The expression of nerve growth factor receptor on Schwann cells and the effect of these cells on the regeneration of axons in traumatically injured human spinal cord

To investigate the effects of Schwann cells and nerve growth factor receptor (NGFR) on the regeneration of axons, autopsy specimens of spinal cord from 21 patients with a survival time of 2 h to 54 years after spinal cord trauma were studied using immunohistochemistry and electron microscopy. Regenerating sprouts of axons could be observed as early as 4 days after trauma. At 4.5 months after trauma, many regenerating nests of axons appeared in the injured spinal cord. The regeneration nests contained directionally arranged axons and Schwann cells. Some axons were myelinated. In injured levels of the spinal cord, the Schwann cells exhibited an increased expression of NGFR within spinal roots. These results show that an active regeneration process occurs in traumatically injured human spinal cord. The NGFR expressed on Schwann cells could mediate NGF to support and induce the axon regeneration in the central nervous system.