Knockout animals in which a gene encoding a SASPase has been deleted (hereinafter, referred to as SASPase KO animals) are provided. The SASPase KO animals deficient in expression of functional SASPase were produced by deleting a gene encoding a stratified epithelium-specific protease, SASPase, through targeted disruption. The SASPase KO animals showed a significant increase in wrinkles on the sides of the body and so on. The SASPase KO animals find utility as animal models of wrinkles.
