Hyperbaric oxygen treatment has different effects on nerve regeneration inacellular nerve and muscle grafts

Effects of hyperbaric oxygen treatment (HBO) on nerve regeneration in acell ular nerve and muscle grafts were investigated in rats. Nerve and muscle gr afts were made acellular by freeze-thawing and the obtained grafts were use d to bridge a 10-mm gap in the sciatic nerve on the left and right sides, r espectively. Rats were treated with HBO (100% oxygen for 90 minutes at 2.5 atmospheres absolute pressure ATA) twice a day for 7 days. Axonal outgrowth , Schwann cell migration and invasion of macrophages were examined 10 days after the graft procedure by staining neurofilaments, S-100 proteins and th e macrophage antibodies ED1 and ED2, respectively. Axonal outgrowth and Sch wann cell migration in acellular nerve grafts were superior to that found i n the acellular muscle grafts. However, there was no difference between HBO -treated and nontreated rats in acellular nerve grafts. Such a difference w as found in acellular muscle grafts concerning both axonal outgrowth and Sc hwann cell migration from the proximal nerve end. No differences in the con tent of macrophages or neovascularization (alkaline phosphatase staining) i n either of the grafts and treatments were seen. It is concluded that there is a differential effect of HBO-treatment in acellular nerve and muscle gr afts and that HBO-treatment has no effect on the regeneration process in ac ellular nerve grafts, in contrast to fresh cellular nerve grafts where a be neficial effect has previously been reported.