摘要To the Editor:Hair loss or alopecia is a very common disease,which has the potential to impact the quality of life,physical attractiveness,and interpersonal relationships.In recent years,lasers and light therapy have been used as alternative or supplementary therapy for hair loss.In 2007,low-level laser therapy was approved by the United States Food and Drug Administration as a safe and effective treatment on hair loss.[1] The non-ablative 1550 nm fractional laser also appears to be useful for increasing hair density in patients with androgenetic alopecia.[2] Moreover,our previous study found that ablative CO2 fractional laser therapy in combination with hair growth factors proves more effective for the treatment of patients with androgenetic alopecia than topical hair growth factors alone.[3] However,the detailed mechanisms underlying hair re-growth and injury induced by the laser remains unclear.In the present study,we assessed the expression of several inflammatory cytokines related to wound healing and Wnt signal pathway molecules at different time points before and after CO2 fractional laser therapy.Potential mechanisms behind fractional CO2 laser-induced hair growth were then explored in mice.