Oral administration of Lactilactobacillus curvatus LB-P9 promotes hair regeneration in mice

   This study was designed to examine the effect of Lactilactobacillus curvatus LB-P9 on hair regeneration. The treatment of LB-P9 conditioned medium (CM) increased the proliferation of both hair follicle dermal papilla cells (hFDPCs) and hair germinal matrix cells (hGMCs). Moreover, the expression levels of hair growth factors such as vascular endothelial growth factor (VEGF) and fibroblast growth factor 7 (FGF-7) were significantly elevated in hGMCs co-cultured with LB-P9. After time-synchronized depilation, mice were orally administered with either 4×10⁷ colony forming unit (CFU) of LB-P9 (low dose) or 4×10⁸ CFU of LB-P9 (high dose), once daily for 4 weeks. Compared with the vehicle (phosphate-buffered saline, PBS)-administrated group, the LB-P9-treated groups exhibited accelerated hair regrowth rate and enhanced hair thickness in a dose-dependent manner. Supporting this observation, both hair follicle numbers and the dermal thickness in skin tissues of the LB-P9-treated groups were increased, compared to those of the vehicle-treated group. These results might be explained by the increased level of β-catenin and number of hair follicle stem cells (hFSCs) (CD34⁺CD49f⁺ cells) in the skin tissues of mice administered with LB-P9, compared to the vehicle-treated mice. Also, increased serum levels of hair growth factors such as VEGF and insulin-like growth factor-1 (IGF-1), and superoxide dismutase (SOD) were found in the LB-P9-treated groups, compared to those of the vehicle-treated group. Taken together, these results might demonstrate that the oral administration of LB-P9 promotes hair regeneration by the enhancement of dermal papilla proliferation through the stimulation of hair growth factor production.