[Time limit of repairing old sciatic nerve defect in rats].
OBJECTIVE
To investigate the time limit of repairing old sciatic nerve defect in rats and observe the repair effect of autogenous nerve transplantation on old sciatic nerve defect in rats.


METHODS
Thirty-six SD rats of clean grade were randomized into 6 groups (n=6 per group). The animal model of nerve defect was made by transecting left sciatic nerve at the mid-thigh level. For groups A1, B1 and C1, defects were repaired by the contralateral autogenous nerve transplantation 1, 3 or 6 months after nerve damage and for the control groups of A2, B2 and C2, defects were not repaired. After operation, the gait, toe skin and leg muscle were examined weekly. Three months after autograft, a combination of electrophysiology examination, fluoro gold (FG) retrograde tracing and histological assessment including light microscopy, TEM was utilized to investigate the nerve functional recovery.


RESULTS
Lameness and foot skin ulcers were observed in each group after nerve damage. At 2 months after autograft, such denervation symptoms were only improved in groups A1 and B1. At 3 months after autograft, the motor conduction velocity was (21.84 +/- 6.74), (20.02 +/- 4.17) and (16.09 +/- 8.21) m/s in groups A1, B1 and C1, respectively, showing no statistically significant difference between them (P > 0.05). The amplitude of compound muscle action potential (CAMP) was (12.68 +/- 4.38), (9.20 +/- 3.43) and (1.22 +/- 0.39) mV in groups A1, B1 and C1, respectively, indicating significant differences between groups A1, B1 and group C1 (P < 0.05). No CAMP was evident in groups A2, B2 and C2. FG retrograde tracing conducted 3 months after autograft showed that the positive cells were most common in group A1 with big soma, mild in group B1 and lest in group C1 with smallest soma. Gastrocnemius Masson staining showed that the fiber morphology of gastrocnemius in groups A1 and B1 was close to normal, while the rest 4 groups had an obvious atrophy of muscle fiber. The fiber cross-section area was (340.73 +/- 118.46), (299.88 +/- 119.75), (54.33 +/- 53.43), (78.60 +/- 51.38), (65.62 +/- 25.36), and (40.93 +/- 28.22) microm2 in groups A1, B1, C1, A2, B2 and C2, respectively, indicating a significant difference between groups A1, B1 and groups C1, A2, B2 (P < 0.05). Neurohistology observation showed that more regenerated nerve fibers were observed in group A1 and B1, but less in group C1. The myelin sheath was thick in groups A1 and B1, while it was thin in group C1. Only SCs and hyperplastic collagen fiber were found in groups A2, B2 and C2.


CONCLUSIONS
Autogenous nerve transplantation is capable of repairing 1- and 3-month sciatic nerve defect to some degree in rat, but repair effect is not obvious on 6-month sciatic nerve defect in rats.
Yao
Jian
J
Department of Histology and Embryology, Medical School of Nantong University, Key Laboratory of Neuroregeneration of Jiangsu Province, Nantong Jiangsu, 226001, P.R. China.
Lin
Xiaozhe
X
Tian
Hong
H
Shi
Wei
W
Jiao
Haishan
H
Wang
Xiaodong
X
D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D008297:Male; D009416:Nerve Regeneration; D010523:Peripheral Nervous System Diseases / Q000601:surgery*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000473:pathology / Q000601:surgery*; D013116:Spinal Cord / Q000637:transplantation*; D014182:Transplantation, Autologous