Evaluation of ex vivo melanogenic response to UVB, UVA, and visible light in facial melasma and unaffected adjacent skin
Giovana Piteri Alcântara, Ana Cláudia Cavalcante Espósito, Thainá Oliveira Felicio Olivatti, Melissa Mari Yoshida, Hélio Amante Miot
Abstract
BACKGROUND: The independent role of solar radiation in the differential melanogenesis between melasma and adjacent skin is unknown. OBJECTIVES: To assess the melanogenic responses of skin with facial melasma and of the adjacent skin to UVB, UVA, and visible light, in an ex vivo model. METHODS: , respectively. Subsequently, all samples were kept for 72 hours in a dark environment and stained by Fontana-Masson to assess basal layer pigmentation, dendrites, and melanin granulation. RESULTS: Effective melanogenesis was observed in the basal layer in melasma and in the normal adjacent skin after all irradiations (p < 0.01), with the following median increment: UVB (4.7% vs. 8.5%), UVA (9.5% vs. 9.9%), and visible light (6.8% vs. 11.7%), with no significant difference between anatomical sites. An increase in melanin granulation (coarser melanosomes) was observed only after irradiation with UVA and only in the skin with melasma (p = 0.05). An increase in the melanocyte dendrite count induced by UVB radiation was observed in both anatomical sites (p ≤ 0.05). STUDY LIMITATIONS: Use of an ex vivo model, with independent irradiation regimes for UVB, UVA, and visible light. CONCLUSIONS: Melanogenesis induced by UVB, UVA, and visible light was observed both in melasma and in the adjacent skin. The morphological patterns suggest that different irradiations promote individualized responses on the skin with melasma.