Sorting of regenerating rat sciatic nerve fibers with target-derived molecules

The functional outcome of microsurgical repair of divided nerves is disappo inting since many regenerating axone fail to reach appropriate targets. Sor ting of regenerating axone according to target tissue might be used to impr ove functional regeneration. The aim of the present study is to see if rege nerating axone can be sorted into functionally different bundles with targe t-derived molecules. The proximal stump of the adult rat sciatic nerve was sutured into the inlet of a silicon Y-tube. The two branches of the Y-tube were filled with agarose primed with filtrates prepared from skin and muscl e homogenates from the operated rat. The tibial and sural nerves were inser ted in the two branches of the Y-tube. Six weeks later the sciatic nerve ax ons showed vigorous regeneration into both branches. Electron microscopic e xamination of regenerated nerve segments showed numerous myelinated and unm yelinated axone. The proportion of myelinated axons was significantly large r in the muscle-gel branch than in the skin-gel branch. Retrograde tracing from the nerve regenerates with Fast Blue and Fluoro-Ruby showed that ventr al horn neurons at L4-L5 segmental levels were preferentially labeled from the muscle-gel branch. Neurons in corresponding dorsal root ganglia were la beled from both Y-tube branches (no significant numerical difference). A fe w neurons of both types contained both tracers. Measurements revealed that sensory neurons labeled from the muscle-gel branch were significantly large r (mean perikaryal area 870 mum(2)) than neurons labeled from the skin-gel branch (mean area 580 mum(2)). We conclude that regenerating motor and sens ory axone can be sorted with target-derived molecules. (C) 2001 Academic Pr ess.