Deer antler innervation and regeneration

Nervous system injuries are a major cause of impairment in the human society. Up to now, clinical approaches have failed to adequately restore function following nervous system damage. The regenerative cycle of deer antlers may provide basic information on mechanisms underlying nervous system regeneration. The present contribution reviews the actual knowledge on the antler innervation and the factors responsible for its regeneration and fast growth. Growing antlers are profusely innervated by sensory fibers from the trigeminal nerve, which regenerate every year reaching elongation rates up to 2 cm a day. Antler nerves grow through the velvet in close association to blood vessels. This environment is rich in growth promoting molecules capable of inducing and guiding neurite outgrowth of rat sensory neurons in vitro. Conversely, endocrine regulation failed to show effects on neurite outgrowth in vitro, in spite of including hormones of known promoting effects on axon growth. Additional studies are needed to analyze unexplored factors promoting on growth in antlers such as electric potentials or mechanical stretch, as well as on the survival of antler innervating neurons.