Orthopedic Department of the First Affiliated Hospital to Shanxi Medical University, Taiyuan   030001, Shanxi Province, China

Rui Mi★, Master, Physician, Orthopedic Department of the First Affiliated Hospital to Shanxi Medical University, Taiyuan   030001, Shanxi Province, China Mi R, Liu Q, Wu D. Nerve allograft regeneration and immunological tolerance of rats with sciatic nerve transplantation after intragastric pretreatment with ultraviolet B-irradiated donor splenocytes. Neural Regen Res 2008;3(5):517-20

Abstract

BACKGROUND: Nerve allograft rejection is an unavoidable problem for nerve allografts. Traumatic peripheral nerve injuries are commonly reconstructed using autogenous nerve grafts. However, this form of reconstruction is limited by insufficient autologous nerves for large gap repairs and by morbidity at the nerve donor site.

OBJECTIVE: To examine sciatic nerve regeneration and immune tolerance reaction after intragastric administration of ultraviolet B-irradiated (UVB) donor splenocytes.

DESIGN, TIME AND SETTING: A complete randomized grouping design and controlled experiment. The experiments were conducted in the Department of Orthopedics, the First Affiliated Hospital to Shanxi Medical University, China, between March and October 2007.

MATERIALS: Fourteen adult male SD rats and fourteen male Wistar rats, weighing 250–300 g, were randomly matched as donors and acceptors. A further seven male SD rats (weight 250–300 g, age 12–16 weeks) were used for nerve isografts. Immune preparations and the Epics XL flow cytometer were purchased from B-D Company, USA. A computer-assisted electromyograph machine was provided by Keypoint P, Dantel Company, Denmark.

METHODS: Splenocytes from Wistar rats were isolated, purified, and cultured, and then irradiated with ultraviolet B. In the first control group (Group 1), the SD rats received a syngeneic SD nerve isograft. In the second control group (Group 2), the SD rats received a nerve allograft from Wistar rats without pretreatment. In the oral-tolerance treated group (Group 3), the SD recipient rats were inoculated with 2.5×10⁷ Lewis UVB-irradiated donor splenocyte cells by intestinal tract administration at seven days before transplantation.

MAIN OUTCOME MEASURES: (1) The recent end and the middle and distal end of the transplanted nerve were cut at 8 and 12 weeks after operation. Recovery of nerve regeneration was measured with HE staining using the total number, density, and diameter of the nerve fibers. (2) The level of CD25+T lymphocytes in peripheral blood was detected with the Epics XL flow cytometer at one week after operation. (3) The bilateral sciatic nerves were exposed from the sciatic notch up to 0.5 mm beyond the distal graft site at eight weeks post-engraftment. Bipolar platinum stimulating electrodes were placed under the sciatic nerve proximally and the mean conduction velocity was recorded with recording electrodes on the posterior tibial nerve at 0.3 cm distal to the nerve graft.

RESULTS: Eight weeks after operation, total axon number and fiber density in Group 3 were higher than that in Group 1 (P < 0.05), neural regeneration in Group 3 was lower than that in Group 1 (P < 0.05) , The level of CD25⁺T lymphocytes in peripheral blood of Group 3 was significantly lower than that of Group 2 (P < 0.05). There was no significant difference between Group 3 and Group 1 (P > 0.05). At eight weeks post-engraftment the mean conduction velocity of Group 3 approximated that of Group 1. The untreated allografts in Group 2 demonstrated no measurable recovery of conduction velocity.

CONCLUSION: Pretreatment with a single intragastric dose of UVB-modified donor antigen specifically induced tolerance to peripheral nerve allografts in rats.

Key Words: sciatic nerve; transplantation, homologous; immune tolerance

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