5-Fluorouracil’s Pro-pigmentary Action: Unveiling the Role of CXCL12 Secretion by Dermal Fibroblasts

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5-Fluorouracil’s Pro-pigmentary Action: Unveiling the Role of CXCL12 Secretion by Dermal Fibroblasts

Vitiligo, an acquired pigmentary disorder affecting about 1% of the global population, is characterized by depigmented skin patches due to immune destruction of epidermal melanocytes. While UVB-based phototherapy is a common first-line treatment, many patients show poor responses, highlighting the need for new strategies. Recent observations suggest that 5-fluorouracil (5-FU) combined with therapeutic trauma can improve repigmentation in vitiligo patients unresponsive to conventional treatments. This study explores whether 5-FU has an extra-genotoxic activity to recruit melanocytes.

1. Animal Experiments

  • Mouse Model: Homozygous transgenic Dct-LacZ breeder mice were used. Wounds were created on dorsal and tail skins, and treated with 5% 5-FU or normal saline. Neoepithelium tissue was harvested on the 3rd, 7th, and 21st day for X-Gal staining.
  • Results: LacZ-positive melanocytes were more numerous in 5-FU-treated wound margins. In cryosections, they were found in the outer root sheath and interfollicular epidermis of 5-FU-treated dorsal skin wounds, while barely seen in controls. This indicates 5-FU stimulates melanocyte mobilization and migration during wound healing.

2. Cell Culture and Assays

  • Fibroblast Culture: Primary mouse dermal fibroblasts were cultured. Murine melan-a melanocytes were also cultured.
  • siRNA Transfection: siRNA targeting murine CXCL12 (siCXCL12) and a scrambled control were used. Efficiency was tested by qRT-PCR and Western blotting.
  • X-Gal Staining: Skin samples and cryosection sections were fixed and stained with X-Gal.
  • Transwell Migration Assays: Assessed melanocyte migration. Melanocytes were seeded in upper chambers, fibroblasts (with or without 5-FU treatment) in lower chambers. AMD3100 (CXCR4 antagonist) was used to block CXCR4.
  • Immunofluorescent and FITC-phalloidin Staining: Examined CXCL12 expression and F-actin changes.

3. Key Findings

  • CXCL12 Upregulation: Immunofluorescent staining showed increased CXCL12 in 5-FU-treated wound margins. 5-FU upregulated CXCL12 mRNA and protein in cultured fibroblasts.
  • Melanocyte Migration: Inhibition of the CXCL12/CXCR4 axis (using siCXCL12 or AMD3100) suppressed melanocyte migration. F-actin staining showed a coarse pattern in melanocytes treated with 5-FU-treated fibroblast conditioned medium, indicating actin polymerization.

4. Discussion

  • Melanocyte Recruitment: CXCL12/CXCR4 axis is crucial for melanocyte migration. 5-FU-induced CXCL12 upregulation likely recruits melanocytes.
  • Clinical Implications: 5-FU’s pro-pigmentary activity may be useful in vitiligo treatment, especially for UVB-resistant patients. Future work will investigate CXCL12/CXCR4 axis activation in vitiligo lesions.

This study reveals that 5-FU stimulates dermal fibroblasts to secrete CXCL12, activating the CXCL12/CXCR4 axis to drive melanocyte chemotactic migration. It provides new insights into 5-FU’s role in vitiligo repigmentation.

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doi:10.1097/CM9.0000000000001689

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