Cells and Materials


Bridging a severed peripheral nerve with a tubular conduit, "entubulation repair" , allows manipulation of the microenvironment encountered by regenerating axons. In the present study, we placed the ends of severed mouse sciatic nerves into nonpermeable Tygon tubes to bridge a 4 mm nerve gap. The tube lumen was filled with either a collagen or laminin matrix. The matrices formed a stable 3-D structure connecting both proximal and distal stumps, and provided a scaffolding for the regenerating axons and their supporting cells. We examined with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy, the initial events of axonal and cellular ingrowth in the first 12 days post-section. Both of the core matrices within the tube lumen became surrounded first by a loose trabecular matrix and then by a concentric sheet of flat cells. Our previous studies have shown that at early time points following entubulation repair more axons crossed a 4 mm nerve gap through tubes filled with laminin compared to collagen matrices. In the present study, we found a faster ingrowth of supporting cells, and associated axons in the lamininenriched matrices. This earlier axonal outgrowth did not appear to be related to the total density of nonneuronal cells. Rather, the axonal ingrowth into the tube was dependent on the greatest distance that non-neuronal cells had grown into the matrix.