DORSAL ROOT REGENERATION INTO TRANSPLANTS OF DORSAL OR VENTRAL HALF OF EMBRYONIC SPINAL CORD

概要

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Adult cut dorsal root axons regenerate into the transplants of embryonic spinal cord (ESC) and form functional synapses within the transplants. It is unknown whether the growth is specific to transplants of dorsal half of ESC, a normal target of most dorsal root axons, or whether it is due to properties shared by transplants of ventral half of ESC. We used calcitonin gene-related peptide (CGRP) immunohistochemistry to label to the subpopulations of regenerated adult dorsal root axons, quantitative analysis to compare the extent of dorsal root regeneration, and also compare neuronal composition within both transplants. Adult Sprague-Dawley rats received intraspinal grafts of dorsal or ventral half ESC (E14), and the L4 or L5 dorsal root was cut and juxtaposed to the transplants. Three months later sagittal sections were prepared for CGRP immunohistochemistry and Nissl-Myelin stain. Dorsal root axons regenerated into both kinds of transplants, but growth into dorsal half of ESC was more robust than that into ventral half of ESC. Histograms of the perikaryal area showed that the transplants of dorsal half ESC consisted of small neurons predominantly, whereas transplants of ventral half ESC consisted neurons of variable sizes with abundant myelination. These results indicate that both kinds of ESC may help to rebuild damaged spinal reflex circuits after spinal cord injury.