Blind-ended semipermeable guidance channels support peripheral nerve regeneration in the absence of a distal nerve stump.

The presence of a distal nerve segment is considered to be essential for peripheral nerve regeneration through impermeable synthetic guidance channels. The use of a perm-selective material may provide a more appropriate regenerating environment by allowing solute exchange across the wall of the channel. We compared perm-selective acrylic copolymer (AC) channels with impermeable silicone elastomer (SE) channels in terms of regeneration in the absence of a distal nerve stump. Cohorts of 6 animals received AC and SE channels for either 4 or 8 weeks, with the distal end of the polymer tube left open in half of the animals, and plugged with the same polymer ('capped') in the other half. Capped and uncapped AC channels contained regenerated nerve cables which extended fully to the distal end of the channel, whereas capped SE channels contained only 1 mm long granulomatous tissue cables, and uncapped SE channels showed small cables with only a few myelinated axons. The nerve cables regenerated in uncapped AC channels were smaller and contained fewer myelinated axons than those observed in capped AC channels. Capped AC channels sleeved with a tight-fitting silicone tube to render them impermeable, showed no regenerated tissue within their lumen. The use of a perm-selective channel may have allowed the influx of nutrients and growth factors from the external environment while concentrating factors released by the proximal nerve stump.