| Objective:We have synthesized a novel amphoteric polymer material（Nano drug）which can slowly release H2S by wrapping USPIO in it（USPIO-Nano drug）and have given it the characteristics of integration of diagnosis and treatment.The purpose of this study is to investigate the effects of novel amphoteric polymers on acute heart transplantation rejection and their potential as imaging molecular probes.Materials and Methods:In the stage of rat heart transplantation,we used Wistar rats as heart donors and SD rats as recipients to carry out cervical heart transplantation.In the operation preparation stage,we prepared the skin preparation,disinfection,towel laying and so on.During the operation,the right external jugular vein and the right common carotid artery were isolated,ligated and severed,and then the above vessels were everted to the cannula,fixed and washed.In the donor operation stage,we made a U-shaped incision from the lower abdomen to the diaphragm of the anesthetized rats,injected heparin sodium through the inferior vena cava to make the rats whole body heparin sodium,then opened the chest,took the heart and immersed in HTK solution for preservation.In the stage of heart transplantation,the donor heart was placed in the operation area of the recipient rat,the aorta of the donor heart was connected with the common carotid artery of the recipient rat by cannula method,and the pulmonary artery of the donor heart was connected to the external jugular vein of the rat,then the blood supply was opened,the donor heart was resuscitated,and the operation was completed.In the stage of synthesizing new amphoteric polymer materials:the synthesis of materials requires five steps,which are the synthesis of zwitterionic carboxylic acid betaine（DHCB）,the synthesis of aldehyde monomer（DHCHO）,the synthesis of small molecule hydrogen sulfide donors,synthesis of amphiphilic polyurethane hydrogen sulfide donor and preparation of final hydrogen sulfide micelles.After synthesis,NMR,IR,particle size and dispersion index,TEM,potential,Release curve of hydrogen sulfide in vitro and Cytotoxicity test were examined.In the stage of exploring the effect of Nano drugs on acute rejection immunity of rat heart transplantation:a total of 72 rat heterotopic heart transplantation models were included in this part of the study,which were used to construct blank control group（blank group）,Na HS exogenous H2S donor group（Na HS group）and new amphoteric polymer material exogenous H2S donor group（Nano group）,respectively,and the corresponding drug intervention was carried out in each group after operation.At the planned time point,each rat took a blood sample and underwent a heart transplant MRI scan,and the heart graft was taken after the MRI scan.He staining was used to observe the pathological state of myocardial tissue,ELISA was used to detect the content of cytokines in serum,and immunofluorescence was used to observe the infiltration of M1/M2 macrophages and CD8+T lymphocytes in heart tissue.In order to explore the effect of the new amphoteric polymer materials on the MR characterization of r acute cardiac output in rats,we used two slightly different polymer materials,namely Nano drug and USPIO-Nano drug:this part of the study is a continuation of the previous stage,and the experimental objects are 72 rats in the previous stage.At first,we performed MRI T2 mapping scanning on the transplanted hearts of three groups of rats,and obtained the average T2 value characteristics of myocardial tissue under different drug interventions at different time points of acute rejection;then USPIO or USPIO-Nano was used as a contrast agent for MR Imaging,T2Mapping scans were performed on the transplanted hearts of Blank group rats and Nano group rats.The average T2 value of the corresponding myocardial tissues were obtained with the assistance of USPIO and USPIO-Nano,and compared with the previous average T2 values that did not involve USPIO.The values are subtracted to obtain an average T2 value that can quantify macrophages.Results:The research group independently researched and developed a new type of zwitterionic polymer material that can slowly release H2S,which has super hydrophilicity,excellent antifouling properties,and good biocompatibility.At the same time,by wrapping the USPIO into it,it gives the new characteristics of the integrated diagnosis and treatment of the material.H2S has the ability to reduce myocardial damage during acute rejection.H2S regulates the polarization of macrophages to M2 type.After the intervention of H2S,the pro-inflammatory factors in the serum of the recipient rats decreased and the anti-inflammatory factors increased,and the decrease in IL-17 was the most significant.In the acute rejection model of the heart,the average T2 value of myocardial tissue increases with the progress of the acute discharge reaction.After H2S intervention,during the acute rejection of cardiac transplantation,the average T2value of Nano group and Na HS group was lower than that of Blank group.Using USPIO/USPIO-Nano as MR contrast agent-assisted imaging,it was found that the corresponding average T2values of myocardial tissue in the Blank group and Nano group were lower than those without contrast agent-assisted imaging.Conclusion:1.Nano drugs can change the ratio of M1/M2 of macrophages,reduce the pro-inflammatory effect of macrophages,increase the anti-inflammatory effect of macrophages,reduce the expression of NF-κB pathway in myocardial tissue,and inhibit the production of IL-17,Inhibit the production of ROS and the direct scavenging effect on hydrogen peroxide and superoxide anion to reduce myocardial damage when acute cardiac rejection occurs.2.Nano drugs in the blood can be swallowed by macrophages,thereby increasing the concentration of H2S in local myocardial tissue,and inhibiting the proliferation of CD8+cells and slowing down the development of acute rejection in the heart.3.The T2 value characteristics of myocardial tissue based on MR T2Mapping technology have a good positive predictive ability for the occurrence of acute rejection of transplanted heart.The average T2 value of myocardial tissue can intuitively and acutely reflect the change of free water in the myocardial tissue,and then the occurrence of acute cardiac rejection can be monitored based on the change of the average T2 value of the transplanted heart.4.With the aid of USPIO imaging,MRI can more sensitively monitor the occurrence and development of acute cardiac rejection.Using USPIO as an MR contrast agent,through the change of the average T2 value of myocardial tissue before and after injection,it can quantitatively reflect the infiltration of myocardial tissue macrophages,so that the occurrence of acute discharge can be accurately monitored.The time when USPIO-assisted imaging exerts the best diagnostic performance is when the acute rejection of heart transplantation has just developed to the Grade 1R stage.5.USPIO-Nano drugs can be used as MR molecular bioimaging probes and have the characteristics of integrated diagnosis and treatment.USPIO-Nano can enhance the ability of MRI to monitor the occurrence and development of acute rejection of the heart,and at the same time realize the balance of high-sensitivity bioimaging and effective treatment. |
PDF Full Text Request