The regenerative nature of hair follicle (HF) stem cells (SCs) facilitates HF cycling and support skin regeneration. Indeed, a reduction in HF SC number has been implicated as a key factor in skin and HF aging and in the development of hair disorders, such as androgenetic alopecia and the autoimmune hair loss disorder, lichen planopilaris. Fruit SC-derived extracts reportedly have positive effects on the regenerative capacity of primary human epidermal SCs. Namely, treatment with apple or grape SC extract increased the colony forming efficacy of primary human epidermal SCs, even under UV stimulation, and restored the organogenic potential of “old” (passage 14) primary human epidermal SCs to generate 3D epidermis in vitro. The purpose of this study was to investigate the impact of an apple (Malus domestica) SC extract (ACE) on human HF biology, and in particular on K15+ HF bulge SCs, using ex vivo human HF organ culture. Full length HFs, derived from two healthy donors, were treated with various concentrations of ACE (0.1% and 0.3%). Our results showed that neither tested concentration was cytotoxic, as evidenced by similar rates of LDH release into the medium and number of melanin clumps compared to vehicle. ACE, at both concentrations, did not significantly affect HF elongation, hair matrix keratinocyte proliferation and apoptosis, or anagen to catagen switch. However, the treatment with the higher concentration of ACE (0.3%) tendentially increased the expression of the HF epithelial SC marker K15, and significantly up-regulated the number of K15+ cells in the bulge. Therefore, our pilot data suggest that ACE specifically targets and selectively influences HF bulge SCs biology. While other investigations are required to discern whether ACE also impacts on the function of HF K15+ SCs, the current study indicates that ACE may be useful in cosmetic formulations to reverse the reduction in the number of bulge SCs reported in skin and HF aging/senescence and hair loss disorders.

An apple stem cell-derived extract increases epithelial stem cells number in the hair follicle bulge