Hyperinnervation inhibits organ-level regeneration in mammalian skin

Some mammalian tissues can replace lost cells within one lineage, but organ-level regeneration—restoring diverse cell types across lineages—remains rare. Here we show that late embryonic full-thickness skin injuries heal by regenerating epithelial, mesenchymal, neuronal, and vascular lineages with proper connectivity. However, this ability is lost soon after birth, leading to a failure to restore most cell types and hyperinnervation of the wound bed. Single-cell sequencing identified a postnatal wound-specific fibroblast (PWF) population absent after embryonic wounding. Through an in vivo screen, we discovered three PWF-enriched genes—Timp1, Cxcl12, and Ccl7—that inhibit organ-level regeneration and cause hyperinnervation when overexpressed in embryonic wounds. Reducing hyperinnervation by depleting Cxcl12 in fibroblasts or inhibiting synaptic release enables postnatal skin to regenerate diverse lineages after injury. Our study identifies mechanisms transitioning an organ from regenerative to non-regenerative, discovers fibroblast-driven hyperinnervation as a key barrier, and demonstrates removing this barrier unlocks organ-level regeneration.