Enhancement of axon growth by detergent-extracted nerve grafts

BACKGROUND: The immunogenicity of nerve allografts is responsible for their rejection. We have developed a method for preparing cell-free nerve grafts using lysophosphatidylcholine to remove cells, axons, and myelin sheaths. METHODS: The remaining intact nerve extracellular matrix is the extracted nerve graft (eNG). Cultured neonatal Schwann cells were micro-injected into the eNG to form recellularized nerve grafts (rNG). eNG, rNG, and normal isografts (15 mm long) were implanted in the peroneal nerves of F-344 rats. Ten rats were given an eNG on the right, and an isograft on the left. Ten rats were given an rNG on the right, and a sham operation on the left. Sham operation was used as the control and the isograft was used as the benchmark procedure. Walking track analysis was performed every 15 days after surgery to determine the peroneal functional index. Morphometric analysis of the distal peroneal nerve and extensor digitorum muscle weight were analyzed 3 months after surgery. RESULTS: The three types of grafted legs had the classical effect observed after peripheral nerve repair, with decreased functional ability, decreased target muscle weight, fewer large nerve fibers, and more small nerve fibers. Isografts, eNG, and rNG all had similar patterns of peroneal functional index improvement after implantation. The extensor digitorum longus muscle weight and axon counts for the three types of graft were not statistically different. Hence, eNG and rNG can enhance nerve regeneration in the same way as isografts. The host Schwann cells that invaded the implanted eNG probably acted in the same fashion as the cultured Schwann cells injected into the rNG and the resident cells of isografts. CONCLUSIONS: The great permeability of the longitudinally oriented matrix of eNG to cells is, therefore, a major advantage over the reported poor permeability of freeze-thawed nerve grafts.