What if we could learn how to regenerate human bones by studying deer antlers? It sounds strange, but that's exactly what a group of scientists are trying to do. Deer antlers grow back each spring, sometimes at the rate of 2,5cm (one inch) per day. Now, scientists want to figure out how to use the cells that fuel this growth to give humans the same ability to regenerate limbs.
In a study published in Science (I link it here), a team from Northwest Polytechnic University in Xi'an, China, was successful in transplanting deer antler blastema progenitor cells onto the foreheads of mice, which turned into small stumps within 45 days.

A unique ability among mammals
Deer antlers are the only known mammalian organ that regenerates each year, and they are also one of the fastest growing tissues. The study examining the blastema in deer identified the cells responsible for springtime regeneration of the antlers. Scientists found that in the weeks before the antlers dropped, stem cells were abundant in the stumps (the part that stays 'fixed' in a deer's antlers). These cells transform into progenitor cells of the horn blastema after the fall and then harden into cartilage and bone.
Although many mammals have the same type of self-renewing cells, only deer use them to regenerate their antlers. This study suggests that mammals may have a distinctive regeneration mechanism. The successful transfer of these cells from deer to mice raises hopes that one day there may be a "clinical application in the regeneration of human limbs," as the study claims. “The induction of human cells into horn blastema-like cells could be used in the regenerative medicine also to treat skeletal injuries".

Limb regeneration, a possible future?
Research on deer blastema is truly revolutionary, it seems. If one day we end up with an arm again after an amputation, maybe we'll know who to thank.