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A major roadblock in implementing engineered tissues clinically lies in their limited vascularization. After implantation, such tissues do not integrate with the hostʼs circulation as quickly as needed, commonly resulting in loss of viability and functionality. This study presents a solution to the vascularization problem that could enable the survival and function of large, transplantable, and vascularized engineered tissues. The technique allows vascularization of a cell laden hydrogel through angiogenesis from a suturable tissue-engineered vascular graft (TEVG) constructed from electrospun polycaprolactone with macropores. The graft is surrounded by a layer of cell-laden gelatin-methacryloyl hydrogel. The constructs are suturable and possess mechanical properties like native vessels. Angiogenesis occurs through the pores in the graft, resulting in a hydrogel containing an extensive vascular network that is connected to an implantable TEVG. The size of the engineered tissue and the degree of vascularization can be increased by adding multiple TEVGs into a single construct. The engineered tissue has the potential to be immediately perfused by the patient's blood upon surgical anastomosis to host vessels, enabling survival of implanted cells. These findings provide a meaningful step to address the longstanding problem of fabricating suturable pre-vascularized tissues which could survive upon implantation in vivo. Creating vascularized engineered tissues that can be transplanted and rapidly perfused by the host blood supply is a major challenge which has limited the clinical impact of tissue engineering. In this study we demonstrate a technique to fabricate vascularized tissue constructs via angiogenesis from a suturable tissue-engineered vascular graft. The macroporous graft is surrounded with hydrogel, allowing endothelial cells to migrate from the lumen and vascularize the hydrogel layer with capillary-like structures connected to the macrovessel. The graft has comparable mechanical properties to native blood vessels and larger constructs can be fabricated by incorporating multiple grafts. These constructs could potentially be connected surgically to the circulation at an implantation site to support their immediate perfusion and survival. [Display omitted] [ABSTRACT FROM AUTHOR]

IntroductionThis study evaluates the efficacy of uncrosslinked porcine collagen coated vascular grafts (UPCCVG) in facilitating neointima formation and endothelialization.MethodsPrior to coating, the uncrosslinked porcine collagen underwent comprehensive characterization employing SDS-PAGE, image analysis, circular dichroism and immunogenicity. The PET substrate of the vascular graft was coated with collagen solution utilizing the dip-coating method. Water permeability, blood leakage resistance, radial compliance, hemolysis, cytotoxicity and cell proliferation of UPCCVG in vitro were studied. Subsequent in vivo evaluation involved the implantation of UPCCVG as a substitute for the porcine abdominal aorta. Digital subtraction angiography (DSA) was employed to evaluate UPCCVG patency post-implantation, while histology, immunohistochemistry, and scanning electron microscopy were utilized to assess neointima formation and endothelialization. The in vivo thrombosis of UPCCVG was analyzed simultaneously to further characterize its blood compatibility.ResultsThe uncrosslinked collagen demonstrated high purity, maintaining its triple helix structure and molecular weight akin to the type I bovine collagen standard substrate, indicative of preserved biological activity and low immunogenicity. UPCCVG exhibited water permeability, blood leakage resistance, radial compliance and blood compatibility comparable to commercial grafts. DSA revealed satisfactory patency of UPCCVG without evidence of stenosis or swelling at the 3-week post-implantation mark. Histological analysis illustrated well-developed neointima with appropriate thickness and controlled proliferation. Immunohistochemistry confirmed the presence of endothelial cells (VWF positive) and smooth muscle cells (α-SMA positive) within the neointima, indicating successful endothelialization. Moreover, the morphology of the neointima surface closely resembled that of the natural artery tunica intima, oriented along the direction of blood flow.DiscussionUPCCVG, composed of uncrosslinked porcine collagen, demonstrates promising potential in fostering neointima formation and endothelialization while mitigating intimal hyperplasia. This biocompatible uncrosslinked porcine collagen merits further investigation for its clinical applications in vascular reconstruction.

Background Implantation of the left atrial appendage occluder (LAAO) has been proven to prevent stroke effectively in patients with atrial fibrillation who cannot tolerate anticoagulants. Incomplete endothelization of LAAO may cause device‐related thrombus, and currently no good image modality exists to clearly see LAAO endothelialization. We aimed to use coronary optic coherence tomography (OCT) to visualize LAAO endothelialization. Methods and Results We enrolled 14 patients (72.8±9.4 years old) undergoing pulmonary vein isolation with a preexisting LAAO implanted more than 1 year ago (5 Watchman and 9 Amulet). After pulmonary vein isolation, we did OCT via steerable sheath and coronary guiding catheter to adjust OCT probe location and injected contrast medium to visualize the LAAO surface. In vitro testing was also performed to see the bare occluder. In vitro OCT showed the surface of the bare device as an interrupted granule pattern, which included the Watchman surface polytetrafluoroethylene membrane string, Amulet disc metal strut, and inner polytetrafluoroethylene membrane string. In the implanted Watchman, OCT showed endothelialization as a smooth surface layer with noninterrupted coarser granules. In the implanted Amulet, OCT showed endothelialization as thin (early) or thick (late) endothelialization layer covering struts with OCT shadows. Among patients with Watchman, 2 showed no, 2 early, and 1 complete endothelialization. Among patients with Amulet, 2 showed no, 3 early, and 4 late endothelialization. Conclusions We demonstrated the feasibility of OCT to visualize LAAO endothelization with high resolution. Further studies are needed to determine antithrombotic regimens if incomplete endothelization is detected. A new OCT catheter may be designed specifically for LAAO.

ABSTRACT Introduction and objectives: Delayed vascular healing may induce late stent thrombosis. Optical coherence tomography (OCT) is useful to evaluate endothelial coverage. The objective of this study was to compare stent coverage and apposition in non-complex coronary artery lesions treated with durable polymer-coated everolimus-eluting stents (durable-polymer EES) vs biodegradable polymer-coated everolimus-eluting stents (biodegradable-polymer EES) vs polymer-free biolimus-eluting stents (BES) 1 and 6 months after stent implantation. Methods: Prospective, multicenter, non-randomized study that compared the 3 types of DES. Follow-up angiography and OCT were performed 1 and 6 months later. The primary endpoint was the rate of uncovered struts as assessed by the OCT at 1 month. Results: A total of 104 patients with de novo non-complex coronary artery lesions were enrolled. A total of 44 patients were treated with polymer-free BES, 35 with biodegradable-polymer EES, and 25 with durable-polymer EES. A high rate of uncovered struts was found at 1 month with no significant differences reported among the stents (80.2%, polymer-free BES; 88.1%, biodegradable-polymer EES; 82.5%, durable-polymer EES; P = .209). Coverage improved after 6 months in the 3 groups without significant differences being reported (97%, 95%, and 93.7%, respectively; P = .172). Conclusions: In patients with de novo non-complex coronary artery lesions treated with durable vs biodegradable vs polymer-free DES, strut coverage and apposition were suboptimal at 1 month with significant improvement at 6 months.

Carotid endarterectomy (CEA) with patch angioplasty is the most effective treatment for carotid artery stenosis. However, the use of existing vascular patches is often associated with thrombosis, restenosis, calcification and other complications.Objective: to develop biodegradable patches for arterial reconstruction, containing vascular endothelial growth factor (VEGF) or arginyl-glycyl-aspartic acid (RGD), and comparatively evaluate their biocompatibility and efficacy in in vitro experiments and during preclinical trials in large laboratory animal models.Materials and methods. Biodegradable patches, made from a mixture of poly(3-hydroxybutyrate-co-3- hydroxyvalerate (PHBV) and poly(ε-caprolactone) (PCL), were fabricated by electrospinning and modified with VEGF or the peptide sequence RGD in different configurations. In in vitro experiments, the surface structure, physicomechanical and hemocompatibility properties were evaluated. In in vivo experiments, we evaluated the effectiveness of the developed vascular patches for 6 months after implantation into the carotid artery of 12 sheep. The quality of remodeling was assessed using histological and immunofluorescence studies of explanted specimens.Results. The PHBV/PCL/VEGF patches had physicomechanical characteristics closer to those of native vessels and their biofunctionalization method resulted in the smallest drop in strength characteristics compared with their unmodified PHBV/PCL counterparts. Modification with RGD peptides reduced the strength of the polymer patches by a factor of 2 without affecting their stress-strain behavior. Incorporation of VEGF into polymer fibers reduced platelet aggregation upon contact with the surface of the PHBV/PCL/VEGF patches and did not increase erythrocyte hemolysis. At month 6 of implantation into the carotid artery of sheep, the PHBV/PCL/ VEGF patches formed a complete newly formed vascular tissue without signs of associated inflammation and calcification. This indicates the high efficiency of the VEGF incorporated into the patch. In contrast, the patches modified with different configurations of RGD peptides combined the presence of neointimal hyperplasia and chronic granulomatous inflammation present in the patch wall and developed during bioresorption of the polymer scaffold.Conclusion. PHBV/PCL/VEGF patches have better biocompatibility and are more suitable for vascular wall reconstruction than PHBV/PCL/RGD patches.

The covalent functionalization of synthetic peptides allows the modification of different biomaterials (metallic, polymeric, and ceramic), which are enriched with biologically active sequences to guide cell behavior. Recently, this strategy has also been applied to decellularized biological matrices. In this study, the covalent anchorage of a synthetic peptide (REDV) to a pericardial matrix decellularized via Schiff base is realized starting from concentrated peptide solutions (10−4 M and 10−3 M). The use of a labeled peptide demonstrated that as the concentration of the working solution increased, the surface density of the anchored peptide increased as well. These data are essential to pinpointing the concentration window in which the peptide promotes the desired cellular activity. The matrices were extensively characterized by Water Contact Angle (WCA) analysis, Differential Scanning Calorimetry (DSC) analysis, geometric feature evaluation, biomechanical tests, and preliminary in vitro bioassays. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases are a major global health challenge. Blood vessel disease and dysfunction are major contributors to this healthcare burden, and the development of tissue-engineered vascular grafts (TEVGs) is required, particularly for the replacement of small-diameter vessels. Silk fibroin (SF) is a widely used biomaterial for TEVG fabrication due to its high strength and biocompatibility. However, the stiffness of SF is much higher than that of native blood vessels (NBVs), which limits its application for vascular tissue engineering. In this study, SF was plasticized with glycerol to produce TEVGs exhibiting similar stiffness and ultimate tensile strength to those of NBVs. The electrospun SF/glycerol TEVGs exhibited mechanical properties comparable to NBVs and supported the in vitro proliferation of essential vascular cells-endothelial and smooth muscle cells. After 5 days of culture, the TEVGs exhibited an endothelial monolayer in the lumen, demonstrating their potential for functional vascular tissue regeneration. Our study demonstrates the feasibility of producing TEVGs from SF with tailored mechanical properties, paving the way for more functional and durable TEVGs for future clinical applications., (© 2024 The Author(s). Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

Rapid formation of innovative, inexpensive, personalized, and quickly reproducible artery bioresorbable stents (BRSs) is significantly important for treating dangerous and sometimes deadly cerebrovascular disorders. It is greatly challenging to give BRSs excellent mechanical properties, biocompatibility, and bioabsorbability. The current BRSs, which are mostly fabricated from poly-l-lactide (PLLA), are usually applied to coronary revascularization but may not be suitable for cerebrovascular revascularization. Here, novel 3D-printed BRSs for cerebrovascular disease enabling anti-stenosis and gradually disappearing after vessel endothelialization are designed and fabricated by combining biocompatible poly (p-dioxanone) (PPDO) and 3D printing technology for the first time. We can control the strut thickness and vessel coverage of BRSs by adjusting the printing parameters to make the size of BRSs suitable for small-diameter vascular use. We added bis-(2,6-diisopropylphenyl) carbodiimide (commercial name: stabaxol®-1) to PPDO to improve its hydrolytic stability without affecting its mechanical properties and biocompatibility. In vitro cell experiments confirmed that endothelial cells can be conveniently seeded and attached to the BRSs and subsequently demonstrated good proliferation ability. Owing to the excellent mechanical properties of the monofilaments fabricated by the PPDO, the 3D-printed BRSs with PPDO monofilaments support desirable flexibility, therefore offering a novel BRS application in the vascular disorders field. [ABSTRACT FROM AUTHOR]

Cell manipulation using external magnetic fields has been proposed to accelerate the neck reendothelization of saccular unruptured stented intracranial aneurysms. This work presents a computational fluid dynamics (CFD) model of a Saccular Brain Aneurysm that incorporates a helicoidal stent. An Eulerian-Lagrangian model implemented in ANSYS-Fluent is used to simulate the hemodynamics in the aneurysm. In silico studies have been conducted to describe the incidence of the magnetic field direction, frequency and amplitude on the blood hemodynamics and particle capture efficiency, when an external magnetic field is used to trap magnetically labeled particles traveling through the aneurysm. It is found that the magnetic field direction affects the particle concentration in the target region. Simulation results show that the highest particle capture efficiency is obtained with a 1T magnetic field amplitude in an open bore MRI scanner, when a permanent magnet is used.

The need for small-diameter grafts for replacing the damaged area of the blood pool is still very high. These grafts are very popular for coronary artery bypass grafting. Polymeric synthetic grafts are an alternative to autografts. A promising area of tissue engineering is the creation of a biodegradable graft. It can serve as the basis for de novo generation of vascular tissue directly in the patient’s body. Optimization of the polymer composition of products has led to improved physicomechanical and biocompatible properties of the products. However, the improvements are still far from needed. One of the decisive factors in the reliability of a small-diameter vascular graft is the early formation of endothelial lining on its inner surface, which can provide atrombogenic effect and full lumen of the future newly formed vessel. To achieve this goal, grafts are modified by incorporating bioactive molecules or functionally active peptide sequences into the polymer composition or immobilizing on its inner surface. Peptide sequences include cell adhesion site – arginine-glycine-aspartic acid (RGD peptide). This sequence is present in most extracellular matrix proteins and has a tropism for integrin receptors of endothelial cells. Many studies have shown that imitation of the functional activity of the natural extracellular matrix can promote spontaneous endothelization of the inner surface of a vascular graft. Moreover, configuration of the RGD peptide determines the survival and differentiation of endothelial cells. The linker through which the peptide is crosslinked to the polymer surface determines the bioavailability of the RGD peptide for endothelial cells.

The development of large-scale human liver scaffolds equipped with interconnected flow channels in three-dimensional space offers a promising strategy for the advancement of liver tissue engineering. Tissue-engineered scaffold must be blood-compatible to address the demand for clinical transplantable liver tissue. Here, we demonstrate the construction of 3-D macro scaffold with interconnected flow channels using the selective laser sintering (SLS) fabrication method. The accuracy of the printed flow channels was ensured by the incorporation of polyglycolic acid (PGA) microparticles as porogens over the conventional method of NaCl salt leaching. The fabricated scaffold was populated with Hep G2, followed by endothelization with endothelial cells (ECs) grown under perfusion of culture medium for up to 10 days. The EC covered scaffold was perfused with platelet-rich plasma for the assessment of hemocompatibility to examine its antiplatelet adhesion properties. Both Hep G2-covered scaffolds exhibited a markedly different albumin production, glucose metabolism and lactate production when compared to EC-Hep G2-covered scaffold. Most importantly, EC-Hep G2-covered scaffold retained the antiplatelet adhesion property associated with the perfusion of platelet-rich plasma through the construct. These results show the potential of fabricating a 3-D scaffold with interconnected flow channels, enabling the perfusion of whole blood and circumventing the limitation of blood compatibility for engineering transplantable liver tissue. [ABSTRACT FROM AUTHOR]

Rapid formation of innovative, inexpensive, personalized, and quickly reproducible artery bioresorbable stents (BRSs) is significantly important for treating dangerous and sometimes deadly cerebrovascular disorders. It is greatly challenging to give BRSs excellent mechanical properties, biocompatibility, and bioabsorbability. The current BRSs, which are mostly fabricated from poly-l-lactide (PLLA), are usually applied to coronary revascularization but may not be suitable for cerebrovascular revascularization. Here, novel 3D-printed BRSs for cerebrovascular disease enabling anti-stenosis and gradually disappearing after vessel endothelialization are designed and fabricated by combining biocompatible poly (p-dioxanone) (PPDO) and 3D printing technology for the first time. We can control the strut thickness and vessel coverage of BRSs by adjusting the printing parameters to make the size of BRSs suitable for small-diameter vascular use. We added bis-(2,6-diisopropylphenyl) carbodiimide (commercial name: stabaxol®-1) to PPDO to improve its hydrolytic stability without affecting its mechanical properties and biocompatibility. In vitro cell experiments confirmed that endothelial cells can be conveniently seeded and attached to the BRSs and subsequently demonstrated good proliferation ability. Owing to the excellent mechanical properties of the monofilaments fabricated by the PPDO, the 3D-printed BRSs with PPDO monofilaments support desirable flexibility, therefore offering a novel BRS application in the vascular disorders field.

Advances in the development of vascular substitutes for small-sized arteries are ongoing because the present grafts do not entirely meet the requirements of native equivalents and are suboptimal in clinical performance. This study aims to develop a tri-layered vascular construct mimicking natural tissue using polyester blends and to investigate its endothelization through in vitro studies as a potential small-caliber vascular graft. The innermost layer is obtained by dip coating as a tubular porous film with a lumen diameter of 3 mm and a pore size of ≤8 µm. Circumferentially aligned electrospun fiber (diameter 100-800 nm) with a deviation angle of 15° are deposited over the porous film forming the intermediate layer. The random electrospun fibers (diameter 100-1100 nm) deviating at different angles are wrapped as the outermost layer. The mechanical properties of the tri-layered vascular construct are determined to be 44.80 ± 14.80 MPa for Young's modulus and 4.25 ± 0.75 MPa for ultimate tensile strength. MTS and cell behavior studies show that the isolated human umbilical cord vein endothelial cells proliferate and line the lumen of the vascular substitute. The vascular construct developed, with its biomimetic architecture, mechanical features, size, and endothelization, can be tested with in vivo studies., (© 2023 The Authors. Macromolecular Bioscience published by Wiley‐VCH GmbH.)

Background and Purpose: New coated flow diverters (FDs) claim antithrombotic properties and increased arterial wall integration. The aim of this study is to compare in vivo endothelial coverage of coated and uncoated FD in the context of different antiplatelet regimens., Methods: Different FDs (Silk Vista - SV, Pipeline with Shield technology - PED shield and Surpass Evolve - SE) were implanted in the aorta of rabbits, all 3 in each animal with 3 different antiplatelet regimens: no antiplatelet therapy, aspirin alone, or aspirin and ticagrelor. Four weeks after FD implantation, angiography, flat-panel CT, and optical coherence tomography (OCT) were performed before harvesting the aorta. Extensive histopathology analyses were performed including environmental scanning electron microscopy (ESEM), multiphoton microscopy (MPM) and histological staining with qualitative and/or quantitative assessment of device coverage., Results: All 23 FDs that were implanted remained patent without hyperplasia. Qualitative stent coverage assessment revealed that there were no statistically significant differences between the FD groups (p = 0.19, p = 0.45, p = 0.40, and p = 0.84 for OCT, ESEM, MPM and histology, respectively). Quantitative neointimal measurement of histological sections also showed similar results in all 3 FD groups (p = 0.70). However, there were significant differences between the 3 groups of antiplatelet regimens (p = 0.07) with a higher rate in the no antiplatelet group (p = 0.05 versus aspirin alone and p = 0.03 versus aspirin and ticagrelor)., Conclusion: Our study provides evidence that FD integration into the arterial wall is similar with coated (PED shield) and uncoated devices (SV, SE), regardless of the antiplatelet regimen. FD integration with specific surface coverage should be promoted., Trial Registration: APAFIS #2022011215518538., (Copyright © 2023 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

In this study, we designed and synthetized artificial vascular scaffolds based on nanofibers of collagen functionalized with hyaluronic acid (HA) in order to direct the phenotypic shape, proliferation, and complete endothelization of mouse primary aortic endothelial cells (PAECs). Layered tubular HA/collagen nanofibers were prepared using electrospinning and crosslinking process. The obtained scaffold is composed of a thin inner layer and a thick outer layer that structurally mimic the layer the intima and media layers of the native blood vessels, respectively. Compared with the pure tubular collagen nanofibers, the surface of HA functionalized collagen nanofibers has higher anisotropic wettability and mechanical flexibility. HA/collagen nanofibers can significantly promote the elongation, proliferation and phenotypic shape expression of PAECs. In vitro co-culture of mouse PAECs and their corresponding smooth muscle cells (SMCs) showed that the luminal endothelialization governs the biophysical integrity of the newly formed extracellular matrix (e.g., collagen and elastin fibers) and structural remodeling of SMCs. Furthermore, in vitro hemocompatibility assays indicated that HA/collagen nanofibers have no detectable degree of hemolysis and coagulation, suggesting their promise as engineered vascular implants.

Background: Implantation of the left atrial appendage occluder (LAAO) has been proven to prevent stroke effectively in patients with atrial fibrillation who cannot tolerate anticoagulants. Incomplete endothelization of LAAO may cause device-related thrombus, and currently no good image modality exists to clearly see LAAO endothelialization. We aimed to use coronary optic coherence tomography (OCT) to visualize LAAO endothelialization., Methods and Results: We enrolled 14 patients (72.8±9.4 years old) undergoing pulmonary vein isolation with a preexisting LAAO implanted more than 1 year ago (5 Watchman and 9 Amulet). After pulmonary vein isolation, we did OCT via steerable sheath and coronary guiding catheter to adjust OCT probe location and injected contrast medium to visualize the LAAO surface. In vitro testing was also performed to see the bare occluder. In vitro OCT showed the surface of the bare device as an interrupted granule pattern, which included the Watchman surface polytetrafluoroethylene membrane string, Amulet disc metal strut, and inner polytetrafluoroethylene membrane string. In the implanted Watchman, OCT showed endothelialization as a smooth surface layer with noninterrupted coarser granules. In the implanted Amulet, OCT showed endothelialization as thin (early) or thick (late) endothelialization layer covering struts with OCT shadows. Among patients with Watchman, 2 showed no, 2 early, and 1 complete endothelialization. Among patients with Amulet, 2 showed no, 3 early, and 4 late endothelialization., Conclusions: We demonstrated the feasibility of OCT to visualize LAAO endothelization with high resolution. Further studies are needed to determine antithrombotic regimens if incomplete endothelization is detected. A new OCT catheter may be designed specifically for LAAO.

The development of large-scale human liver scaffolds equipped with interconnected flow channels in three-dimensional space offers a promising strategy for the advancement of liver tissue engineering. Tissue-engineered scaffold must be blood-compatible to address the demand for clinical transplantable liver tissue. Here, we demonstrate the construction of 3-D macro scaffold with interconnected flow channels using the selective laser sintering (SLS) fabrication method. The accuracy of the printed flow channels was ensured by the incorporation of polyglycolic acid (PGA) microparticles as porogens over the conventional method of NaCl salt leaching. The fabricated scaffold was populated with Hep G2, followed by endothelization with endothelial cells (ECs) grown under perfusion of culture medium for up to 10 days. The EC covered scaffold was perfused with platelet-rich plasma for the assessment of hemocompatibility to examine its antiplatelet adhesion properties. Both Hep G2-covered scaffolds exhibited a markedly different albumin production, glucose metabolism and lactate production when compared to EC-Hep G2-covered scaffold. Most importantly, EC-Hep G2-covered scaffold retained the antiplatelet adhesion property associated with the perfusion of platelet-rich plasma through the construct. These results show the potential of fabricating a 3-D scaffold with interconnected flow channels, enabling the perfusion of whole blood and circumventing the limitation of blood compatibility for engineering transplantable liver tissue.

To improve the endothelization of 3D matrices produced by electrospinning we propose adding cyclo(RGDfC) peptide conjugated to human serum albumin (HSA) (HSA-c(RGDfC)) to the electrospinning solution. HSA-c(RGDfC) has been prepared using a bifunctional linker with N-hydroxysuccinimide and maleimide groups, and the product has been confirmed by 1Н NMR spectroscopy. Electrospun matrices have been fabricated from the solutions of 3% polyurethane Tecoflex EG-80A with 10% HSA and 0.01–1.3% HSA–c(RGDfC) (relative to Tec) in 1,1,1,3,3,3-hexafluoro-2-propanol. The presence of HSA and the cyclo(RGDfC) peptide on the surface of electrospun matrices has been confirmed by FTIR spectroscopy. The structure of matrices has been examined by scanning electron microscopy. The ability of the matrices to facilitate the adhesion of primary human umbilical vein endotheliocytes (HUVECs) has been studied. The presence of HSA–c(RGDfC) conjugate in the matrices enhanced cellular adhesion in a dose dependent manner with a maximum effect at 1% HSA-c(RGDfC). [ABSTRACT FROM AUTHOR]

The hemocompatibility of vascular grafts made from poly(ethylene terephthalate) (PET) is insufficient due to the rapid adhesion and activation of blood platelets that occur upon incubation with whole blood. PET polymer was treated with NHx radicals created by passing ammonia through gaseous plasma formed by a microwave discharge, which allowed for functionalization with amino groups. X-ray photoelectron spectroscopy characterization using derivatization with 4-chlorobenzaldehyde indicated that approximately 4% of the –NH2 groups were associated with the PET surface after treatment with the gaseous radicals. The functionalized polymers were coated with an ultra-thin layer of heparin and incubated with fresh blood. The free-hemoglobin technique, which is based on the haemolysis of erythrocytes, indicated improved hemocompatibility, which was confirmed by imaging the samples using confocal optical microscopy. A significant decrease in number of adhered platelets was observed on such samples. Proliferation of both human umbilical vein endothelial cells and human microvascular endothelial cells was enhanced on treated polymers, especially after a few hours of cell seeding. Thus, the technique represents a promising substitute for wet-chemical modification of PET materials prior to coating with heparin.

Tissue-engineered vascular grafts (TEVGs) have emerged as a potential alternative to autologous grafts for replacing small-diameter blood vessels during bypass surgery. The axial alignment of endothelial cells (ECs) and the circumferential alignment of smooth muscle cells (SMCs) are crucial for functional native blood vessels (NBVs). However, achieving this cellular alignment in TEVGs remains a formidable challenge. In this study, TEVGs were developed using a low-cost technique that aligned ECs axially and SMCs circumferentially within hours. The TEVGs comprised an electrospun polycaprolactone (PCL) layer and a gelatin methacryloyl (GelMA) cast layer. A freezing-induced alignment technique was developed that partially aligns the electrospun fibers axially, thereby promoting rapid axial alignment of ECs. Furthermore, SMCs cultured in a GelMA layer with intermediate stiffness (5-12 kPa) surrounding a PCL tube could promote conformation of the SMCs to the curvature of the PCL tube, resulting in their spontaneous circumferential alignment. Additionally, the TEVGs demonstrated mechanical properties similar to those of NBVs, which could facilitate future translation. This approach represents a significant advance in tissue engineering, enabling the fabrication of TEVGs with appropriate mechanical properties that recapitulate key NBV cell structural features within hours using a scalable and accessible method.

Background In-stent restenosis and poor re-endothelization usually follow percutaneous transluminal coronary angioplasty, even using drug-eluting stents, due to inflammation and oxidative stress. Medical ozone has antioxidant and anti-inflammatory properties and has not been evaluated in this context. Objectives To evaluate whether ozonotherapy might reduce restenosis following bare metal stents implantation in relation to the redoxin system in pigs. Methods Twelve male Landrace pigs (51 ± 9 kg) underwent percutaneous transluminal circumflex coronary arteries bare metal stent implantation under heparine infusion and fluoroscopical guidance, using standard techniques. Pigs were randomized to ozonetherapy (n = 6) or placebo (n = 6) treatment. Before stenting (24 h) and twice a week for 30 days post-stenting, venous blood was collected, ozonized and reinfused. Same procedure was performed in placebo group except for ozonation. Both groups received antiplatelet treatment. Histopathology and immunohistochemistry studies were performed. Results Severe inflammatory reaction and restenosis with increase in the immunohistochemical expression of thioredoxin-1 were observed in placebo group 30 days after surgery. Oppositely, ozonetherapy drastically reduced inflammatory reaction and restenosis, and showed no increase in the Trx-1 immunohistochemical expression 30 days after surgery. Immunolabeling for Prx-2 was negative in both groups. Ozonated autohemotherapy strikingly reduced restenosis 30 days following PTCA with BMS implantation in pigs. Conclusions Stimulation of the redoxin system by ozone pretreatment might neutralize oxidative damage from the start and increase antioxidative buffering capacity post-injury, reducing further damage and so the demand for antioxidant enzymes. Our interpretation agrees with the ozone oxidative preconditioning mechanism, extensively investigated. [ABSTRACT FROM AUTHOR]

The hemocompatibility of vascular grafts made from poly(ethylene terephthalate) (PET) is insufficient due to the rapid adhesion and activation of blood platelets that occur upon incubation with whole blood. PET polymer was treated with NHx radicals created by passing ammonia through gaseous plasma formed by a microwave discharge, which allowed for functionalization with amino groups. X-ray photoelectron spectroscopy characterization using derivatization with 4-chlorobenzaldehyde indicated that approximately 4% of the -NH2 groups were associated with the PET surface after treatment with the gaseous radicals. The functionalized polymers were coated with an ultra-thin layer of heparin and incubated with fresh blood. The free-hemoglobin technique, which is based on the haemolysis of erythrocytes, indicated improved hemocompatibility, which was confirmed by imaging the samples using confocal optical microscopy. A significant decrease in number of adhered platelets was observed on such samples. Proliferation of both human umbilical vein endothelial cells and human microvascular endothelial cells was enhanced on treated polymers, especially after a few hours of cell seeding. Thus, the technique represents a promising substitute for wet-chemical modification of PET materials prior to coating with heparin. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) are well-known for their biocompatibility but their intrinsic inert property hampers cell-matrix interactions. Surface modifications are thus necessary to widen their use for biomedical applications. In this work, surface modifications of PU were achieved first by incorporating polyhedral oligomeric silsesquioxane (POSS), followed by alteration of the surface topography via the breath figures method. Subsequently, surface chemistry was also modified by immobilization of gelatin molecules through grafting, for the enhancement of the surface cytocompatibility. Scanning electron microscopy (SEM) was used to verify the formation of highly ordered microstructures while static contact angle, FTIR and XPS confirmed the successful grafting of gelatin molecules onto the surfaces. In vitro culture of human umbilical vein endothelial cells (HUVECs) revealed that endothelial cell adhesion and proliferation were significantly enhanced on the gelatin-modified surfaces, as shown by live/dead staining and WST-1 proliferation assay. The results indicated that the combination of the strategies yielded an interface that improves cell attachment and subsequent growth. This enhancement is important for the development of higher quality biomedical implants such as vascular grafts. [ABSTRACT FROM AUTHOR]

Endothelial cell-coated stents have attracted interest as an ideal treatment method for preventing restenosis following stent deployment to the peripheral locations. In an attempt to evaluate the proliferation and differentiation activities of human umbilical vein endothelial cells (HUVECs), the acetylated polysaccharide, pullulan acetate (PA), loaded with vascular endothelial growth factor (VEGF) (PA/V), a major potential factor influencing vascularization, was examined as a coating for peripherally placed stents. The surface of the PA/V-coated stents observed by scanning electron microscopy was smoother than that of the bare nitinol stents. In an in vitro study, the HUVECs attached to PA/V-coated stents survived and proliferated well compared to the bare stents or stents with only a PA coating (without VEGF). These results were supported by in vivo tests using nude mice. In addition, histology and immunohistochemistry analyses showed that mature endothelial cell-specific markers were expressed at high levels by HUVECs attached to PA-coated stents when VEGF was released. These results suggest that coating stents with PA/V provides a new effective approach for increasing endothelization and prevents stent restenosis. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We analyse the leucocyte and endothelial cell response to polybromostyrene–polystyrene (PS/PBrS) and the poly-n-butylmethacrylate–polystyrene (PnBMA/PS) systems, both in flat form or nanostructured surfaces consisting of nanohills with increasing hill height (13–95 nm). Experiments were carried out first with blood leucocytes alone, endothelial cells (of three different types) alone, and finally, using blood cells and endothelized nanosurfaces. Blocking monoclonal antibodies specific for CD11, CD29, CD31, CD54, CD166 were used to analyse whether and to what extent adhesion molecules could be involved in the adherence of both blood leucocytes and endothelial cells to different nanosurfaces. Expression of CD29 (beta-1 integrin), CD54 (ICAM-1) and CD166 (ALCAM) on blood leucocytes was dependent on the hill height, being most prominent with 13 nm (PS/PBrS) and 45 nm hill (PnBMA/PS) nanosurfaces. Adherence of a human microvascular endothelial cell line and umbilical primary endothelial cells was also related to hill height, being most prominent with 13 nm hill height. An indirect correlation was observed between the extent of endothelization and the degree of leucocyte adherence. In cases of low to medium extent of endothelization, the adherence of monocytes and granulocytes was mediated by the expression of CD166, CD29 and CD11a (alpha-L integrin), CD29, CD31 (PECAM-1), respectively. Scanning electron microscopy studies showed the predominant emission of pseudopodia at the holes of the surfaces and the focal contacts with the nanosurfaces. Our studies emphasize the relevance of testing functional properties in co-culture experiments in the development and optimization of nanosurfaces for biomedical application. [Copyright &y& Elsevier]

In this study, we designed and synthetized artificial vascular scaffolds based on nanofibers of collagen functionalized with hyaluronic acid (HA) in order to direct the phenotypic shape, proliferation, and complete endothelization of mouse primary aortic endothelial cells (PAECs). Layered tubular HA/collagen nanofibers were prepared using electrospinning and crosslinking process. The obtained scaffold is composed of a thin inner layer and a thick outer layer that structurally mimic the layer the intima and media layers of the native blood vessels, respectively. Compared with the pure tubular collagen nanofibers, the surface of HA functionalized collagen nanofibers has higher anisotropic wettability and mechanical flexibility. HA/collagen nanofibers can significantly promote the elongation, proliferation and phenotypic shape expression of PAECs. In vitro co-culture of mouse PAECs and their corresponding smooth muscle cells (SMCs) showed that the luminal endothelialization governs the biophysical integrity of the newly formed extracellular matrix (e.g., collagen and elastin fibers) and structural remodeling of SMCs. Furthermore, in vitro hemocompatibility assays indicated that HA/collagen nanofibers have no detectable degree of hemolysis and coagulation, suggesting their promise as engineered vascular implants. [ABSTRACT FROM AUTHOR]

Endothelization of the luminal surface of vascular grafts is required for their long-term functioning. Here, we have cultivated human endothelial cells (HUVEC) on different 3D matrices to assess cell proliferation, gene expression and select the best substrate for endothelization. 3D matrices were produced by electrospinning from solutions of poly(D,L-lactide-co-glycolide) (PLGA), polycaprolactone (PCL), and blends of PCL with gelatin (Gl) in hexafluoroisopropanol. Structure and surface properties of 3D matrices were characterized by SEM, AFM, and sessile drop analysis. Cell adhesion, viability, and proliferation were studied by SEM, Alamar Blue staining, and 5-ethynyl-2'-deoxyuridine (EdU) assay. Gene expression profiling was done on an Illumina HiSeq 2500 platform. Obtained data indicated that 3D matrices produced from PCL with Gl and treated with glutaraldehyde provide the most suitable support for HUVEC adhesion and proliferation. Transcriptome sequencing has demonstrated a minimal difference of gene expression profile in HUVEC cultivated on the surface of these matrices as compared to tissue culture plastic, thus confirming these matrices as the best support for endothelization. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the anti-proliferative and anti-inflammatory effects of ezetimibe/simvastatin (E/S) after drug-eluting stent (DES) implantation in a porcine coronary restenosis model. Pigs were randomized into two groups in which the coronary arteries (23 pigs) had DES. Stents were deployed with oversizing (stent/artery ratio 1.3:1) in porcine coronary arteries. Fifteen pigs were taken 10/20 mg of E/S and eight pigs were not taken E/S. Histopathologic analysis was assessed at 28 days after stenting. In neointima, most inflammatory cells were lymphohistiocytes. Lymphohistiocyte count was not different between two groups (337+/-227 vs. 443+/-366 cells, P=0.292), but neointima area was significantly smaller (1.00+/-0.49 mm(2) vs. 1.69+/-0.98 mm(2), P=0.021) and percent area stenosis was significantly lower (23.3+/-10% vs. 39+/-19%, P=0.007) in E/S group compared with control group. There were no significant differences in fibrin score (1.99+/-0.79 vs. 1.81+/-0.88, P=0.49), endothelial score (1.75+/-0.66 vs. 1.80+/-0.59, P=0.79), and the percent of endothelium covered lumen (43+/-21% vs. 45+/-21%, P=0.84) between E/S group and control group. Combined therapy with ezetimibe and simvastatin inhibits neointimal hyperplasia, but does not inhibit inflammatory infiltration and arterial healing after DES implantation in a porcine coronary restenosis model.