The application of tissue-engineered fish swim bladder vascular graft

PEDOT-Integrated Fish Swim Bladders as Conductive Nerve Conduits

Advanced artificial nerve conduits offer a promising alternative for nerve injury repair. Current research focuses on improving the therapeutic effectiveness of nerve conduits by optimizing scaffold materials and functional components. In this study, a novel poly(3,4-ethylenedioxythiophene) (PEDOT)-integrated fish swim bladder (FSB) is presented as a conductive nerve conduit with ordered topology and electrical stimulation to promote nerve regeneration. PEDOT nanomaterials and adhesive peptides (IKVAV) are successfully incorporated onto the decellularized FSB substrate through pre-coating with polydopamine. The obtained PEDOT/IKVAV-integrated FSB substrate exhibits outstanding mechanical properties, high electrical conductivity, stability, as well as excellent biocompatibility and bioadhesive properties. In vitro studies confirm that the PEDOT/IKVAV-integrated FSB can effectively facilitate the growth and directional extension of pheochromocytoma 12 cells and dorsal root ganglion neurites. In addition, in vivo experiments demonstrate that the proposed PEDOT/IKVAV-integrated FSB conduit can accelerate defective nerve repair and functional restoration. The findings indicate that the FSB-derived conductive nerve conduits with multiple regenerative inducing signals integration provide a conducive milieu for nerve regeneration, exhibiting great potential for repairing long-segment neural defects.

Disturbed flow in the juxta-anastomotic area of an arteriovenous fistula correlates with endothelial loss, acute thrombus formation, and neointimal hyperplasia

Clinical failure of arteriovenous neointimal hyperplasia (NIH) fistulae (AVF) is frequently due to juxta-anastomotic NIH (JANIH). Although the mouse AVF model recapitulates human AVF maturation, previous studies focused on the outflow vein distal to the anastomosis. We hypothesized that the juxta-anastomotic area (JAA) has increased NIH compared with the outflow vein. AVF was created in C57BL/6 mice without or with chronic kidney disease (CKD). Temporal and spatial changes of the JAA were examined using histology and immunofluorescence. Computational techniques were used to model the AVF. RNA-seq and bioinformatic analyses were performed to compare the JAA with the outflow vein. The jugular vein to carotid artery AVF model was created in Wistar rats. The neointima in the JAA shows increased volume compared with the outflow vein. Computational modeling shows an increased volume of disturbed flow at the JAA compared with the outflow vein. Endothelial cells are immediately lost from the wall contralateral to the fistula exit, followed by thrombus formation and JANIH. Gene Ontology (GO) enrichment analysis of the 1,862 differentially expressed genes (DEG) between the JANIH and the outflow vein identified 525 overexpressed genes. The rat jugular vein to carotid artery AVF showed changes similar to the mouse AVF. Disturbed flow through the JAA correlates with rapid endothelial cell loss, thrombus formation, and JANIH; late endothelialization of the JAA channel correlates with late AVF patency. Early thrombus formation in the JAA may influence the later development of JANIH.NEW & NOTEWORTHY Disturbed flow and focal endothelial cell loss in the juxta-anastomotic area of the mouse AVF colocalizes with acute thrombus formation followed by late neointimal hyperplasia. Differential flow patterns between the juxta-anastomotic area and the outflow vein correlate with differential expression of genes regulating coagulation, proliferation, collagen metabolism, and the immune response. The rat jugular vein to carotid artery AVF model shows changes similar to the mouse AVF model.

Fish swim bladders as valve leaflets enhance the durability of transcatheter aortic valve replacement devices

Transcatheter aortic valve replacement (TAVR) has emerged as an effective therapy for inoperable patients with severe aortic stenosis (AS). However, calcification-induced limited durability restricts its application. Fish swim bladders (FSB), which are resistant to calcific degeneration, offer a viable solution to this challenge. In this study, we developed a new TAVR device using FSB as the valve leaflet. Furthermore, the in vitro durability, in vivo performance, and size selection of this TAVR device were assessed by an experimental study and finite element analysis. A self-expandable TAVR device was fabricated by suturing the FSB films into a 23 mm nitinol alloy frame. Further, hemodynamic performance, such as effective orifice area, transvalvular pressure difference and regurgitant fraction, the durability was tested by the pulsatile flow test and accelerated fatigue test, according to the ISO 5840-3. The effect of release size on hydrodynamic performance was also investigated. Finally, the in vivo performance of the TAVR device were examined using a porcine implantation model. The results showed that the strength of the FSB films satisfied the requirements for valve leaflets. The hemodynamic performance of the FSB TAVR device met the requirements of ISO 5840-3 standards. After 400 million cycles, the FSB showed no fiber loss, torn, perforation, or other valve failure phenomena. In porcine models, the devices were well-positioned, functioned well with no stenosis immediately after the operation. Collectively, we successfully developed a TAVR device with FSB as valve leaflets that exhibited good fatigue resistance. STATEMENT OF SIGNIFICANCE: The source of material for the leaflets of commercialized biological heart valves (BHVs) is mainly bovine pericardium, but this material suffers the following problems: large and uneven thickness of the material, the presence of α-Gal and Neu5Gc antigens, and the susceptibility to structural valve degradation (SVD). New material for BHVs leaflets is rarely reported. In this study, we prepared a transcatheter aortic valve (TAV) and performed long-term in vitro and short-term in vivo studies using fish swim bladder (FSB) as the leaflets. The study confirmed that FSB TAV device can complete 400 million fatigue tests and maintain the good morphology of the leaflets, and that it still maintains good functionality after a certain amount of compression, indicating that FSB is a promising material for leaflets.

Swim bladder-derived biomaterials: structures, compositions, properties, modifications, and biomedical applications

Animal-derived biomaterials have been extensively employed in clinical practice owing to their compositional and structural similarities with those of human tissues and organs, exhibiting good mechanical properties and biocompatibility, and extensive sources. However, there is an associated risk of infection with pathogenic microorganisms after the implantation of tissues from pigs, cattle, and other mammals in humans. Therefore, researchers have begun to explore the development of non-mammalian regenerative biomaterials. Among these is the swim bladder, a fish-derived biomaterial that is rapidly used in various fields of biomedicine because of its high collagen, elastin, and polysaccharide content. However, relevant reviews on the biomedical applications of swim bladders as effective biomaterials are lacking. Therefore, based on our previous research and in-depth understanding of this field, this review describes the structures and compositions, properties, and modifications of the swim bladder, with their direct (including soft tissue repair, dural repair, cardiovascular repair, and edible and pharmaceutical fish maw) and indirect applications (including extracted collagen peptides with smaller molecular weights, and collagen or gelatin with higher molecular weights used for hydrogels, and biological adhesives or glues) in the field of biomedicine in recent years. This review provides insights into the use of swim bladders as source of biomaterial; hence, it can aid biomedicine scholars by providing directions for advancements in this field.

Influences of Polyphenols on the Properties of Crosslinked Acellular Fish Swim Bladders: Experiments and Molecular Dynamic Simulations

Acellular fish swim bladders (AFSBs) are a promising biomaterial in tissue engineering, however, they may suffer from rapid degradation due to enzyme invasion. In this work, natural polyphenols, including epigallocatechin gallate (EGCG), proanthocyanidin (PC), tannic acid (TA) and protocatechuic acid (PCA), were utilized to improve the properties of AFSBs through crosslinking modifications. Fourier transform infrared (FTIR) results indicate that the triple helix of the collagen in AFSBs is well preserved after crosslinking. The differential scanning calorimetry (DSC), water contact angle (WCA) and in vitro degradation tests indicate that the polyphenol-crosslinked AFSBs exhibit improved thermal stability, enzymatic stability, hydrophilicity and mechanical properties. Among them, EGCG with multiple phenolic hydroxyl groups and low potential resistance is more favorable for the improvement of the mechanical properties and enzymatic stability of AFSBs, as well as their biocompatibility and integrity with the collagen triple helix. Moreover, the crosslinking mechanism was demonstrated to be due to the hydrogen bonds between polyphenols and AFSBs, and was affected by the molecular size, molecular weight and the hydroxyl groups activity of polyphenol molecules, as clarified by molecular dynamic (MD) simulations. The approach presented in this work paves a path for improving the properties of collagen materials.

[Silver Ion Decreases Foreign Body Reaction and Venous Neointimal Hyperplasia through the Inhibition of Interleukin-33 Expression]

INTRODUCTION

Vascular prosthetic grafts are widely used in vascular surgery; however, graft infection remains a major concern. Silver-coated vascular grafts have demonstrated anti-infection properties in clinical settings; however, whether the silver irons influence foreign body reaction or neointimal hyperplasia remains unclear.

METHODS

Sodium alginate and hyaluronic acid (SA/HA) hydrogel patches loaded with rhodamine, with or without silver, were fabricated. Patches were implanted in the subcutaneous or abdominal cavity and inferior vena cava of rats. Samples were harvested on day 14 and examined via immunohistochemical and immunofluorescence analyses.

RESULTS

Silver hydrogel was found to decrease the foreign body reaction; after subcutaneous and abdominal cavity implantation in rats, the capsule was found to be thinner in the silver hydrogel group than in the control hydrogel group. The silver hydrogel group had fewer CD68-positive cells and proliferating cell nuclear antigen and interleukin-33 (IL-33) dual-positive cells than the control hydrogel group. Additionally, the silver hydrogel patch reduced the neointimal thickness after patch venoplasty in rats, and the number of IL-33- and IL-1β-positive cells was lower than that in the control patch.

CONCLUSION

Silver-loaded SA/HA hydrogel patches decreased the foreign body reaction and venous neointimal hyperplasia in rats by the inhibition of IL-33 expression.

Hydrostatic pressure under hypoxia facilitates fabrication of tissue-engineered vascular grafts derived from human vascular smooth muscle cells in vitro

Biologically compatible vascular grafts are urgently required. The scaffoldless multi-layered vascular wall is considered to offer theoretical advantages, such as facilitating cells to form cell-cell and cell-matrix junctions and natural extracellular matrix networks. Simple methods are desired for fabricating physiological scaffoldless tissue-engineered vascular grafts. Here, we showed that periodic hydrostatic pressurization under hypoxia (HP/HYP) facilitated the fabrication of multi-layered tunica media entirely from human vascular smooth muscle cells. Compared with normoxic atmospheric pressure, HP/HYP increased expression of N-myc downstream-regulated 1 (NDRG1) and the collagen-cross-linking enzyme lysyl oxidase in human umbilical artery smooth muscle cells. HP/HYP increased N-cadherin-mediated cell-cell adhesion via NDRG1, cell-matrix interaction (i.e., clustering of integrin α5β1 and fibronectin), and collagen fibrils. We then fabricated vascular grafts using HP/HYP during repeated cell seeding and obtained 10-layered smooth muscle grafts with tensile rupture strength of 0.218-0.396 MPa within 5 weeks. Implanted grafts into the rat aorta were endothelialized after 1 week and patent after 5 months, at which time most implanted cells had been replaced by recipient-derived cells. These results suggest that HP/HYP enables fabrication of scaffoldless human vascular mimetics that have a spatial arrangement of cells and matrices, providing potential clinical applications for cardiovascular diseases. STATEMENT OF SIGNIFICANCE: Tissue-engineered vascular grafts (TEVGs) are theoretically more biocompatible than prosthetic materials in terms of mechanical properties and recipient cell-mediated tissue reconstruction. Although some promising results have been shown, TEVG fabrication processes are complex, and the ideal method is still desired. We focused on the environment in which the vessels develop in utero and found that mechanical loading combined with hypoxia facilitated formation of cell-cell and cell-matrix junctions and natural extracellular matrix networks in vitro, which resulted in the fabrication of multi-layered tunica media entirely from human umbilical artery smooth muscle cells. These scaffoldless TEVGs, produced using a simple process, were implantable and have potential clinical applications for cardiovascular diseases.

Acellular fish skin for wound healing

Fish skin grafting as a new skin substitute is currently being used in clinical applications. Acceleration of the wound healing, lack of disease transmission, and low cost of the production process can introduce fish skin as a potential alternative to other grafts. An appropriate decellularization process allows the design of 3D acellular scaffolds for skin regeneration without damaging the morphology and extracellular matrix content. Therefore, the role of decellularization processes is very important to maintain the properties of fish skin. In this review article, recent studies on various decellularization processes as well as biological, physical, and mechanical properties of fish skin and its applications with therapeutic effects in wound healing were investigated.

Decellularized fish swim bladder patch loaded with mesenchymal stem cells inhibits neointimal hyperplasia

We previously showed decellularized fish swim bladder can be used as vascular patch and tube graft in rats, mesenchymal stem cells (MSCs) have showed the capability to inhibit neointimal hyperplasia in different animal models. We hypothesized that decellularized fish swim bladder patch loaded with MSCs (bioinspired patch) can inhibit neointimal hyperplasia in a rat aortic patch angioplasty model. Rat MSCs were grown in vitro and flow cytometry was used to confirm their quality. 3.6 × 10⁵ MSCs were mixed into 100 μl of sodium alginate (SA)/hyaluronic acid (HA) hydrogel, two layers of fish swim bladders (5 mm × 5 mm) were sutured together, bioinspired patch was created by injection of hydrogel with MSCs into the space between two layers of fish swim bladder patches. Decellularized rat thoracic aorta patch was used as control. Patches were harvested at days 1 and 14 after implantation. Samples were examined by histology, immunohistochemistry, and immunofluorescence. The decellularized rat thoracic aorta patch and the fish swim bladder patch had a similar healing process after implantation. The bioinspired patch had a similar structure like native aorta. Bioinspired patch showed a decreased neointimal thickness (p = .0053), fewer macrophages infiltration (p = .0090), and lower proliferation rate (p = .0291) compared to the double layers fish swim bladder patch group. Decellularized fish swim bladder patch loaded with MSCs can inhibit neointimal hyperplasia effectively. Although this is a preliminary animal study, it may have a potential application in large animals or clinical research.

Preparation of extracellular matrix of fish swim bladders by decellularization with supercritical carbon dioxide

Fish swim bladders used to be considered as byproducts or waste in fishery; however, they are potential materials for biological medicine with abundant collagen. In this work, an efficient noncytotoxic decellularization process using sodium dodecyl sulfate (SDS) ternary system assisted with supercritical carbon dioxide (scCO2) as the green extraction fluid and ethanol (ET) as the cosolvent has been developed to harvest acellular fish swim bladders (AFSBs). The experimental results show that the tissue treated by SDS assisted with scCO2 and ethanol at 37 °C and 25 MPa can be decellularized thoroughly and maintains intact fibers and uniform pore distribution, which resulting in a tensile strength of 5.61 MPa and satisfactory biocompatibility. Meanwhile, the residual SDS content in scCO2/SDS/ET ternary system is 0.0122% which is significantly lower than it in scCO2/SDS system due to the enhanced mass transfer rate of SDS in tissues by scCO2 with ethanol. The synergy between SDS and ethanol can enhance the diffusion coefficient and the solubility of SDS in scCO2, which reduced the contact time between SDS and tissues. Meaningfully, the results obtained in this work can not only provide a novel strategy to produce acellular matrix with superior properties, but also offer a further understanding of the decellularization through scCO2 extraction processing with the synergy of suitable detergent/cosolvent.

Response of cardiovascular environment to sulfonated hyaluronic acid with higher sulfur content

Sulfonated hyaluronic acid (S-HA) has been shown to promote endothelialization in the treatment of cardiovascular diseases according to amounts of investigations. In this study, two kinds of S-HA with higher sulfur content were obtained successfully. Through a series of cell experiments, it was found that the S-HA with higher sulfur content not only possessed stronger ability of promoting the growth and migration of endothelial cells, regulating the phenotype of smooth muscle cells, but also had stronger anti-inflammatory function. Furthermore, all the S-HA molecules are very compatible with blood.

Delivery of rivaroxaban and chitosan rapamycin microparticle with dual antithrombosis and antiproliferation functions inhibits venous neointimal hyperplasia

Neointimal hyperplasia is a complex process after vascular interventions, acute platelet deposition and smooth muscle cell proliferation both contributed to this process. There are still no perfect solutions to solve this problem. Rivaroxaban is a novel anticoagulant that has been widely used in clinic, it has a good pharmacological effects both in vivo and in vitro. Chitosan microparticle rapamycin (MP-rapa) was fabricated, interspaces of polyglycolic acid (PGA) scaffold were used as a reservoir of MP-rapa, and the scaffold was coated with hyaluronic acid rivaroxaban (MP-rapa-riva). Scanning electronic microscopy (SEM) photographs were taken and water contact angles were measured, rat inferior vena cava (IVC) patch venoplasty model was used; patches were harvested at day 14 and examined by immunohistochemistry and immunofluorescence. SEM photographs showed the microparticles rapamycin were inside the interspace of the scaffold, hyaluronic acid rivaroxaban was also successfully coated onto the surface of the scaffold. There was a thinner neointima, fewer proliferating cell nuclear antigen (PCNA) positive cells, fewer macrophages in the MP-rapa and MP-rapa-riva grafts compared to the control PGA graft. The result showed that this scaffold with dual anticoagulation and antiproliferation functions can effectively inhibit venous neointimal hyperplasia, although this is an animal experiment, it showed promising potential clinical application in the future.

Extracellular Matrix Coatings on Cardiovascular Materials—A Review

Vascular transplantation is an effective and common treatment for cardiovascular disease (CVD). However, the low biocompatibility of implants is a major problem that hinders its clinical application. Surface modification of implants with extracellular matrix (ECM) coatings is an effective approach to improve the biocompatibility of cardiovascular materials. The complete ECM seems to have better biocompatibility, which may give cardiovascular biomaterials a more functional surface. The use of one or several ECM proteins to construct a surface allows customization of coating composition and structure, possibly resulting in some unique functions. ECM is a complex three-dimensional structure composed of a variety of functional biological macromolecules, and changes in the composition will directly affect the function of the coating. Therefore, understanding the chemical composition of the ECM and its interaction with cells is beneficial to provide new approaches for coating surface modification. This article reviews novel ECM coatings, including coatings composed of intact ECM and biomimetic coatings tailored from several ECM proteins, and introduces new advances in coating fabrication. These ECM coatings are effective in improving the biocompatibility of vascular grafts.

Wood-Derived Vascular Patches Loaded With Rapamycin Inhibit Neointimal Hyperplasia

Background: Patches are commonly used to close blood vessels after vascular surgery. Most currently used materials are either prosthetics or animal-derived; although natural materials, such as a leaf, can be used as a patch, healing of these natural materials is not optimal; rhodamine and rapamycin have been used to show that coating patches with drugs allow drug delivery to inhibit neointimal hyperplasia that may improve patch healing. Wood is abundant, and its stiffness can be reduced with processing; however, whether wood can be used as a vascular patch is not established. We hypothesized that wood can be used as a vascular patch and thus may serve as a novel plant-based biocompatible material.

Method: Male Sprague–Dawley rats (aged 6–8 weeks) were used as an inferior vena cava (IVC) patch venoplasty model. After softening, wood patches coated with rhodamine and rapamycin were implanted into the rat subcutaneous tissue, the abdominal cavity, or the IVC. Samples were explanted on day 14 for analysis.

Result: Wood patches became soft after processing. Patches showed biocompatibility after implantation into the subcutaneous tissue or the abdominal cavity. After implantation into the IVC, the patches retained mechanical strength. There was a significantly thinner neointima in wood patches coated with rapamycin than control patches (146.7 ± 15.32 μm vs. 524.7 ± 26.81 μm; p = 0.0001). There were CD34 and nestin-positive cells throughout the patch, and neointimal endothelial cells were Eph-B4 and COUP-TFII-positive. There was a significantly smaller number of PCNA and α-actin dual-positive cells in the neointima (p = 0.0003), peri-patch area (p = 0.0198), and adventitia (p = 0.0004) in wood patches coated with rapamycin than control patches. Piezo1 was expressed in the neointima and peri-patch area, and there were decreased CD68 and piezo1 dual-positive cells in wood patches coated with rapamycin compared to control patches.

Conclusion: Wood can be used as a novel biomaterial that can be implanted as a vascular patch and also serve as a scaffold for drug delivery. Plant-derived materials may be an alternative to prosthetics or animal-based materials in vascular applications.

Composite Coating Prepared with Ferulic Acid to Improve the Corrosion Resistance and Blood Compatibility of Magnesium Alloy

Magnesium (Mg) alloy has been used for medical vascular stents because of its good biocompatibility and degradability, but its rapid degradation and poor blood compatibility limits its further application. In this study, ferulic acid (FA) was conjugated onto the polydopamine (PDA) deposited Mg-Zn-Y-Nd alloy to prepare a PDA/FA multi-functional coating with better corrosion resistance and blood compatibility. The results suggest that the PDA/FA coating possessed potential application for surface modification of a medical Mg alloy.

Egg Shell Membrane as an Alternative Vascular Patch for Arterial Angioplasty

Introduction: The egg shell membrane (ESM) is always considered as waste, but recent studies have shown that it has the potential to yield rapid re-endothelialization in vitro. We hypothesized that ESM and heparin-conjugated ESM (HESM) can be used as arterial patch in a rat aortic angioplasty model.

Method: Sprague-Dawley rat (200 g) abdominal aortic patch angioplasty model was used. Decellularized rat thoracic aorta (TA) patch was used as the control; ESM patch was made of raw chicken egg; heparin-coated ESM (HESM) patch was made by using dopamine; anticoagulation properties were verified using platelet adhesion tests; the TA, ESM, and HESM patches were implanted to the rat aorta and harvested at day 14; and the samples were examined by immunohistochemistry and immunofluorescence.

Result: The ESM patch showed a similar healing process to the TA patch; the cells could migrate and infiltrate into both patches; there was a neointima with von Willebrand factor-positive endothelial cells; the endothelial cells acquired arterial identity with Ephrin-B2- and dll-4-positive cells; there were proliferating cell nuclear antigen (PCNA)-positive cells, and PCNA and alpha smooth muscle actin dual-positive cells in the neointima in both groups. Heparin was conjugated to the patch successfully and showed a strong anticoagulation property in vitro. HESM could decrease mural thrombus formation after rat aortic patch angioplasty.

Conclusion: The ESM is a natural scaffold that can be used as a vascular patch; it showed a similar healing process to decellularized TA patch; HESM showed anticoagulation property both in vitro and in vivo; and the ESM may be a promising vascular graft in the clinic.

Swim bladder as an alternative biomaterial for bioprosthetic valves

Valvular structural deterioration and calcification are the main indications for secondary intervention after bioprosthetic valve replacement, promoting an urgent requirement for more durable cardiovascular biomaterials for clinical applications. The swim bladder of carp we introduced in this study has several advantages as a raw biomaterial when compared to the bovine pericardium. First, the results of in vitro assays demonstrated that the cross-linked carp swim bladder exhibited superior biocompatibility compared to the bovine pericardium, and the anti-calcification property was verified by subcutaneous implantation experiments in rats. Furthermore, the cross-linked swim bladder tissue was sutured on a cobalt-chromium alloy stent to fabricate a pulmonary bioprosthetic valve, and then the feasibility and durability of the bioprosthetic valve were proved by a fatigue test in vitro. Finally, a sheep pulmonary bioprosthetic valve replacement in situ experiment further confirmed the superior calcification resistance, immune-compatibility, endothelialization, and hemodynamic properties of the swim bladder, suggesting that it might be used as an alternative biomaterial for bioprosthetic valves.