Identification of unique mesenchymal subpopulations for regenerating follicular and interfollicular epithelia after devastating necrosis in the skin graft

We investigated chronological changes of the skin graft in mice for 15 days at single cell-transcriptomic levels. We found devastating necrotic changes in the dermal and epidermal tissues at post-operated day 3, (POD3), followed by significant regeneration processes of the follicular and interfollicular tissues after POD 6. Dermal papilla cells in the necrotic milieu exserted significant activation of Wnt signaling pathway and Sox2 and Fgf7 expressions, all of those are critical for follicular development in the fetal skin. We further identified a unique mesenchymal subpopulation, which expressed keratinocyte-specific genes, such as Krt5 and Epcam, as well as Irf6, a transcriptional factor to induce mesenchymal to epithelial transition (MET). Our data revealed significant contribution of the unique mesenchymal cell populations for the follicular and interfollicular epithelial regeneration after severe necrosis in the skin graft.