity in PD is partially mediated by the increased connectivity strength between BG and dSMN (indirect effect = - 1.358, 95% CI: - 2.997, - 0.147). Our results advanced our understanding of the interactions between neuromelanin hypopigmentation in SN and altered FCs of functional networks in PD and suggested the potential of multimodal metrics for early diagnosis and monitoring the response to therapies.

Associations of 24-Hour Rest-Activity Rhythm Fragmentation, Cognitive Decline, and Postmortem Locus Coeruleus Hypopigmentation in Alzheimer's Disease.

OBJECTIVE: While studies suggested that locus coeruleus (LC) neurodegeneration contributes to sleep-wake dysregulation in Alzheimer's disease (AD), the association between LC integrity and circadian rest-activity patterns remains unknown. Here, we investigated the relationships between 24-hour rest-activity rhythms, cognitive trajectories, and autopsy-derived LC integrity in older adults with and without cortical AD neuropathology. METHODS: This retrospective study leveraged multi-modal data from participants of the longitudinal clinical-pathological Rush Memory and Aging Project. Indices of 24-hour rest-activity rhythm fragmentation (intradaily variability) and stability (interdaily stability) were extracted from annual actigraphic recordings, and cognitive trajectories were computed from annual cognitive evaluations. At autopsy, LC neurodegeneration was determined by the presence of hypopigmentation, and cortical AD neuropathology was assessed. Contributions of comorbid pathologies (Lewy bodies, cerebrovascular pathology) were evaluated. RESULTS: Among the 388 cases included in the study sample (age at death = 92.1 ± 5.9 years; 273 women), 98 (25.3%) displayed LC hypopigmentation, and 251 (64.7%) exhibited cortical AD neuropathology. Logistic regression models showed that higher rest-activity rhythm fragmentation, measured up to ~7.1 years before death, was associated with increased risk to display LC neurodegeneration at autopsy (odds ratio [OR] = 1.46, 95% confidence interval [CI95%]: 1.16-1.84, pBONF = 0.004), particularly in individuals with cortical AD neuropathology (OR = 1.56, CI95%: 1.15-2.15, pBONF = 0.03) and independently of comorbid pathologies. In addition, longitudinal increases in rest-activity rhythm fragmentation partially mediated the association between LC neurodegeneration and cognitive decline (estimate = -0.011, CI95%: -0.023--0.002, pBONF = 0.03). INTERPRETATION: These findings highlight the LC as a neurobiological correlate of sleep-wake dysregulation in AD, and further underscore the clinical relevance of monitoring rest-activity patterns for improved detection of at-risk individuals. ANN NEUROL 2024;95:653-664.

ISG15-USP18 Dysregulation by Oxidative Stress Promotes IFN-γ Secretion from CD8+ T Cells in Vitiligo.

Excessive oxidative stress is thought to play pathologic roles in cellular senescence and autoimmune disorders by inducing inflammation and breaking down immune tolerance. In this study, we sought to identify the factors linking oxidative stress to autoimmunity and cellular senescence in vitiligo, where elevated oxidative stress plays an important role. RNA sequencing analysis of hydrogen peroxide-treated melanocytes revealed upregulation of ISG15. The upregulation of ISG15 was observed in vitiligo skin tissues as well as in the blood of patients with vitiligo, whereas USP18 downregulation was observed in vitiligo melanocytes and vitiligo skin tissues. Oxidative stress induced hypermethylation of the USP18 promoter region in keratinocytes and melanocytes, and USP18 promoter hypermethylation was also confirmed in vitiligo skin tissues. Our results indicate that USP18 promoter hypermethylation caused by oxidative stress increases ISG15 expression in keratinocytes and melanocytes along with senescence changes, leading CD8+ T cells to produce IFN-γ, the main pathogenic cytokine in vitiligo. Therefore, the ISG15-USP18 network may be important in oxidative stress-induced autoimmunity and cellular senescence in vitiligo pathogenesis.

Basement membrane thickness helps to differentiate hypopigmented mycosis fungoides from clinical and pathological mimickers.

BACKGROUND: Hypopigmented mycosis fungoides (HMF) is a relatively rare subtype of mycosis fungoides (MF). The diagnosis of HMF can be quite challenging in case of insufficient diagnostic criteria due to the diverse conditions that present with hypopigmented lesions. This study aimed to evaluate the usefulness of the assessment of the basement membrane thickness (BMT) in the diagnosis of HMF. METHODS: A retrospective study was conducted on biopsy specimens of 21 HMF and 25 non-HMF cases who presented with hypopigmented lesions. The thickness of the basement membrane was evaluated in periodic acid-Schiff (PAS)-stained sections. RESULTS: The mean BMT was significantly higher in the HMF group than in the non-HMF group (P < 0.001). The best cut-off value of mean BMT for the detection of HMF verified in ROC analysis was 32.7 µm (P < 0.001) with a sensitivity of 85.7% and a specificity of 96%. CONCLUSION: Evaluation of BMT can be a useful tool to distinguish HMF from other causes of hypopigmented lesions in doubtful cases. We suggest the use of " BMT more than 33 µm" as a histopathologic criterion of HMF.

Diagnosing Disorders of Hypopigmentation and Depigmentation in Patients with Skin of Color.

Skin hypopigmentation and depigmentation disorders are a top concern for patients with skin of color seeking care from a dermatologist. The visual contrast between involved and uninvolved skin in these disorders makes them particularly burdensome for patients with skin of color. These disorders may have a wide differential of diagnosis, as patients with skin of color may present differently or more frequently than White patients for certain conditions. Clues from a comprehensive history and physical examination with standard lighting and a Wood's light are essential for clinching the diagnosis, although a biopsy may be warranted in special cases.

Efficacy and Safety of 5-Fluorouracil Tattooing to Repigment Idiopathic Guttate Hypomelanosis: A Split-Body Randomized Trial.

BACKGROUD: Idiopathic guttate hypomelanosis (IGH) is a common skin disorder with no standard treatment. OBJECTIVE: Assess the efficacy and safety of 5-fluorouracil (5FU) compared with saline, delivered using a tattoo machine, to repigment IGH lesions. METHODS: This split-body randomized single-blinded trial recruited adults with symmetrical IGH lesions. A tattoo machine was used to deliver 5FU in IGH lesions of 1 limb and saline in the contralateral limb. Outcomes were the number of achromic lesions 30 days after treatment compared with baseline, patient satisfaction, and local or systemic adverse events. RESULTS: Twenty-nine patients (28 women) were included. The median number of achromic lesions decreased significantly in 5FU-treated limbs (baseline: 32, interquartile range (IQR) 23-37 × post-treatment: 12, IQR 6-18, p = .000003) and saline-treated limbs (baseline: 31, IQR 24-43 × post-treatment: 21, IQR 16-31, p = .000006), but reduction was significantly more pronounced in 5FU-treated limbs ( p = .00003). All participants were satisfied or very satisfied with results on 5FU-treated limbs. There were no adverse events. CONCLUSION: 5-fluorouracil delivery using a tattoo machine was more effective than saline to repigment IGH lesions, with high patient satisfaction and no adverse events.Clinicaltrials.gov : NCT02904564.

Acral Speckled Hypomelanosis: A Case Report and a Review of Literature.

BACKGROUND: Acral speckled hypomelanosis is a very rare pigmentation disorder that appears early in life with hypopigmented macules on background of normal skin, occurring on the acral parts. CASE REPORT: We report a 9-year-old female patient with a 3-year duration of progressive, hypopigmented, confetti-like macules occurring symmetrically on the dorsum of both hands and feet. Biopsy showed normal number of melanocytes with no evidence of macromelanosomes using special stains for melanocytes. CONCLUSION: Acral speckled hypomelanosis is a relatively, recently, discovered entity, with only 9 cases reported to date, and our case is the 10th. The exact etiopathogenesis is not yet known.

The possible role of Wnt/ß-catenin signalling in vitiligo treatment.

Vitiligo is a common chronic skin disease which has an adverse impact on patients' life. Its pathogenesis is complex, involving autoimmunity and oxidative stress (OS). Autoimmunity leads to the loss of epidermal melanocytes and the formation of the depigmented patches of the disease. Treatment of vitiligo should control the exaggerated immune response to arrest the progress of active disease, and then promote melanocytes to repigmentation. Wnt/ß-catenin signalling pathway has been of recent interest in vitiligo. Wnt/ß-catenin signalling pathway is downregulated in vitiligo. Upregulation of Wnt/ß-catenin signalling possibly control vitiligo autoimmune response by protecting melanocyte from OS damage, inhibiting CD8+ T cell effector cell differentiation and enhancing Treg. Wnt/ß-catenin signalling plays a critical role in the melanocyte regeneration by driving the differentiation of melanocyte stem cells (McSCs) into melanocytes. Promoting Wnt/ß-catenin signalling can not only arrest the progress of active disease of vitiligo but also promote repigmentation. Some of the main effective therapies for vitiligo are likely to work by activating Wnt/ß-catenin signalling. Agents that can enhance the effect of Wnt/ß-catenin signalling may become potential candidates for the development of new drugs for vitiligo treatment.

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.

Adolescent extra-truncal progressive macular hypomelanosis.

Two adolescent females presented to outpatient clinic with isolated, non-scaly, asymptomatic hypopigmented macules and patches on the arm(s). Both cases had Wood's lamp exams notable for extralesional punctiform coral-red perifollicular fluorescence on the back and faint intralesional enhancement. In one case, biopsy was performed and deemed consistent with progressive macular hypomelanosis. The patient had complete response to antimicrobial therapy and sun exposure.

Fentanyl transdermal patches induced chemical leucoderma.

Chemical leucoderma is defined as hypopigmentation or vitiligo-like hypomelanosis caused by repeated chemical exposure, and the diagnosis can be made clinically. Chemical leucoderma induced by fentanyl transdermal patches is rare. This case report involves a 53-year-old man with chronic back pain caused by herniated nucleus pulposus at the L4-L5 level. The patient had used fentanyl transdermal patches for about 2 years. Depigmented lesions were observed in the areas where fentanyl transdermal patches had been applied. Chemical leucoderma was the most likely diagnosis. There remains a debate regarding whether there is a fentanyl dose-response relationship and whether the duration of exposure is relevant. Spontaneous repigmentation may occur after discontinuing the chemical exposure, and follow-ups are recommended to monitor whether spontaneous repigmentation occurs. Additionally, several treatment options have been proposed as specific treatments for chemical leucoderma, including psoralens, corticosteroids, calcineurin inhibitors, immunosuppressive agents and phototherapy.

Clinical Features, Histological Characteristics, and Disease Outcomes of Mycosis Fungoides in Children and Adolescents: A Nationwide Multicentre Cohort of 46 Patients.

BACKGROUND: Our objective was to describe the clinical, histological characteristics, and disease outcome of a cohort of mycosis fungoides (MF) diagnosed during childhood including disease status at adulthood. METHODS: This is a retrospective multicentre survey of patients aged under 18 years at diagnosis with histologically confirmed MF. Patients' clinical and histological characteristics, treatments, and disease outcome (for patients followed for more than 12 months) were analysed. RESULTS: Forty-six patients were included (median age at diagnosis: 11 years; M:F sex ratio: 3:1) with 39 (85%) followed for at least 12 months. Thirty-nine patients (85%) had stage I MF. Hypopigmented patches were observed in 48% and folliculotropism in 43% patients. Immunophenotype of the skin infiltrate was predominantly CD8+ in 17% of patients. Initial management included a wait-and-see strategy in 6/39 (15%), skin-directed treatment in 27 (69%), and systemic treatment in 6 (15%) patients, respectively, with partial or complete clinical response (PR or CR) observed in 28 patients (72%). 14/39 patients (36%) relapsed after initial response. After a median follow-up period of 54 months, disease status at last news was PR or CR in 31/39 (79%), stable disease in 6 (15%), and progression in 2 (5%) patients. Histological transformation was observed in 3/39 (8%). Of the 15 patients followed until adulthood, 13 (87%) had persistent MF. DISCUSSION: This survey confirms the high frequency of hypopigmented and folliculotropic lesions and of CD8+ immunophenotype compared to adult MF patients. The long-term course is usually indolent but transformation may occur sometimes long after disease onset and the disease may persist during adulthood.

Determinação da atividade antitirosinase e antioxidante de Myrsine coriacea (Sw. ) R. Br. ex Roem. & Schult. (Primulaceae) / Determination of the antityrosinase and antioxidant activity of Myrsine coriacea (Sw. ) R. Br. ex Roem. & Schult. (Primulaceae)

myrsine coriacea (Sw.) R. Br. ex Roem. & Schult. (Primulaceae) conhecida popularmente como capororoquinha ou capororoca, é amplamente distribuída nas regiões sul e sudeste do Brasil. As espécies desse gênero apresentam um potencial antioxidante e anti-inflamatório, que pode ser acessado na busca de novos ativos para o tratamento de desordens pigmentares da pele. Desta forma, este trabalho teve como objetivos avaliar o potencial antitirosinase e antioxidante de extratos e frações de M. coriacea e identificar os possíveis compostos responsáveis por essas atividades. Foram realizados ensaios para avaliar o potencial antioxidante das amostras através do método do DPPH, enquanto a capacidade hipopigmentante das amostras foi avaliado pela inibição da enzima tirosinase. Como complemento, foram determinados os teores de compostos fenólicos totais e flavonoides através dos métodos colorimétricos empregando o reagente Folin-Ciocalteau e AlCl3. Adicionalmente, os extratos de M. coriacea tiveram avaliados seus potenciais citotóxicos utilizando diferentes linhagens tumorais humanas. O perfil fitoquímico de M. coriacea foi analisado por cromatografia a gás acoplada com espectrometria de massas (CG-EM) e cromatografia em camada delgada (CCD) com padrões. Nessas análises foram identificados 34 compostos, sendo o ácido palmítico e o palmitato de etila os compostos majoritários nas amostras de M. coriacea. O extrato bruto das folhas apresentou o maior teor de fenólicos totais, enquanto a fração de acetato de etila das folhas teve o maior teor de flavonoides. Contudo, o extrato bruto dos frutos apresentou a melhor atividade antioxidante de todas as amostras analisadas, apresentando também a melhor atividade antitirosinase. Dentre os compostos anotados, mandenol, ácido -linoleico e o linolenato de etila foram os compostos considerados como possíveis inibidores da tirosinase, com boa interação molecular com a enzima nas análises de ancoragem molecular in silico. Das amostras analisadas com relação a inibição de crescimento frente as células tumorais, a amostra da fração de clorofórmio das folhas foi a que apresentou potencial antitumoral frente as células de adenocarcinoma de cólon (HCT116)

myrsine coriacea (Sw.) R. Br. ex Roem. & Schult. (Primulaceae) popularly known as capororoquinha or capororoca, is widely distributed in southern and southeastern Brazil. Myrsine species have an antioxidant and anti-inflammatory potential, which can be accessed in the search for new actives for the treatment of skin pigmentation disorders. Thus, this work aimed to evaluate the antityrosinase and antioxidant potential from extracts and fractions of M. coriacea and to identify the probable compounds responsible for these activities. Assays were performed to evaluate the antioxidant potential of the samples using the DPPH method, while the hypopigmentation capacity of the samples was evaluated by the tyrosinase inhibition. As a complement, the amounts of total phenolic compounds and flavonoids were determined through colorimetric methods using the Folin-Ciocalteau reagent and AlCl3. Additionally, M. coriacea extracts had their cytotoxic potential evaluated using different human tumor cell lines. M. coriacea phytochemical profile was obtained by gas chromatography coupled with mass spectrometry (GC-MS) and thin layer chromatography (TLC) with standards. In these analyses, 34 compounds were identified, with palmitic acid and ethyl palmitate as the major compounds in M. coriacea samples. The leaf crude extract presented the highest total phenolics contents, while the leaf ethyl acetate fraction had the highest flavonoid amounts. However, the fruit crude extract showed the best antioxidant and antityrosinase activities of all analyzed samples. Among the annotated compounds, mandenol, -linoleic acid and ethyl linolenate were the compounds considered as putative tyrosinase inhibitors, presenting good molecular interaction with the enzyme active site in the in silico molecular docking analysis. The leaf chloroform fraction was the only sample that showed an antitumor potential against colon adenocarcinoma cells (HCT116)

Current Debates on Etiopathogenesis and Treatment Strategies for Vitiligo.

Vitiligo is an acquired, chronic, and progressive depigmentation or hypopigmentation characterized by the destruction of melanocytes and the occurrence of white patches or macules in the skin, mucosal surface of eyes, and ears. Melanocytes are the melanin pigment-producing cells of the skin which are destroyed in pathological conditions called vitiligo. Approximately 0.5 - 2.0% of the population is suffering from vitiligo, and a higher prevalence rate of up to 8.8% has been reported in India. It is caused by various pathogenic factors like genetic predisposition, hyperimmune activation, increased oxidative stress, and alteration in neuropeptides level. Genetic research has revealed a multi- genetic inheritance that exhibits an overlap with other autoimmune disorders. However, melanocytes specific genes are also affected (such as DDR1, XBP1, NLRP1, PTPN22, COMT, FOXP3, ACE, APE, GSTP1, TLR, SOD, and CTLA-4). A number of therapeutic options are employed for the treatment of vitiligo. The topical corticosteroids and immunomodulators are currently in practice for the management of vitiligo. Phototherapies alone and in combinations with other approaches are used in those patients who do not respond to the topical treatment. The main focus of this review is on the etiopathological factors, pharmacological management (phototherapy, topical, systemic, and surgical therapy), and herbal drugs used to treat vitiligo.

Unveiling idiopathic guttate hypomelanosis: pathology, immunohistochemistry, and ultrastructural study.

BACKGROUND: Idiopathic guttate hypomelanosis (IGH) is a pigment disorder of unknown etiology. Despite its high prevalence and the unaesthetic appearance of the lesions, there are relatively few histological studies on this disorder. This is an important gap to understanding its pathogenesis. OBJECTIVES: To assess the microscopic structure of IGH lesions compared to normal adjacent skin areas and the possible interaction between melanocytes and the subjacent dermis. METHODS: In this cross-sectional study, we took biopsy specimens of hypochromic lesions and adjacent normal skin from 20 patients with IGH. We analyzed the fragments using routine stains, immunohistochemistry, and electron microscopy. RESULTS: We found superficial dermal fibrosis in 90% (18/20) of our IGH cases and unreported keratinocyte cytoplasmic changes on electron microscopy. CONCLUSION: Our results suggest an interaction between melanocytes and the subjacent dermis in IGH. These findings can help to understand melanocyte biology and the pathogenesis of other achromic lesions.

A novel pathogenic RHOA variant in a patient with patterned cutaneous hypopigmentation associated with extracutaneous findings.

RHOA-related neuroectodermal syndrome is characterised by linear skin hypopigmentation along Blaschko's lines associated with alopecia, leukoencephalopathy, facial and limb hypoplasia, and ocular, dental, and acral anomalies. Herein, we report a patient with patterned cutaneous hypopigmentation with a similar phenotype due to a novel postzygotic RHOA variant (c.210G>T; p.Arg70Ser). This illustrates that the complexity of the orchestration of morphogenesis and organogenesis can be affected by different variants in the same gene.