Evaluation of Melanocytes and T-cells in Vitiliginous Skin Pre- and Post-Narrow-Band UVB Phototherapy

BACKGROUND: Vitiligo is an autoimmune disorder characterized by the destruction of epidermal melanocytes, leading to white lesions devoid of pigmentation. The destruction of epidermal melanocytes is driven by tissue-resident and circulating immune cells that maintain an inflammatory milieu. Two percent of the global population suffers from vitiligo, with a higher prevalence reported in the Indian population. Narrow-band UV-B (NBUVB) phototherapy is commonly used as an economical, non-invasive, and well-tolerated treatment modality. NBUVB promotes the migration of melanocyte stem cells (MelSC) to the epidermis, thus restoring pigmentation in affected individuals. AIMS AND OBJECTIVES: This study aimed to investigate the histological and gene expression changes in Indian vitiligo patients pre- and post-NBUVB phototherapy. PATIENTS AND METHODS: Indian patients with stable vitiligo underwent NBUVB monotherapy, administered thrice weekly for three months, to induce repigmentation. Single 3 mm skin biopsies were taken from vitiligo lesions pre- and post-NBUVB phototherapy for histopathological and gene expression analysis. A contralateral pigmented region was considered as the control skin from the same patient. RESULTS: Following NBUVB monotherapy, melanocytes were restored in the epidermis of vitiligo patients and produced melanin pigment. The mean area of pigmentation post-NBUVB therapy was 2.94% ± 0.97%, compared to 0.11% ± 0.19% in vitiligo lesions before NBUVB therapy. Following NBUVB phototherapy, melanocytes migrating from the hair bulge upregulated key genes in melanocyte differentiation (PAX3) and melanogenesis (KIT, TYR, DCT/TRP2). In addition to the favorable clinical outcome of repigmentation, NBUVB was effective in reducing the skin T-cells, indicating successful immunosuppression. LIMITATIONS: The major limitation of our study was the limited sample size of our patient cohort. CONCLUSIONS: Our study reaffirms the therapeutic efficacy of NBUVB in promoting repigmentation in an Indian cohort of vitiligo patients. Furthermore, NBUVB is effective in reducing CD3+ skin-resident T-cells, widely considered a major contributor to the pathogenesis of the disease.