While keratinocytes are the primary recipients of melanin, and mast cells can contribute to inflammation, recent research highlights the crucial role of dermal fibroblasts in melasma pathogenesis. Photoaged fibroblasts in the dermis of melasma lesions produce increased levels of stem cell factor (SCF) and basic fibroblast growth factor (bFGF), which stimulate melanocyte proliferation and activity. They also influence the extracellular matrix, contributing to the overall dysregulation of pigmentation. Langerhans cells are antigen-presenting cells and are not directly implicated in melanogenesis in melasma.
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