Study On The Localization And Expression Profile Of FGF20(Fibroblast Growth Factor 20),FGFR2 And FGFR3 Of Mouse Hair Follicle Formation And Development

Hair follicle is an unique skin appendage.Each hair follicle perpetually goes through three stages:anagen,catagen and telogen.According to previous researches on hair follicle growth cycle,we found that skin is formed placodes at the day of embryonic 14 when the hair follicles begin to develop.For postnatal mouse,the time of anagen is about from 1st to 11th after birth,the catagen phase is about from 12th to 20th,and the telogen phase is at 21st.Subsequently,hair follicle will enter the next growth cycle.Studies have shown that the fibroblast growth factor family plays roles in hair follicle development.For example,FGF20 plays an important role in the formation of primary and secondary dermal condensation of mouse.The severe epidermal hypoplasia was found in mice null for FGFR2.There is no report about the expression of FGF20 and its receptors(FGFR2 and FGFR3)in the embryonic hair follicle formation period and the first hair follicle growth cycle of mouse.In this study,we choose mouse back skin tissue during E13-E18 and 1/5/8/11/15/17/21/23 d.We used technique of immunohistochemistry,Western Blot and Real-time PCR to detect the expression profile of FGF20,FGFR2 and FGFR3 in mouse embryonic hair follicle formation stage and the first hair follicle growth cycle.The results were as follows:During the stage on mouse embryo hair follicle formation,the results of immunohistochemistry showed that FGF20 and FGFR3 protein were almost no expression at E13.From E14 to E18,they were located in epidermis cells,placode and hair peg.FGFR2 protein was also located in epidermis cells,placode and hair peg,and always had a stronger positive signal in epidermis cells.Compared to its expression in other periods,the analyse results of RT-PCR,Western Blot as well as optical the density showed that the expression of FGF20 and FGFR3 were the lowest at E13 and the thighest at E16.The expression of FGFR2 was the lowest at E13.During the first hair follicle growth cycle,the results of immunohistochemistry showed that FGF20,FGFR2 and FGFR3 protein were widely located in epidermis,root sheath,hair papilla and sebaceous glands and so on.Compared to its expression in other periods,the data of RT-PCR,Western Blot as well as optical density showed the expression of FGF20 was the highest at 21 d and the lowest at 23 d,and that of FGFR2 was the highest at 5 d and the lowest at 15 d,and that of FGFR3 was the highest at 11d and the at 21 d.These results suggest that:(1)During the stage of mouse embryo hair follicle formation,FGF20 and FGFR3 may play a role in the stage of placode to bulbous hair peg.FGFR2 may play a stimulative role in the formation of hair follicles.(2)During the first hair follicle cycle of postnatal mouse,FGF20 may play an stimulative role in the stage of anagen to catagen.FGFR2 may play an stimulative role of early anagen of hair follicle growth and FGFR3 may also play an active role during hair follicle growth.(3)During hair follicle formation stage of mouse embryo,FGF20 may play a role by binding FGFR3.During the first hair follicle growth cycle,the expression of FGF20 was not consistent with FGFR2 and FGFR3.It suggests that FGF20 may not be the main ligand of FGFR2 and FGFR3.