Reindeer do not drive a flying sleigh on Christmas eve. But they may yet deliver great gifts to humans.
Medical researchers are studying deer because they do something few other animals do: sprouting and shedding antlers annually. All male deer—and female reindeer too—regenerate antlers. With the antlers, the animals also grow new nerve cells, which intrigues neuroscientists Manuel Nieto-Díaz at the National Paraplegics Hospital, in Toledo, Spain and Wolgang Pita-Thomas at Washington University in St. Louis, Missouri. They believe these deer cells hold the secret to stimulating nerve cell growth in injured humans and are examining antlers in an effort to copy the process.
A few months after young deer are born, males (and female reindeer) sprout two knobs on their forehead called pedicles, which will turn to antlers over the spring. As the days grow longer, the pedicles form a bud, covered in a fuzzy layer of skin and fur, called velvet, which carries calcium- and phosphorous-rich blood to this area, building up antler tissue over time. Under the velvet, cartilage forms, eventually becoming bone.
During the growth phase, cartilage is sensitive, containing nerve cells that alert deer to potential harm to their forming antlers. After about three months, blood flow through the velvet stops, and that furry outer layer cracks and is itchy. Uncomfortable, the deer scratch against trees peeling velvet off in bloody sheets to finally reveal fully-formed antlers.
Unlike human bones, formed antlers have no nerve cells, so they stop signaling pain. At that point, they work as weapons and accessories, and the deer use them to fight, hunt, and woo.
The velvet phase may hold the secret to regenerating nerve cell growth in humans. Inside the velvet are long nerve sections called axons that grow rapidly. “Axons are the wiring…. They’re the part of the nerve that transmits information,” Nieto-Díaz explained to KQED Radio.
Deer axons are unique because they regenerate, whereas in humans and most other animals new nerve formation is much more limited. Patients with nerve damage to their limbs often cannot recover mobility because the nerve cells are dead. Growing axons especially for these patients may help them recover mobility. If Neto-Diaz and Pita-Thomas can figure out what makes deer axons grow again and again, they could, they think, simulate this effect in humans.
The neuroscientists have already isolated three proteins in deer antlers that seem key to axon regeneration. To find these, they snipped the tips off growing antlers of anesthetized live deer and cultured the cuts in a lab. The velvet created a substance containing numerous proteins, which were added to rat neurons individually to identify those contributing most to rapid axon growth, and then were tested in combination.
Rat neurons laid on a surface of three deer antler proteins—nerve growth factor, periostin, and laminin—grew about four times faster than naturally, the scientists found. Still, Nieto-Diaz was disappointed, calling the growth rate “decent but not amazing” as it’s nowhere near that of deer antlers, which can grow from a quarter-inch to nearly an inch in a day.
The next step for the neuroscientists will be measuring the proteins’ effect on neuron growth in live rats. While they work on that, the deer will again shed their antlers this winter, growing new bones in spring.