Current advances in stem cell-based therapies for hair regeneration.

Alopecia is resulted from various factors that can decrease the regeneration capability of hair follicles and affect hair cycles. This process can be devastating physically and psychologically. Nevertheless, the available treatment strategies are limited, and the therapeutic outcomes are not satisfactory. According to the possible pathogenesis of nonscarring alopecia, especially androgenetic alopecia, recovering or replenishing the signals responsible for hair follicle stem cells activation is a promising strategy for hair regeneration. Recently, stem cell-based therapies, especially those based on the stem cell-derived conditioned medium (CM), which is secreted by stem cells and is rich in paracrine factors, have been widely explored as the hair regenerative medicine. Several studies have focused on altering the composition and up-regulating the amount of secretome of the stem cells, thereby enhancing its therapeutic effects. Besides, stem cell-derived exosomes, which are present in the CM as message entities, are also promising for hair regrowth. In this review, the up-to-date progress of research efforts focused on stem cell-based therapies for hair regeneration will be discussed, including their therapeutic potentials with respective merits and demerits, as well as the possible mechanisms.