Spatiotemporal progress of nerve regeneration in a tendon autograft used for bridging a peripheral nerve defect

We have previously shown that a tendon autograft from the rat tail can supp ort regeneration across a gap in the continuity of the rat sciatic nerve. I n this study, we characterized the spatiotemporal progress of regeneration in such a graft bridging a 10-mm defect in the sciatic nerve of the rat. Re generation was assessed 7, 10, 14 or 18 days postoperatively, by immunocyto chemistry for axons, Schwann cells, and macrophages and histochemistry for blood vessels. Axonal regrowth into the grafts showed an initial delay peri od of 6.8 days, whereafter axons grew at a rate of 1.0 mm/day. Schwann cell s grew into the grafts from both the proximal and distal nerve segments, pr oximally just ahead of the axonal front. Macrophages were initially prefere ntially located at the periphery of the grafts, but gradually increased ins ide the grafts. Blood vessels entered the grafts from both the proximal and distal aspects of the severed nerve. The onset of vascularization appeared to coincide with axonal regeneration into the grafts. (C) 1999 Academic Pr ess.