Low-intensity-ultrasound-accelerated nerve regeneration using cell-seeded poly(D,L-lactic acid-co-glycolic acid) conduits: an in vivo and in vitro study.

This study investigated the effects of low intensity ultrasound on seeded Schwann cells within poly(DL-lactic acid-co-glycolic acid) (PLGA) conduits by in vitro and in vivo trials for peripheral nerve regeneration. The possible differences in the ultrasonic effects when using biodegradable and non-biodegradable materials as the conduits were also studied, using silicone rubber tubes as comparisons. In the in vitro study, seeded Schwann cells were cultured in serum deprivation culture medium that simulated the environment of mechanical trauma on injury nerve site. After 12, 24, and 48 h, only the PLGA conduit groups exposed to 0.05 W/cm(2), 3 min/treatment of ultrasound exhibited decreased LDH release and increased MTT values compared to the sham groups. Based on the results of the in vitro experiment in LDH and MTT testing, the silicone conduits with seeded Schwann cells group was ignored in the in vivo study. The PLGA nerve conduits seeded with Schwann cells (9 x 10(3) cells) were implanted to 15-mm right sciatic nerve defects in rats. Each conduit received 12 ultrasonic treatment sessions over 2 weeks after 1 day of rest. Ultrasound was applied as follows: frequency, 1MHz; intensity, 0.3 W/cm(2) (SATP); treatment, 5 min/day. Implanted graft specimens were harvested for histological analysis at 8 weeks following surgery. PLGA groups (with and without Schwann cells) treated with pulsed ultrasonic stimulation were found to have significantly greater number and area of regenerated axons at the mid-conduit of implanted grafts, as compared to the sham groups. Ultrasonic stimulation on silicone groups was found to induce a mass of fibrous tissues that covered the nerve conduits and retarded axon regeneration.

In vitro and in vivo effects of Ginkgo biloba extract EGb 761 on seeded Schwann cells within poly(DL-lactic acid-co-glycolic acid) conduits for peripheral nerve regeneration.

This study investigated the effects of Ginkgo biloba (EGb 761) extract on seeded Schwann cells within poly(DL-lactic acid-co-glycolic acid) (PLGA) conduits by in vitro and in vivo trials for peripheral nerve regeneration. The seeding efficiency of Schwann cells in serum-deprived culture medium, which simulated the environment of mechanical trauma on an injured nerve site, was improved by adding different dosages of EGb 761 (0, 1, 10, 20, 50, 100, 200 microg/mL). The analytical results showed enhanced cell attachment and survival, reduced LDH release and increased MTT values, particularly in the range 10-100 microg/mL. The PLGA nerve conduits seeded with Schwann cells (6 x 10(3) cells) and filled with gelatin containing EGb 761 (0, 10, 50, 100 microg/mL) were implanted to 10-mm right sciatic nerve defects in rats. Autograft was performed as another control. Electromyography was assessed based on the motor unit action potential (MUAP) and fibrillation potential (Fib) at 2, 4, and 6 weeks during all periods. The specimens of the experimental and control groups were harvested for histological analysis at 6 weeks after surgery. The Fib was found to gradually decay, and the MUAP was found not to be present until 4 weeks after surgery. Meanwhile, the experimental groups were all statically better than the control group (without EGb 761) and autografts were observed at 6 weeks, especially at the concentration of 10 microg/mL, where there was higher amplitude of MUAP and a significantly larger number of myelinated axons. This study concluded that a proper concentration of EGb 761 (10-50 microg/mL) promoted seeding efficiency of Schwann cells in a tissue-engineered PLGA conduit. Addition of EGb 761 in Schwann cells-seeded conduit could increase the total number of myelinated axons in nerve regeneration and improve peripheral nerve functional recovery.