Nerve regeneration chamber: evaluation of exogenous agents applied by multiple injections

In this laboratory, a silicone chamber model for peripheral nerve regeneration in adult rats has been developed and used to define basic principles of the regenerative events, such as the sequential stages being followed during 'spontaneous' regeneration in vivo and the role of neuronotrophic- and neurite-promoting factors as well as extracellular matrix molecules. Each of the defined stages seems amenable to experimental modulation. Previous attempts to enhance regeneration included increasing the volume of the nerve chambers along with the modification of fibrin matrix formation by prefilling with saline (PBS) or matrix precursors. We present here the results of a series of experiments on the effects of exogenous biochemical agents applied by multiple injections into these in vivo chambers. Out of a variety of agents screened, a mixture of laminin (L), testosterone (T), ganglioside GM 1 (G), and catalase (C) was shown to advance substantially the progress of regeneration in 16 day chambers, as compared to PBS-prefilled and PBS-injected controls. LTGC-treatment at day 0, 6, and 10 postimplantation caused an increasingly frequent occurrence of cellular elements in cross-sections obtained from the middle (S5) of the chambers (i.e. 5 mm from the proximal stump), which was 2-fold for vessels, 3-fold for Schwann cells, and 10-fold for axons. When only sections containing axons 3 mm from the proximal stump (S3) were compared in experimental and control groups, computerized area measurements also revealed an average 2-fold difference for the cross-sectional size of the whole regenerate, the endoneurium and the space occupied by blood vessels.