Regrowth of calcitonin gene-related peptide (CGRP) immunoreactive axons from the chronically injured rat spinal cord into fetal spinal cord tissue transplants.

Fetal spinal cord tissue was transplanted into either a hemisection or complete transection lesion site at lumbar levels of the adult rat spinal cord that had been produced 3, 6, or 11 weeks prior to grafting. Tissue sections containing the graft and adjacent regions of the host spinal cord were processed for calcitonin gene-related peptide immunoreactivity (CGRP-IR) 2-6 months later. Numerous CGRP-IR axons within laminae I, II, V and X of the host spinal cord were observed crossing the graft-host interface as they spread diffusely throughout the caudal-rostral extent of the transplants. Many of these immunolabeled axons terminated in a distinct bouton-like formation. These results indicate that within the chronically injured spinal cord at least one-specific neuronal population retains the potential for regrowth in a long-term injury condition and that this capacity for axonal elongation can be sustained by the presence of fetal spinal cord tissue grafts.