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Szafron JM, Heng EE, Boyd J, Humphrey JD, Marsden AL. Hemodynamics and Wall Mechanics of Vascular Graft Failure. Arterioscler Thromb Vasc Biol 2024; 44:1065-1085. [PMID: 38572650 PMCID: PMC11043008 DOI: 10.1161/atvbaha.123.318239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 03/12/2024] [Indexed: 04/05/2024]
Abstract
Blood vessels are subjected to complex biomechanical loads, primarily from pressure-driven blood flow. Abnormal loading associated with vascular grafts, arising from altered hemodynamics or wall mechanics, can cause acute and progressive vascular failure and end-organ dysfunction. Perturbations to mechanobiological stimuli experienced by vascular cells contribute to remodeling of the vascular wall via activation of mechanosensitive signaling pathways and subsequent changes in gene expression and associated turnover of cells and extracellular matrix. In this review, we outline experimental and computational tools used to quantify metrics of biomechanical loading in vascular grafts and highlight those that show potential in predicting graft failure for diverse disease contexts. We include metrics derived from both fluid and solid mechanics that drive feedback loops between mechanobiological processes and changes in the biomechanical state that govern the natural history of vascular grafts. As illustrative examples, we consider application-specific coronary artery bypass grafts, peripheral vascular grafts, and tissue-engineered vascular grafts for congenital heart surgery as each of these involves unique circulatory environments, loading magnitudes, and graft materials.
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Affiliation(s)
- Jason M Szafron
- Departments of Pediatrics (J.M.S., A.L.M.), Stanford University, CA
| | - Elbert E Heng
- Cardiothoracic Surgery (E.E.H., J.B.), Stanford University, CA
| | - Jack Boyd
- Cardiothoracic Surgery (E.E.H., J.B.), Stanford University, CA
| | - Jay D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT (J.D.H.)
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2
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Behr J, Irvine SA, Thwin C, Shah AH, Bae MK, Zussman E, Venkatraman S. Matching Static and Dynamic Compliance of Small‐Diameter Arteries, with Poly(lactide‐
co
‐caprolactone) Copolymers: In Vitro and In Vivo Studies. Macromol Biosci 2020; 20:e1900234. [DOI: 10.1002/mabi.201900234] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 11/06/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Jean‐Marc Behr
- School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
| | - Scott Alexander Irvine
- School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
| | - Chaw‐Su Thwin
- School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
| | - Ankur Harish Shah
- School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
| | - Min‐Chul Kraun Bae
- School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
| | - Eyal Zussman
- Nano Engineering groupFaculty of Mechanical EngineeringTechnion–Israel Institute of Technology Haifa 32000 Israel
| | - Subbu Venkatraman
- School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
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Di Franco S, Amarelli C, Montalto A, Loforte A, Musumeci F. Biomaterials and heart recovery: cardiac repair, regeneration and healing in the MCS era: a state of the "heart". J Thorac Dis 2018; 10:S2346-S2362. [PMID: 30123575 PMCID: PMC6081365 DOI: 10.21037/jtd.2018.01.85] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 01/12/2018] [Indexed: 01/31/2023]
Abstract
Regenerative medicine is an emerging interdisciplinary field of scientific research that, supported by tissue engineering is, nowadays, a valuable and reliable solution dealing with the actual organs shortage and the unresolved limits of biological or prosthetic materials used in repair and replacement of diseased or damaged human tissues and organs. Due to the improvements in design and materials, and to the changing of clinical features of patients treated for valvular heart disease the distance between the ideal valve and the available prostheses has been shortened. We will then deal with the developing of new tools aiming at replacing or repair cardiac tissues that still represent an unmet clinical need for the surgeons and indeed for their patients. In the effort of improving treatment for the cardiovascular disease (CVD), scientists struggle with the lack of self-regenerative capacities of finally differentiated cardiovascular tissues. In this context, using several converging technological approaches, regenerative medicine moves beyond traditional transplantation and replacement therapies and can restore tissue impaired function. It may also play an essential role in surgery daily routine, leading to produce devices such as injectable hydrogels, cardiac patches, bioresorbable stents and vascular grafts made by increasingly sophisticated biomaterial scaffolds; tailored devices promptly fabricated according to surgeon necessity and patient anatomy and pathology will hopefully represent a daily activity in the next future. The employment of these devices, still far from the in vitro reproduction of functional organs, has the main aim to achieve a self-renewal process in damaged tissues simulating endogenous resident cell populations. In this field, the collaboration and cooperation between cardiothoracic surgeons and bioengineers appear necessary to modify these innovative devices employed in preclinical studies according to the surgeon's needs.
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Affiliation(s)
- Sveva Di Franco
- Department of Anaesthesiology and Critical Care Medicine, L. Vanvitelli University, Naples, Italy
| | - Cristiano Amarelli
- Department of Cardiovascular Surgery and Transplants, Monaldi Hospital, Azienda dei Colli, Naples, Italy
| | - Andrea Montalto
- Department of Heart and Vessels, Cardiac Surgery Unit and Heart Transplantation Center, S. Camillo-Forlanini Hospital, Rome, Italy
| | - Antonio Loforte
- Department of Cardiovascular Surgery and Transplantation, S. Orsola-Malpighi Hospital, Bologna University, Bologna, Italy
| | - Francesco Musumeci
- Department of Heart and Vessels, Cardiac Surgery Unit and Heart Transplantation Center, S. Camillo-Forlanini Hospital, Rome, Italy
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Affiliation(s)
- J. Van De Voorde
- Laboratory ot Normal and Pathological Physiology, University of Gent - Belgium
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Abstract
Despite intensive research, the success of artificial small-diameter vascular grafts has yet to match that of natural grafts like the saphenous vein. One of the possible reasons is mechanical mismatch of the graft to the host vessel. The study of compliance (dilatability under pressure) has not been conclusive, especially after a series of recent investigations on vein graft evolution. Lately, the focus has been shifting towards more detailed characteristics, like anastomic behaviour, longitudinal elasticity, and flow-related variables. When the relevant property is identified, it should be included in the criteria for design and use of vascular prostheses.
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Affiliation(s)
- L.J. Brossollet
- Biomechanics Laboratory, Georgia Institute of Technology, Atlanta - USA
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Karrer L, Duwe J, Zisch AH, Khabiri E, Cikirikcioglu M, Napoli A, Goessl A, Schaffner T, Hess OM, Carrel T, Kalangos A, Hubbell JA, Walpoth BH. PPS-PEG Surface Coating to Reduce Thrombogenicity of Small Diameter ePTFE Vascular Grafts. Int J Artif Organs 2018; 28:993-1002. [PMID: 16288437 DOI: 10.1177/039139880502801006] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Aims Patency failure of small vascular synthetic grafts is still a major problem for coronary and peripheral revascularization. Thus, three new surface coatings of small synthetic grafts were tested in an acute pig model to evaluate their thrombogenicity (extracorporeal arterio-venous shunt) and in a chronic rat model to evaluate the tissue reaction they induced (subcutaneous implantation). Methods In five domestic pigs (25–30 kg) an extracorporeal femoro-femoral arterio-venous shunt model was used. The study protocol included first a non-heparinized perfusion sequence followed by graft perfusion after 10,000 UI iv heparin. Grafts were perfused for 3 and 9 minutes. The following coatings were tested on ePTFE grafts: poly-propylene sulphide (PPS) – poly-ethylene glycol (PEG) (wet and dry applications) as well as carbon. Two sets of control were used, one dry and one wet (vehicle only). After perfusion grafts were examined by scanning electron microscopy for semiquantitative assessment (score 0–3) of cellular and microthrombi deposition. To assess tissue compatibility, pieces of each material were implanted subcutaneously in 16 Wistar rats. At 2, 4, 8, 12 weeks four animals each were sacrificed for semi-quantitative (score 0–3) histologic evaluation of tissue reaction. Results In the pig model, cellular deposition and microthrombi formation increased over time. In non-heparinized animals, the coatings did not improve the surface characteristics, since they did not prevent microthrombi formation and cellular deposition. In heparinized animals, thrombogenicity was lowest in coated grafts, especially in PPS–PEG dry (P&0.05), and highest in controls. Cell deposition was lowest in PPS–PEG dry, but this difference was not statistically significant vs. controls. In the rat model, no significant differences of the tissue reaction could be shown between materials. Conclusion While all coatings failed to add any benefit for lowering tissue reaction, surface coating with PPS–PEG (dry application) reduced thrombogenicity significantly (in heparinized animals) and thus appears to be promising for improving graft patency of small synthetic vascular prostheses.
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Affiliation(s)
- L Karrer
- Department of Cardiovascular Surgery, University Hospital (HCUG), Geneva--Switzerland
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Ong CS, Zhou X, Huang CY, Fukunishi T, Zhang H, Hibino N. Tissue engineered vascular grafts: current state of the field. Expert Rev Med Devices 2017; 14:383-392. [PMID: 28447487 DOI: 10.1080/17434440.2017.1324293] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Conventional synthetic vascular grafts are limited by the inability to remodel, as well as issues of patency at smaller diameters. Tissue-engineered vascular grafts (TEVGs), constructed from biologically active cells and biodegradable scaffolds have the potential to overcome these limitations, and provide growth capacity and self-repair. Areas covered: This article outlines the TEVG design, biodegradable scaffolds, TEVG fabrication methods, cell seeding, drug delivery, strategies to reduce wait times, clinical trials, as well as a 5-year view with expert commentary. Expert commentary: TEVG technology has progressed significantly with advances in scaffold material and design, graft design, cell seeding and drug delivery. Strategies have been put in place to reduce wait times and improve 'off-the-shelf' capability of TEVGs. More recently, clinical trials have been conducted to investigate the clinical applications of TEVGs.
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Affiliation(s)
- Chin Siang Ong
- a Division of Cardiac Surgery , Johns Hopkins Hospital , Baltimore , MD , USA
| | - Xun Zhou
- a Division of Cardiac Surgery , Johns Hopkins Hospital , Baltimore , MD , USA
| | - Chen Yu Huang
- b Department of Physics & Astronomy , Johns Hopkins University , Baltimore , MD , USA
| | - Takuma Fukunishi
- a Division of Cardiac Surgery , Johns Hopkins Hospital , Baltimore , MD , USA
| | - Huaitao Zhang
- a Division of Cardiac Surgery , Johns Hopkins Hospital , Baltimore , MD , USA
| | - Narutoshi Hibino
- a Division of Cardiac Surgery , Johns Hopkins Hospital , Baltimore , MD , USA
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Furukoshi M, Moriwaki T, Nakayama Y. Development of an in vivo tissue-engineered vascular graft with designed wall thickness (biotube type C) based on a novel caged mold. J Artif Organs 2015; 19:54-61. [PMID: 26265146 DOI: 10.1007/s10047-015-0859-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 07/29/2015] [Indexed: 11/27/2022]
Abstract
Small-diameter biotube vascular grafts developed by in-body tissue architecture had high patency at implantation into rabbit carotid arteries or rat abdominal aortas. However, the thin walls (34 ± 14 μm) of the original biotubes made their implantation difficult into areas with low blood flow volumes or low blood pressure due to insufficient mechanical strength to maintain luminal shape. In this study, caged molds with several windows were designed to prepare more robust biotubes. The molds were assembled with silicone tubes (external diameter 2 mm) and cylindrical covers (outer diameter 7 mm) with 12 linear windows (1 × 9 mm). After the molds were embedded into beagle dorsal subcutaneous pouches for 4 weeks, type C (cage) biotubes were obtained by completely extracting the surrounding connective tissues from the molds and removing the molds. The biotube walls (778 ± 31 μm) were formed at the aperture (width 1 mm) between the silicone rods and the covers by connective cell migration through the windows of the covers. Excellent mechanical properties (external pressure resistance, approximately 4 times higher than beagle native femoral arteries; burst strength, approximately 2 times higher than original biotubes) were obtained. In the acute phase of implantation of the biotubes into beagle femoral arteries, perfect patency was obtained with little stenosis and no aneurysmal dilation. The type C biotubes may be useful for implantation into peripheral arteries or veins in addition to aortas.
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Affiliation(s)
- Maya Furukoshi
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka, 565-8565, Japan
| | - Takeshi Moriwaki
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka, 565-8565, Japan
| | - Yasuhide Nakayama
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka, 565-8565, Japan.
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Yao R, Wong JY. The effects of mechanical stimulation on controlling and maintaining marrow stromal cell differentiation into vascular smooth muscle cells. J Biomech Eng 2015; 137:020907. [PMID: 25429403 DOI: 10.1115/1.4029255] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Indexed: 12/21/2022]
Abstract
For patients suffering from severe coronary heart disease (CHD), the development of a cell-based tissue engineered blood vessel (TEBV) has great potential to overcome current issues with synthetic graft materials. While marrow stromal cells (MSCs) are a promising source of vascular smooth muscle cells (VSMCs) for TEBV construction, they have been shown to differentiate into both the VSMC and osteoblast lineages under different rates of dynamic strain. Determining the permanence of strain-induced MSC differentiation into VSMCs is therefore a significant step toward successful TEBV development. In this study, initial experiments where a cyclic 10% strain was imposed on MSCs for 24 h at 0.1 Hz, 0.5 Hz, and 1 Hz determined that cells stretched at 1 Hz expressed significantly higher levels of VSMC-specific genetic and protein markers compared to samples stretched at 0.1 Hz. Conversely, samples stretched at 0.1 Hz expressed higher levels of osteoblast-specific genetic and protein markers compared to the samples stretched at 1 Hz. More importantly, sequential application of 24-48 h periods of 0.1 Hz and 1 Hz strain-induced genetic and protein marker expression levels similar to the VSMC profile seen with 1 Hz alone. This effect was observed regardless of whether the cells were first strained at 0.1 Hz followed by strain at 1 Hz, or vice versa. Our results suggest that the strain-induced VSMC phenotype is a more terminally differentiated state than the strain-induced osteoblast phenotype, and as result, VSMC obtained from strain-induced differentiation would have potential uses in TEBV construction.
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Lima AC, Mano JF. Micro/nano-structured superhydrophobic surfaces in the biomedical field: part II: applications overview. Nanomedicine (Lond) 2015; 10:271-97. [DOI: 10.2217/nnm.14.175] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The properties of surfaces define the acceptance and integration of biomaterials in vivo, as well as the material's efficiency when used at research or manufacturing levels. The presence of micro/nano-topographical structures and low surface energies could bring several advantages when highly repellent surfaces are employed in the biomedical field. Biomimetic superhydrophobic surfaces have been explored for diverse applications: as an intrinsic characteristic of biomaterials to be implanted; as materials that exhibit special interactions with biological entities; or to be used in ex vivo applications. This article aims to focus on the main motivations and requirements in the biomedical field that pushed for the utilization of superhydrophobic surfaces as suitable alternatives, as well as the great evolution of applications that have emerged in the last few years.
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Affiliation(s)
- Ana Catarina Lima
- 3B's Research Group – Biomaterials, Biodegradables & Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Ave Park, 4806-909 Taipas, Guimarães, Portugal
- ICVS/3B's – PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - João F Mano
- 3B's Research Group – Biomaterials, Biodegradables & Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Ave Park, 4806-909 Taipas, Guimarães, Portugal
- ICVS/3B's – PT Government Associate Laboratory, Braga/Guimarães, Portugal
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Toth C, Klarik Z, Kiss F, Toth E, Hargitai Z, Nemeth N. Early postoperative changes in hematological, erythrocyte aggregation and blood coagulation parameters after unilateral implantation of polytetrafluoroethylene vascular graft in the femoral artery of beagle dogs. Acta Cir Bras 2014; 29:320-7. [PMID: 24863320 DOI: 10.1590/s0102-86502014000500006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 03/18/2014] [Indexed: 11/21/2022] Open
Abstract
PURPOSE The failure of small-caliber vascular grafts still means a serious problem. Concerning the early postoperative complications we aimed to investigate the hemostaseological and hemorheological aspects of this issue in a canine model. METHODS In the Control group only anesthesia was induced. In the Grafted group under general anesthesia a 3.5-cm segment was resected unilaterally from the femoral artery and replaced with a PTFE graft (diameter: 3 mm). On the 1st-3rd-5th-7th and 14th postoperative days the skin temperature of both hind limbs was measured, and blood sampling occurred for hematological, hemostaseological and hemorheological tests. RESULTS The skin temperature of the operated versus intact limbs did not differ. In the Grafted group leukocyte count was elevated by the 1st postoperative day, while platelet count increased over the entire follow-up period. Fibrinogen concentration rose on the 1st-5th days, activated partial thromboplastin time increased on the 3rd-7th days. Erythrocyte aggregation was enhanced significantly on the 1st-5th days. In specimens taken on the 14th day, histologically we found matured thrombus narrowing the graft lumen. CONCLUSIONS Small-caliber PTFE graft implantation into the femoral artery caused significant changes in several hemostaseological and hemorheological parameters. However, better clarifying the factors leading to early thrombosis of these grafts needs further studies.
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Affiliation(s)
- Csaba Toth
- Institute of Surgery, Faculty of Medicine, University of Debrecen, Hungary
| | - Zoltan Klarik
- Institute of Surgery, Faculty of Medicine, University of Debrecen, Hungary
| | - Ferenc Kiss
- Institute of Surgery, Faculty of Medicine, University of Debrecen, Hungary
| | - Eniko Toth
- Institute of Surgery, Faculty of Medicine, University of Debrecen, Hungary
| | - Zoltan Hargitai
- Department of Pathology, Kenezy Hospital, University of Debrecen, Hungary
| | - Norbert Nemeth
- Institute of Surgery, Kenezy Hospital, University of Debrecen, Hungary
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Xiong GM, Yuan S, Tan CK, Wang JK, Liu Y, Yang Tan TT, Tan NS, Choong C. Endothelial cell thrombogenicity is reduced by ATRP-mediated grafting of gelatin onto PCL surfaces. J Mater Chem B 2014; 2:485-493. [DOI: 10.1039/c3tb20760a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pavia FC, La Carrubba V, Ghersi G, Brucato V. Poly-left-lactic acid tubular scaffolds via diffusion induced phase separation: Control of morphology. POLYM ENG SCI 2012. [DOI: 10.1002/pen.23273] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Xu W, Zhou F, Ouyang C, Ye W, Yao M, Xu B. Mechanical properties of small-diameter polyurethane vascular grafts reinforced by weft-knitted tubular fabric. J Biomed Mater Res A 2010; 92:1-8. [PMID: 19165779 DOI: 10.1002/jbm.a.32333] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Polyester filament yarns of different Deniers were knitted into tubular fabrics with different densities and thicknesses on a specially designed weft-knitting machine. The developed tubular fabric was used to reinforce polyurethane vascular graft and thus a kind of composite vascular graft was fabricated with a small inner diameter of 4 mm. Tensile properties of the reinforced composite vascular grafts were compared with the control tubular fabric and the pure PU vascular grafts. Elasticity and strength of the reinforced vascular grafts were improved compared with the weft-knitted tubular fabrics. Strength of the reinforced composite vascular grafts was almost 5-10 times of the strength of the pure PU vascular grafts. As the PU content increased in the reinforced composite vascular grafts, the wall thickness of the vascular graft and its strength increased, but the initial modulus of the reinforced composite vascular grafts remained similar to that of the weft-knitted tubular fabric, and the PU content showed little influence on the initial modulus of the reinforced composite vascular grafts. Microporous structure can also be fabricated in the wall of the reinforced composite vascular grafts.
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Affiliation(s)
- Weilin Xu
- Hubei New Textile and Its Application Key Laboratory, Wuhan University of Science and Engineering, Wuhan 430073, People's Republic of China
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Hinds MT, Ma M, Tran N, Ensley AE, Kladakis SM, Vartanian KB, Markway BD, Nerem RM, Hanson SR. Potential of baboon endothelial progenitor cells for tissue engineered vascular grafts. J Biomed Mater Res A 2008; 86:804-12. [DOI: 10.1002/jbm.a.31672] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Buddingh KT, Zeebregts CJ, Tilanus MEC, Roofthooft MTR, Broens PMA. Large neonatal thoracoabdominal aneurysm: case report and review of the literature. J Pediatr Surg 2008; 43:1361-4. [PMID: 18639697 DOI: 10.1016/j.jpedsurg.2008.02.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 01/31/2008] [Accepted: 02/05/2008] [Indexed: 11/19/2022]
Abstract
We present a neonate with a large saccular aneurysm of the thoracoabdominal aorta, extending from the intrathoracic aorta to the left common iliac artery. No underlying cause could be identified. Despite an early diagnosis, the aneurysm was deemed inoperable because of the lengthy involvement and the frail aspect of all visceral arteries. A review of the literature on congenital abdominal aortic aneurysm in infants was conducted. Eleven cases of live-born infants with a congenital abdominal aortic aneurysm have previously been published. None of them involved as large a part of the thoracic and abdominal aorta as the case presented here.
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Affiliation(s)
- K Tim Buddingh
- Division of Paediatric Surgery, Department of Surgery, University Medical Center Groningen, 9700 RB Groningen, The Netherlands
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Ishii Y, Sakamoto SI, Kronengold RT, Virmani R, Rivera EA, Goldman SM, Prechtel EJ, Hill JG, Damiano RJ. A novel bioengineered small-caliber vascular graft incorporating heparin and sirolimus: Excellent 6-month patency. J Thorac Cardiovasc Surg 2008; 135:1237-45; discussion 1245-6. [DOI: 10.1016/j.jtcvs.2007.09.077] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 09/04/2007] [Accepted: 09/17/2007] [Indexed: 12/01/2022]
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18
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Cole J, Watterson J, O'Reilly M. Blood Flow Characteristics in a Femoral Artery Bypass Graft. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/apj.5500110203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kuivaniemi H, Platsoucas CD, Tilson MD. Aortic aneurysms: an immune disease with a strong genetic component. Circulation 2008; 117:242-52. [PMID: 18195185 DOI: 10.1161/circulationaha.107.690982] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Helena Kuivaniemi
- Center for Molecular Medicine and Genetics and Department of Surgery, Wayne State University School of Medicine, 540 E Canfield Ave, Detroit, MI 48201, USA.
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Ishii Y, Kronengold RT, Virmani R, Rivera EA, Goldman SM, Prechtel EJ, Schuessler RB, Damiano RJ. Novel Bioengineered Small Caliber Vascular Graft With Excellent One-Month Patency. Ann Thorac Surg 2007; 83:517-25. [PMID: 17257981 DOI: 10.1016/j.athoracsur.2006.09.053] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 09/06/2006] [Accepted: 09/07/2006] [Indexed: 11/28/2022]
Abstract
BACKGROUND A bioengineered microporous polycarbonate-siloxane polyurethane graft has been developed for coronary artery bypass grafting. Biological agents can be impregnated into its absorbable collagen and hyaluronan microstructure and stable macrostructure to promote patency. The objective of this study was to examine the biological performance and biomechanical characteristics of this graft. METHODS Heparin-sirolimus (HS) or heparin-sirolimus-vascular endothelial growth factor (HSV) grafts were manufactured for this study. Heparin (40 U) was embedded in the microstructure of the graft for early elution from the graft wall. Heparin (100 U) and sirolimus (450 microg) were incorporated into the macrostructure of the graft for late elution. Vascular endothelial growth factor was also embedded in the microstructure of the graft. Both grafts (3.6 mm internal diameter, 24 mm length) were implanted into the abdominal aortas of rabbits (n = 36) to compare with heparin-alone (H) grafts (n = 9). At 4 hours, 1 day, and 1, 2, and 4 weeks after surgery, the grafts were removed for histologic, immunohistochemical, and biomechanical evaluations. RESULTS The patency rate of all grafts was 100% at each time point. None of grafts had stenosis after surgery. Endothelial cells were observed at 4 weeks after surgery in the HS, HSV, and H grafts. Although there was no significant difference of neointima thickness among the HS, HSV, and H grafts (136 +/- 75, 93 +/- 64, and 125 +/- 90 microm; p = 0.08), the H grafts did have more cellular infiltration in the graft than the HS or HSV grafts. There was neocapillary formation inside the graft wall at 4 weeks in all grafts. The graft macrostructure was unchanged based on biomechanical evaluation 4 weeks after surgery. CONCLUSIONS A unique drug-eluting graft had excellent patency at 1 month and may encourage luminal endothelialization without excessive intimal hyperplasia. Although vascular endothelial growth factor did not improve intimal formation, cell infiltration, or vascularization, sirolimus might inhibit cell proliferation. Further long-term study would need to evaluate the efficacy of impregnated sirolimus.
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Affiliation(s)
- Yosuke Ishii
- Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA
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Aper T, Schmidt A, Duchrow M, Bruch HP. Autologous Blood Vessels Engineered from Peripheral Blood Sample. Eur J Vasc Endovasc Surg 2007; 33:33-9. [PMID: 17070080 DOI: 10.1016/j.ejvs.2006.08.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 08/26/2006] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Although many efforts have been made to generate small-diameter (< or =5mm) vascular grafts by means of tissue engineering, improvement in patency and functionality still remains a great challenge. It is our hypothesis that to achieve long-term functionality and patency, not only the complete lining with endothelial cells but also full biocompatibility is essential. DESIGN The aim was the development of a conduit from a scaffold and endothelial progenitor cells (EPC) separated from peripheral blood of a single donor. MATERIALS AND METHODS EPC and a fibrin preparation were separated from porcine peripheral blood. Fibrin segments were generated seeded with EPC and were perfused in a bioreactor in vitro. RESULTS From 100ml blood 12-15 cm long fibrin tubes were successfully generated lined with endothelial-like cells. Seeded tubes showed a remarkable elasticity and burst strength up to 90 mm mercury. CONCLUSIONS Stable fibrin tubes were successfully generated completely lined with an endothelium-like monolayer from fibrin and EPC, both isolated from the same volume of blood. Although their stability is not those needed for arterial grafting, our results raise the hope, that with distinct improvements in future studies functional autologous vascular grafts could be engineered from the patient's own blood.
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Affiliation(s)
- T Aper
- Department of General and Vascular Surgery, Klinikum Hannover Oststadt - Heidehaus Hannover, Germany.
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22
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Tao SF, Chen L, Zheng YX, Xu Y, Chen J, Yu H. Proliferation of endothelial cell on polytetrafluoroethylene vascular graft materials carried VEGF gene plasmid. J Zhejiang Univ Sci B 2006; 7:421-8. [PMID: 16691635 PMCID: PMC1474000 DOI: 10.1631/jzus.2006.b0421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To investigate whether vascular endothelial growth factor (VEGF) gene plasmid carried by polytetrafluoroethylene (PTFE) vascular graft materials could transfect endothelial cells (ECs) and promote their growth. METHODS PTFE vascular graft materials carried with pCDI-hVEGF(121), pCDI or pEGFP were incubated in Tris-buffer solution and the values of optical density of 260 nm at different time were plotted, then the DNA controlled release curve was made. ECs derived from human umbilical vein were seeded on the pCDI-hVEGF(121)/pCDI/pEGFP-PTFE materials or tissue culture plates, ECs numbers were counted and VEGF protein concentrations at different time were measured by enzyme-linked immunoadsorbent assay method. Green fluorescent protein (GFP) expression in ECs on pEGFP-PTFE materials was examined with fluorescence microscopy. RESULTS The controlled release curve showed that the gene released from PTFE materials was rapid within 8 h, then slowed down and that the gene released continuously even after 72 h. At 24, 72 and 120 h, ECs number and proliferation rate of pCDI-hVEGF(121)-PTFE materials were higher than those of pCDI or pEGFP-PTFE materials (P<0.05). VEGF protein concentration of pCDI-hVEGF(121)-PTFE materials was higher than that of pCDI or pEGFP-PTFE materials at 6, 24, 72 and 120 h (P<0.01). GFP expression in ECs on the pEGFP-PTFE materials could be detected by fluorescence microscopy. CONCLUSION PTFE graft can be used as a carrier of VEGF gene plasmid, VEGF gene carried by PTFE can transfect ECs and promote ECs growth.
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Affiliation(s)
- Si-feng Tao
- Department of Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
| | - Li Chen
- Department of Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- †E-mail:
| | - Yi-xiong Zheng
- Department of Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
| | - Yuan Xu
- Department of Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
| | - Jian Chen
- Department of Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
| | - Hong Yu
- Department of Surgery, School of Medicine, University of Miami, Miami, Fla 33101, USA
- Vascular Biology Institute, School of Medicine, University of Miami, Miami, Fla 33101, USA
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Lermusiaux P, How TV, Black RA. A new device for in vitro evaluation of thrombogenicity. Med Eng Phys 2006; 28:389-93. [PMID: 16185909 DOI: 10.1016/j.medengphy.2005.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2004] [Revised: 05/30/2005] [Accepted: 07/07/2005] [Indexed: 11/19/2022]
Abstract
A device to measure the time of coagulation of whole blood has been designed in order to facilitate testing of thrombogenicity of biomaterials. The principle of operation of the apparatus is to record the time taken for a sphere to fall through a sample of blood. The coagulation time is defined here as the time from collection of the blood sample to coagulation, coagulation having deemed to have occurred when the sphere is prevented from falling by the presence of the fibrin-cell network. The device was tested with homogeneous fluids of different viscosity, milk containing different amounts of rennin and calcium chloride and non anti-coagulated whole blood obtained from five volunteers. Repeat measurements made with each homogeneous fluid show that the variance in the transit time of the sphere is small and consistent with small dispersion. In contrast, the onset of coagulation in milk and blood samples was readily detected. The clotting of milk was highly dependant on the concentration of rennin and calcium chloride. The coagulation time of blood samples from five individuals ranged from 23 to 33 min but simultaneous measurements of samples from the same individual in two identical devices agreed to within +/-1 min in all cases. This device may be easily adapted for use in studies to determine the thromboresistance of biomaterials where the onset of coagulation of whole blood in contact with different materials may be readily compared.
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Affiliation(s)
- P Lermusiaux
- Unité de Chirurgie Vasculaire, CHU Trousseau, Tours, France
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24
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Khorasani MT, Shorgashti S. Fabrication of microporous polyurethane by spray phase inversion method as small diameter vascular grafts material. J Biomed Mater Res A 2006; 77:253-60. [PMID: 16392129 DOI: 10.1002/jbm.a.30613] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Microporous polyurethane vascular prostheses with a 4 mm diameter and 0.3-0.4 mm wall thickness were fabricated by a spray phase inversion technique. In this study, the effect of distance between spray guns (SG) and rotating mandrel (RM), the effect of rate of rotating mandrel (RRM), and the type of nonsolvent on pore morphology of PU films were evaluated using scanning electron microscopy (SEM) technique. It was observed that when the distance between SG and RM was increased or the rate of RM was decreased, the porosity of PU films increased and consequently the tensile strength decreased and compliance value increased. Compliance was measured in vitro by volume and vessel diameter changes. Furthermore, when the coagulant (water) was changed to the water/methanol, the porosity of PU film increased and porous morphology changed to filamentous morphology. Attachment of anchorage dependent cells, namely L929 fibroblast cells, were investigated in stationary culture conditions. The cells adhesion and cells growth were studied using optical photomicrographs. The results show that by increasing the porosity content of PU films would consequently increase the cell ingrowths.
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Affiliation(s)
- M T Khorasani
- Biomaterial Department, Iran Polymer and Petrochemical Institute, Tehran, Islamic Republic of Iran.
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25
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Affiliation(s)
- N Rhodes
- UK Centre for Tissue Engineering, Department of Clinical Engineering, University of Liverpool, UK.
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26
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Abstract
BACKGROUND There is an increased need for alternative, synthetic, small-diameter vascular grafts due to a growing segment of the population who suffer from ischemic heart disease and lack suitable autologous vein grafts for use in coronary artery bypass grafting (CABG). We hypothesized that a cell-mediated extracellular matrix (ECM) modification of ePTFE would stimulate increased vascularization within the graft and thus promote lumenal endothelialization in a 1-mm rat abdomenal aortic implant model. METHODS AND RESULTS Expanded polytetrafluoroethylene (ePTFE) vascular grafts (1 mm i.d.) were modified on the ablumenal surface with ECM deposited by the HaCaT or II-4 cell lines and implanted intrapositionally into the descending aorta of rats. Five weeks after implantation, all samples were patent and examination of the grafts demonstrated that the ECM modified samples exhibited extensive ablumenal vascularization and tissue incorporation compared to nonmodified samples. Also, ECM modified grafts had a cellular lining, while the nonmodified grafts were void of a cellular lining except for a limited pannus ingrowth. CONCLUSION HaCaT and II-4 cell ECM modifications of ePTFE increase new blood vessel growth in association with the graft, and the II-4 cell modification results in formation of an endothelial monlayer on the lumenal surface of the graft.
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Affiliation(s)
- Kameha R Kidd
- Biomedical Engineering Program, University of Arizona, Tucson, AZ 85724, USA
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27
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Berglund JD, Mohseni MM, Nerem RM, Sambanis A. A biological hybrid model for collagen-based tissue engineered vascular constructs. Biomaterials 2003; 24:1241-54. [PMID: 12527265 DOI: 10.1016/s0142-9612(02)00506-9] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Various approaches to tissue engineering a small diameter blood vessel have historically relied upon extended culturing periods and/or synthetic materials to create mechanical properties suitable to withstand the hemodynamic stresses of the vasculature. In this work, we present the concept of a construct-sleeve hybrid (CSH) graft, which uses a biological support to provide temporary reinforcement while cell-mediated remodeling of the construct occurs. Support sleeves were fabricated from Type I collagen gels and crosslinked with glutaraldehyde, ultraviolet, or dehydrothermal treatments. Uniaxial tensile testing of acellular sleeves revealed increased stiffness moduli and tensile stresses with crosslinking treatments. A second collagen layer containing cells was molded about the sleeve to create a CSH. After in vitro culture, CHSs with uncrosslinked (UnXL) and glutaraldehyde treated (Glut) sleeves exhibited significant increases in mechanical strength (20.4-fold and 121-fold increases in ultimate stress, respectively) compared to unreinforced control constructs. Burst testing produced similar findings with peak pressures of 100 and 650mmHg in the UnXL and Glut CSHs, respectively. Construct compaction, cell viability, and histological examination demonstrated that the function of most cells remained unimpaired with the incorporation of the biological support sleeve.
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Affiliation(s)
- Joseph D Berglund
- School of Chemical Engineering, Georgia Institute of Technology, 30332, Atlanta, GA, USA
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Cole JS, Watterson JK, O'Reilly MJG. Numerical investigation of the haemodynamics at a patched arterial bypass anastomosis. Med Eng Phys 2002; 24:393-401. [PMID: 12135648 DOI: 10.1016/s1350-4533(02)00038-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intimal hyperplasia at arterial bypass graft anastomoses is a major factor responsible for graft failure. A revised surgical technique, incorporating a Taylor vein patch into the distal anastomosis of PTFE grafts, results in a decrease in intimal hyperplasia and improved patency rates. Numerical simulations of pulsatile, non-Newtonian blood flow through life-like femorodistal bypass models have been performed to determine whether haemodynamic benefits arise from the modified geometry of the Taylor anastomosis. In a conventional bypass, the distal anastomotic flow exhibited considerable spatial and temporal variations. Steep spatial gradients in the shearing force acted along the floor during systole. The effect of the Taylor geometry was to reduce gradually the momentum of the blood approaching the junction. Thus, flow disturbances were abated, undesirable flow separation at the toe was diminished, and a less adverse floor shear stress distribution prevailed in that case. Intimal thickening should be alleviated at the toe in the Taylor model where separation is reduced, and where the thrombogenic graft surface is replaced with a vein patch. Intimal hyperplasia on the floor may be inhibited in the Taylor model due to more favourable shear stresses. The improved flow through the patched anastomosis should contribute to its enhanced performance.
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Affiliation(s)
- J S Cole
- School of Aeronautical Engineering, The Queen's University of Belfast, Belfast BT9 5AG, Northern Ireland, UK.
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Toes GJ, van Muiswinkel KW, van Oeveren W, Suurmeijer AJH, Timens W, Stokroos I, van den Dungen JJA. Superhydrophobic modification fails to improve the performance of small diameter expanded polytetrafluoroethylene vascular grafts. Biomaterials 2002; 23:255-62. [PMID: 11763862 DOI: 10.1016/s0142-9612(01)00103-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To determine whether superhydrophobic modification of small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts improves the performance of these grafts, we assessed neointima formation and platelet deposition in standard and superhydrophobic modified ePTFE grafts. Standard and superhydrophobic vascular grafts were implanted in the carotid arteries of two rabbits and two pigs. Furthermore, standard and superhydrophobic vascular patches were implanted in the carotid arteries of seven pigs. After 4 weeks of implantation all patches were removed and histomorphometric data were analyzed. The early thrombotic effect of superhydrophobic modification was examined by quantifying platelet glycoprotein receptor IIIa deposition onto each type of vascular graft after 15 min of in vitro circulation with human blood. All superhydrophobic and standard ePTFE vascular grafts occluded 15 min to 1 h after implantation in both rabbit and pig carotid arteries. All implanted patches remained patent and were completely covered by endothelium. Superhydrophobic modification of ePTFE vascular grafts did not lead to less neointima formation and resulted in significantly more platelet deposition than did standard ePTFE vascular grafts. Thus, superhydrophobic modification does not improve the performance of small diameter ePTFE vascular grafts.
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Affiliation(s)
- G J Toes
- Department of Pathology, University Hospital Groningen, The Netherlands.
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30
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Seifalian AM, Salacinski HJ, Punshon G, Krijgsman B, Hamilton G. A new technique for measuring the cell growth and metabolism of endothelial cells seeded on vascular prostheses. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2001; 55:637-44. [PMID: 11288093 DOI: 10.1002/1097-4636(20010615)55:4<637::aid-jbm1058>3.0.co;2-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
For the improvement of vascular graft patency, an endothelial cell (EC) lining is desirable. It is essential that the EC remains viable after being seeded onto the prosthetic graft. The aim of this study was to adapt an Alamar redox assay (ABRA) as a technique to monitor the viability of ECs seeded on prosthetic grafts. To test the graft types, we seeded human umbilical vein ECs on compliant polyurethane (CPU), expanded polytetrafluoroethylene, and Dacron at a density of 2 x 10(5) cell/cm(2). After 24 h of incubation, ABRA was added, and the absorbance was measured at 4, 8, and 24 h. To assess seeded cell concentrations on grafts, we seeded CPU at densities ranging from 1 x 10(5) to 8 x 10(5) cell/cm(2). The validity of the test was assessed with sodium azide and mitomycin C, known physiological perturbators. ABRA reduction demonstrated that ECs were viable and functional postseeding on the prosthetic grafts. A significant correlation was observed with ABRA reduction and cell concentrations (p < 0.001). The acid phosphatase assay demonstrated enzyme activity in the cells, but they were not maintained under normal physiological conditions. The ABRA bioreduced product was soluble, stable, and noncytotoxic over 24 h. The assay is independent of the geometry or physiochemistry of the graft type. The technique allows the continuous assessment of the metabolism and viability of seeded cells, is simple to perform, and does not destroy the cells or graft materials.
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Affiliation(s)
- A M Seifalian
- Vascular Haemodynamic Laboratory, University Department of Surgery, Royal Free and University College Medical School, University College London and the Royal Free Hospital, London, England.
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31
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Girton TS, Oegema TR, Grassl ED, Isenberg BC, Tranquillo RT. Mechanisms of stiffening and strengthening in media-equivalents fabricated using glycation. J Biomech Eng 2000; 122:216-23. [PMID: 10923288 DOI: 10.1115/1.429652] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have recently reported that glycation can be exploited to increase the circumferential tensile stiffness and ultimate tensile strength of media-equivalents (MEs) and increase their resistance to collagenolytic degradation, all without loss of cell viability (Girton et al., 1999). The glycated MEs were fabricated by entrapping high passage adult rat aorta SMCs in collagen gel made from pepsin-digested bovine dermal collagen, and incubated for up to 10 weeks in complete medium with 30 mM ribose added. We report here on experiments showing that ME compaction due to traction exerted by the SMCs with consequent alignment of collagen fibrils was necessary to realize the glycation-mediated stiffening and strengthening, but that synthesis of extracellular matrix constituents by these cells likely contributed little, even when 50 micrograms/ml ascorbate was added to the medium. These glycated MEs exhibited a compliance similar to arteries, but possessed less tensile strength and much less burst strength. MEs fabricated with low rather than high passage adult rat aorta SMCs possessed almost ten times greater tensile strength, suggesting that alternative SMCs sources and biopolymer gels may yield sufficient strength by compositional remodeling prior to implantation in addition to the structural remodeling (i.e., circumferential alignment) already obtained.
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Affiliation(s)
- T S Girton
- Department of Chemical Engineering, University of Minnesota, Minneapolis 55455-0132, USA
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32
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Toes GJ, van den Dungen JJ, Haan J, Hermens RA, van Oeveren W. Fluorescence labeling to study platelet and leucocyte deposition onto vascular grafts in vitro. Biomaterials 1999; 20:1951-8. [PMID: 10514073 DOI: 10.1016/s0142-9612(99)00100-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Platelets and leucocytes are important participants in the response of the body to small diameter vascular grafts implanted into the arterial circulation. A sensitive and quick method for measuring platelet and leucocyte deposition contributes to material evaluation. With a newly developed fluorescence labeling method we examined the deposition of platelets and leucocytes onto vascular grafts in vitro. Human platelets and leucocytes were isolated and labeled with the fluorescence label Europium trichloride (EuCl3). After reconstitution of the labeled cells in plasma their functionality appeared intact and competitive with unlabeled cells. Eu-labeled platelets or leucocytes were then incubated with expanded polytetrafluoroethylene (ePTFE), Dacron and polyurethane (PU) vascular grafts in autologous plasma. Beta-thromboglobin and thromboxane release from platelets and beta-glucuronidase release from leucocytes during the incubation experiments were measured. Platelets and leucocytes deposited significantly less onto ePTFE compared to Dacron and polyurethane (P < 0.01). Our results are in accordance with results of in vivo studies using radio-active labeling to study platelet and leucocyte deposition. However, a new finding was that this reduced cell deposition may in part be due to possible toxic effects of ePTFE, shown by increased haemolysis and beta-thromboglobin release.
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Affiliation(s)
- G J Toes
- Department of Biomedical Engineering, University of Groningen, The Netherlands
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33
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Jeschke MG, Hermanutz V, Wolf SE, Köveker GB. Polyurethane vascular prostheses decreases neointimal formation compared with expanded polytetrafluoroethylene. J Vasc Surg 1999; 29:168-76. [PMID: 9882801 DOI: 10.1016/s0741-5214(99)70358-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE Synthetic grafts have been increasingly used for complex vascular reconstructions in patients with limited autologous vein availability. Materials currently in use induce increased stenosis and graft thrombosis compared with autologous vein, especially in smaller vessels. We examined whether grafts constructed of a porous biodegradation-resistant polycarbonate polyurethane (PU) exert better biocompatibility in terms of faster endothelialization and decreased chronic proliferation of intimal cells compared with expanded polytetrafluoroethylene (ePTFE). METHODS PU or ePTFE interposition grafts were implanted into the abdominal aortas of male Sprague-Dawley rats (PU, n = 37; ePTFE, n = 32). Grafts were removed at days 1, 7, 14, 28, and 56 and 6 months and were evaluated by immunohistochemical, electron microscopic, and morphometric techniques. Bromodeoxyuridine (BrdU) was injected at 1 and 24 hours before death to determine cellular proliferation. Endothelial cells and smooth muscle cells were identified with antibodies to von Willebrand factor and alpha-actin, respectively. RESULTS The luminal surface of PU grafts took 4 weeks to completely endothelialize, whereas ePTFE grafts took 24 weeks (P <.05). Neointimal cell proliferation was lower in PU grafts compared with ePTFE at 56 days (1.4 +/- 0.1 versus 8.6 +/- 1.5, P <.001) and at 6 months (0.15 +/- 0.002 versus 3.4 +/- 0.5, p <.001). Neointimal thickness at 6 months after implantation was 3.2 +/- 0.8 micrometer for PU compared with 10.3 +/- 3.1 micrometer for ePTFE (P <.05). CONCLUSION Polycarbonate polyurethane small vascular prostheses promoted faster luminal endothelialization, induced less chronic intimal proliferation, and produced a significantly thinner neointima than ePTFE grafts. These findings suggest that aliphatic-polycarbonate urethanes may offer advantages over standard materials such as ePTFE for vascular graft construction.
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Affiliation(s)
- M G Jeschke
- University of Texas Medical Branch, Department of Surgery, Shriners Hospital for Children, Galveston, Tex 77550, USA
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Hedeman Joosten PP, Verhagen HJ, Heijnen-Snyder GJ, van Vroonhoven TJ, Sixma JJ, de Groot PG, Eikelboom BC. Thrombogenesis of different cell types seeded on vascular grafts and studied under blood-flow conditions. J Vasc Surg 1998; 28:1094-103. [PMID: 9845661 DOI: 10.1016/s0741-5214(98)70036-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BACKGROUND Small-diameter vascular grafts tend to have an early and high occlusion rate. Cell seeding on the luminal surfaces of small-diameter vascular prostheses may provide an antithrombotic lining and improve both the short-term and the long-term patency rates. We studied the net results of procoagulant and anticoagulant properties of seeded grafts under blood-flow conditions, and we compared the different available types of donor cells. METHODS Monolayers of liposuction-derived cultured human microvascular endothelial cells (MVECs), human adult endothelial cells (HAECs), human umbilical vein endothelial cells (HUVECs), and human mesothelial cells (MCs) that had been seeded on expanded polytetrafluoroethylene (ePTFE) grafts were perfused with marginally anticoagulated blood (20 U/mL low molecular weight heparin; shear rate, 400/s, 10 minutes) or with non-anticoagulated blood (shear rate, 100/s, 5 minutes). The thrombin and fibrin generation in time was studied with the measurement of the plasma levels of prothrombin fragment 1 and 2 (F 1+2) and of fibrinopeptide A (FPA). The plain ePTFE graft was taken as a control. RESULTS When the seeded MCs were perfused with recirculating anticoagulated blood, a linear generation of F 1+2 in time was seen, with high levels of F 1+2 and FPA after 10 minutes (4.38 nmol/L and 362 ng/mL, respectively). Allopurinol was added, and the MCs generated less F 1+2 than the HAECs (0.7 nmol/L vs 1.86 nmol/L; P <.05). No fibrin formation was seen. The MVECs generated low amounts of F 1+2 (0.7 nmol/L; 10 minutes), and the HUVECs and the plain ePTFE graft generated the lowest amounts of F 1+2 (0.26 and 0.25 nmol/L, respectively). When the MCs were perfused with non-anticoagulated blood, high amounts of thrombin and fibrin were generated immediately and constantly and could not be decreased with allopurinol. The perfusion of the plain ePTFE graft showed a dramatic increase in F 1+2 and FPA levels towards the end of the experiments. The seeded HAECs, HUVECs, and MVECs inhibited this increase. These results were confirmed by means of scanning electron microscopy. CONCLUSION Vascular prostheses that are seeded with cultured MCs are highly procoagulant. Standard ePTFE graft prostheses also initiate coagulation, which supports the idea of cell seeding. The endothelial cells, of which the MVECs are the most readily available, seem to preserve their anticoagulant properties after being seeded on vascular grafts.
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Affiliation(s)
- P P Hedeman Joosten
- Departments of Surgery and Haematology, University Hospital Utrecht, Utrecht, The Netherlands
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35
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Barocas VH, Girton TS, Tranquillo RT. Engineered alignment in media equivalents: magnetic prealignment and mandrel compaction. J Biomech Eng 1998; 120:660-6. [PMID: 10412446 DOI: 10.1115/1.2834759] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We predicted and measured the evolution of smooth muscle cell (SMC) orientation in media-equivalents (MEs) for four fabrication conditions (F-, M-, F+, M+) under Free or Mandrel compaction (F/M) with and without magnetic prealignment of the collagen fibrils in the circumferential direction (+/-). Mandrel compaction refers to SMC-induced compaction of the ME that is constrained by having a nonadhesive mandrel placed in the ME lumen. Predictions were made using our anisotropic biphasic theory (ABT) for tissue-equivalent mechanics. Successful prediction of trends of the SMC orientation data for all four fabrication cases was obtained: maintenance of the initial isotropic state for F-, loss of initial circumferential alignment for F+, development of circumferential alignment for M-, and enhancement of initial circumferential alignment for M+. These results suggest two mechanisms by which the presence of the mandrel leads to much greater mechanical stiffness in the circumferential direction reported for mandrel compacted MEs relative to free compacted MEs: (1) by inducing an increasing circumferential alignment of the SMC and collagen, and (2) by inducing a large stress on the SMC, resulting in secretion and accumulation of stiffening components.
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Affiliation(s)
- V H Barocas
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis 55455-0132, USA
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36
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Noh I, Goodman SL, Hubbell JA. Chemical modification and photograft polymerization upon expanded poly(tetrafluoroethylene). JOURNAL OF BIOMATERIALS SCIENCE. POLYMER EDITION 1998; 9:407-26. [PMID: 9648024 DOI: 10.1163/156856298x00532] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Poly(tetrafluoroethylene) (PTFE) films were surface-modified by employing a reaction solution of benzophenone and sodium hydride in anhydrous dimethylformamide at a temperature of 150 degrees C for 12 h. Electron spectroscopy for chemical analysis (ESCA) showed defluorination, oxygen incorporation, and extensive unsaturation within the treated PTFE surfaces. The suitably of these reduced PTFE films as substrates for graft polymerization was initially assessed via photograft polymerization of the sodium salt of styrenesulfonic acid (SS-Na), which permitted unequivocal surface analysis by the introduction of a new atom, as well as poly(ethylene glycol) monoacrylate (PEG-Ac). All photograpt polymerization was performed employing ultraviolet irradiation with 2,2-dimethoxy-2-phenylacetophenone as an initiator. Photograft polymerization of SS-Na was verified by further reduction of fluorine atomic content and the appearance of new sulfur and sodium atomic peaks on ESCA survey spectra, and that of PEG-Ac was verified by further reduction of fluorine atomic content and increase of atomic percent ratio of O/C from ESCA survey spectra as well as appearance of a new ester peak on high resolution ESCA C 1s spectra. Dynamic water contact angles on reduced and PEG-Ac photograft polymerized films were measured and showed that the PTFE film surface became more hydrophilic after reduction (from 120 to 89 deg) and the reduced film became more hydrophilic after photograft polymerization with PEG-Ac (from 89 to 36 deg). Modification of the complete surface of expanded PTFE (ePTFE), i.e. of the lumenal, outside and pore surfaces, was performed by employing the reaction described above, except at 105 degrees C for 1 day, followed by photograft polymerization of PEG-Ac. ESCA was performed on the superficial surfaces (i.e. the lumen and exterior) as well as on cross-sections of the ePTFE to permit analysis of the pore surfaces. This analysis showed that both the initial surface reduction and subsequent photograft polymerization were successful as indicated from F/C and O/C atomic percent ratios from ESCA survey spectra, from overall peaks shapes of high resolution ESCA C 1s spectra and from generation of new ester peaks on high resolution ESCA C 1s spectra of ePTFE graft polymerized with PEG-Ac, which demonstrated an O/C atomic percent ratio close to that of PEG-Ac homopolymer. Low voltage scanning electron microscopy confirmed minimal morphological damage to the ePTFE microstructure after reduction and graft polymerization. The approach explored thus provides a means for modulation of biological interactions at ePTFE surfaces with only minimal modification of material morphology, with some surface texture appearing on a length scale of 50-100 nm.
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Affiliation(s)
- I Noh
- Department of Chemical Engineering, University of Texas, Austin 78712, USA
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37
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Sapienza P, di Marzo L, Cucina A, Corvino V, Mingoli A, Giustiniani Q, Ziparo E, Cavallaro A. Release of PDGF-BB and bFGF by human endothelial cells seeded on expanded polytetrafluoroethylene vascular grafts. J Surg Res 1998; 75:24-9. [PMID: 9614852 DOI: 10.1006/jsre.1997.5260] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND The majority of endothelial cell (EC) seeded graft failures are due to anastomotic neointimal fibrous hyperplasia. We investigated the PDGF-BB and bFGF release in vitro by umbilical vein EC seeded on precoated expanded polytetrafluoroethylene (ePTFE) prostheses. MATERIALS EC harvested from human umbilical veins were seeded into ePTFE (30 microns internodal distance, 1 cm2 in diameter) disks. ePTFE disks uncoated or precoated with collagen type I, fibronectin, and Matrigel were used, and EC seeded into plastic wells coated as ePTFE disks or uncoated plastic wells served as controls. Scanning electron microscopy study assessed EC coverage. The presence of bFGF and PDGF-BB in serum-free conditioned media from EC seeded into ePTFE grafts and EC seeded into wells was determined by the inhibition antibody-binding assay 72 h after seeding. RESULTS EC coverage was similar in uncoated and coated ePTFE grafts. The release of PDGF-BB and bFGF by EC seeded into ePTFE grafts was significantly higher than that observed in EC seeded into plastic wells. The release of PDGF-BB and bFGF was independent from the various substrates used in the experiments in EC seeded into either ePTFE grafts or plastic wells. CONCLUSIONS Our findings pointed out that in seeded ePTFE grafts, anastomotic smooth muscle cell proliferation and intimal thickening could take place underneath an intact endothelium because seeded EC may release several growth factors.
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Affiliation(s)
- P Sapienza
- First Department of Surgery, University of Rome, La Sapienza, Italy
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38
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Ritter EF, Kim YB, Reischl HP, Serafin D, Rudner AM, Klitzman B. Heparin coating of vascular prostheses reduces thromboemboli. Surgery 1997; 122:888-92. [PMID: 9369888 DOI: 10.1016/s0039-6060(97)90329-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Synthetic conduits made from currently available materials are suboptimal for use in small-diameter vascular reconstruction because of their high surface thrombogenicity, which leads to failure. METHODS In this study control, heparin-irrigated, or heparin-bonded expanded polytetrafluoroethylene (ePTFE) grafts (4 mm long by 1 mm inner diameter) were implanted to reconstruct the iliac artery in male rats. The cremaster muscle was isolated as an island flap based on branches of the iliac artery downstream from the graft. Emboli were quantitated by using intravital fluorescent microscopy of the cremaster muscle's microcirculation. RESULTS The mean number of emboli observed per animal during a 20-minute period was 91 for the control group, 84 for the heparin-irrigated group, and 22 for the tridodecylmethylammonium chloride (TDMAC)-heparin group. The mean area of each embolus was 1057 microns 2 for control, 940 microns 2 for heparin-irrigated, and 808 microns 2 for TDMAC-heparin-coated grafts (p < 0.05 for TDMAC-heparin versus control or heparin-irrigated). CONCLUSIONS A TDMAC-heparin coating of ePTFE microvascular prostheses significantly reduces downstream microemboli.
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Affiliation(s)
- E F Ritter
- Department of Surgery, Duke University Medical Center, Durham, N.C. 27710-3906, USA
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39
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Kreitz MR, Webber WL, Galletti PM, Mathiowitz E. Controlled delivery of therapeutics from microporous membranes. I. Fabrication and characterization of microporous polyurethane membranes containing polymeric microspheres. Biomaterials 1997; 18:597-603. [PMID: 9134159 DOI: 10.1016/s0142-9612(96)00153-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This paper describes a process for the inclusion of polymer microspheres in microporous polyurethane tubes and membranes. These composites were fabricated via a spray, phase-inversion technique using Cardiothane 51, a medical grade polyurethane, and either spray-dried poly(D,L-lactide-co-glycolide 50:50) microspheres or commercially available fluorescent polystyrene-latex microspheres. Characterization of the polyurethane membranes was performed using Fouriertransform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, hydraulic permeability testing, scanning electron microscopy, and visible and fluorescence light microscopy. The results indicated the feasibility of layering microspheres throughout the microporous membrane or wall of the microporous tube, and the potential of such composite structures for local delivery of bioactive substances.
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Affiliation(s)
- M R Kreitz
- Department of Molecular Pharmacology and Biotechnology, Brown University, Providence 02912, USA
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40
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Henry FS, Collins MW, Hughes PE, How TV. Numerical investigation of steady flow in proximal and distal end-to-side anastomoses. J Biomech Eng 1996; 118:302-10. [PMID: 8872251 DOI: 10.1115/1.2796011] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Steady flow in model proximal and distal end-to-end bypass anastomoses were simulated numerically. The predictions were compared to whole field measurements of the flow in in vitro models, and were shown to match well the general features of the measured flows. The predictions confirmed that the flows in end-to-side anastomoses are complex and three dimensional, and contain areas that could allow long residence times. Careful examination of the predictions revealed certain features of the flows not seen easily in the experiments. Shear stress and pressure on the vessel walls were predicted, and areas known to be prone to intimal hyperplasia were shown to correspond to areas of high spatial gradient of shear stress. Two anastomosis angeles, 30 and 45 deg, were considered, and it was shown that the more acute angle may have some benefit in terms of the levels of shear gradients and the power required to drive the flow through the anastomosis.
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Affiliation(s)
- F S Henry
- Thermo-Fluids Engineering Research Centre, City University, London, UK
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41
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Cho JS, Ouriel K, DeWeese JA, Green RM, Chen GY, Stoughton J. Thrombus formation on polytetrafluoroethylene surfaces: the importance of von Willebrand factor. CARDIOVASCULAR SURGERY (LONDON, ENGLAND) 1995; 3:645-51. [PMID: 8745188 DOI: 10.1016/0967-2109(96)82864-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The importance of von Willebrand factor (vWf) in the formation of platelet-fibrin thrombi on expanded polytetrafluoroethylene (ePTFE) surfaces was studied in an in vitro system, perfusing non-anticoagulated human blood over ePTFE grafts for 3 min at varying shear rates (100, 500 and 1500/s shear). Platelet (111In) and fibrin (125I) deposition was assessed on ePTFE surfaces in the presence and relative absence of vWf, achieved by use of polyclonal anti-vWf antibody (anti-vWf Ab). A total of 29 perfusions were performed. Increasing shear rate was associated with greater platelet deposition in the presence of vWf (p < 0.001). This shear-dependent rise in platelet deposition was not observed when vWf was blocked by anti-vWf Ab (P < 0.1), confirming the role of vWf in platelet deposition at high shear rates. Fibrin deposition increased with increasing shear rate in the presence of vWf (P < 0.01). Inhibiting vWf abolished the shear-dependent increase in fibrin deposition. These data suggest that vWf plays a critical role in platelet and fibrin thrombus formation on ePTFE surfaces. These effects are particularly important under conditions of high shear rate. These mechanisms may lead to the observed pathologic thrombus formation and platelet-dependent neointimal processes occurring at areas of high shear rate within the anastomotic regions of ePTFE grafts.
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Affiliation(s)
- J S Cho
- Department of Surgery, University of Rochester School of Medicine and Dentistry, New York, USA
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42
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Tunstall A, Eberhart RC, Prager MD. Endothelial cells on Dacron vascular prostheses: adherence, growth, and susceptibility to neutrophils. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1995; 29:1193-9. [PMID: 8557721 DOI: 10.1002/jbm.820291006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Human umbilical vein endothelial cells (HUVEC) on knitted and woven Dacron prostheses were compared with HUVEC on smooth surfaces (tissue culture polystyrene, PET film, and Natrix) with regard to adherence, growth, and susceptibility to injury by neutrophils (PMN). These are properties of importance for successful seeding or coating of prostheses. For prosthetic material of given macroscopic dimensions, more endothelial cells (EC) adhered than to smooth surfaces. However, the prostheses had a greater effective surface area as determined by the number of EC at confluency. When this parameter was taken into account, fewer EC were found adherent to prosthetic material per unit effective surface area than for the smooth surface substrates. Growth on prostheses was clearly inferior to that on smooth surfaces, and EC on prostheses were more susceptible to attack by activated PMN than on smooth surfaces. These differences may reflect the topographic differences in cells attached to fibers where they assume more distorted shapes by stretching to span fibers.
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Affiliation(s)
- A Tunstall
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas 75235-9031, USA
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43
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Gosselin C, Ren D, Ellinger J, Greisler HP. In vivo platelet deposition on polytetrafluoroethylene coated with fibrin glue containing fibroblast growth factor 1 and heparin in a canine model. Am J Surg 1995; 170:126-30. [PMID: 7543261 DOI: 10.1016/s0002-9610(99)80270-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND We previously reported that the coating of expanded polytetrafluoroethylene (ePTFE) with fibrin glue containing fibroblast growth factor 1 (FGF-1) and heparin accelerates endothelial coverage of grafts implanted into animals. We report here the effect of this surface modification on early platelet deposition. MATERIALS AND METHODS Nine dogs received 7-cm ePTFE grafts, 60-microns internodal distance, 4-mm internal diameter, as bilateral aortoiliac implants, one coated (luminal cross section and abluminal surface) with fibrin glue (fibrinogen 32.1 mg/mliters, thrombin 0.32 U/mliters) containing FGF-1 (11 ng/mliters and heparin (250 U/mliters), the other uncoated. After 5, 30, or 120 minutes of circulation with blood containing autologous platelets radiolabelled with indium 111, gamma emissions were quantitated on explants and correlated to surface areas measured by computerized planimetry. RESULTS Both global and segmental comparisons showed significantly (P < 0.05, Student's t-test) less platelet deposition on coated than on uncoated grafts after 120 minutes of circulation, but no difference at 5 and 30 minutes. CONCLUSIONS In this model, ePTFE coating with fibrin glue containing FGF-1 and heparin shows no adverse effect on early platelet deposition.
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Affiliation(s)
- C Gosselin
- Department of Surgery, Loyola University Medical Center, Maywood, Illinois
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44
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Hughes PE, How TV. Flow structures at the proximal side-to-end anastomosis. Influence of geometry and flow division. J Biomech Eng 1995; 117:224-36. [PMID: 7666660 DOI: 10.1115/1.2796005] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Flow structures were visualized in transparent polyurethane models of proximal side-to-end vascular anastomoses, using planar illumination of suspended tracer particles. Both the effects of geometry and flow division were determined under steady and pulsatile flow conditions, for anastomosis angles of 15, 30, and 45 degrees. The flow patterns were highly three-dimensional and were characterized by a series of vortices in the fully occluded distal artery and two helical vortices aligned with the axis of the graft. In steady flow, above a critical Reynolds number, the flow changed from a laminar regime to one displaying time-dependent behavior. In particular, significant fluctuating velocity components were observed in the distal artery and particles were shed periodically from the occluded artery into the graft. Pairs of asymmetric flow patterns were also observed in the graft, before the onset of the time-dependent flow regime. The critical Reynolds number ranged from 427 to 473 and appeared to be independent of anastomosis angle. The presence of a patent distal artery had a significant effect on the overall flow pattern and led to the formation of a large recirculation region at the toe of the anastomosis. The main structures observed in steady flow, such as vortices in the distal artery and helical flow in the graft, were also seen during the pulsatile cycle. However, the secondary flow components in the graft were more pronounced in pulsatile flow particularly during deceleration of the flow waveform. At higher mean Reynolds numbers, there was also a greater mixing between fluid in the occluded arterial section and that in the graft.
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Affiliation(s)
- P E Hughes
- Department of Clinical Engineering, University of Liverpool, United Kingdom
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45
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Greco RS, Kim HC, Donetz AP, Harvey RA. Patency of a small vessel prosthesis bonded to tissue plasminogen activator and iloprost. Ann Vasc Surg 1995; 9:140-5. [PMID: 7540408 DOI: 10.1007/bf02139655] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To test the thrombosis resistance of a vascular prosthesis coated with antithrombogenic agents, we evaluated a small vessel prosthesis of expanded polytetrafluoroethylene (ePTFE) implanted in the rat aorta and removed 1 week following surgery. Control grafts consisted of 1 mm internal diameter ePTFE. Experimental grafts consisted of 1 mm internal diameter ePTFE noncovalently bonded to tissue plasminogen activator (tPA) and iloprost using the surfactant tridodecylmethylammonium chloride. After 1 week the grafts were harvested, patency was determined, and histologic specimens were prepared for electron microscopy. Six of 10 control grafts were thrombosed, whereas 9 of 10 tPA-iloprost-bonded grafts were patent (p < 0.03). Of concern, there was an unexpectedly high mortality rate in the tPA-iloprost group compared to the control group among animals that died before completion of the study. Evaluation of the safety of these drugs must, therefore, be an early component of future experiments. Nevertheless, these studies indicate that a small vessel prosthesis bonded to tPA and iloprost may ameliorate some of the complications associated with early graft failure.
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Affiliation(s)
- R S Greco
- Department of Surgery, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick 08903, USA
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46
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How TV, Marois Y, Guidoin R, Black RA. Effect of geometric taper on thrombosis in vascular prostheses: an ex vivo study. JOURNAL OF BIOMATERIALS SCIENCE. POLYMER EDITION 1995; 6:111-22. [PMID: 7947477 DOI: 10.1163/156856294x00248] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A common method of assessing the thrombogenicity of prosthetic arterial grafts is to determine the amount of platelets and fibrin that accumulates on their surfaces. This study was designed to compare thrombus formation in cylindrical and tapered vascular grafts (angle of taper 0.5 deg) made from the same biomaterial. Turbulence was generated upstream of the grafts by means of a 75% axi-symmetric stenosis. In general, turbulence is dissipated by the effect of blood viscosity, whereas in a tapered graft, there is an additional reduction in the intensity of turbulence owing to the effect of converging flow through the taper. The aim of this study was to assess the effect of turbulence on thrombus formation in cylindrical and tapered grafts. After blood had circulated for 2 and 4 h through the cylindrical and tapered grafts, which formed part of two parallel ex vivo circuits, platelet deposition and fibrinogen uptake were measured by means of a radioisotope technique. Although the flow disturbances were less in the tapered grafts, no significant difference in platelet and fibrin deposition in the two types of graft was observed at 2 h. For the longer perfusion time, however, increased platelet and fibrin activity was recorded in the annular vortex region in the tapered grafts. In general, neither platelets nor fibrin accumulated in areas of high turbulence intensity.
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Affiliation(s)
- T V How
- Department of Clinical Engineering, University of Liverpool, UK
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47
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Craig WS, Cheng S, Mullen DG, Blevitt J, Pierschbacher MD. Concept and progress in the development of RGD-containing peptide pharmaceuticals. Biopolymers 1995; 37:157-75. [PMID: 7534489 DOI: 10.1002/bip.360370209] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The cell adhesion domain, arginine-glycine-aspartic acid (RGD), has been incorporated into synthetic peptides to perform either of two modes of drug action, antagonist or agonist. Short, conformationally constrained peptides have been developed as antagonists for the platelet membrane glycoprotein complex, the integrin alpha IIb beta 3, using cell-based and integrin-based assays. In combination with a comparative molecular modeling study, these results have helped identify common conformational elements in the pharmacophore of this class of molecules. Peptides are presented that are highly potent, integrin specific, and that possess reduced pharmacological side effects. Also presented is the development of a peptide that modifies, noncovalently, the surfaces of a wide variety of synthetic materials used in medical implants. The agonist activity of [corrected] this molecule is evident from its ability to stimulate cell attachment on these surfaces. This is shown to translate into an in vivo activity of faster and more complete tissue integration, and a reduction in foreign body response.
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Affiliation(s)
- W S Craig
- Telios Pharmaceutical, Inc., San Diego, California 92121
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48
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Tunstall A, Eberhart RC, Prager MD. Comparison of tissue factor and prostacyclin production by human umbilical vein endothelial cells on Dacron vascular prostheses and Dacron smooth films. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1994; 28:1233-8. [PMID: 7829552 DOI: 10.1002/jbm.820281013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The functional capacity of human umbilical vein endothelial cells (HUVEC) grown on Dacron (polyethylene terephthalate; PET) vascular prosthetic material was compared with the function of cells on smooth surfaced PET, tissue culture polystyrene (TCPS), and Natrix-coated TCPS. Prosthetic materials include two knitted fabrics (Bionit I and II) and two woven preparations (DeBakey Soft Woven and Extra Low Porosity). Two entities produced by HUVEC that influence blood coagulation were assessed: the procoagulant tissue factor (TF) and the anticoagulant prostacyclin (PGI2). Although TF activity was stimulated on all substrates by endotoxin (LPS), there was no difference among prostheses and no difference among smooth surface materials, but TF was reduced in cells on the prosthetic materials relative to those on smooth surface substrates. The reduced TF production by HUVEC on prosthetic material could be reversed by returning them to TCPS. In contrast, PGI2 production on prostheses was comparable to that on smooth surfaces for both stimulated and unstimulated cells. Stimulation with histamine (1 microM) gave a 2.4-fold increase in PGI2 whereas mellitin (10 micrograms/ml) increased production 12.5-fold. The differential response of HUVEC with regard to these two coagulation factors, one of which is secreted and the other membrane bound, may reflect the distorted shape of cells on fibers of the prosthesis.
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Affiliation(s)
- A Tunstall
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas 75235-9031
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49
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Ryu GH, Park S, Kim M, Han DK, Kim YH, Min B. Antithrombogenicity of lumbrokinase-immobilized polyurethane. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1994; 28:1069-77. [PMID: 7814434 DOI: 10.1002/jbm.820280912] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Lumbrokinase is a potent fibrinolytic enzyme purified from the earthworm, Lumbricus rubellus. We immobilized 18 IU/cm2 of lumbrokinase to polyurethane using maleic anhydride methylvinyl ether copolymer (MAMEC) as an enzyme carrier, and the proteolytic and fibrinolytic activities of immobilized lumbrokinase were assayed. Immobilized lumbrokinase retained about 34% of its activity, compared with soluble lumbrokinase activity. Immobilized lumbrokinase showed stability against thermal inactivation and degradation and within a various pH range. The optimal pH of immobilized lumbrokinase shifted 1.0 pH unit upward compared with soluble enzyme. Upon exposure to the human whole blood, less amount of 125I-fibrinogen was adsorbed to lumbrokinase-immobilized surface than to the polyurethane control surface. The lumbrokinase-immobilized surface showed less platelet adhesion than did the MAMEC-grafted surface. At the early stage of platelet adhesion, the number of adhered platelets increased on the lumbrokinase-immobilized surface with increasing time; yet, the platelet number drastically decreased on the lumbrokinase-immobilized surface after 80 min incubation. This suggests that lumbrokinase-immobilized polyurethane digested the adsorbed fibrinogen and inhibited platelet adhesion on the surface, probably by inhibiting fibrinogen adsorption to be highly antithrombogenic. Clinical applications of this material to artificial organs should be developed in the near future.
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Affiliation(s)
- G H Ryu
- Department of Biomedical Engineering, College of Medicine, Seoul National University, Korea
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50
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Kennedy JP. Novel Designed Polyisobutylene-Based Biopolymers: Synthesis, Characterization, and Biological Testing of Amphiphilic Chameleon Networks. JOURNAL OF MACROMOLECULAR SCIENCE PART A-PURE AND APPLIED CHEMISTRY 1994. [DOI: 10.1080/10601329408545881] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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