Abstract:

        Objective  To investigate hair follicle pattern of fetal, neonatal and adult mouses. Methods  The different development process of hair follicle in C57BL/6 mice were observed using several methods, including paraffin and frozen ultrathin sections, HE staining, AP activity staining, oil red O staining and apoptotic cells identification. Results  The hair follicles section started to develop in the E15.5 fetal mouse of C57BL/6 and the back skin became thicker gradually in the E18.5 fetal mouse with more hair follicles appeared. The most of hair follicles of the 1st day suckling mice born would grow into the fourth stage of hair follicle development with the numbers of hair follicles increasing quickly. At the 4th day after born of immature mice, the most of hair follicles continued to develop, but the number of hair follicles remained unchange. The hair follicles of the 9th day suckling mice would grow into the 8th stage of hair follicle development. For 9d adult mouse after depilation, 95% of the hair follicles entered the growth stage Ⅳ, in the first 17d, 63.3% of the hair follicles entered the degradation period and in the first 22d of, 85% of the hair follicles grew into the degradation period.  Conclusions  The hair follicle of fetal mouse starts at E15.5 and from E17.5 to 3 days after birth. The number of hair follicles will increase rapidly, therefore, this period can be used to explore the mechanism of hair follicle regeneration.

Key words: Hair follicle, Hair follicle development, Hair follicle stages, AP staining