Illustration of a reindeer (Rangifer tarandus) with antlers. Both male and female reindeer grow antlers, which are shed and regrown every year. While the antlers are growing they are covered in a highly vascular form of skin known as velvet. Tissue regeneration studies have shown that while reindeer back skin scars after wound healing, velvet doesnt. The difference is due to fibroblasts cells, which produce connective tissue such as collagen, the main structural protein in the skin. Fibroblasts in the back skin are mature cells that react to a wound with an inflammatory response, while fibroblasts in antlers react with a regenerative response that is similar to that in foetuses. These insights into tissue regeneration could be used to treat severe injuries in humans.