Interleukin-1 beta promotes sensory nerve regeneration after sciatic nerve injury

Nerve injury brings about axonal disconnection, and thus axonal extension is one of the important steps for nerve regeneration. Expression of the pro-inflammatory cytokine interleukin-1 beta (IL-1β) is increased at the early stage of nervous system injury, and previously IL-1β has been reported to promote neurite outgrowth by inhibiting RhoA activity in vitro. However, the effect of IL-1β on axonal extension in vivo has not been obvious. Now we examine whether IL-1β takes advantages on sciatic nerve regeneration. Sciatic nerves of rats are transected and sutured, and IL-1β or PBS is locally administered for 2 weeks. Although IL-1β does not influence on motor functional recovery, it promotes sensory functional recovery, estimated by toe pinch test, and increases the number and the area of neurofilament-positive axons at 12 weeks compared with PBS. Moreover IL-1β, which promotes Schwann cell proliferation and thus may inhibit myelination, does not impair remyelination, estimated by myelin basic protein. These findings suggest that IL-1β may contribute to sensory nerve regeneration following sciatic nerve injury by promoting axonal extension.