| Objective: To establish the model of ureteral stricture caused by thermal injury in miniature pigs,and to explore an effective method for the treatment of ureteral stricture by inserting rapamycin sustained-release metal stent into the model of ureteral stricture to observe whether it can alleviate the tissue fibrosis of ureteral stricture.Methods: In this experiment,12 female Guangxi Bama miniature pigs weighing(25.5 ±3.0)kg were randomly divided into two groups: 6 animals in each group(12 ureters).Each group was divided into operation group(6 ureters)and contralateral normal control group(6 ureters).Self-made electrocoagulation device was used after general anesthesia.The middle ureter of the operation group was treated with circular multi-point electrocoagulation under ureteroscope,while the contralateral control group was only explored by ureteroscopy.Single photon emission computed tomography(SPECT),retrograde ureterography and ureteroscopy were performed before operation,on the 30 th and 90 th day after operation,respectively.On the 30 th and 90 th day after operation,the two groups of animals were killed successively.The injured ureteral tissue of the operation group and the control group were taken for histopathological examination to understand the ureteral stricture.Then,the 18 Guangxi Bama female minipigs that successfully established the stenosis model were divided into 3 groups according to the random number table method(n is the number of ureters),namely the stenosis model group(n=6)and the bare metal stent group(n= 6)and the rapamycin stent group(n=6);the contralateral ureter was randomly selected as the normal control group(n=6).Four weeks after stent implantation,SPECT was performed to detect the changes of bilateral renal function.Retrograde ureterography and ureteroscopy were used to evaluate stenosis,stent displacement or shedding.The corresponding ureteral tissues were taken for pathological and immunohistochemical detection of fibrosis and epithelial changes.RT-PCR and Westernblot methods were used to detect the expression of TGF-β 1,Smad3,4EBP1,e IF4 E m RNA and protein.Results: 1.The Changes of renal function and inner diameter of ureter after establishment of stenosis model: The model of ureteral stricture was successfully established.On the 30 th day after the operation,all the modeled animals showed typical signs of ureteral stenosis in the middle of the ureter.SPECT showed that the glomerular filtration rate(GFR)of the surgery group gradually decreased with time,and the half-emission time was prolonged.The normal control group had a compensatory increase in GFR and no change in half-line time.The inner diameter of the stenotic segment measured on the 30 th day after ureterography in the stricture group was 1.70±0.127 mm(n=6),and the inner diameter of the normal control group was 3.433±0.155 mm(n=6),and the difference was statistically significant(t= =29.797,P<0.05).The inner diameter of the stenotic segment measured on the 90 th day after operation in the stenosis group was 1.360±0.175mm(n=6),and the inner diameter of the normal control group was 3.70±0.089mm(n=6),and the difference was statistically significant(t=29.066,P<0.05).2.The results of renal function examination after stent intervention: there was no ureteral stricture in the normal control group,but ureteral stricture was formed in the stricture model group,and GFR decreased gradually after the early compensatory increase.No stent exfoliation and displacement were found in the bare metal stent group.Retrograde ureterography showed that the lumen of the narrow segment was blocked and the contrast medium could not pass smoothly.There was a large amount of urothelial hyperplasia on the surface of the stent,and the stent was obviously covered by granulation tissue.GFR was not improved compared with that before operation.In rapamycin stent group,there was no stent exfoliation and displacement.Retrograde angiography showed that the narrow lumen was unobstructed,the stent was not covered by epithelial and granulation tissue,and GFR was improved compared with that before operation.3.Histopathological examination: hematoxylin-eosin(HE)staining in the stenosis group showed that the wall of the vessel was significantly thickened,the lumen became narrower,and a large number of inflammatory cells could be seen under the mucosa.Masson staining showed that a large number of collagen fibers proliferated and arranged disorderly,resulting in thickening of the wall.The changes of HE staining and Masson staining in bare stent group were similar to those in stenosis group.HE staining and Masson staining showed that the wall thickening and lumen narrowing in rapamycin stent group were better than those in bare stent group,and the proliferation of collagen fibers was significantly decreased.Immunohistochemistry showed that the positive expressions of TGF-β1,Smad3,4EBP1 and e IF4 E in ureteral tissue were significantly increased in stenosis group and bare stent group,and ureteral epithelium accumulated and arranged disorderly.The positive expressions of TGF-β1,Smad3,4EBP1 and e IF4 E in ureteral tissue in rapamycin stent group were significantly different from those in bare stent group(P < 0.05).The ureteral epithelium in rapamycin stent group was neatly arranged than that in bare stent group.4.The m RNA and protein expressions of TGF-β1,Smad3,4EBP1,e IF4 E in the rapamycin stent group were lower than those in the stenosis group and the bare metal stent group,and the difference was statistically significant(P<0.05).There was no significant difference in the expression levels of TGF-β1,Smad3,4EBP1,e IF4 E m RNA and protein between the stenosis group and the bare metal stent group(P>0.05),which were higher than those in the normal control group(P<0.05).Conclusions: The animal model of ureteral stricture in pigs was successfully established by electrocoagulation under ureteroscopy.this method is simple and feasible,and is more in line with the pathological mechanism of iatrogenic ureteral injury.it is an ideal method to construct the animal model of intraluminal ureteral stricture.Rapamycin sustained-release metal stent can effectively improve ureteral stricture after thermal injury,inhibit the expression of fibrosis factor TGF-β1 and Smad3 m RNA and protein,block the ureteral remodeling induced by m TOR,and inhibit the expression of 4EBP1,e IF4 E m RNA and protein.Drug sustained-release stents have potential value in the treatment of iatrogenic ureteral stricture and are worthy of further study. |
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