The Combined Use Of Modified Chitosan And Methylprednisolone Could Promote Nerve Repair In SD Rat Sciatic Nerve Injury

BACKGROUND:Chitosan is a kind of natural polycationic biological polysaccharide, with good biocompatibility and biodegradability, which has been widely used not only in the prevention of postoperative abdominal adhesions, but also in nerve repair, skin repair, bone and cartilage repair, and so on. Methylprednisolone is a kind of intermediate-acting glucocorticoid, which has the effect of anti-inflammation, immunosuppression and improving the microenvironment around nerve injury. Previous studies have shown that the application of methylprednisolon after peripheral nerve injury can promote nerve regeneration.OBJECTIVE:To observe the effect of the modified chitosan and methylprednisolone combination on nerve repair in a SD rat sciatic nerve injury model, and to explore an effective and safe new treatment to improve peripheral nerve regeneration and repair.METHODS:60 six-week-old SD rats were randomly divided into five groups (n=12) regardless of their sex, with group 1 for modified chitosan, group 2 for methylprednisolone, group 3 for the modified chitosan and methylprednisolone combination, group 4 for physiological saline,and group 5 for sham operation. In the former 4 groups, the sciatic nerve anastomosis was done immediately after nerve cut, and then, the rats were given 1ml modified chitosan, lOmg methylprednisolone, 1ml modified chitosan and 10mg methylprednisolone, 1ml physiological saline, respectively, according to different groups. In group 5, the sciatic nerve was not cut off. Incision was sutured layer by layer for every rat, with intramuscular gentamicin to prevent infection. Then observe the claw extending reflex recovery from operation every day, and calculate the sciatic nerve conduction velocity, the remnant rate of gastrocnemius wet weight, the diameter and the section area of gastrocnemius cells after 4 weeks,8 weeks, and 12 weeks, respectively. Light microscopy and transmission electron microscopy were used to observe the histological change of sciatic nerve.RESULTS:No accidental death and postoperative infection occurred during the experiment in 60 SD rats, without missing data. Skin wounds healed after eight days in all rats. The right lower limb paralysis occurred gradually after surgery in ABCD four groups of rats with sciatic nerve transection and anastomosis. Rats in groups A, B, C and D began to recover exhibition claw reflection in 25,25,22 and 26 days after surgery, and all recovered after 32,33,28 and 38 days from surgery, respectively. Rats in roup C showed earlier in the claw extending reflex recovery (24.0±2.0d), with statistical significance (P<0.05). There was no significant difference between group A and B. Measurement of sciatic nerve conduction velocity after 4,8 and 12 weeks from surgery showed that sciatic nerve conduction velocity in group E was the fastest, and group D was the slowest. Group C was faster than groups A and B and D(P<0.05). Group A was faster than group B, without significant difference (P> 0.05).Determination of the gastrocnemius wet weight residual rates after 4,8 and 12 weeks from surgery showed that the rates in groups A, B, C and D were decreased gradually, significantly lower than in group E (P<0.05). Group D declined faster than groups A, B and C, with significant difference between group C and D (P <0.05).Determination after 4,8 and 12 weeks from surgery showed that the diameter and the section area of gastrocnemius cells were reduced gradually in groups A, B, C and D. Compared with group E, group D reduced most than other groups. The diameter and the section area of gastrocnemius cells in group C reduced significantly milder than those in group D (P<0.05).Observation after 4,8 and 12 weeks from surgery showed that sciatic nerve adhesion was severer in groups D and E than that in groups A. B and C. Adhesion was milder in group C than in groups A and B, with statistical significance (P<0.05). Observation with electron microscopy after 12 weeks showed that the nerve fibers through anastomotic were significantly increased, with more consistent thickness and disposition of nerve fibers, and less neurodegeneration in group C than in groups A, B, D and E. They were similar in group A and B, better than group D and E.CONCLUSION:1.Both modified chitosan and methylprednisolone could prevent anastomotic adhesion and scar. The combined use of modified chitosan and methylprednisolone could significantly reduce the incidence of adhesion and scar.2.The combined use of modified chitosan and methylprednisolone could promote peripheral nerve regeneration and reinnervation of end-organ.3.The results showed that the combined use of modified chitosan and methylprednisolone could promote regeneration of sciatic nerve injury. However, the functional recovery still could not reach to the previous level. Therefore, we need further research to explore new methods of repairing peripheral nerve injury.