Do Melanocytes Have a Role in Controlling Epidermal Bacterial Colonisation and the Skin Microbiome?

Area of Science:

• Dermatology
• Immunology
• Microbiology

Background:

• Melanocytes produce melanin for UV protection and may play a role in innate skin immunity.
• The skin microbiome involves a complex balance between commensal and pathogenic bacteria.

Purpose of the Study:

• To investigate the impact of melanocytes on epidermal bacterial growth.
• To determine if melanocytes regulate immune gene expression in a 3D skin model.

Main Methods:

• Developed a 3-cell full-thickness human skin equivalent with melanocytes, fibroblasts, and keratinocytes.
• Compared bacterial colonization and immune gene expression in pigmented vs. unpigmented skin equivalents.
• Utilized immunohistochemistry and alpha-melanocyte-stimulating hormone (α-MSH) stimulation.

Main Results:

• Functional melanocytes significantly decreased bacterial colonization (Staphylococcus epidermidis, Corynebacterium striatum, Cutibacterium acnes).
• Melanocytes modulated the expression of immune-response genes (S100A9, DEFB4A, IL-4R) upon microbial exposure.
• Differences in immune gene expression were observed between pigmented and unpigmented skin equivalents.

Conclusions:

• Functional melanocytes enhance skin's innate immunity against bacterial pathogens.
• The 3D skin equivalent model is valuable for studying skin pigmentation, immunity, and microbiome interactions.
• This model offers new research avenues for skin disorders, melanoma, UV damage, and microbiome research.