Objective      To determine the expression profile of TNFR-1 in the hair follicles of mice at different phase and explore its importance.       Methods      RT-PCR

Western blot analysis and immunofluorescence staining with paraffin section were adopted to detect the expression and distribution of TNFR-1 in mouse hair follicles at 4 time points

P8d

P15d

P18d and P24d respectively. Hair shaft differentiation marker AE13 was tested by immunofluorescence staining. The apoptosis of the hair follicle was detected by TUNEL staining.       Results      The expression intensity of TNFR-1 were distinct in all 4 time points in the skin. The results of Western blot analysis were consistent with those of RT-PCR

showing that from the middle anagen to very late anagen

TNFR-1 presented high expression. In the catagen and telogen

the expression of TNFR-1 was becoming lower than that of very late anagen

and stayed at a very low level. Immunofluorescence staining showed that in the anagen

TNFR-1 was mainly distributed in the epidermis

matrix

inner root sheath (IRS) and hair shaft. In the very late anagen phase

there was significant expression of TNFR-1 in the outer root sheath (ORS). In the catagen phase

TNFR-1 was distributed in the epidermis and ORS

and expressed specifically and highly in the second hair germ.There was very low expression of TNFR-1 in the epidermis and club hair in the telogen phase. AE13 was expressed in the epidermis

hair cortex and hair cuticle in the anagen. In the catagen

there was a specific and high expression of AE13 in the hair shaft

especially in the proximal end of the hair shaft

that is

in the area of keratinization and club hair formation. During the telogen

there was a low expression of AE13 in the epidermis and hair club. Through TUNEL staining

apoptotic cells were found in the epidermis

hair shaft

IRS and hair matrix during the anagen. In addition

apoptotic cells were observed in the ORS during late anagen

in the epidermis

ORS and proximal end of the hair shaft during catagen

and in the epidermis

hair club

bulge and sebaceous gland during the telogen.       Conclusion      TNFR-1 is expressed specifically and spatiotemporally in the hair follicle cycle

and its expression is significantly high in the middle anagen to very late anagen

and reduced and maintained in a mild level in the catagen and telogen phase

which is involved in cell differentiation and pro-apoptosis of hair follicle.