Rete ridges reveal distinct epidermal programs shaping mammalian skin

Across mammals, rete ridges form through a BMP-driven epidermal program that is distinct from the development of hair follicles and sweat glands, linking epidermal thickening with dermal pockets. The timing of ridge formation aligns perinatally in humans and pigs, and has been observed in dolphins and bears, while neonatal pig wounds can regenerate rete ridges de novo. The authors also show that mouse fingerpad rete ridges require epidermal BMP signaling, leading to the idea that evolution replaced discrete skin appendage programs with an interconnected epidermal–dermal network. This work has implications for regenerative approaches to restore epidermal structures after injury or disease.