The Establishment Of Two Animal Models Of Benign Airway Stenosis And The Therapeutic Effect Of Mitomycin C On Airway Stenosis

Benign airway stenosis is the airway stricture caused by the destruction of the airway wall of various nonmalignant tumors.As tracheal intubation and airway stents are widely used for the treatment of critically ill patients,the cases of airway stenosis have increased gradually.The animal models of benign airway stenosis were established by endotracheal intubation and stent implantation.We compared the difference of airway stenosis models established by these two methods,so as to provide a benign airway stenosis model for clinical research in the future.Mitomycin C(MMC)is an antitumor drug that inhibits the proliferation of fibroblasts.Some studies believe mitomycin C can inhibit the occurrence of benign airway stenosis.However,some studies suggest mitomycin C can not inhibit its occurrence and even play an opposite role.The purpose of this study was to explore the role of mitomycin C in the treatment of airway stenosis.Part one Comparison of two animal models of benign airway stenosisObjective: The animal models of benign airway stenosis were established by endotracheal intubation and stent placement,and the differences between the two models of airway stenosis were compared.Methods:6 beagle dogs were randomly divided into group A and group B.Each group had 6 beagle dogs.The dogs in group A were modeled by tracheal intubation,and the dogs in group B were built by stent placement.Group A: 3 beagle dogs were intubated through oral trachea after general anesthesia,and the pressure of the capsule was 200 mm Hg for 24 hours.Group B: endotracheal coated self-expanded metal stents were placed after general anesthesia in 3 beagle dogs.The two groups were examined by bronchoscopy on first day,seventh day,fourteenth day and twenty-first day after modeling,respectively,and pathological changes were observed on twenty-first day.Results:All the experimental dogs were able to recover successfully.Group A: the pathological results of 3 weeks after extubation showed that the granulation tissue in the endotracheal cavity was obviously proliferated and the tracheal cartilage was narrowed,and the stenosis was 21~64%.Pathological results showed that the tracheal ciliated cells were missing,the lamina propria was inflammatory cell infiltration,some cells were degenerated and necrotic,and the collagen fibers increased.Group B: 3 weeks after stent implantation,polypoid dysplasia appeared on the stent port.Some of the lumens were severely narrowed.The stenosis degree was 36~47%.Pathological results showed that the mucous ciliated columnar cells were replaced by squamous cells,a large number of plasma cells infiltrated in the lamina propria,mucus glands increased,collagen fibers proliferated,some cells degenerated and necrotic,the cartilage membrane was intact,and no obvious necrosis was found in chondrocytes.Conclusion:1.Through the tracheal intubation balloon,the inflated pressure of 200 mmHg lasted for 24 hours.After 3 weeks,the structure of the trachea was damaged and the granulation tissue was proliferated.A stenosis model with tracheal contracture can be formed.2.Through the coated metal stent with a diameter of 20 mm and a length of 50 mm in the trachea,the airway stenosis model based on granulation tissue could be formed after 3 weeks.Part two The role of mitomycin C in the prevention and treatment of restenosis after airway stent implantationObjective: To determine whether mitomycin C can effectively inhibit the proliferation of tracheal granulation tissue after endotracheal stent implantation.Methods:A model of benign airway stenosis was made by stent placement in 9 beagles.They were randomly divided into three groups,with 3 in each group.3 in low concentration group,3 in high concentration group and 3 in control group.The formation of granulation tissue was observed on seventh day after the stent implantation.The low concentration group was injected with mitomycin C with 0.4mg/ml concentration of 1ml in the granulation tissue.Mitomycin C with 1ml concentration of 0.8mg/ml was injected into the high concentration group,and the equivalent phosphate buffer solution was injected into the control group.The bronchoscopy was observed on fourteenth day and twenty-first day,and the pathological analysis was performed on twenty-first day to observe the changes of the trachea wall after the stent implantation.Results:After the experiment,all of them could recover smoothly.Three weeks later,the granulation tissue was visible on the upper and lower two ports of the stent.The stenosis of the low concentration group was about 19~32%,the stenosis of the high concentration group was about 16~21%,and the stenosis of the control group was about 36~47%.Conclusion: 0.4mg/ml and 0.8mg/ml mitomycin C can inhibit the proliferation of granulation tissue and reduce the degree of airway stenosis.