The effects of low-intensity ultrasound on peripheral nerve regeneration in poly(DL-lactic acid-co-glycolic acid) conduits seeded with Schwann cells

This study attempted to improve the efficacy of peripheral nerve regeneration, using the stimulus of low-intensity ultrasound (US) on poly(DL-lactic acid-co-glycolic acid) (PLGA) nerve guidance conduits seeded with Schwann cells. The possible differences between the ultrasonic effects of biodegradable and nonbiodegradable materials used as conduits were also investigated, by comparison with a group of silicone conduits. The PLGA conduits were seeded with or without Schwann cells (6 X 103 cells). All conduits were implanted 10 mm into right sciatic nerve defects in rats and underwent 12 ultrasonic treatment sessions over 2 weeks. Ultrasound was applied at a frequency of 1 MHz and an intensity of 0.2 W/cm(2) spatial average temporal peak (SATP) for 5 min/day. Histologic analysis was used to evaluate the recovery of the nerve after 6 weeks. Ultrasonically stimulated animals, especially those whose PLGA conduits, seeded with Schwann cells, exhibited considerably more myelinated axons with a larger mean area at the mideonduit of the implanted grafts than those in any other group. Ultrasonic stimulation of a silicone conduit induced the generation of mass fibrous tissues that covered the nerve conduits and retarded axon regeneration. These results showed that ultrasonic stimulation may directly stimulate the seeded Schwann cells within the PLGA conduits to regenerate nerves. Nevertheless, the applying of US may not allow incorporation with the silicone rubber as a material from which to form nerve guidance conduits. (C) 2004 World Federation for Ultrasound in Medicine Biology.