Peripheral nerve regeneration through nerve guides seeded with adult Schwann cells

This study tested the usefulness of Schwann cells in the repair of a severed nerve with a biosynthetic bridge or guide. Reinforced collagen nerve guides were used to bridge an Is mm gap in the sciatic nerve of 21 young adult rats. The animals were divided into three groups and the guides were filled with: (i) more than 0.5 x 10(6) cultured syngeneic adult Schwann cells (group L, n = 12); (ii) less than 0.5 x 10(6) Schwann cells (Group S, n = 6); and (iii) phosphate buffered saline (control, n = 3). Schwann cells were pre-labelled with Hoechst dye. Regeneration was assessed functionally and histologically at 1, 2, 3 and 6+ months after surgery. Group L animals showed numerous regenerated axons surrounded by implanted Schwann cells within the first month. The total number of myelinated fibres (12.5 x 10(3)) remained above normal unoperated values (7 x 10(3)) in long-term animals. Regenerated axons were found in Group S in the third month, but no Hoechst labelled cells were found. The number of myelinated fibres (3.9 x 10(3)) remained below normal values in long-term animals. Control guides failed to support axonal regeneration. Functional recovery was evident at week 20 (Group L) and week 30 (Group S) after surgery, with no difference in function between the two groups by the end of the study. Supplementing guides with Schwann cells enhances regeneration of peripheral axons over a distance normally prohibitive. This effect is greatest in the early stages of regeneration (1-3 months) and is dependent on the number of cells implanted.