Fetal skin possesses the ability to regenerate completely: complete regeneration of skin.

Until a certain developmental stage, cutaneous wounds in mammalian fetuses heal rapidly without scars with complete regeneration of the skin. In the process of fetal wound healing, inflammatory responses, granulation proliferation, and scar formation that are observed in adults are not seen. Numerous studies have reported the causes of fetal scarless cutaneous regeneration, including reduced expression of TGF-β1 and higher levels of hyaluronan in the extracellular matrix, from the viewpoints of molecular biology and cellular biology, but the mechanisms are not completely understood. Although a variety of substances that inhibit scar formation have been investigated, currently it is almost impossible for adult cutaneous wounds to heal completely without scars. Except for a few animal species, perfect regeneration after wounding can occur only during the gestation period. By strictly comparing the stages before and after the transition from the regeneration of skin to scarring, it will be possible to investigate the mechanisms of cutaneous regeneration.