Peripheral nerve repair across a gap studied by repeated observation in a new window implant chamber

We have developed a new peripheral nerve chamber system which allows high resolution observation of the cellular events involved in nerve regeneration. The growth into the chamber is confined to a two-dimensional sheet resembling tissue culture. An intact blood supply forms within the chamber and by 100 days the nerve bridging the chamber has a nearly normal perineurium surrounding unmyelinated and myelinated axons. Degenerating axons are very rarely seen. The early growth in the chamber has a tendency to spread widely and form a two-dimensional sheet. This results in morphologies similar to those found in tissue culture and facilitates observation of individual elements. The initially wide tissue growth gradually re-models to form a bridge with a constant width similar to the width of the peroneal nerve. Occasionally a 'side arm' containing myelinated axons was retained even though the majority of axons appeared to loop back and rejoin the main bridge. Prefilling the chamber with Matrigel did not produce a significant enhancement of growth rate over that found following prefilling with sterile saline but did result in a more normally organized structure in the long term. Proximal ingrowth occurred at a similar rate in the absence of the distal stump. The structure of the proximal stump in the absence of the distal stump was similar to the structure when both stumps were present, including the presence of myelinated axons near the proximal port by 20 days. However, at subsequent stages the absence of a distal stump led to withdrawal of the proximal growth.