Alginate, a bioresorbable material derived from brown seaweed, enhances elongation of amputated axons of spinal cord in infant rats

Freeze-dried alginate sponge crosslinked with covalent bonds was developed in our laboratory and has been demonstrated to enhance peripheral nerve reg eneration. In this study, we examined spinal cord repair using alginate spo nge in infant rats. On postnatal day 8-12, the spinal cord was transversely resected at Th7-Th8 to produce a 2-mm gap The gay was filled with alginate sponge in the alginate group. For the control group, the gap was left empt y. In the alginate group, the recovery of evoked electromyogram and sensory -evoked potentials 6 weeks after surgery indicated that elongation of axons could establish electrophysiologically functional projections through the gap. A histological study revealed that myelinated and unmyelinated axons, surrounded by a perineurial-like structure, had elongated across the gap. A n immunohistochemical examination revealed that elongation of astrocytic pr ocesses and/or migration of astrocytes into the alginate sponge was induced , whereas astrocyte gliosis was reduced at the interface between the implan ted alginate and the host spinal cord, compared with the control group. How ever, a horseradish peroxidase tracing study revealed ascending and descend ing fibers had also elongated into the gap and reentered the other stump of the transected spinal cord beyond the gap. These results suggest that algi nate might provide a permissive microenvironment for elongation of spinal c ord axons. (C) 2000 John Wiley & Sons, Inc. J Biomed Mater Res 54: 373-384, 2001.