The Application Of Tissue-engineered Fish Swim Bladder Vascular Graft

Background and purposeSmall-diameter(6 mm)vascular grafts have a poor long-term postoperative patency,with more than half of patients with below-knee bypass grafts necessitating amputation within a year.Despite the fact that polyester and expanded polytetrafluoroethylene(ePTFE)prosthetic vessels have been regularly utilized for over half a century,their long-term patency is often inadequate.As a result of their excellent patency rates,autologous vessels are still the preferred choice for vascular grafts.Although autologous veins have good long-term patency,there are issues in the clinic,such as a lack of suitable autologous veins for bypass surgery patients and a diameter mismatch between the autologous vein and the vessel to be repaired,and spiral vein grafts are rarely used due to the high technical requirements of this approach.Several vascular grafts,including frozen allogeneic human umbilical vein grafts and allografts,have been created for clinical application.Allogeneic tissues can be utilized as bioengineered vascular scaffolds,and there are a number of commercially available allogeneic decellularized patches made from swine or bovine pericardium.Advances in physiology,cell biology,and biomanufacturing,combined with recent advances in tissue engineering,suggest that the next generation of tissue-engineered vascular grafts may become mainstream in the surgical treatment of vascular disease,similar to the transition from first-generation repair materials to advanced polymer fabric grafts.Because the cellular components are eliminated during decellularization,decellularized allogeneic vascular scaffolds retain the extracellular matrix,retaining structural integrity,and are less immunoreactive.In therapeutic application,chitosan derived from crab and shrimp shells looks to be a promising substance.As a result,we hypothesize that some fish organs could be similarly treated and turned into vascular graft scaffolds for clinical use.Carassius auratus is a common and readily available fish in China.The swim bladder is a fish organ that is made up of collagen,elastin,and glycosaminoglycans and is responsible for the fish’s raising and sinking.Collagen derived from the swim bladder is identical to collagen found in mammals.Each 700-800 g freshwater fish can produce a 5-7 cm swim bladder,indicating that this collagen material as a vascular scaffold source is resource sustainable.Methods1.Swim bladder decellularization and surface coatingDecellularized fish bladders were treated by soaking them in CHAPS buffer for 12 hours,removing the wash,and then soaking them in sodium dodecyl sulfate buffer for 24 hours before washing them in PBS to completely remove the detergent.The hyaluronic acid-coated samples were immersed in rapamycin solution(2 mg/ml)pre-activated using water-soluble carbodiimide solution,and the decellularized swim bladders were incubated at 37℃ for 6 h for rapamycin drug-coating treatment after being washed three times with phosphate-buffered saline.2.Decellularized fish bladders as patch-like vascular grafts in the rat abdominal aorta and inferior vena cavaFresh decellularized swim bladders(control group)and rapamycin-coated swim bladders(rapamycin-coated group)were trimmed into 3×1 mm patches and implanted into the abdominal aorta and inferior vena cava of rats,and H&E,immunohistochemistry,and immunofluorescence were used to see if fresh fish fat could be used for angioplasty and if rapamycin coating could inhibit intimal hyperplasia.3.Application of decellularized fish bladders as tube vascular grafts in the rat abdominal aorta and inferior vena cavaFresh decellularized swim bladders(control group)and swim bladders coated with rapamycin drug were both implanted into the abdominal aorta and inferior vena cava of rats,and H&E,immunohistochemistry,and immunofluorescence were used to see if fresh fish fat could be used in vascular in situ grafts to replace intact arterial or venous vessels,and if rapamycin coating could inhibit endothelial proliferation.Results1.Without losing structural integrity or their appropriateness for in vivo testing,decellularized swim bladders can be successfully coated with rapamycin.The surface was smooth before decellularization but rough after decellularization,according to scanning electron microscopy(SEM);following rapamycin coating,the surface was smooth and patterned.Water contact angle(WCA)studies revealed that the WCA was tiny in fresh swim bladders,but it grew larger following decellularization,with no significant difference between decellularized and rapamycin-coated swim bladders.Fresh,decellularized,and rapamycin-coated patches had equal burst strength and suture retension,with greater burst strength and suture retension when compared to decellularized rat thoracic aorta(d-TA).Rapamycin was released for up to 14 days in vitro.2.The rapamycin coating reduced the patch’s neointima thickness in both the artery and vein.The patch and the artery or vein were entirely united 14 days later.Both arteries and veins were patent,and no aneurysms or other complications formed.In both arteries and veins,the rapamycin-coated group had much thinner neointima compared to the decellularized swim bladder group alone,as well as significantly fewer cells and thinner outer membrane thickness in the patches.The rapamycin coating had no effect on the patch surface reendothelialization.3.In both arterial and venous tube grafts,rapamycin coating reduced neointimal thickness.All abdominal aortic tube grafts remained patent after 14 days,whereas all three inferior vena cava tube grafts in the control group were occluded,whereas all rapamycin-coated inferior vena cava tube grafts remained patent.In the abdominal aorta and inferior vena cava,histological staining revealed considerable neointima thinning on the luminal surface of rapamycin-coated tube grafts.In comparison to control tube grafts,the number of cells in rapamycin-coated tube grafts was also reduced.Conclusions1.Decellularized swim bladders have been used as patch and tube grafts in rat arteries,and their capacity to support endothelial cell migration and proliferation in vitro and in vivo has been demonstrated.2.Rapamycin-coated decellularized fish bladder vascular patches and tubular artificial vessels can effectively inhibit endothelial hyperplasia3.Decellularized swim bladders are a promising collagen-based graft that can be surface-coated for potential clinical applications.