| Objective:By building animal models of artificial vascular replacement in different vascular environment with Diannan Small-ear Pigs, studying the morphological characteristics and ultrastructural of formative neointima in artificial artery, and checking mRNA and protein expressiones of plasminogen activator inhibitor-1 (PAI-1) in intima of artificial blood vessels after operation, this thesis was aimed at investigating the function of natural endothelialization and anti-thrombus in different artery and vascular environment after artificial vascular replacement, and meanwhile, providing theoretical foundation for safety and feasibility of reconstruction operation of pulmonary artery by applying artificial blood vessel in central type lung cancer.Material and Methods:1.27 adult Diannan small ear pigs, no limit to gender, weighing from 25kg to 30kg, were used as experimental animals to establish animal model of artificial vascular replacement. They were divided into three groups randomly:9 pigs in the group of pulmonary artery,9 in the group of thoracic aorta, and 9 in the group of inferior vena cava, and each corresponding artery was replaced by vascular prosthesis. Based on the sample collection time, the above three groups were divided randomly into two-week group, three-month group and six-month group. 2. The replaced vessels would be checked respectively after 2 weeks,3 months and 6 months to evaluate how clear or narrow they are or whether there was any thrombogenesis with percutaneous color Doppler ultrasound and ruller. The patency rate of each group would be statisted for difference.3. All the pigs were anatomized on schedule, and endothelial cell ultrastructure, the degree of neointimal hyperplasia and endometrial hyperplasia of vascular prosthesis in different environments would be observed under light microscope and scanning electron microscope. The results would be recorded and differences would be analyzed statistically.4. Endothelial coverage of artificial vessel was examined by means of immunohistochemical method and differences were compared statistically.5. Meanwhile, expression level of PAI-1 protein and PAI-lgene of vascular prosthesis intima in each group are examined via Western Blot and PCR respectively. By comparing with the PAI-1 protein and PAI-lgene level of normal vessel intima and making comparison within each group, the differences of PAI-1 gene and PAI-1 protein level was found.Results:All animals survived after operation. No infection and hemorrhagic complication occur except for two cases of ascites caused by thrombosis and one case of wound infection in the inferior vena cava groups. Scanning electron microscope finded that the endothelial cells in inferior vena cavas were almost round, and were oval in pulmonary artery, were long fusiform in thoracic vein; Artery endothelial cells arranged closely but vein endothelial arranged loosely. Vascular color Doppler:No found the thrombosis neither in pulmonary artery group nor in thoracic aorta group. However, we found 5 cases thrombosises in the inferior vena cava group,including 2 cases of peritoneal effusion.Direct observation of thrombus:The patency rate for the diameter stenos of artificial blood vessel were not more than 50%:the inferior vena cava group was (4/9); the pulmonary artery group was (9/9); the thoracic aorta group was (9/9).Intimal hyperplasia of inferior vena cava vein group was more hevavier than that in thoracic aorta and pulmonary artery groups (P<0.05); no significant between thoracic aorta and pulmonary artery groups (P>0.05). Grafts under three different environments basically complete endothelialization with 6 months. No statistical difference was found after comparing the results of the pulmonary artery and the thoracic aorta group at certain time point. Compared with the other two groups, the inferior vena cava group showed slow endothelialization and strong intimal hyperplasia (P<0.05). The expressions of PAI-1 gene and protein were low within normal vascular intima(control group). However, the expression got significantly higher in the artificial blood vessel within 2 weeks after operation. The expressions of PAI-1mRNA and protein in 2-week and 3-month was higher than the normal group (P<0.05). As time extends, the expression amount decreases. The expressions of inferior vena cava group in the 6-month increases compared with the normal group was statistically significant, but the thoracic aorta groups and pulmonary artery groups both slightly higher than the normal group and has no statistical significance in the 6-month (P>0.05). At each time point, differences of the expression of PAI-1 gene and protein between the thoracic aorta group and pulmonary artery group have no statistical significance (P>0.05). But the fact that the expression of PAI-1 gene and protein of the inferior vena cava group was higher than that of the other two groups was statistically significant (P<0.05).Conclusion:Our preliminary results showed that e-PTFE artificial blood-vessel can basically complete endothelialization within 6 months. Compared in three different vascular environment, vascular grafts were more prone to forming thrombus in inferior vena cava and the patency rate was lower than that of the thoracic aorta group and pulmonary artery group; the PAI-lmRNA and protein expression in endothelial cells and vascular endothelial cells is closely related to the function of anti thrombosis Besides, compared with the inferior vena cava group, the pulmonary artery and the thoracic aorta group are faster in endothelialization and lighter in intimal hyperplasia and lower in expression of PAI-1 protein, which was statistically significant. Therefore, vascular prosthesis under the environment of pulmonary artery and thoracic aorta had some advantage in terms of reducing intimal hyperplasia, accelerating the process of endothelialization and anti thrombosis. So based on the current mature condition of large-scaled vascular prosthesis, it could be concluded that pulmonary artery vascular prosthesis was safe and clinically feasible. However, due to the short research time and few animal case, the results of this experiment was largely limited and we need further research on the long-term patency rate, immunogenicity and stability of vascular prosthesis. |
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