Permeable tubes increase the length of the gap that regenerating axons can span.

After placement of stumps of transected rat sciatic nerve in an impermeable tube, the maximum gap the axons can span is 10 mm. The present study shows that the regenerating axons cross much longer gaps if the tube is made permeable. This improvement does not require another nerve as a transplant nor the preplacement of extracellular materials in the tube. Possible mechanisms for this improvement are discussed.