Identification of Keratin 5-Expressing Fibroblasts for Regenerating Keratinocytes in the Necrotic Skin Graft.

Skin transplantation is commonly used to compensate for normal cutaneous tissues in full-thickness wounds or surgically excised skin. Despite complete termination of initial blood flow, transplanted skin usually maintains its dermal and epidermal structures without scar formation. However, the precise role of engrafted cells in maintaining epidermal and dermal homeostasis remains unclear. In this study, we investigated the chronological changes in neonatal full-thickness skin grafts on mice at the histological and single-cell transcriptomic levels. We found devastating necrotic changes in the dermal and epidermal tissues on postoperative day 3, followed by significant regeneration of follicular and interfollicular tissues after postoperative day 6. We identified a unique mesenchymal subpopulation that expressed keratinocyte-specific genes (keratin 5 gene K rt 5, Epcam, and Irf6) involved in mesenchymal-epithelial transition. Mesenchymal cells transitioning to epithelial cells showed keratinocyte differentiation activity both in vitro and in vivo. These results highlight the contribution of unique mesenchymal cell populations to epithelial regeneration after severe necrosis of a skin graft.