后根轴突再生重建感觉传入通路的实验研究

Study on reconstruction of afferent pathway after repairing transected dorsal root

目的 将后根分别与脊神经节中枢突支（后根）和周围突支（脊神经）吻合,为通过后根再生重建感觉传入通路奠定组织学基础.方法 SD大鼠74只随机分为三组,左侧为正常对照侧,右侧为手术侧.A组将L4后根近断端L6后根远断端吻合;B组将L4脊神经出椎间孔2 mm处切断,近断端与L6后根远断端吻合;C组手术操作同B组,但不吻合作为假手术组.术后3个月以逆行神经示踪、脊髓后根入口（dorsal root entry zone,DREZ）降钙素基因相关肽（calcitonin gene-related peptide,CGRP）阳性轴突分布、脊神经节和脊髓后角神经元存活率、光镜和透射电镜评价轴突再生效果.结果 逆行神经示踪证实B组再生轴突轴浆运输功能恢复良好.A组和B组均可见轴突再生通过吻合口,神经纤维数量和髓鞘厚度与正常对照侧比较差异无统计学意义;但A组轴突再生停止于DREZ,脊髓后角CGRP阳性纤维分布密度低于B组和正常对照侧,差异有统计学意义.三组L6脊神经节神经元存活率与正常对照侧比较差异无统计学意义;A组和C组L4脊髓后角神经元存活率低于B组和正常对照侧,差异有统计学意义.结论 后根与脊神经吻合后不影响脊髓后角神经元存活,神经纤维再生、轴浆运输能通过DREZ进入脊髓,是一种理想的修复感觉传导通路的方式.

Objective To provide the morphological evidence for sensory pathway by the repair of dorsal root （DR） in which received transected and anastomosed with central processes （DR） and peripheral processes （spinal nerve） respectively. Methods 74 SD rats were divided into three groups randomly. Group A： the distal ending of L6 DR was sutured to the proximal ending of the L4 DR in right side. Group B： the postganglionic spinal nerve of L4 was cut at a point 2 mm to intervertebral foramen and its proximal stump was reconnected to the distal ending of L6 DR in right side. Group C： under the same operative manipulation on group B, but no anastomosis was performed to serve as the sham operation group. The left side was kept intact and served as a normal control in all groups. The repairing results of DR axonal regeneration were evaluated at 3 months after operation by retrograde tracing, the density of positive Calcitonin gene-related peptide （CGRP） axon in dorsal root entry zone （DREZ）, survival rate of neurons in DR ganglia and posterior horn, light and transmission electron microscope. Results HRP retrograde tracing demonstrated axonal axoplasmic transport of regenerative nerve recovered well in group B. Regenerative fibers were found. There was no difference between group A or B and normal control with regard to the number of myelinated axons and the thickness of myelin. Regenerating axon stop at the DREZ in group A and the density of positive CGRP were lower than those in group B and normal control. Survival rate of neurons in L6 DR ganglia had no difference among all groups. However, in posterior horn, a significant increase in death was seen in group A and sham group. Conclusion The ability of axonal regeneration was effective and with no disservice to neurons in posterior horn following anastomosis of postganglionic spinal nerve and dorsal root, by which axoplasmic transport across the DREZ into the spinal cord.