移植损伤对移植静脉影响的实验研究

EXPERIMENTAL STUDIES ON EFFECT OF GRAFTING INJURY TO VEIN GRAFT

目的探讨移植静脉再狭窄的机制,明确移植损伤对移植静脉的影响。方法健康新西兰大白兔36只,随机选取一侧将股静脉翻转后移植于同侧股动脉缺损(静-动组),另一侧将同等长度股静脉截取后行原位缝合(静-静组),另取正常股静脉作为对照组(取自静-动组移植前静脉的一部分)。均于术后4周取移植静脉段,行HE染色、弹力纤维的维多利亚蓝染色观察移植静脉管壁组织学变化;增殖细胞核抗原(proliferatingcellnuclearantigen,PCNA)免疫组织化学染色观察管壁细胞增殖情况;电镜观察管壁细胞超微结构改变。结果静-静组血管壁中膜平滑肌细胞增殖,但内膜(3.50±0.41μm)、中膜(12.23±1.59μm)厚度无明显变化;静-动组内膜、中膜细胞均增殖,内膜(25.60±3.21μm)、中膜(21.30±2.47μm)厚度较对照组、静-静组均增加,差异有统计学意义(P<0.01)。对照组未见PCNA阳性细胞,静-静组内膜(5.9%±1.3%)、中膜(23.4%±3.4%)PCNA阳性细胞百分比均小于静-动组内膜(16.4%±1.9%)、中膜(36.5%±3.7%),差异有统计学意义(P<0.01)。静-静组透射电镜下可见内皮细胞扁平,游离端有绒毛样突起,细胞排列紧密,中膜平滑肌细胞增殖;静-动组透射电镜下可见内皮细胞增殖明显,增殖的内皮细胞形态不规则,细胞间隙增宽,内膜中可见大量平滑肌细胞,基底膜不完整,中膜平滑肌细胞明显增殖;对照组内皮细胞形态及排列与静-静组相似,只是中膜平滑肌细胞未见增殖。结论静脉移植后可导致血管管壁细胞增殖,如合并血流动力学变化则会发生更严重的细胞增殖和迁移,导致管腔狭窄;减少移植损伤,改善移植静脉的微循环,成为预防移植静脉再狭窄的理论基础之一;静-静移植的动物模型,有助于探寻静脉移植后再狭窄的机制。

Objective To study the mechanism of restenosis of the vein graft and the effect of the grafting injury to the vein graft. Methods One side of the 36 healthy rabbits was randomly chosen as the V-A group, and on the side a 1. 5-cm-long femoral vein was obtained, and an 0. 5 cm-long segment of the obtained femoral vein was separated as the control group. The remaining 1-cm-long femoral vein was inverted and was autogenously implanted into the femoral artery on the same side of the rabbit. The other side of the rabbits was chosen as the V-V group, and on this side a 1-cm-long femoral vein was obtained ex vivo and then was sutured in situ. The vein grafts on both sides were harvested 4 weeks after operation. The specimens from the harvested vein grafts were stained with HE and the elastic fiber Victoria blue for an observation on the histological changes in the walls of the vein grafts, and the specimens were also stained by the immunohistochemistry of the proliferating cell nuclear antigen （PCNA） for an observation on the wall cell proliferation of the vein grafts. The changes in the uhrastructure of the proliferated wall cells of the vein grafts were observed under electron microscope. The two sides of the rabbits were compared. Results The smooth muscle cells of the media developed hyperplasia, but the intima and the media remained unchanged in their thickness （3.50± 0. 41 μm,12.23 ± 1.59 μm） in the V-V group, with no difference when compared with the control group （3.40±0.37 μm, 12. 14±1. 62 μm）; however, when compared with the V-A group （25.60±3. 21 μm, 21. 30±2.47 μm）, there was a significant difference in the thickness （P 〈 0.01）. There were no cells positive for PCNA by the immunohistochemistry examination in the control group. The cells positive for PCNA were found in the intima and the media in both the V-V group and the V-A group; however, the percentage of the cells positive for PCNA in the intima and the media was significantly greater in the V-A group than in the V-V group （16.4%±1.9% and 36.5%±3.7% vs 5.9%±1.3% and 23.4%±3.4%, P〈0.01）. In the V-V group, the endothelial cell could be observed under transmission electron microscope, which was flat and had a process-like villus at its free end, and the endothelial cells were closely arranged and had hyperplasia of the smooth muscle cells in the media. But in the V-A group, the endothelial cells had an obvious hyperplasia with an irregular shape and a widened space between the cells, and in the intima a great amount of the smooth muscle cells could be observed, which had a broken basement membrane. The smooth muscle cells also had an obvious hyperplasia in the media. The shape and alignment of the endothelial cells in the control group were similar to those in the V-V group, but the hyperplasia of the smooth muscle cells was not observed in the media. Conclusion The grafting injury can cause hyperplasia of the vascular wall cells, and if the hemodynamics is changed simultaneously, more serious hyperplasia and cell migration can be observed from the media to the intima, resulting in restenosis of the blood vessels. So, if we can reduce the grafting injury and improve the microcirculation of the vein graft, we may find out the methods of preventing restenosis of the vein graft. The animal model of the V-V graft can help to understand the mechanism of restenosis of the vein graft.