Cavernous nerve regeneration by biodegradable alginate gel sponge sheet placement without sutures

Alginate, a biodegradable polysaccharide, may be applied to facilitate nerve regeneration. We attempted to regenerate excised cavernous nerves by filling the gap with a biodegradable alginate gel sponge sheet without sutures. Bilateral cavernous nerves of male Wistar rats were excised to make an approximately 2-mm gap. A piece of freeze-dried alginate sheet was then placed over the gap to cover each stump without suturing (alginate group). We also performed sham operations (sham group) and bilateral nerve excision alone (excision group). Erection was confirmed visually by mating behavior in 9%, 36% and 73% of alginate rats at 2, 4, and 12 weeks, respectively. In contrast, no excision rats had an erection. At 12 weeks postoperatively, electrical stimulation of the pelvic plexus increased intracavernous pressure in the sham group and alginate rats with restored erectile function. However, no increase occurred in the excision group. In a retrograde neural tracing study with FluoroGold at 12 weeks, rich FluoroGold-positive cells were observed in the sham group and alginate rats with restoration, but very few were found in the excision group. Double-labeled immunochemistry with anti-S-100 and beta-tubulin III antibodies showed that the neural gap was connected with the regenerated nerve fibers at 12 weeks. The results of our animal study have demonstrated that by simply filling the nerve gap using an alginate sheet, the cavernous nerve can be regenerated and erectile function may be restored.