This article describes a 30-mm regeneration of severed peripheral nerve axons along collagen filaments. Two thousand or 4000 31-mm-long collagen filaments were grafted to bridge a 30-mm defect of the rat sciatic nerve. A collagen tube was grafted as a control. The mean number and mean fiber diameter of regenerated myelinated axons were 330 +/- 227 and 2.7 +/- 0.9 microm in the distal end of the 2000 collagen-filaments nerve guide, and 564 +/- 275 and 2.5 +/- 1.1 microm in the distal end of the 4000 collagen-filaments nerve guide at 12 weeks postoperatively, whereas in the distal end of the collagen tube, no regenerated axon was found. These results suggest that the collagen filaments guide axons of the rat's sciatic nerve to regenerate for 30 mm and act as a scaffold for axonal regeneration. Thirty-millimeter nerve regeneration of a 1-mm-diameter rat sciatic nerve by an artificial nerve guarantees a clinical application of the implant which should be very important for patients and surgeons.

We report the first success of functional restoration of transected rabbit spinal cord using collagen-filament nerve scaffold. We grafted 5 mm-long 6000 collagen filaments parallel to the axis of the spinal cord to bridge 3 mm defects of 21 adult rabbit spinal cords; 18 rabbits were used as controls. Of the 39 rabbits, 22 survived the experimental period. At 12 weeks postoperatively, regenerated axons crossed the proximal spinal cord-implant interfaces in four out of six rabbits. At 24 weeks postoperatively, regenerated axons crossed the proximal and distal spinal cord-implant interfaces in four out of six rabbits. At 24 weeks postoperatively, the Basso-Beattie-Bresnahan (BBB) locomotor rating scale scores of the rabbits in the collagen-filament grafted group were 4.7 +/- 2.3, while the score in the control group was 2.8 +/- 0.5. The BBB scale scores of the grafted group were significantly better than the control group. The results suggest that the collagen-filament nerve scaffold supports the axonal regeneration of the transected spinal cord and the restoration of function when grafted parallel to the axis of the spinal cord. The functional restoration appeared to be permanent, raising the possibility of therapeutic application in humans.

The collagen filaments support the axonal regeneration of the transected spinal cord and the restoration of function.

The restoration of function of transected adult mammalian spinal cord without living tissue has not been reported previously. We report the first success of functional restoration of transected spinal cord without living tissue. We grafted collagen filaments parallel or transverse to the axis of the spinal cord to bridge 5-mm defects of 47 adult rat spinal cords. Twenty-five rats were used as a control. Of the 72 rats, 42 rats survived the experimental period. At 4 weeks postoperatively, regenerated axons crossed the proximal and distal spinal cord-implant interfaces in all 5 rats of the parallel-grafted group. At 12 weeks postoperatively, the rats in the parallel-grafted group (8 rats) could walk, run, and climb with hind-forelimb coordination. The somatosensory-evoked potentials were seen. Results suggest that the collagen filaments support the axonal regeneration of the transected spinal cord and the restoration of function when grafted parallel to the axis of the spinal cord. The functional restoration appeared to be permanent, raising the possibility of therapeutic application in humans.