The Effects Of Tannic Acid Post-treatment On Glutaraldehyde-fixed Bovine Jugular Vein Conduit

Background: Because of its several intrinct advantages over other types of valved conduits, recently, the glutaraldehyde (Glut)-fixed bovine jugular vein (BJV) has been widely used for fight ventricular outflow tract (RVOT) reconstruction in the field of cardiovascular surgery. However, several clinical reports showed its high rate of dysfunction and failure, which maybe result from its distant anastomic stenosis, dilatation, calcification and thrombosis etc. Some drawbacks of Glut, the cross-linking agent of this conduit, maybe related. Any efforts to overcome these drawbacks of Glut may help improve the durability and longevity of the conduit. To achieve this objective, we modified the Glut-fixed BJV wall with TA post-treatment in the current study.PartⅠAnti-calcification, Anti-inflammation and Elastic Fiber-stabilizing Effects of Tannic Acid Post-treatment on Glutaraldehyde-fixed Bovine Jugular Vein Walls in Rat Subcutaneous ModelObjective: Current study evaluated the use of tannic acid (TA) post-treatment to mitigate the elastic fiber degeneration, calcification and inflammation of glutaraldehyde (Glut)-fixed bovine jugular vein walls. The mechanisms underlying these roles of TA were also preliminarily explored.Methods: Freshly harvested BJV walls were fixed with Glut or Glut/TA, respectively. These fixed BJV walls then were implanted subcutaneously in 3-week-old rats and retrieved at 21 and 60 days after implantation. Explants underwent the following examinations: (1) calcium and elastin content analysis, (2) histology and immunohistochemistry staining, and (3) reverse transcription-polymerase chain reaction study.Results: Over the total course of implantation, there were progressive elastic fiber degradation and calcification within the Glut-fixed BJV walls. In contrast, well-preserved elastic fibers (p＜0.01 for 21- and 60-day time points) and significantly less calcification (p＜0.01 for 21- and 60-day time points) were showed within the Glut/TA-fixed tissues at two corresponding intervals. Additionally, the Glut/TA-fixed BJV walls revealed significantly reduced inflammatory infiltration compared with the Glut-fixed tissue after 21-day implantation (p＜0.05). Moreover, there were less matrix metalloproteinase-9 and tenascin-C expressions within Glut/TA-fixed BJV walls than its Glut-fixed counterpart after 21-day implantation (p＜0.05)Conclusions: TA post-treatment is effective in mitigating the inflammatory reactions, elastic fiber degradation and calcification within Glut-fixed BJV walls in rat subdermal model. Of these, the anti-calcification effect of TA maybe related to its capability of stabilizing elastic fiber and mitigating inflammation response and the express of MMP-9 and TN-C. PartⅡEvaluation of Glutaraldehyde/Tannic acid-Fixed Bovine Jugular Vein in Term of Physico-chemical Property, Hemocompatibility and BiocompatibilityObjective: This study was undertaken to evaluate the effects of tannic acid(TA) post-treatment on glutaraldehyde(Glut)-fixed BJV walls in term of their changes of physico-chemical property, hemocompatibility and biocompatibility.Methods: Fresh BJV walls were treated with Glut or Glut/TA, respectively, and then were measured as follow: (1) physico-chemical property evaluation which included shrinkage temperature study, resistance to collagenase and elastase digestion study, biomechanical properties study and Fourier transform infrared spectrum study for molecular structure; (2)hemocompatibility evaluation which included dynamic cruor time test, blood platelet adhesion test, D-dimeride determination and complement activation test. Additionally, the Glut/TA treated BJV walls were also subjected to biocompatibility evaluation, which included cell culture cytotoxic test, skin allergy test, intracutaneous stimulation test, primary skin stimulation test, hemolysis test, general acute toxicity test and pyrogenicity test according to the manual of the national standards of medical materials.Results: When compared with its Glut-fixed counterpart, Glut/TA-fixed BJV wall showed apparent advantages in term of its characteristics as fellow: (1) physico-chemical properties: including①higher shrinkage temperature(88.83±0.16℃vs. 90.77±1.26℃, p＜0.01);②more resistance to collagenase(31.28±5.16% vs. 8.55±4.54%, p＜0.01) or elastase digestion(18.34±5.97% vs. 4.83±2.16%, p＜0.01);③slightly raised stength and distensibility;④the binding of TA to JBV wall tissue.(2) Hemocompatibility:①The curve of absorbance-clotting time of bovine jugular veins treated with tannic acid declined more slowly than that of bovine jugular veins only treated with glutaraldehyde.②Blood platelet adhesion of bovine jugular veins treated with tannic acid was fewer than that of control group.③The D-dimeride contents of all bioprostheses are in normal level, and there was no significant difference between test and control groups(p＞0.05).④In complement activation test, the level of complement C3a in test group was lower than that of control group(p＜0.05). Additionally, for Glut/TA-fixed BJV walls, the biocompatibility studies showed:①There was no obvious change of cell attachment, morphology and proliferation after L-929 mouse fibroblasts were treated by extracts or degenerated products. The toxicity gradation of the material of the material was 0～1.②The results of skin stimulative and sensitive test were negative. The primary irritation index (PII) in intracutaneous stimulation test was 0.4(no significant difference compared with control).③Bovine jugular veins treated with tannic acid showed no toxicity in general acute toxicity test.④The rate of hemolysis was 0.7%, which was lower than the standard criteria(5%).⑤Increase of the rectal temperature of 3 rabbits was less than 1.4℃and average increase of temperature＜0.6℃/rabbit.Conclusion: TA post-treatment not only enhanced the cross-linking and stabilized the elastic fibers of Glut-fixed BJV walls, but also improved its hemocompatibility. Additionally, the biocompative characteristics of Glut/TA treated BJV are in conformity with the national standards for medical materials. These results allow further in vivo animal experiments. PartⅢHemodynamic and Histological Performances of Glutaraldehyde/Tannic acid-Fixed Bovine Jugular Vein Conduit for Right Ventricular Outflow Tract Reconstruction in Sheep ModelObjective: This study was undertaken to investigate the effect of tannic acid (TA) post-treatment on the hemodynamic and histological performance of glutaraldehyde (Glut)-fixed bovine jugular vein (BJV) conduit for right ventricular outflow tract (RVOT) reconstruction in sheep model.Methods: The fresh valved BJV conduits were fixed with Glut or Glut/TA, respectively, and then were implanted in the RVOT position of eight sheep (n=3 for Glut and 5 for Glut/TA) with the main natural pulmonary arteries completely ligated. After 6 and 12 months the conduits were explanted. Peak RV-PA pressure gradient study and echocardiography were performed at implantation and retrieval. Macroscopic and microscopic observations were conducted on the explants. Additionally, calcium content of the explanted conduit walls was also quantitatively determined.Results: The surgical feasibility of Glut/TA treated BJV was acceptable during its implantion as a valved conduit for RVOT reconstruction. Two animals unexpectedly died of pneumonic complications. The remaining sheep survived until sacrifice. At completion of implantation, the conduits of two groups performed similarly with respect to hemodynamic parameters. At retrieval, echocardiography study revealed obvious valvular regurgitation and mild-to-moderate conduit dilatation in Glut group, and significantly elevated peak RV-PA pressure gradients also existed. Additionally, there were apparent thrombosis, inflammation, calcification and elastic fiber degeneration in Glut-fixed BJV wall samples. In Glut/TA group, however, neither valvular regurgitation nor conduit dilatation was detected, and the pressure gradient remained trivial. Additionally, the wall structure was well preserved without apparent thrombosis or histological deterioration in Glut/TA group.Conclusions: The surgical feasibility of Glut/TA treated BJV was acceptable. TA post-treatment not only mitigated the thrombosis, inflammation, elastic fiber degeneration and calcification of Glut-fixed BJV, but also improved the hemodynamic performance of the conduit in the sheep RVOT position.