Sustained bFGF-release tubes for peripheral nerve regeneration: Comparison with autograft

BACKGROUND: Despite numerous articles on the use of artificial nerve conduits, autologous nerve transplants remain the most effective for nerve repair. To improve this technique, the authors examined conduits containing gelatin hydrogel as a carrier enabling the sustained release of basic fibroblast growth factor (bFGF). METHODS: To confirm sustained bFGF release in vivo, nerve-guide tubes containing iodine-125-labeled bFGF with or without gelatin hydrogel were implanted under the skin of mice, and the remaining radioactivity was measured. Next, a 15-mm segment of the sciatic nerve was resected and repaired with autologous nerve (group 1), a tube with gelatin hydrogel and bFGF (group 2), a tube with bFGF alone (group 3), or a tube only (group 4). Histologic and functional analyses were performed for 16 weeks after surgery. RESULTS: The radioactivity from iodine-125-labeled bFGF incorporated into gelatin hydrogel decreased more slowly than iodine-125-labeled bFGF alone. Four weeks after surgery, significantly more regenerating axons were detected in group 2 than in groups 3 and 4, but the axonal density in group 2 was lower than in group 1. Similarly, the animals in group 2 showed significantly better motor performance than those in groups 3 and 4, but worse than those in group 1. The animals in groups 1 and 2 showed significantly better sensory recovery than those in groups 3 and 4. CONCLUSIONS: The nerve-guide tube containing gelatin hydrogel and bFGF promoted axonal regeneration after peripheral nerve injury, but not as well as autologous transplants. Understanding the limitations of this technique will facilitate its improvement for clinical applications.