The Effects of the Recombinant Human Amelogenin Protein (rHAM⁺) Application on Healing of Transected Sciatic Nerve

Injury to the nervous system is often associated with permanent impairment. Spontaneous regeneration leading to recovery of function rarely occurs. Previously, we have shown that in-vivo application of the recombinant human amelogenin (rHAM+) brought about significant regeneration of various injured mesenchymal tissues. During amelogenin induced regeneration of transected skeletal ligament, correct orientation of the proprioceptive nerve endings was detected, which might indicate regeneration of the proprioceptive sensation. Our goal in this study is to evaluate the ability of rHAM+ to induce structural and functional regeneration of fully transected rat sciatic nerve. The right sciatic nerve of 8 weeks old female rats was transected sharply and repaired immediately end-to-end. 1µg/µl of rHAM+ dissolved in its carrier propylene glycol alginate (PGA) was applied onto the repair site of the experimental groups. To the control group PGA carrier alone was applied. Rats were followed for three months, during this time functional recovery was evaluated using footprint analysis. Three months after operation the ratios between the weights of right and left (non-operated side) gastrocnemius- soleus muscles was calculated. The sciatic nerve was harvested and prepared for histological and immunohistochemical analyses, using a monoclonal antibody against neurofilaments. Three months after injury, footprint analysis improved and gastrocnemius- soleus muscle weight ratio were significantly higher in experimental groug treated with 1µg/µl rHAM+ (0.91), compared to the control group (0.67). Neurofilaments staining indicated Wallerian degeneration changes with fibrotic tissue filling the transection zone in the control, in the experimental (1µg/µl rHAM+) many more bundles of exons passed through the transected area, and fewer nuclei were evident. Our preliminary results indicate that 3 months after application of 1µg/µl rHAM+ onto acute sciatic nerve transection, there is partial functional and structural healing of the nerve, significantly better than in the control group. We are currently evaluting other concentrations of rHAM+.