If you live in a cold climate, some days any exposed skin is at risk of frostbite. But if we had antifreeze coursing through our veins, we’d be resistant to winter’s bite. And that's not as crazy as it sounds. Scientists have recently demonstrated that mice, genetically engineered to produce an antifreeze protein, are better able to fight off frostbite. Although other animals have this survival skill, it’s the first time it’s been replicated in a mammal.

Biological Thermostats

In the animal kingdom, there are two types of animals: those that can regulate their body temperatures, endotherms, and those that cannot, ectotherms. Mammals are endotherms, and they rely on metabolic and physical processes to maintain a constant internal body temperature. Ectotherms, like many frogs and fish, are at the mercy of external factors to maintain body temperature. When it’s extremely cold out, ice crystals can form inside animals' tissues. Those crystals stab cells and tissues to death, which is why severe cases of frostbite often lead to gangrene and amputations. For ectotherms living in northern latitudes, it’s essential to prevent ice crystals from forming in their blood. They do this by naturally producing antifreeze proteins that stunt the development of icy needles. Humans, on the other hand, can only add more layers to prevent their limbs from freezing.

Building Frost Resistance

One creature known to produce an antifreeze protein is the black-legged tick. In cold conditions, it deploys a protein called IAFGP, which binds to ice nuclei and prevents crystal growth. To see if a similar trick could work in mammals, scientists genetically engineered a line of mice that expressed IAFGP. They gave them some anesthetic and dipped their tails into a bath at -71 degrees Fahrenheit for four minutes. Mice that weren’t genetically engineered didn't fare well. Within hours, 93 percent showed signs of frostbite, and within 7 to 10 days, their tails self-amputated. (The mice were all given pain medication in their water during the recovery phase.) Their genetically engineered counterparts, however, were remarkably protected. Just 38 percent of the antifreeze-producing mice lost their tails. The IAFGP protein does indeed appear capable of working its magic in a mammal. Researchers published their results Tuesday in the journal PLOS One.

So What?

We humans won’t be cold-resistant mutants anytime soon. The proteins would seem to have promise in treating or preventing frostbite, but genetic tinkering with humans isn't as doable as it is with mice. And it isn't clear how humans could incorporate these proteins into their bodies if at all. The approach could have more immediate benefits for parts of humans rather than their whole body. Researchers believe antifreeze proteins could aid in extending the shelf life of donated organs, by allowing them to be stored at freezing temperatures without causing damage. So until our veins are coursing with ice-resisting proteins, we suggest hats and mittens remain your constant allies in the fight against bitter cold.

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