Vitiligo and the melanocyte reservoir

Abstract

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.

Melanocyte-specific CD8+ T cells are associated with epidermal depigmentation in a novel mouse model of vitiligo

“…This is an important issue in terms of skin repigmentation. Hair follicle melanocytes are known to provide a resource for regeneration of epidermal melanocytes and eventual repigmentation of skin [15,16]. Therefore, our vitiligo model can be used to study repigmentation mechanisms and drug development for repigmentation of vitiligo lesions.…”

Differentiated melanocyte cell division occurs in vivo and is promoted by mutations in Mitf

“…In humans, a small percentage of melanocytes appear to divide in skin homeostasis (Jimbow et al, 1975) and differentiated melanocytes may contribute to re-pigmentation in wound-healing and vitiligo, although the primary melanocyte reservoir is thought to be from undifferentiated melanocytes (Cui et al, 1991;Falabella, 2009;Falabella and Barona, 2009;Hirobe, 1988;Tanimura et al, 2011). Many aggressive melanomas, including BRAF V600E melanomas, maintain differentiation characteristics in situ (Broekaert et al, 2010;Ohsie et al, 2008).…”

Efeitos da aplicação do L.A.S.E.R. HeNe e do ultravioleta B no vitiligo

“…No vitiligo, é provável que o mecanismo de repigmentação com UVB esteja relacionado à produção de mediadores in lamatórios na pele, que estimulam a migração e a proliferação dos melanócitos (19,22,23,24 Para que a repigmentação ocorra por estimulação, os melanócitos devem estar presentes em número adequado. É de especial importância enfatizar que os folículos pilosos estão ausentes nas palmas das mãos, nas plantas dos pés, nas mucosas ou semimucosas, e, portanto, essas áreas tornam-se particularmente refratárias a todas as terapias, pois o reservatório de melanócitos está faltando; no entanto, um padrão de repigmentação difuso é frequentemente observado (13,20).…”

“…Independentemente do mecanismo, (I) queratinócitos, (II) ibroblastos, melanoblastos (III) e melanócitos (IV) podem todos ser envolvidos na repigmentação do processo de vitiligo (5). A repigmentação depende de melanócitos disponíveis a partir de três fontes possíveis: da unidade do folículo piloso, que é o principal fornecedor de células de pigmento; da borda das lesões de vitiligo; e dos melanócitos nas zonas afetadas despigmentadas (13).…”