Comparative study on repairing effects at different time points after peripheral nerve injury / 中国组织工程研究

ABSTRACT

BACKGROUND:It is proved by a number of experiments that such a structure as Bungner band-Schwann cell-basilar membrane,which is formed at 2 or 3 weeks after nerve injury,is the ideal microenvironment for neural regeneration. However,the sprouting of nerve fiber close to broken ends takes place at several hours after nerve injury,which shows that the regeneration of nerve fiber and the formation of required microenvironment don't occurred at the same time.OBJECTIVE:To investigate the best repairing time for peripheral nerve injury.DESIGN,TIME AND SETTING:A randomized control animal experiment was performed in the Animal Experiment Centre,Harbin Medical University from June 2007 to June 2008.MATERIALSA total of 20 New Zealand rabbits were randomly divided into four groups,namely,an immediate repairing group and the other three groups that were repaired respectively at week 2,week 4 and month 3 after injury.METHODS:Peripheral nerve injury models of New Zealand rabbits were established. The immediate repairing group received suture immediately after injury;For the other three groups,the two broken ends of their nerves were fixed on sarcoiemmas temporarily and their wounds were sutured layer by layer. Then they were opened respectively at week 2,week 4 and month 3 after injury,to receive epineural suture with non traumatic 10-0 nylon suture under operating microscope,after which wounds were sutured again.MAIN OUTCOME MEASURES:Nerve electrophysiological observation,axon number,light microscope and electron microscope observation of sutured nerve segments in each group.RESULTS:Nerves repaired at week 2 after injury had a slower nerve conduction velocity than those at week 4 and month 3 after injury (P＜0.01);There was no difference of significance between the immediate repairing group and the group repaired at week 2 after injury (P＞0.05). According to the comparison among the four groupsit had the best repairing effect to repair nerve at week 2 after injury,with normal course and neat arrangement of nerve fibers,vascular proliferation in nerve fibers,myelin sheaths with better structure,Schwann ceils with active function,as well as regenerated axons with intensively arranged microfilaments;Repairing at week 4 after injury had the worst effect,with rare nerve fivers disorderly arranged,myelin sheath and axons significantly degenerated,most nerve fibers demyelinated with axons disappeared,and no regenerated nerve fibers seen;Repairing at month 3 saw the worse repairing effect,with more nerve fiber damaged and disorderly arranged,myelin sheath and axons significantly degenerated,nerve fibers rarely regenerated,less Schwann cells,as well as cytoplasm did not well develope;The effect of immediate repairing after injury was better,with nerve fibers unobviously damaged and well arranged,myelin sheath and axons lightly degenerated,large amounts of myelin sheaths regenerated in nerve fibers,Schwann cells increased obviously,as well as cytoplasms better-developed. Axon counting result was better in the group repaired at week 2 after injury than the otherthree groups,with the minimum in the group repaired at week 4 after injury.CONCLUSION:Repairing at week 2 after injury can get a better result than at any other time points,accordingly two weeks after nerve injury is the best time for repairing peripheral nerve injury.