Induction of repulsive guidance molecule in neurons following sciatic nerve injury

Repulsive guidance molecule (RGM) is a protein implicated in both axonal guidance and neural tube closure. We examined the expression of RGMa in the spinal cord after the sciatic nerve crush by immunohistochemistry. Although there was no RGMa immunoreactivity under naïve conditions in the dorsal horn, a weak signal for RGMa was found at 24 h after the nerve crush, and this signal was progressively increased in the NeuN-positive neurons in the ipsilateral dorsal horn from superficial to deep layers at 10 days after surgery. In the neurons of the ipsilateral ventral horn, RGMa was also induced at 10 days after surgery, whereas no RGMa signal could be observed in naïve conditions or at 24 h after surgery. Thus, RGMa expression is upregulated both in the ipsilateral dorsal and ventral horns in response to the sciatic nerve injury. We next examined the effects of complete Freund's adjuvant (CFA)-induced inflammation on RGMa expression in the spinal cord. However, no RGMa expression was observed at 24 h and 10 days after the CFA injection in the dorsal horn, suggesting that RGMa is not involved in inflammation-induced gyperalgesia. Our present study demonstrates that induction of RGMa is associated with the peripheral nerve injury.