Ultrastructural analysis of peripheral-nerve regeneration within a nerve conduit.

The purpose of this study was to observe the cellular components of regenerating peripheral nerves within a nerve conduit. Rat sciatic nerves were placed in a silicone conduit with a 5-mm gap between nerve endings. At weekly intervals for 6 weeks, 70-nm sections of nerve tissue from the conduit were obtained for ultrastructural observation. The principal cellular components by the end of the first week were macrophages and fibroblasts. By the end of the second week, both myelinated and unmyelinated nerve fibers began to pass through the entire conduit. By the end of the fifth week, nerve fibers were present at various levels of maturity, with no evidence of inflammatory or immunologic response. By the end of the sixth week, the percentage of nerve fibers was 86 percent of the cellular components. This analysis provides cellular data on which to base additional research regarding functional outcomes when using nerve conduits.