Effects Of Botulinum Toxin Type A On Human Hair Growth And Immune Privilege Of Hair Follicle

Objective:To investigate the regulatory effect of botulinum toxin A(BTXA)on the growth and immune privilege using in vitro human hair follicle culture model and interferon y(IFN-y)induced hair follicle immune privilege collapsed model.Methods:Normal scalp tissues with intact hair follicles in frontotemporal region of adult male were collected.Human anagen hair follicles were isolated under microscope and divided into control group,BTXA group and IFN-y group.(1)An in vitro culture model of human Hair follicles was established and cultured for 8 consecutive days.The effects of BTXA and IFN-y on human hair growth were observed by recording the growth length of hair follicles and morphological changes of hair bulbs(Hair cycle score,HCS).(2)IFN-y(75 IU/ml)induced collapse model of immune privilege was established.The effects of BTXA on the modulation of immune privilege were observed by detecting the expression of human leukocyte antigen(HLA)-ABC,β2-microglobulin and HLA-DP/DQ/DR using reverse transcription polymerase chain reaction(RT-PCR)and immunohistochemistry.Results:(1)On the 2nd,4th,6th,8th day of hair follicle organ culture,the hair follicle length of each group was no significant difference compared with control group.(2)The morphological changes of the hair bulbs showed anagen like pattern on 4th day.Analysis of HCS showed ecah group was no significant difference copared with control group.On the 8th day of culture,the morphological changes of the hair bulbs showed catagen like pattern.Analysis of HCS showed ecah group was no significant difference copared with control group.(3)In semi-quantitative RT-PCR analysis,75 IU/ml IFN-γ significantly induced ectopic HLA-ABC mRNA expression compared with control group(P<0.01),BTXA significantly down-regulated IFN-y induced ectopic HLA-ABC mRNA expression(P<0.01),these down-regulated effects were especially evident in 10 IU/ml BTXA.(4)In immunohistochemical analysis,75 IU/ml IFN-γ induced ectopic HLA-ABC,β2-microglobulin and HLA-DP/DQ/DR protein expression in the proximal hair bulb epithelium(P<0.01);10 IU/ml BTXA significantly down-regulated ectopic HLA-ABC,β2-microglobulin and HLA-DP/DQ/DR protein expression which induced by IFN-y in the proximal hair bulb epithelium(P<0.01).Conclusion:(1)BTXA has no significant effect on human hair growth in vitro.(2)BTXA has a protective effect on the collapse of follicular immune privilege induced by IFN-y in vitro,and its regulatory mechanism still needs further study.