Investigating ruxolitinib's anti-inflammatory and pigmentation-promoting properties in vitiligo skin ex vivo

Summary: Abstract Body: Vitiligo is a multifactorial autoimmune skin disorder characterized by skin depigmentation due to melanocyte loss. The limitation of available treatment options demands models to explore vitiligo patho-mechanisms and test therapies. This study aimed at assessing the suitability of an optimized vitiligo skin organ culture model for preclinical drug evaluation, while mechanistically evaluating the impact of Ruxolitinib (Ruxo), an FDA-approved JAK1/JAK2 inhibitor. Biopsies from (peri-)lesional (marginal biopsy) and non-lesional skin of vitiligo patients were either freshly embedded for immunofluorescence staining or cultured ex vivo with or without Ruxo for 24h (RNA-Seq) or 96h (immunostaining). (Peri-)lesional samples showed reduced melanin content, immature (SOX10+) and mature (GP100+) melanocyte numbers, and increased pathogenic (CD3+NKG2D+) and memory T cell numbers (CD3+CD69+CD103-, CD3+CD69+CD103+) compared to non-lesional skin. These findings indicate that the selected (peri-)lesional biopsy sites are ideal to evaluate the characteristic diseased phenotype. Ruxo-treated samples exhibited elevated melanin content, increased percentages and reduced apoptosis of mature/immature melanocytes (MITF+/caspase 3+), and significantly or tendentially fewer CD3+CD69+ or CD3+CD69+CD103+ memory T-cells, respectively, in the epidermis, compared to vehicle controls. Furthermore, Ruxo decreased pro-inflammatory gene expression of, for instance type I interferon signalling and pro-inflammatory chemo- and cytokines. Ruxo also upregulated genes associated with melanocyte biology, indicating promotion of skin re-pigmentation. This ex vivo model highlights the effectiveness of Ruxo in restoring pigmentation and reducing inflammation, which is in concordance with clinical observations, and also reveals preventive changes of Ruxo in non-lesional skin. Therefore, it provides a valuable platform for studying vitiligo pathobiology and to advance therapeutic development. Thomas Rouille¹, Joana Vioal-Söhnlein¹, Karin I. Pappelbaum¹, Markus Fehrholz¹, Ilaria Piccini¹, Janin Edelkamp¹, Marta Bertolini¹ 1. QIMA Life Sciences, QIMA Monasterium, Münster, Germany. Pigmentation, Melanoma, and Melanoma Immune Surveillance