Abstract: [Abstract] Objective   To observe the difference in epidermal stem cell number and function between wild-type (WT) mice and the third generation of Terc knockout (G3Terc-/-) mice. Methods   Flowcytometry was used to analyse and sort epidermal stem cells;Quantitative real-time PCR to analyse the relative expression level of p21 in epidermal stem cells; The ability of self-renewal was reflected by the number of colonies formed by epidermal stem cells. Results   Ratio of basal and suprabasal epidermal stem cells in WT mice were 9.56% and 1.22% respectively, ratio of basal and suprabasal epidermal stem cell in G3Terc-/- mice were 17.36% and 2.92%. Relative p21 expression level in G3Terc-/- mice was 6.40 fold to WT mice; Number of colonies formed by WT mice epidermal stem cells were 280.2 per 104cell,number of colonies formed by G3Terc-/- mice epidermal stem cells were 29.28 per 104 cell, it has significant difference in the above results（p<0.05）.Conclusion   Compared to WT mice, epidermal stem cells in G3Terc-/- mice were aging.

Key words: Knockout mice, Skin aging, telomerase