Certain species of amphibians and reptiles have defensive traits that allow them to escape predators, including the ability to lose and regenerate tissue, known as autotomy. Tissue regeneration is much more limited in mammals, however. Researchers have therefore depended on amphibian and reptile species to study wound healing, but their findings have been difficult to translate to humans due to the vast differences in biology between such species and mammals.

A new report describes two species of African spiny mouse (Acomys kempi and Acomys percivali) that can shed and regrow large portions of its skin, including hair follicles (Nature published online 27 September 2012; doi:10.1038/nature11499). Malcolm Maden (University of Florida, Gainesville) and collaborators at the University of Nairobi (Kenya) and Mpala Research Center (Nanyuki, Kenya) found that the skin of these mice easily tears upon handling, leading to large open wounds or skin loss that can total up to 60% of the animal's surface area. This likely developed as a defense mechanism that allows the mouse to release itself from a predator's grasp.

The team compared the mechanical properties of the skin of spiny mice and that of regular laboratory mice (Mus musculus). They found that Mus skin was 20 times stronger than Acomys skin, and nearly 77 times more energy was required to break it. Spiny mouse skin was also less elastic, probably because the large hair follicles and associated glands take up more space in the skin, reducing the overall amount of connective tissue. The spiny mice were able to heal their wounds much faster than the lab mice, restoring their skin and hair follicles within 3 d. Additionally, spiny mouse skin did not scar. Unlike scar tissue, in which collagen fibers arrange into dense, organized bundles, the regenerating wounds maintained the looser collagen organization of undamaged tissue.

The researchers also tested whether the spiny mice could regenerate tissue to heal ear punch wounds, an ability that has been observed in rabbits but few other mammalian species. The mice were able to regenerate all tissue types, including skin, hair follicles, adipose cells and cartilage, except muscle.

In the future, the scientists plan to explore how the pathways regulating regeneration in the spiny mouse are modulated to produce tissue regrowth instead of scarring. One possibility is that the immune response is modulated to direct the healing process away from scar production toward tissue regeneration.