Novel Transplantation of Preconditioned Schwann Cells Following Spinal Cord Contusion Injury

Background Context: Post-injury recovery in the peripheral nervous system (PNS) is based on the proregenerative relationship between axons and Schwann cells. Previous experiments in our group have shown compressive mechanical stress to be important in stimulating the regenerative behavior of Schwann cells.

Purpose: To determine whether transplantation of peripheral nerves to the injured spinal cord improves functional recovery in a contusion model.

Methods: Sprague-Dawley rats were used to create a moderate contusion injury of the spinal cord with a pneumatic impactor. Peripheral nerve grafts were obtained from rat sciatic nerve, either untreated or subjected to mechanical compression for two weeks. Transplantation of grafts to the contused area of cord at one-week post-injury was performed following resection of the glial scar. A subset of the animals underwent sham transplantation. Another group of animals underwent a sham operation in which the cord was exposed and 2 mm of friable glial scar excised, without transplantation. Functional outcome was measured using the Basso, Beattie, Bresnahan (BBB) locomoter rating scale, and obtained preoperatively and weekly thereafter for six weeks. Spinal cord tract labeling and harvest were then performed, for later histological analysis.

Results: Both transplanted groups had significantly higher BBB scores versus the untransplanted controls in the early postoperative period (p<0 .05). Mechanical compression of the transplanted peripheral nerve did not have a significant effect on functional outcome. Glial scar excision without transplantation produced significantly worse recovery in early postoperative period versus and sham operation (p<0.05).

Conclusions: Peripheral nerve transplantation significantly improved functional recovery following contusion spinal cord injury in rats. Mechanical pre-conditioning of the transplanted nerve did not have a significant clinical effect on recovery, but these grafts may improve axonal regeneration, suggesting that the animal should be evaluated at later time points.