Improved Study On Artificial Biological Heart Valve Crosslinked By Procyanidins

Heart valve diseases have a significant higher mortality. Many of them need artificial heart valve replacement. There are two type of artificial heart valves: mechanical heart valves (MHVs) and bioprosthetic heart valves (BHVs). Xenografts are typically composed of either porcine aortic tissues or bovine pericardial tissues. The common way to prepare xenogenic valves is the treatment of the animal valves with glutaraldehyde, a chemical cross-linking reagent, to increase durability. Advantages of xenografts include an unlimited supply of donor tissue, superior hemodynamics and lower thromboembolic complications when compared to mechanical valves, which are associated with a significant risk of thromboembolism and require lifelong treatment with anti-coagulation drugs. However, the glutaraldehyde crosslinked xenografts are far less durable, more susceptible to calcification and subject to progressive tissue deterioration.Glutaraldehyde (GA) preserved biological tissues have been used in bioprosthetic heart valves (BHVs) since late1960s. This preservation can form crosslinks between the extracellular matrix (ECM) molecules, resulting in resistance to enzymatic degradation, reducing immunogenicity and sterilizing tissue. However, the GA-crosslinked BHV are far less durable, more susceptible to calcification and easier subject to progressive tissue deterioration. Therefore, other crosslinking reagents have been studied to improve the performance of BHVs, such as glycerol and alginate, genipin, adipyl dichloride and quercetin. But up till now they have not been reported to be used clinically.Recently, procyanidins (PCs) has been reported crosslinking effect on heart valve with increased mechanical properties, anti-calcification potential and flexibility. Furthermore, PCs are natural polyphenolic flavan, widely available in fruits, vegetables, nut, seed, flowers, and barks. They are non-toxicity with many bioactivities, such as anti-thrombogenesis, anti-bacteria and anti-inflammatory. They are often used as cardiovascular protector and free-radical scavengers. Based on these properties, we hypothesis that pretreated with PC would improve the performance of the GA crosslinking BHV. In this study, the heart valve matrices were treated with PC before GA crosslinking and crosslinked with1mg/mL PC under pH6condition, in vitro the mechanical properties, stability, anti-calcification potential, blood compatibility, cytocompatibility, and anti-bacterial effect were evaluated.The aim of this part is to modify GA crosslinking method using PC co-crosslinking to produce a much ideal material with higher compatibility for BHV preparation. Porcine aortic AHVM was crosslinked by8mg/mL PC for4h and then by1.25mg/mL GA for44h. The co-crosslinked AHVM was tested for cytocompatibility, blood compatibility and immunogenicity. In this part, co-crosslinked valvular ECMs indicated higher tensile strength than GA-crosslinked one. In addition, co-crosslinked ECMs were more store stability in D-hanks and more effective antibacterial activity than PC-crosslinked.The results showed that the in vitro adhesion rate of valvular interstitial cells on co-crosslinked AHVM was increased by59%(78.75%-19.75%) when compared with that of GA-crosslinking. There was no difference in hemolysis between co-and GA-or PC-crosslinked AHVM. The co-crosslinked AHVM exhibited significant anti-thrombosis effect (193±15.5platelets) when compared with that of GA-crosslinked (292.6±24.93platelets). Furthermore, co-crosslinked AHVM displayed lower immunogenicity than that of GA-crosslinked (49.33%±6.3%vs95.27%±5.26%, cell adhesive rate). These results suggest that co-crosslinked AHVM has high potential to be used for preparation of BHVs.Progressive degeneration and calcification of GA crosslinked tissues used in valvular surgery restrict their longterm clinical performance. This limited biological stability may be attributable to the inability of GA to adequately protect certain tissue components such as elastin from enzymatic attack. The aim of our studies was to develop novel heart valve crosslinking echniques targeted specifically at elastin stabilization by using1mg/mL PC ubder pH6condition, a plant polyphenol capable of protecting elastin and collagen from digestion by specific enzymes. In present studies we demonstrated that heart valve crosslinked with pH6/PC-1was softer than GA-crosslinked. Compared with GA and pH7.4/PC-1, pH6/PC-1also decreased calcification in the SBF model by16.3μg/mg and6.4μg/mg. There was no difference in hemolysis between pH6/PC-l and GA-or PC-crosslinked AHVN. The pH6/PC-1-crosslinked AHVM exhibited significant anti-thrombosis effect (31.16%±2.51%) when compared with that of GA-crosslinked (45.2%±2.56%). Those resulte shown that heart valve crossolinked by pH6/PC-1has been superior to GA and PC-1in mechanical properties and blood compatibility. So the heart valve crossolinked by pH6/PC-1implants might be significantly extend the clinical durability of these tissue replacements.