Evaluation of transected spinal cord regeneration in the rat.

Rat spinal cords were subjected to a 200 g/cm force acceleration injury at T10. Ten days later, the cords were totally transected at T10 and the rats separated into two groups: group C (controls) had the spinal cord realigned end-to-end; group X had 3 mm trimmed from proximal and distal cord stumps and a semifluid collagen matrix (CM) bioimplant was inserted in the gap. The CM polymerized to a firm gel at body temperature within 2 h. All rats were maintained 90 days posttransection (dpt). At 90 dpt, they were examined for local spinal cord blood flows, somatosensory evoked potentials, and a neurological evaluation. After killing, the cords were processed for electron and light microscopy and monoamine histofluorescence. The results indicated that CM can support the growth of central neurites, fibroblasts, and an adequate anastomotic network of blood vessels. Control scar tissue does not promote the presence of nerve fibers and blood vessels to the extent observed in the CM. Somatosensory evoked potential early waveforms were present in CM-bioimplanted rats but not in controls. No rat regained walking ability at 90 dpt but muscle tone and strength appeared better in CM-implanted than in control rats. We conclude that a CM bridge can provide a well vascularized, relatively nonhostile environment for central neurites and catecholaminergic axons extending from the proximal spinal cord tissue across the CM bridge and into the distal stump.