Table 2.

Comparative summary of the participation of developmental signaling pathways in mammalian skin development and repair

Signaling pathway	Skin compartmenta	Skin development	Skin repair
Wnt/β-catenin	Dermis	Development of the dermis [41, 43, 44]	Reconstitution of the dermis: fibroblast numbers, cellularity; fibroblast behavior; matrix production [53, 55, 56, 58, 60, 62]
	Epidermis and associated structures	Development and morphogenesis of hair follicles [24, 26, 46–48]	Regeneration of hair follicles in large wounds [7]
TGF-β1	Dermis	Role to be deciphered; expressed in developing dermis [217, 218]	Reconstitution of the dermis; fibroblast proliferation and behavior; matrix production; myofibroblast formation; wound contraction [87–89, 91, 92, 100–102, 107]
	Epidermis and associated structures	No significant role in hair follicle development [84]	Inhibitory role in re-epithelialization [92, 102, 106]
Notch	Dermis	Role to be deciphered	May be involved in dermal reconstitution:  macrophage behavior [130]; angiogenesis [129–131]; effect on matrix [130]
	Epidermis and associated structures	Epidermal differentiation [26, 123–125]	Role to be deciphered
Sonic hedgehog	Dermis	Role to be deciphered; in non-mammals (chick embryo), it does not induce differentiation of dermatome (precursor of dermis) [219]	May be involved in dermal reconstitution: effects on matrix, vascularity, and cellularity [140, 141]
	Epidermis and associated structures	Development and morphogenesis of hair follicles [46, 132, 134, 135, 138]	Present in regenerated hair follicles [7]; not expressed by wound keratinocytes [142]

^a“Epidermis and associated structures” includes the hair follicle and its associated structures (such as the dermal papilla).