The Role Of 1,25-Dihyroxyvitamin D₃ On Hair Regeneration In C57BL/6 Mice

Object:To investigate the effect of 1,25-Dihyroxyvitamin D₃ on hair regeneration in C57BL/6 mice.Methods:The male C57BL/6 mice（3⁴weeks old and hair follicles in telogen）were randomly divided into 5 groups,7 mice in each group,including Control grup,3-MA group,RAPA group,VD₃ group and VD₃+RAPA group.Hair regeneration model of C57BL/6 mice was induced on the dosal skin by depilation,hair regrowth process was observed afterward.On 14d,skin tissue was collected.The morphological changes of hair follicles was detected by Hematoxylin and eosin（HE）,the expression levelsofP62,Ki67,DDIT4inhairfollicleswereassessedby Immunohistochemistry（IHC）,the protein expression levels related to autophagy was detected by Western Blot（WB）.Immunoflurescennce（IF）,double-labeled staining of CD34 and CD49f was performed to show the hair follicle stem cells.Results:Compared with the Control group,the color change and hair regrowth of the VD₃ group and 3-MA group were significantly accelerated,the hair follicle papilla was enlarged,and the number of hair follicles increased,The expression of P62and Ki67 in hair follicle epithelial cells increased significantly;At the same time,the number of hair follicle stem cells with double-labelled of CD34 and CD49f increased significantly,However,the above were reversed after treatment with RAPA.In the skin tissue of the plucking area,the expression of total autophagy-related protein（LC3BII/I and Beclin1）were elevated in RAPA group and VD₃ group than that of Control group,both of them were decreased in 3-MA group compared to Control group.Compared with the RAPA group,the color change and hair growth in the VD₃+RAPA group were accelerated,and the hair follicle papilla increased,the number of hair follicles increased,The expression of P62 and Ki67 in hair follicle epithelial cells were increased,and the number of hair follicle stem cells was significantly increased,all above changes were between VD₃ group and RAPA group.Compared with RAPA group and VD₃ group,the expression of LC3BII/I and Beclin1 in the skin tissue of VD₃+RAPA group were increased.The expression level of DDIT4 in hair follicle epithelial cells of VD₃ group was lower than Control group,3-MA group and RAPA group was not significantly different from that of Control group,and in VD₃+RAPA group was lower than RAPA group,The expression level of DDIT4 was no significant difference between the VD₃group and VD₃+RAPA group.Conclusion:（1）Autophagy is an important cyclical regulation mechanism of hair follicle epithelial cells.（2）1,25（OH）₂D₃ can significantly promote the regrowth of dosal hair in C57BL/6 mice,which may related to the inhibition of DDIT4 expression in hair follicle cells,inhibit the formation of mTOR complex,inhibit autophagy and promote proliferation of hair follicle cells.