Isolating RNA from precursor and mature melanocytes from human vitiligo and normal skin using laser capture microdissection

Combination of 308-nm excimer laser and piperine promotes melanocyte proliferation, migration, and melanin content production via the miR-328/SFRP1 axis

OBJECTIVE

Both piperine and a 308-nm excimer laser have significant curative effects on vitiligo. This study mainly explored the molecular mechanism of a 308-nm excimer combined with piperine in regulating melanocyte proliferation.

METHODS

Epidermal melanocytes were cultured in piperine solution, and the cells were irradiated by an XTRAC excimer laser treatment system at 308-nm output monochromatic light. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were for detecting the expression levels of genes or proteins. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and Transwell method was for assessing cell viability and migration capacity. The content of melanin was also detected.

RESULTS

The combination of the 308-nm excimer laser and piperine enhanced the cell proliferation, migration, and melanin production of melanocytes and upregulated the level of miR-328, and restraint of miR-328 reversed the influence of the 308-nm excimer laser and piperine. Secreted frizzled-related protein 1 (SFRP1) is a direct target gene of miR-328, and miR-328 can inhibit the expression of SFRP1 and elevate the protein level of the Wnt/β-catenin signaling pathway.

CONCLUSION

The 308-nm excimer laser combined with piperine may be more efficient than piperine alone in the remedy of vitiligo, and the miR-328/SFRP1 and Wnt/β-catenin pathways are participated in the proliferation, migration, and melanin synthesis of melanocytes.

Human Endogenous Retrovirus K Rec forms a Regulatory Loop with MITF that Opposes the Progression of Melanoma to an Invasive Stage

The HML2 subfamily of HERV-K (henceforth HERV-K) represents the most recently endogenized retrovirus in the human genome. While the products of certain HERV-K genomic copies are expressed in normal tissues, they are upregulated in several pathological conditions, including various tumors. It remains unclear whether HERV-K(HML2)-encoded products overexpressed in cancer contribute to disease progression or are merely by-products of tumorigenesis. Here, we focus on the regulatory activities of the Long Terminal Repeats (LTR5_Hs) of HERV-K and the potential role of the HERV-K-encoded Rec in melanoma. Our regulatory genomics analysis of LTR5_Hs loci indicates that Melanocyte Inducing Transcription Factor (MITF) (also known as binds to a canonical E-box motif (CA(C/T)GTG) within these elements in proliferative type of melanoma, and that depletion of MITF results in reduced HERV-K expression. In turn, experimentally depleting Rec in a proliferative melanoma cell line leads to lower mRNA levels of MITF and its predicted target genes. Furthermore, Rec knockdown leads to an upregulation of epithelial-to-mesenchymal associated genes and an enhanced invasion phenotype of proliferative melanoma cells. Together these results suggest the existence of a regulatory loop between MITF and Rec that may modulate the transition from proliferative to invasive stages of melanoma. Because HERV-K(HML2) elements are restricted to hominoid primates, these findings might explain certain species-specific features of melanoma progression and point to some limitations of animal models in melanoma studies.

Melanocyte Precursors in the Hair Follicle Bulge of Repigmented Vitiligo Skin Are Controlled by RHO-GTPase, KCTD10, and CTNNB1 Signaling

In repigmentation of human vitiligo, the melanocyte (MC) precursors in the hair follicle bulge proliferate, migrate, and differentiate to repopulate the depigmented epidermis. Here, we present a comprehensive characterization of pathways and signals in the bulge that control the repigmentation process. Using biopsies from patients with vitiligo, we have selectively harvested, by laser capture microdissection, MC and keratinocyte precursors from the hair follicle bulge of untreated vitiligo skin and vitiligo skin treated with narrow-band UVB. The captured material was subjected to whole transcriptome RNA-sequencing. With this strategy, we found that repigmentation in the bulge MC precursors is driven by KCTD10, a signal with unknown roles in the skin, and CTNNB1 (encoding β-catenin) and RHO guanosine triphosphatase [RHO GTPase, RHO], two signaling pathways previously shown to be involved in pigmentation biology. Knockdown studies in cultured human MCs of RHOJ, the upmost differentially expressed RHO family component, corroborated with our findings in patients with vitiligo, identified RHOJ involvement in UV response and melanization, and confirmed previously identified roles in melanocytic cell migration and apoptosis. A better understanding of mechanisms that govern repigmentation in MC precursors will enable the discovery of molecules that induce robust repigmentation phenotypes in vitiligo.

The convergence theory for vitiligo: A reappraisal

Vitiligo is characterized by progressive loss of skin pigmentation. The search for aetiologic factors has led to the biochemical, the neurologic and the autoimmune theory. The convergence theory was then proposed several years ago to incorporate existing theories of vitiligo development into a single overview of vitiligo aetiology. The viewpoint that vitiligo is not caused only by predisposing mutations, or only by melanocytes responding to chemical/radiation exposure, or only by hyperreactive T cells, but rather results from a combination of aetiologic factors that impact melanocyte viability, has certainly stood the test of time. New findings have since informed the description of progressive depigmentation. Understanding the relative importance of such aetiologic factors combined with a careful selection of the most targetable pathways will continue to drive the next phase in vitiligo research: the development of effective therapeutics. In that arena, it is likewise important to acknowledge that pathways affected in some patients may not be altered in others. Taken together, the convergence theory continues to provide a comprehensive viewpoint of vitiligo aetiology. The theory serves to intertwine aetiologic pathways and will help to define pathways amenable to disease intervention in individual patients.

Vitiligo: An Update on Pathophysiology and Treatment Options

The pathophysiology of vitiligo is becoming increasingly clarified. In non-segmental vitiligo, early factors include activation of innate immunity, inflammasome activation, oxidative stress, and loss of melanocyte adhesion. Nonetheless, the main mechanism leading to non-segmental vitiligo involves an immune-mediated destruction of melanocytes. Anti-melanocyte-specific cytotoxic T cells exert a central role in the final effector stage. Genetic research revealed a multi-genetic inheritance displaying an overlap with other autoimmune disorders. However, some melanocyte-specific genes were also affected. Segmental vitiligo carries a different pathogenesis with most evidence indicating a mosaic skin disorder. Current management includes topical corticosteroids and immunomodulators. Narrow-band ultraviolet B can be used in patients not responding to topical treatment or in patients with extensive disease. Pigment cell transplantation offers an alternative for the treatment of segmental vitiligo or stable non-segmental lesions. Recent findings have revealed new targets for treatment that could lead to more efficient therapies. Targeted immunotherapy may halt the active immune pathways, although combination therapy may still be required to induce satisfying repigmentation. A recently established core set of outcome measures, new measurement instruments, and biomarker research pave the way for future standardized clinical trials.

Repigmentation of Human Vitiligo Skin by NBUVB Is Controlled by Transcription of GLI1 and Activation of the β-Catenin Pathway in the Hair Follicle Bulge Stem Cells

Vitiligo repigmentation is a complex process in which the melanocyte-depleted interfollicular epidermis is repopulated by melanocyte precursors from hair follicle bulge that proliferate, migrate, and differentiate into mature melanocytes on their way to the epidermis. The strongest stimulus for vitiligo repigmentation is narrow-band UVB (NBUVB), but how the hair follicle melanocyte precursors are activated by UV light has not been extensively studied. To better understand this process, we developed an application that combined laser capture microdissection and subsequent whole transcriptome RNA sequencing of hair follicle bulge melanocyte precursors and compared their gene signatures to that of regenerated mature epidermal melanocytes from NBUVB-treated vitiligo skin. Using this strategy, we found up-regulation of TNC, GJB6, and THBS1 in the hair follicle bulge melanocytes and of TYR in the epidermal melanocytes of the NBUVB-treated vitiligo skin. We validated these results by quantitative real-time-PCR using NBUVB-treated vitiligo skin and untreated normal skin. We also identified that GLI1, a candidate stem cell-associated gene, is significantly up-regulated in the melanocytes captured from NBUVB-treated vitiligo bulge compared with untreated vitiligo bulge. These signals are potential key players in the activation of bulge melanocyte precursors during vitiligo repigmentation.