In studies of skin diseases using culture systems, human primary epidermal cells treated with toxic agents have traditionally been employed. However, as numerous skin disorders are now understood to arise from mutations or deletions in specific genes, it has proven challenging to faithfully recapitulate such conditions using primary cells that are inherently difficult to manipulate genetically. In response to this limitation, Professor Yohei Hirai of the School of Biological and Environmental Sciences has endeavored to establish disease models employing HaCaT cells endowed with epidermal stem cell-like properties through a proprietary de-differentiation protocol, cultured skin tissues from mouse embryos, and epidermal cells derived from embryonic stem (ES) cells. These cell types permit stable and reproducible genetic modifications. As a result of extensive investigations, model systems have been successfully developed, including atopic dermatitis cells with inducible expression of mutant JAK1, and inflammatory skin disease cells capable of HMGB1 knockout and re-expression. The model cells created in this study support stable cultivation and enable temporally controlled induction of pathogenic genes, offering promising utility as screening platforms for the development of therapeutics targeting skin diseases.