Effect of TGF-b1&2 antibodies on fibre counts after nerve repair

Objective: The formation of scar tissue at a site of nerve repair can lead to the development of multiple axonal sprouts to form a neuroma. We have investigated whether the application of a scar-preventing agent to a nerve repair site would reduce axonal branching. Methods: The left sciatic nerve was exposed under general anaesthesia (Fentanyl/Fluanisone 0.8ml/kg & Midazolam 4mg/kg, i.p. Janissen/Roche) in 18 adult Sprague-Dawley rats. In 12 animals the nerve was sectioned and immediately re-approximated using 4 epineurial sutures, and in 6 of these neutralising antibodies to TGF- b1 & TGF- b2 (100µg of each in 100µl PBS, R & D systems) were injected into and around the proximal and distal nerve stumps. The 6 other animals acted as controls. After 7 weeks the nerves were harvested, prepared for light microscopy, and using a sampling protocol the number of myelinated axons in transverse sections 2mm proximal and 2mm distal to the repair site (or equivalent sites in controls) was determined. Results: In controls the fibre counts were not significantly different at the two sites (median proximal: 7454, median distal: 8107, Mann-Whitney U test, p>0.15). In both nerve injury groups the myelinated fibre counts were significantly higher distal to the injury site than in controls (repair 11209, repair + antibodies 12445, p<0.005), but there was no difference between these two groups. There was a significant reduction in cross sectional area of the nerve distally in both repair groups, and a resultant increase in nerve fibre density; these changes were more marked in the antibody group. Conclusions: We conclude that administration of scar preventing antibodies, using this dosing regime, did not reduce the development of multiple axonal sprouts at a sciatic nerve repair site. Supported by the Wellcome Trust.