Many types of artificial conduits have been studied as potential alternatives to short nerve grafts, however long nerve gaps were not successfully reconstructed due to lack of growth potential. Tissue engineering offers the potential to create replacement structures from viable cells and biodegradable polymer conduits. Since they contain living cells, these structures have the potential to grow and induce regeneration. The objectives of this study are to create a biodegradable nerve guide seeded by neurotrophic factor gene-transferred Schwann cells, and to assess in vivo nerve regeneration through the guides.

Schwann cells were isolated from Wistar rat sciatic nerves. Neurotrophic factor genes (BDNF, CNTF and NT3) were transferred into the expanded Schwann cells using adenoviral vector. Western blotting was performed to examine the expression of neurotrophic factors from the gene-transferred Schwann cells. Additionally, culture media of gene-transferred Schwann cells harvested at 3 weeks were supplied for cultured dorsal root ganglia to measure axonal outgrowth on 2nd day by neurofilament staining (n=15). A novel, biodegradable polymer conduit (2 mm in diameter, 20 mm in length) was composed of a polycaprolactone-polylactic acid copolymer reinforced with woven polyglycolic acid. Gene-transferred Schwann cells were seeded into the polymer conduit using Pluronic gel and this hybrid conduits were transplanted to bridge 15mm defects of the Wistar rat sciatic nerve (n=5). Polymer conduits with primary Schwann cells (n=5) and silicone conduits (n=5) were implanted into another set of animals as controls. After 12 weeks, sciatic nerve including conduit was harvested and fixed by glutaraldehyde. At the mid portion of the conduit, cross sections were cut and stained with Toluidine blue to evaluate axonal contents.

Western blotting assay showed higher expression of neurotrophic factors in gene-transferred Schwann cells. The culture media of gene-transferred Schwann cells induced excellent axonal outgrowth (BDNF, CNTF, NT-3 vs. control=118.7�50.5, 130.0�52.7, 99.2�38.3 vs. 62.0�14.4�m, p<0.05). On histological assessments, significant difference between gene-transferred cells-seeded and primary cell-seeded conduits was detected in the total number of myelinatated fibers (BDNF, CNTF, NT-3 vs. control = 3887�767, 2453�1215, 1989�1579 vs. 1470�276, p<0.05) and fiber density (fiber number/mm2�F 17513�1833, 15011�3400, 9573�1495 vs. 9305�2893, p<0.05). These findings suggest that tissue-engineered devices, composed of biodegradable polymer materials and adherent gene-transferred Schwann cells can facilitate nerve regeneration in reconstruction for a long nerve gap.