Combined 5‐aminolevulinic acid and ferric ammonium citrate treatment promotes hair follicle growth by activating dermal papilla cells

Although 5-aminolevulinic acid (5-ALA) has shown potential for hair growth in previous studies, the molecular mechanisms remain unclear. In this study, we investigated the combined effect of 5-ALA with ferric ammonium citrate (FAC) in human hair follicle models. At low micromolar concentrations, 5-ALA/FAC treatment increased proliferation of dermal papilla cells, keratinocytes, fibroblasts, and adipose-derived stem cells, and rapidly activated ERK and AKT signaling. This treatment also upregulated hair-inductive genes and restored their suppression by dihydrotestosterone or oxidative stress. In functional assays, 5-ALA/FAC treatment induced hair follicle-like structures in reconstituted skin and enhanced hair shaft elongation in ex vivo organ culture. These findings indicate that 5-ALA/FAC treatment stimulates human hair follicle growth and support its potential as a therapeutic candidate for hair loss.