| Purpose: l)To investigate the proliferation process of vascular smooth muscle cells (SMCs) and to confirm the peak time of SMCs' proliferation after percutaneous transluminal angioplaty (PTA). 2) To observe the effect of endovascular radiation therapy to SMCs' proliferation and intimal hyperplasia. To study the inhibition of restenosis after PTA by endovascular radiation therapy and to search the mechanism initially. 3) To select the proper irradiation dose .Materials and Methods: 1) 27 female white rabbits whose weight is 2.5 to 3.0 kilogram were divided randomly to the control group and the test group .Each group were divided into the 3rd day group , the 10th day group and the 4th week group according to the sacrificed time. The rabbit in the 4th week group were then divided into 3Gy group, 9 Gy group,18 Gy group, and 36 Gy group. Every group has 3 rabbits. 2) The animal model of right iliac artery stenosis was made by the method of Clowes balloon dilation. The balloon was filled with 32P liquid that act as the radiation source in the test groups. While in the control groups the balloon was filled with saline. 3) Pathology analysis was performed on the lesion sample at different observing time point. Immunohistochemistry and electron microscope analysis were also performed on the control group and the 18Gy irradiation test group.Results: 1) Pathology analysis: On the 3rd day after PTA, a few proliferating SMCs can be seen on the internal elastic lamina in the control group. While in the 18Gy irradiation test group, no proliferating SMCs can be found. On the 1 Oth dayafter PTA, lots of proliferating SMCs can be seen on the vascular intima in the control group; stenosis of the vascular lumen also occurred. In the 18 Gy irradiation test group, only a few proliferating SMCs can be seen, vascular lumen is normal. On the 4th week after PTA, the vessel wall thickened and the vascular lumen narrowed predominantly in the control group. The lumen of the 3Gy and 9Gy irradiation test group also became stenosis, it has no difference compared with the control group(P>0.05). In the 18Gy and 36Gy irradiation test group, the thickness of the vessel wall is normal. Lumen stenosis hadn't occurred(P<0.01). 2)Proliferating Cell Nuclear Antigen (PCNA) immunohistochemistry stain analysis: PCNA label index in the 3rd and 10th day control group is higher than that in the 18Gy irradiation test group (PO.01). The number of positive stain cells of the control group is more in the 10th day group than other groups(P<0.01). On the 4th week, The number of positive stain cells in both the control group and the 18Gy irradiation test group decreased significantly.3)Electron microscope analysis: on the 3rd day after PTA, the SMCs in the control group display a synthetic phenotype. While in the irradiation test group, degeneration and necrosis occurred among SMCs. The synthesis also decreased. On the 4th week after PTA, although SMCs of synthetic phenotype in the control group still can be seen, their number began to decrease .They also differentiated to mature. SMCs in the test group display a contractile phenotype. Nuclear apoptosis can be seen on some of them.Conclusion: l)The SMCs' proliferation and migration to the intima play an important role in the formation of the neointima. It is one of the main reasons that cause restenosis. The proliferation of the SMCs maybe begins at the very time after PTA, arrive the peak on the 10th day, decreases and keeps steady on the 4th week. The proliferation of the intima also becomes steady.2)Endovascular radiation therapy can inhibit the proliferation of SMCs predominantly, thus canprevent the occurrence of restenosis. The dose of 18Gy irradiation is safe and effective in the inhibition of restenosis. While the dose of 3Gy and 9Gy do not have the effect of restenosis inhibition. The dose of 36Gy perhaps can cause poisonous effect. 3) The inhibition of the SMCs' proliferation and collagen's synthesis maybe one of the mechanisms in which endovascular radiation therapy inhibit the re...
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