Tissue regeneration: hair follicle as a model

The Cre-loxP strategy has allowed us to generate the mice whose keratinocytes are devoid of Stat3, which play a pivotal role in the signal transduction following the stimulation with various growth factors/cytokines, such as EGF, HGF, or IL-6. Although keratinocyte-specific Stat3-disrupted mice were born normal with intact skin and the first hair cycle, they exhibited retardation of wound healing and absence of the second hair cycle onward, leading to development of spontaneous skin ulcers and alopecia as they aged. Thus, analyses of these mice reveal that Stat3 in keratinocytes contributes to the regeneration of epidermis and hair cycle process.