M2 macrophages promote wound-induced hair neogenesis

In humans, full-thickness skin excision usually leaves hairless scars, but the definitive evidence for de novo hair regeneration has been shown in skin scars of genetically normal adult mice [1]. This phenomenon was termed wound induced hair neogenesis (WIHN). The fact that hair follicles can be regenerated in vivo in scarred skin without the use of ES cells or iPS cells has high impact on tissue engineering.