Effects of transforming growth factor-beta 1 plasmid on immune tolerance following sciatic nerve transplantation / 中国组织工程研究

ABSTRACT

BACKGROUND: Transforming growth factor (TGF)-β_1, a potent cell growth and proliferation regulatory proteins, plays an important role in development of anti-graft rejection and graft vascular disease. OBJECTIVE: To observe local injection of TGF-β_1 effects on transplant immune rejection following freezing disposal and nerve allograft. DESIGN, TIME AND SETTING: The randomized controlled animal study was performed at the Animal Experimental Center, Harbin Medical University from June 2007 to June 2008. MATERIALS A total of 60 clean SD rats (recipients) were divided into 3 groups autogenous nerve graft group, nerve allograft group, TGF-β_1 plasmid + nerve allograft group, 20 in each group. A total of 40 Wistar male rats served as donors. pAdTrack-CMV-TGF-β_1 plasmid, pAdEasy-1-Bj51833 cells were presented by the Orthopedic Laboratory of Fourth Hospital of Harbin Medical University. METHODS: Longitudinal posterolateral incision was made in 40 donor rats to expose sciatic nerve. The whole bilateral sciatic nerve was cut and placed in sterile frozen tubes for 1 week for use. Under the microscope, connective tissue was cut in the biceps muscle and semi-tendon and semi-membrane gap of recipient rats to expose the sciatic nerve. 1-cm sciatic nerve was cut 0.5 cm below the muscle from the plow-shaped hole. Transplantation of frozen autogenous nerve graft and nerve allograft (nerve at equal size) was separately performed in the autogenous nerve graft and nerve allograft groups. In the TGF-β_1 plasmid + nerve allograft group, pAdTrack-CMV-TGF-β_1 plasmid (40 μg) was injected into the local muscle and two sides of transected sciatic nerve of each rat following nerve allograft transplantation. MAIN OUTCOME MEASURES: Motor nerve conduction velocity, pathology and axonal counting were examined 3, 6, 9 weeks after surgery. RESULTS: Motor nerve conduction velocity was higher in the TGF-β_1 plasmid + nerve allograft group than in the nerve allograft group (P < 0.01), which did not show significant difference compared with the autogenous nerve graft group. Axonal counting was greater in the autogenous nerve graft and TGF-β_1 plasmid + nerve allograft groups compared with the nerve allograft group 9 weeks following surgery (P < 0.01). Using optical microscope and electron microscope, nerve fibers were normal and well arranged in the TGF-β_1 plasmid + nerve allograft group. Nerve fibers presented vascular proliferation, good myelin sheath. Abundant regenerated myelin sheath was found in nerve fiber. The number of Schwann cells was obviously increased, and there were prosperous cytoplasm, a large amount of rough endoplasmic reticulum, clear mitochondria. In regenerated axons, microfilament closely arranged, which was similar to the autogenous nerve graft group. In the nerve allograft group, the optical microscope and electron microscope showed a few nerve fibers, disorderly arranged, significant demyelination, axon degeneration and disappearance, without regenerated fibers. CONCLUSION: Local injection of TGF-β_1 plasmid could reduce immune rejection after cold sciatic nerve allograft transplantation.