Sometimes, you see a new scientific paper, and all you can think is...DANG. NATURE IS COOL.
Behold! The SKIN-SHEDDING MOUSE!
(Hey, looks aren't everything)
Siefert et al. "Skin shedding and tissue regeneration in African spiny mice (Acomys)" Nature, 2012.
There are lots of animals out there that easily lose body parts in order to escape predation. Starfish can go without their limbs, lizards can drop a tail. This process is called "autotomy", and in animals like starfish, sometimes you can get full regeneration of the limb. In mammals, though, if a tail is gone, it's usually gone forever.
But not for these mice.
The mouse in question is the African Spiny Mouse (genus Acomys, but there are two species studied here) which is native to Kenya. The animals are strange because they have this very fragile, weak skin. They have spiky fur, more like spines, on their backs, and they are VERY hard to handle. This isn't because they are difficult, but because when handled, the weak skin tears very easily, leaving huge ugly wounds on the skin. They can lose up to 60% of the skin on their backs in this way.
You'd think that such a wound would be debilitating, but in these mice it's barely an inconvenience. While normal mice take about 5-6 days to heal a smaller wound, the Spiny Mouse does it in HALF the time. The spines on their back grow at super speed to cover the wound, and the wound itself can show a 64% coverage in the first DAY.
How do they do it? The authors examined the collagen in the mouse's skin, and found that, while other mice lay down collagen in thick mats in response to wounds, the Spiny Mouse lays it down in thinner, looser layers, similar to that of normal healthy skin. They also showed a greater abundance of type III collagen, while other mice use type I, which might contribute to the structure of the collagen and the rapid healing.
But what about something that is more complex than the top layer of skin? What about a tissue like an ear, which is skin, and hair, and capillaries, etc? Mice are often tagged for identification by ear piercing or by putting holes in specific places in the ear. In lab mice, these holes are usually pretty permanent, getting smaller with time but not disappearing entirely (like a human ear piercing). But in the Spiny Mouse, these wounds never had a chance. The mice regrew skin, capillaries, and hair. It turns out they can regenerate almost all types of tissue with the exception of muscle.
To regenerate all this, not only do you need nice loose collagen, you also need the formation of a blastema, a mass of cells that can regenerate into various tissues. Blastema formation was thought not to occur in mammals, but it looks like the Spiny Mouse might have something similar, though not exactly a blastema. They can certainly maintain cell proliferation in the area of the wound, as well as laying down collagen and other matrix to promote regeneration. This is a striking difference from normal mice, who usually end up with scar tissue from a different collagen matrix.
While these mice are cool due to this phenomena alone, the further study of their remarkable capabilities could reveal some interesting things about how we heal (or don't), and how we could promote healing and skin regeneration. And it also shows us that, though laboratory mice are wonderful models, there may be more to be found by also studying animals in the world at large.
Seifert AW, Kiama SG, Seifert MG, Goheen JR, Palmer TM, & Maden M (2012). Skin shedding and tissue regeneration in African spiny mice (Acomys). Nature, 489 (7417), 561-5 PMID: 23018966