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Yamamoto Y, Hino A, Kurihara H, Kano K, Serizawa I, Katoh H, Hiruma T. Transitional changes of spacer materials used in carbon-ion radiation therapy. Asia Pac J Clin Oncol 2022; 18:e442-e447. [PMID: 35098680 DOI: 10.1111/ajco.13751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 12/13/2021] [Indexed: 01/01/2023]
Abstract
PURPOSE To evaluate the imaging findings and transitional changes in spacer materials used in carbon-ion radiation therapy MATERIALS: Medical records were retrospectively reviewed, and the maximum thickness, volume, and CT value of spacers were calculated from CT scans. Procedure-related complications were recorded. RESULTS A spacer was surgically placed in six patients in retroperitoneal, presacral, or peritoneal sites. The spacer material was polyglycolic acid (PGA) in four patients and expanded polytetrafluoroethylene (ePTFE) in two patients. The thickness of PGA spacers showed no changes in any patients within 4 weeks, but increased within 6 weeks in one patient and was unchanged or decreased in the remaining patients. PGA spacer volume decreased gradually after placement in three of four patients; this was observed at 4 months in two patients and at 6 months in one patient. The mean CT value of PGA spacers was 83 HU just after placement, and decreased gradually thereafter. Air was seen in the PGA spacers of two patients. Neither ePTFE spacer showed volume changes over time, and the mean CT value was low (mean, -53.7 HU) just after placement but increased rapidly to 145 HU at 2 months. CONCLUSION Spacer imaging findings may vary according to type and may change over time. Familiarity with these features is beneficial for diagnostic radiologists.
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Affiliation(s)
- Yayoi Yamamoto
- Department of Radiology and Interventional Radiology, Kanagawa Cancer Center, Kanagawa, Japan
| | - Ayako Hino
- Department of Radiology and Interventional Radiology, Kanagawa Cancer Center, Kanagawa, Japan
| | - Hiroaki Kurihara
- Department of Radiology and Interventional Radiology, Kanagawa Cancer Center, Kanagawa, Japan
| | - Kio Kano
- Department of Radiation Oncology, Kanagawa Cancer Center, Kanagawa, Japan
| | - Itsuko Serizawa
- Department of Radiation Oncology, Kanagawa Cancer Center, Kanagawa, Japan
| | - Hiroyuki Katoh
- Department of Radiation Oncology, Kanagawa Cancer Center, Kanagawa, Japan
| | - Toru Hiruma
- Department of Musculoskeletal Tumor Surgery, Kanagawa Cancer Center, Kanagawa, Japan
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2
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Hernandez JL, Woodrow KA. Medical Applications of Porous Biomaterials: Features of Porosity and Tissue-Specific Implications for Biocompatibility. Adv Healthc Mater 2022; 11:e2102087. [PMID: 35137550 PMCID: PMC9081257 DOI: 10.1002/adhm.202102087] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 12/17/2021] [Indexed: 12/14/2022]
Abstract
Porosity is an important material feature commonly employed in implants and tissue scaffolds. The presence of material voids permits the infiltration of cells, mechanical compliance, and outward diffusion of pharmaceutical agents. Various studies have confirmed that porosity indeed promotes favorable tissue responses, including minimal fibrous encapsulation during the foreign body reaction (FBR). However, increased biofilm formation and calcification is also described to arise due to biomaterial porosity. Additionally, the relevance of host responses like the FBR, infection, calcification, and thrombosis are dependent on tissue location and specific tissue microenvironment. In this review, the features of porous materials and the implications of porosity in the context of medical devices is discussed. Common methods to create porous materials are also discussed, as well as the parameters that are used to tune pore features. Responses toward porous biomaterials are also reviewed, including the various stages of the FBR, hemocompatibility, biofilm formation, and calcification. Finally, these host responses are considered in tissue specific locations including the subcutis, bone, cardiovascular system, brain, eye, and female reproductive tract. The effects of porosity across the various tissues of the body is highlighted and the need to consider the tissue context when engineering biomaterials is emphasized.
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Affiliation(s)
- Jamie L Hernandez
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
| | - Kim A Woodrow
- Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98195, USA
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3
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Walawalkar S, Verma MK, Almelkar S. Re-endothelization of human saphenous vein scaffold surfaces for bioprosthesis fabrication. J Biomater Appl 2020; 34:1081-1091. [DOI: 10.1177/0885328219898349] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Various in vitro methods have been used for biological and synthetic scaffold fabrication. Some use polymers such as expanded polytetrafluoroethylene (ePTFE), polytetrafluoroethylene (PTFE), and polyethylene terephthalate (PET), while others use allogeneic or xenogeneic biological materials (e.g. blood vessels). While fabricating a biological scaffold, the first step is complete decellularization by enzymes (e.g. trypsin, collagenase, etc.) or chemicals (e.g. SDS, Triton-X, etc.), and the scaffolds should maintain its extracellular matrix (ECM). The second step involves re-endothelization so as to get fully biomimetic graft. In this study, we focused (concentrated) on the fabrication of a human saphenous vein scaffold by using various chemicals. We observed that cationic 1% SDS solution (Group B) performed excellent decellularization without altering the extracellular matrix as compared to the other chemicals like 0.25% trypsin and 70% ethanol (Groups C and D). Decellularization percentage and intactness of ECM (in all tunicae – intima, media, and adventitia) were confirmed based on histology. The PicoGreen assay showed that Group B (1% SDS decellularized scaffold, n = 3) had no detectable residual DNA. Re-endothelization on the complete decellularized scaffold (Group B) was done in both ways, without initial fibrin glue application (Group E) and with prior fibrin glue application (Group F). The vWF and lectin expressions suggested that endothelial cells did not alter their phenotype on human saphenous vein scaffolds. Uniaxial tensile testing revealed no significant differences in strain characteristics and modulus between native tissue and decellularized scaffolds. The live-dead (FDA/PI) and MTT assays confirmed the endothelial cell proliferation and viability, and the scanning electron microscope (SEM) data showed that the cells adhered to the scaffold matrix (Group F). We concluded that an allogeneic human saphenous vein scaffold with desirable properties can be fabricated and re-endothelialized to form a non-thrombogenic intimal surface in vitro using this protocol.
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Affiliation(s)
| | | | - Shahdab Almelkar
- HEALTH BIOLABS, Shree Hospital & Research Institute (SHRI), Kolhapur, India
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4
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Bi SH, Mu B, Tang Z, Fan M, Wang T, Ahmad S. The history of hemodialysis in China. Hemodial Int 2019; 24:269-275. [PMID: 31887231 DOI: 10.1111/hdi.12815] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 11/30/2019] [Accepted: 12/12/2019] [Indexed: 12/18/2022]
Abstract
The technique of hemodialysis was introduced into China more than 50 years ago; and both research and use of clinical hemodialysis began in mid-1960s to late-1960s. A brief review of the history of hemodialysis in China is presented here, including a brief description of pioneers and their contributions, local development and use of dialyzers, hemodialysis machines, and vascular access, and dialysis management and logistics.
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Affiliation(s)
- Shu-Hong Bi
- Department of Nephrology, Peking University Third Hospital, Beijing, China
| | - Bingyao Mu
- Department of Nephrology, Peking University Third Hospital, Beijing, China.,Department of Internal Medicine, Miyun District Hospital, Beijing, China
| | - Ziyong Tang
- Department of Nephrology, Peking University Third Hospital, Beijing, China
| | - Minhua Fan
- Department of Nephrology, Peking University Third Hospital, Beijing, China
| | - Tao Wang
- Department of Nephrology, Peking University Third Hospital, Beijing, China
| | - Suhail Ahmad
- School of Medicine, University of Washington, Seattle, Washington, USA
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5
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Fabrication of aortic bioprosthesis by decellularization, fibrin glue coating and re-endothelization: a cell scaffold approach. Prog Biomater 2019; 8:197-210. [PMID: 31606862 PMCID: PMC6825630 DOI: 10.1007/s40204-019-00122-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 09/27/2019] [Indexed: 12/13/2022] Open
Abstract
Aortic dysfunctions (aneurysm, aortitis) lead to the most serious conditions related to aortic wall with life-threatening complications. The most common modality of management for such conditions is replacement (diseased part) of aorta by a larger diameter stent (reconstructive vascular surgery) which in itself is a big trial. The most natural way is to use a re-endothelized scaffold. Developing a scaffold with biomimetic properties is an experimental aim for most of the scientists and surgeons. We aim to structure a strategy to overcome the well-known problems associated with aorta. In this study, we plan to remold a larger diameter blood vessel such as aorta from xenogeneic origin using different protocols to decellularize and comparing them with normal aorta. The chemicals and enzymes used for bovine aorta decellularization are 1% SDS (group II), 70% ethanol + 0.25% trypsin (group III), 70% ethanol (group IV), and 0.25% trypsin (group V). Group I served as control (without decellularization). Histology and SEM study were conducted for cellular presence/absence in all scaffolds. Later, the scaffolds were coated with the fibrin glue (FG) and endothelial cells were proliferated over them. 3D images were taken showing the remolding of the endothelial cells on FG-coated surfaces. The re-endothelization was confirmed by lectin and vWF+/+ expression. Graft elasticity and burst pressure were confirmed by biomechanical tensile testing. Further, the absence of host tissue DNA and presence of cellular DNA after re-endothelialization were confirmed by PicoGreen assay. The acceptability for metabolically active cellular proliferation on scaffolds and its non-toxicity were proved by cell viability assay. Current findings accomplish that larger diameter aorta extracellular matrix scaffold (group II) can be fabricated and re-endothelialized to develop non-thrombotic surfaces with improved graft patency with promising results compared to other fabricated scaffold groups.
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6
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Shults OG, Shults AA, Orlinskaya NY. [Huge periprosthetic (peritransplant) seroma of a femoropopliteal bypass graft]. ANGIOLOGIIA I SOSUDISTAIA KHIRURGIIA = ANGIOLOGY AND VASCULAR SURGERY 2019; 25:188-193. [PMID: 31503265 DOI: 10.33529/angid2019322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Presented herein is a clinical case report of a huge periprosthetic seroma of a femoropopliteal bypass graft made of polytetrafluoroethylene with a follow-up period and unsuccessful conservative management of more than one year. At 15 months after the primary operation, the bypass graft was retrieved and replaced by a knitted vascular graft made of polyester and impregnated with absorbable modified gelatine to decrease porosity, without relapse of the process of transudation into the periprosthetic space. Histological study of the retrieved conduit demonstrated the absence of formation of the intimal layer on the inner surface of the graft and fibrous capsule on the external surface of the main part of the length of the prosthesis, which, apparently, had provided a possibility of long-term preservation of porosity of the material.
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Affiliation(s)
- O G Shults
- University Clinic, Research Medical University of the Volga Region under the RF Ministry of Public Health, Nizhny Novgorod
| | - A A Shults
- University Clinic, Research Medical University of the Volga Region under the RF Ministry of Public Health, Nizhny Novgorod
| | - N Yu Orlinskaya
- University Clinic, Research Medical University of the Volga Region under the RF Ministry of Public Health, Nizhny Novgorod
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7
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Silva DMS, Lins EM, Marques SRB, Albuquerque AV, Aguiar JLA. Experimental study of femoral vein reconstruction with sugarcane biopolymer tubular graft. Rev Col Bras Cir 2018; 45:e1837. [PMID: 30088524 DOI: 10.1590/0100-6991e-20181837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 05/17/2018] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE to evaluate, through Doppler flowmetry, venography, histology and clinical evolution, the use of sugarcane biopolymer (BP) tubular grafts in the reconstruction of femoral veins in dogs. METHODS we submitted eight adult dogs to femoral vein reconstruction, on the left with BP tubular graft and on the right with autologous vein. In the postoperative period, the animals underwent clinical evaluation and femoral vein Doppler flowmetry. After 360 days, we reoperated the dogs and submitted them to femoral vein phlebography with iodinated contrast. We removed the segments of the femoral veins containing the grafts and sent them for histopathological evaluation. RESULTS the dogs did not present hemorrhage, hematoma, surgical wound infection or operated limb edema. One animal had superficial venous dilatation in the left inguinal region. Phlebography performed 360 days after the first surgery showed that three (37.5%) BP grafts and seven (87.5%) grafts from the control group (C) were patent. In the histopathological evaluation, we found an inflammatory reaction, with neutrophils and lymphocytes on the external surface of both groups. In the intimal layer of the grafts and in the outer layer in the two groups, we observed fibrosis. CONCLUSION based on the results obtained with the experimental model used, BP presents potential to be used as a tubular graft for venous revascularization. However, new research must be performed to confirm its efficacy in the revascularization of medium and large diameter veins, which could allow its use in clinical practice.
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Affiliation(s)
| | - Esdras Marques Lins
- Universidade Federal de Pernambuco, Departamento de Cirurgia, Recife, PE, Brasil
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8
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Wu ML, Panduranga MK, Carman GP. Proliferation of human aortic endothelial cells on Nitinol thin films with varying hole sizes. Biomed Microdevices 2018; 20:25. [PMID: 29484503 DOI: 10.1007/s10544-018-0267-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In this paper, we present the effect of micron size holes on proliferation and growth of human aortic endothelial cells (HAECs). Square shaped micron size holes (5, 10, 15, 20 and 25 μm) separated by 10 μm wide struts are fabricated on 5 μm thick sputter deposited Nitinol films. HAECs are seeded onto these micropatterned films and analyzed after 30 days with fluorescence microscopy. Captured images are used to quantify the nucleus packing density, size, and aspect ratio. The films with holes ranging from 10 to 20 μm produce the highest cell packing densities with cell nucleus contained within the hole. This produces a geometrically regular grid like cellular distribution pattern. The cell nucleus aspect ratio on the 10-20 μm holes is more circular in shape when compared to aspect ratio on the continuous film or larger size holes. Finally, the 25 μm size holes prevented the formation of a continuous cell monolayer, suggesting the critical length that cells cannot bridge is between 20 to 25 μm.
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Affiliation(s)
- Ming Lun Wu
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA.
| | - Mohanchandra K Panduranga
- Department of Aerospace & Mechanical Engineering, University of California, Los Angeles, CA, 90095, USA
| | - Gregory P Carman
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA
- Department of Aerospace & Mechanical Engineering, University of California, Los Angeles, CA, 90095, USA
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9
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Abstract
If God created the saphenous vein for the sake of vascular surgeons, He neglected to create all men equal in respect to the presence of saphenous veins for needed revascularizations. Therefore, the burden of finding alternatives to saphenous veins reverts to the humble ingenuity of man.
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Affiliation(s)
- R. Limet
- 66 Bd de la Constitution 4020 Liege Belgium
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10
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Takenaka K, Kholoussy AM, Yeng Yang, Emara M, Fusaro J, Matsumoto T. The Influence of Supporting Rings on the Healing of the Ringed Expanded Polytetrafluoroethylene Vascular Graft. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/153857448501900503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The influence of supporting rings on the healing of the ringed expanded polytetrafluoroethylene (ePTFE) vascular graft (ringed graft) was studied. In 12 dogs (32-42 kgm), a 4cm segment of each common iliac artery was excised and replaced with an equal length of 6mm ePTFE vascular graft. Ringed graft was used on one side and plain on the other. Dogs were sacrificed at intervals of 1, 2, 4, 6, 8 and 12 weeks. All grafts remained patent. The degree of pannus extension and pannus thickness showed no differences between both grafts at each interval. It was covered by a monolayer of endothelial-like cells as seen by scanning electron microscopy. The growth rates of endothelialization measured from the proximal anastomosis were 1.3 and 1.4 mm/week in the plain and ringed grafts, respec tively. Anastomotic intimal hyperplasia (> 50 microns) was noted in 25% and 33% at the proximal and distal anastomoses, respectively, in both grafts. The outer surface was covered by adherent connective tissue particularly encapsu lating the rings without affecting the non-ringed portion in the ringed grafts. We conclude that the supporting rings of the ePTFE graft have no significant influence on the healing and neointimal development.
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Affiliation(s)
- Kenji Takenaka
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - A. Mohsen Kholoussy
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - Yeng Yang
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - Medhat Emara
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - James Fusaro
- Department of Surgery, Monmouth Medical Center, Long Branch, New Jersey
| | - Teruo Matsumoto
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
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11
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Takenaka K, Mohsen Kholoussy A, Yang Y, Kodellas L, Matsumoto T. The Healing of the Thin-Walled Expanded Polytetrafluoroethylene Vascular Graft. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/153857448501900601] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The objective of this experiment was to investigate the healing of thin-walled reinforced expanded polytetrafluoroethylene (PTFE) vascular graft (thin graft) . In 12 dogs (30-35 kgm), a 4 cm segment of each common iliac artery was excised and replaced with an equal length of PTFE vascular graft, 6mm internal diameter. Standard graft was used on one side and thin graft on the other. Dogs were sacrificed at intervals up to 12 weeks. Pannus extension started at both ends after the first week. The degree of pannus extension and pannus thickness showed no difference between both grafts at each interval. It was covered by a monolayer of endothelial-like cells as seen by scanning electron microscopy. Anastomotic hyperplasia and the growth rates of endothelialization measured from the proximal anastomosis were simi lar. No significant difference was noted in the healing between the thin-walled and standard PTFE vascular grafts for up to 12 weeks.
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Affiliation(s)
- Kenji Takenaka
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - A. Mohsen Kholoussy
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - Yeng Yang
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - Lambros Kodellas
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
| | - Teruo Matsumoto
- Department of Surgery, Hahnemann University School of Medicine, Philadelphia, Pennsylvania
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12
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Caimmi PP, Sabbatini M, Fusaro L, Borrone A, Cannas M. A study of the mechanical properties of ePTFE suture used as artificial mitral chordae. J Card Surg 2016; 31:498-502. [PMID: 27388975 DOI: 10.1111/jocs.12799] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND AND AIM OF THE STUDY We investigated the dimensional and mechanical properties of polyetetrafluorene (ePTFE) sutures used as artificial chordae during mitral valve repair. METHODS Mechanical properties of ePTFE synthetic chordae tendineae were tested with a servo hydraulic testing machine. Several different lengths from 2 to 14 cm were studied under both single and multiple mechanical traction. RESULTS The mechanical behavior of artificial chordae reveals that three centimeters is the length over which we observe a significant increase in stiffness. The chordae stiffness grows further at the length greater than seven centimeters following a low number of traction cycles. CONCLUSION The increase of the length of artificial ePTFE chordae is accompanied by an increasing stiffness that compromises the long-term resistance of the chordae. ePTFE length can alter the performance of artificial chordae. This suggests that mitral valve repairs which anchor ePTFE neochordae to the ventricular apex may have less durability than when anchored to the tips of the papillary muscles.
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Affiliation(s)
- Philippe Primo Caimmi
- Department of Cardiovascular Sugery, San Gaudenzio Clinic, Health Care Group "Policlinico di Monza", Novara, Italy
| | - Maurizio Sabbatini
- Department of Science and Innovation Technology, University Eastern Piedmont, UPO, Alessandria, Novara, Vercelli, Italy
| | - Luca Fusaro
- Department of Health Sciences, Human Anatomy, University Eastern Piedmont, UPO, Alessandria, Novara, Vercelli, Italy
| | - Alessia Borrone
- Department of Pharmacy Science, University Eastern Piedmont, UPO, Alessandria, Novara, Vercelli, Italy
| | - Mario Cannas
- Department of Health Sciences, Human Anatomy, University Eastern Piedmont, UPO, Alessandria, Novara, Vercelli, Italy
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13
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Diethrich EB. Polymeric Covers and Coats for Metallic Stents: Microporous PTFE and the Inhibition of Intimal Hyperplasia. J Endovasc Ther 2016. [DOI: 10.1177/152660289500200305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Edward B. Diethrich
- Department of Cardiovascular Surgery, Arizona Heart Institute & Foundation, and the Cardiovascular Center of Excellence at Healthwest Regional Medical Center, Phoenix, Arizona, USA
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14
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Nishibe T, Kondo Y, Muto A, Dardik A. Optimal Prosthetic Graft Design for Small Diameter Vascular Grafts. Vascular 2016; 15:356-60. [DOI: 10.2310/6670.2007.00053] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Autogenous vein and arterial grafts, such as great saphenous veins and internal mammary and radial arteries, remain the gold standard conduits for vascular reconstruction. Expanded polytetrafluoroethylene (PTFE) grafts, which exhibit little inflammatory and thrombogenic reactivity, are the most commonly used material of choice for small diameter vascular grafts when autogenous grafts are not available. Several modifications of the basic graft have been attempted to enhance graft healing of expanded PTFE grafts, and little but definite experimental and clinical improvement has been achieved so far. The technique of vascular tissue engineering, in combination with stem cell research, may hold the key for the creation of a practical and successful small diameter prosthetic graft.
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Affiliation(s)
- Toshiya Nishibe
- *Department of Surgery, Fujita Health University, Toyoake, Japan; †Department of Vascular Surgery, Yale University School of Medicine, New Haven, CT
| | - Yuka Kondo
- *Department of Surgery, Fujita Health University, Toyoake, Japan; †Department of Vascular Surgery, Yale University School of Medicine, New Haven, CT
| | - Akihito Muto
- *Department of Surgery, Fujita Health University, Toyoake, Japan; †Department of Vascular Surgery, Yale University School of Medicine, New Haven, CT
| | - Alan Dardik
- *Department of Surgery, Fujita Health University, Toyoake, Japan; †Department of Vascular Surgery, Yale University School of Medicine, New Haven, CT
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15
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Chan MG, Miller FJ, Valji K, Kuo MD. Drs. Chan et al respond. J Vasc Interv Radiol 2014; 25:1315-6. [PMID: 25085071 DOI: 10.1016/j.jvir.2014.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 04/09/2014] [Indexed: 11/28/2022] Open
Affiliation(s)
- Michael G Chan
- Department of Radiology, University of California, Los Angeles, Los Angeles, California; Department of Radiology, University of California, San Diego, San Diego, California
| | - Franklin J Miller
- Department of Radiology, University of California, San Diego, San Diego, California
| | - Karim Valji
- Department of Radiology, University of Washington, Seattle, Washington
| | - Michael D Kuo
- Department of Radiology, University of California, Los Angeles, Los Angeles, California
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16
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Dolmatch B. Re: "Evaluating patency rates of an ultralow-porosity expanded polytetrafluoroethylene-covered stent in the treatment of venous stenosis in arteriovenous dialysis circuits". J Vasc Interv Radiol 2014; 25:1315. [PMID: 25085070 DOI: 10.1016/j.jvir.2014.03.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 03/12/2014] [Indexed: 11/18/2022] Open
Affiliation(s)
- Bart Dolmatch
- Department of Interventional Radiology, Palo Alto Medical Foundation, 701 E. El Camino Real, Mountain View, CA 94040
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17
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Williams SK, Kosnik PE, Kleinert LB, Vossman EM, Lye KD, Shine MH. Adipose stromal vascular fraction cells isolated using an automated point of care system improve the patency of expanded polytetrafluoroethylene vascular grafts. Tissue Eng Part A 2013; 19:1295-302. [PMID: 23350681 DOI: 10.1089/ten.tea.2012.0318] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We evaluated the use of an automated, point-of-care instrument to derive canine adipose stromal vascular fraction cells, and the subsequent deposition of these cells onto the luminal surface of an expanded polytetrafluoroethylene (ePTFE) vascular graft for use as a bypass graft. The hypothesis evaluated was that an instrument requiring minimal user interface will provide a therapeutic dose of cells to improve the patency of synthetic vascular grafts in an autologous animal model of graft patency. The stromal vascular fraction (SVF) cells were isolated using an automated adipose tissue processing and cell isolation system and cells sodded onto the surface of an ePTFE vascular graft. Control grafts, used off-the-shelf without cell treatment were used as a control to assess patency effects. Each animal received a control, untreated graft implanted in one carotid artery, and the cell-treated graft implanted in the carotid artery on the contralateral side. The grafts were implanted for 6 months utilizing 12 animals. Results indicate a fully automated adipose tissue processing system will consistently produce functional autologous cells for immediate use in the operating room. Cell-sodded polymeric grafts exhibited improved patency compared to control grafts after 6 month implantation in the canine carotid artery model.
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Affiliation(s)
- Stuart K Williams
- Cardiovascular Innovation Institute, University of Louisville, Louisville, Kentucky 40202, USA.
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18
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Self-assembling peptide scaffolds as innovative platforms for drug and cell delivery systems in cardiac regeneration. Drug Deliv Transl Res 2013; 3:330-5. [DOI: 10.1007/s13346-012-0125-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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19
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Boccafoschi F, Mosca C, Cannas M. Cardiovascular biomaterials: when the inflammatory response helps to efficiently restore tissue functionality? J Tissue Eng Regen Med 2012; 8:253-67. [DOI: 10.1002/term.1526] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/30/2012] [Accepted: 04/03/2012] [Indexed: 01/25/2023]
Affiliation(s)
- F. Boccafoschi
- Department of Health Sciences; University of Piemonte Orientale; “A. Avogadro” 28100 Novara Italy
| | - C. Mosca
- Department of Health Sciences; University of Piemonte Orientale; “A. Avogadro” 28100 Novara Italy
| | - M. Cannas
- Department of Health Sciences; University of Piemonte Orientale; “A. Avogadro” 28100 Novara Italy
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Yao JS, Eskandari MK. Accidental discovery: The polytetrafluoroethylene graft. Surgery 2012; 151:126-8. [DOI: 10.1016/j.surg.2011.09.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 09/22/2011] [Indexed: 11/25/2022]
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Narasimhan S, Aslam S, Lin PH, Bechara CF, Mansouri MD, Darouiche RO. Bacterial translocation across ePTFE vascular graft surfaces. J Infect 2010; 60:486-90. [PMID: 20362612 DOI: 10.1016/j.jinf.2010.03.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/24/2010] [Accepted: 03/25/2010] [Indexed: 10/19/2022]
Abstract
OBJECTIVES Vascular graft infections arise from bacterial colonization of either the external or internal graft surfaces. We assessed whether methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli could translocate through pores of ePTFE grafts. METHODS To assess translocation from the internal to the external surface, we placed 10(5) cfu of bacterial suspension inside ePTFE graft segments and suspended them in sterile broth for 72 h. To assess translocation from the external to the internal surface, we placed sterile broth inside ePTFE segments, and incubated them for 72 h in a bacterial suspension (10(5) cfu/mL). At 72 h, in addition to culturing the sterile broth and bacterial suspensions, the external and internal surfaces were first qualitatively cultured separately and then quantitatively cultured by sonication. RESULTS At 72 h, the sterile broth remained sterile. The bacterial suspensions yielded 10(7)-10(9) cfu/mL. Graft cultures indicated that colonization of one surface with either organism did not result in bacterial translocation to the other surface. Quantitative bacterial counts of the external vs. internal surfaces were significantly different (p < 0.01). CONCLUSIONS MRSA and E. coli do not translocate across ePTFE graft surfaces. These in-vitro findings help elucidate the pathogenesis of graft infections and prompt conduction of validation studies in-vivo.
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Affiliation(s)
- Supriya Narasimhan
- Department of Medicine, Section of Infectious Diseases, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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Abstract
This article discusses the importance of the endothelium for successful vascular grafts derived from both native arteries and synthetic materials. It also discusses the fundamental strategies to endothelialize synthetic grafts in animal experiments and in the clinic, as well as the use of endothelial progenitor cells (EPCs), bone marrow-derived cells, and mesothelium as endothelial substitutes.
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Affiliation(s)
- Michel R Hoenig
- Centre for Research in Vascular Biology, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Australia
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23
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Zilla P, Bezuidenhout D, Human P. Prosthetic vascular grafts: Wrong models, wrong questions and no healing. Biomaterials 2007; 28:5009-27. [PMID: 17688939 DOI: 10.1016/j.biomaterials.2007.07.017] [Citation(s) in RCA: 365] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 07/06/2007] [Indexed: 12/20/2022]
Abstract
In humans, prosthetic vascular grafts remain largely without an endothelium, even after decades of implantation. While this shortcoming does not affect the clinical performance of large bore prostheses in aortic or iliac position, it contributes significantly to the high failure rate of small- to medium-sized grafts (SMGs). For decades intensive but largely futile research efforts have been under way to address this issue. In spite of the abundance of previous studies, a broad analysis of biological events dominating the incorporation of vascular grafts was hitherto lacking. By focusing on the three main contemporary graft types, expanded polytetrafluoroethylene (ePTFE), Dacron and Polyurethane (PU), accumulated clinical and experimental experience of almost half a century was available. The main outcome of this broad analysis-supported by our own experience in a senescent non-human primate model-was twofold: Firstly, inappropriate animal models, which addressed scientific questions that missed the point of clinical relevance, were largely used. This led to a situation where the vast majority of investigators unintentionally studied transanastomotic rather than transmural or blood-borne endothelialization. Given the fact that in patients transanastomotic endothelialization (TAE) covers only the immediate perianastomotic region of sometimes very long prostheses, TAE is rather irrelevant in the clinical context. Secondly, transmural endothelialization seems to have a time window of opportunity before a build-up of an adverse microenvironment. In selecting animal models that prematurely terminate this build-up through the early presence of an endothelium, the most significant 'impairment factor' for physiological tissue regeneration in vascular grafts remained ignored. By providing insight into mechanisms and experimental designs which obscured the purpose and scope of several decades of vascular graft studies, future research may better address clinical relevance.
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Affiliation(s)
- Peter Zilla
- Christian Barnard Department of Cardiothoracic Surgery/Cardiovascular Research Unit, University of Cape Town Medical School, Cape Town, South Africa.
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Brandão ML, Coutinho Netto J, Thomazini JA, Lachat JJ, Muglia VF, Piccinato CE. Prótese vascular derivada do látex. J Vasc Bras 2007. [DOI: 10.1590/s1677-54492007000200007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CONTEXTO: O desenvolvimento de prótese vascular tem sido vital para os avanços e realizações da cirurgia vascular reconstrutora durante as últimas 5 décadas. OBJETIVOS: Desenvolver um novo modelo de prótese vascular microperfurada, confeccionada em tecido recoberto com um composto derivado do látex natural da seringueira (Hevea brasiliensis) e avaliar sua perviedade, trombogenicidade, biocompatibilidade e o processo de cicatrização, além de algumas propriedades mecânicas (adaptabilidade, elasticidade, impermeabilidade e possibilidade de sutura), utilizando como controle a prótese de politetrafluoretileno expandido no mesmo animal. MÉTODOS: Quinze cães foram separados em três grupos de cinco animais. Implantou-se a prótese de tecido e látex microperfurada e, no membro pélvico contralateral, a prótese de politetrafluoretileno expandido em todos os cães. O seguimento pós-operatório foi de 4, 8 e 12 semanas. A apreciação dos resultados foi feita segundo as avaliações clínicas dos pulsos, complicações (coleção líquida, deiscência, granuloma e infecção), arteriografias, análise macroscópica e elétron-micrografias de varredura. RESULTADOS: Os testes estatísticos aplicados não evidenciaram diferenças significativas (p > 0,05) em relação às complicações pós-operatórias e perviedade dos enxertos. Ambas as próteses integraram-se adequadamente aos tecidos circunvizinhos, com um tecido de incorporação formado por fibras colágenas. Constatou-se a presença de neoíntima recoberta por endotélio em toda a extensão da superfície luminal da prótese de tecido e látex microperfurada. Ao contrário, na prótese de politetrafluoretileno expandido, o desenvolvimento endotelial sobre a superfície neointimal limitou-se às regiões próximas às anastomoses. CONCLUSÕES: A prótese de tecido e látex microperfurada demonstrou qualidades estruturais (adaptabilidade, elasticidade, impermeabilidade e possibilidade de sutura) satisfatórias como substituto vascular. Estimulou o crescimento endotelial além das regiões de contato com a artéria nas anastomoses e foi biocompatível no sistema arterial do cão, apresentando adequada integração tecidual.
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Hayabuchi Y, Mori K, Kitagawa T, Sakata M, Kagami S. Polytetrafluoroethylene graft calcification in patients with surgically repaired congenital heart disease: evaluation using multidetector-row computed tomography. Am Heart J 2007; 153:806.e1-8. [PMID: 17452157 DOI: 10.1016/j.ahj.2007.01.035] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Accepted: 01/21/2007] [Indexed: 01/08/2023]
Abstract
BACKGROUND Noninvasive determination of calcified prosthetic polytetrafluoroethylene (PTFE) is important in improving risk stratification. The purpose of this study is to assess the feasibility of multidetector-row computed tomography (MDCT) for the evaluation of PTFE calcification in patients with surgically repaired congenital heart disease and to evaluate the development and characteristics of calcification for specific surgical procedures. METHODS Seventy-six implanted PTFE grafts in 47 patients were evaluated by MDCT (Aquillion 16, Toshiba Corporation, Tokyo, Japan). Explanted PTFE grafts were evaluated histologically in 4 patients who underwent reoperation after MDCT scans. RESULTS Calcification of prosthetic PTFE was detected in 5 of 29 cases (17%) for ventricular septal defect (VSD) patches, 26 of 32 (81%) for right ventricular outflow tract (RVOT) prosthesis, 2 of 8 (25%) for atrial septal patches of the Fontan procedure, and 7 of 7 (100%) for extracardiac conduits of total cavopulmonary connection. The CT attenuation of PTFE revealed significantly different values for VSD patches (114 +/- 61 Hounsfield units [HU]), RVOT prosthesis (243 +/- 132 HU), atrial septal patches (163 +/- 161 HU), and extracardiac conduits (230 +/- 29 HU) (P < .0001). The CT density value of VSD patches was significantly lower than those of RVOT grafts and extracardiac conduits (P < .05). The MDCT findings were consistent with histologic analysis in the evaluation of calcification. CONCLUSIONS This study demonstrates that MDCT enables the evaluation of prosthetic PTFE graft calcification; PTFE grafts in 4 different implantation sites demonstrated distinctive features and the prevalence of calcification.
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Zhang Z, Briana S, Douville Y, Zhao H, Gilbert N. Transmural communication at a subcellular level may play a critical role in the fallout based-endothelialization of dacron vascular prostheses in canine. J Biomed Mater Res A 2007; 81:877-87. [PMID: 17236220 DOI: 10.1002/jbm.a.31124] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A microporous and permeable wall is important for the healing of vascular prostheses, however, the significance of its permeability to soluble substances at subcellular level has not been demonstrated. Polyester arterial prostheses were prepared in such a way that each of them contained three segments, of which at least one segment was impervious and another segment was permeable to water but impermeable to cells. Twenty graft segments were implanted in 7 dogs as a thoraco-abdominal bypass for 2 months. The prostheses were then harvested, photographed, and treated for histological and morphological studies. The low porosity graft capped by two thrombogenic segments was fully endothelialized, proving the fallout mechanism. The striking contrast with its impermeable counterpart demonstrated that a wall permeable to small substances of subcellular level was critical for the endothelial healing. A wide range of water permeabilities did not reveal advantages of high water permeable segments over low water permeable ones. Endothelial ingrowth from anastomoses was also jeopardized in the absence of wall permeability. In conclusion, transmural communication at a subcellular level may have played a critical role in the fallout based-endothelialization of arterial prostheses in canine. This highlights the potential function of perigraft cytokines and growth factors in endothelial healing.
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Affiliation(s)
- Ze Zhang
- Department of Surgery, Laval University, The Research Center of Saint-François d'Assise Hospital, CHUQ, Quebec City, Quebec, Canada.
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Zhang J, Qi H, Wang H, Hu P, Ou L, Guo S, Li J, Che Y, Yu Y, Kong D. Engineering of Vascular Grafts With Genetically Modified Bone Marrow Mesenchymal Stem Cells on Poly (Propylene Carbonate) Graft. Artif Organs 2006; 30:898-905. [PMID: 17181830 DOI: 10.1111/j.1525-1594.2006.00322.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bone marrow mesenchymal stem cells (MSCs) have demonstrated their pluripotency to differentiate into different cell lineages and may be an alternative cell source for vascular tissue engineering. The objective of this study is to create small diameter vessels by seeding and culture of genetically modified MSCs onto a synthetic polymer scaffold produced by an electrospinning technique. A tubular scaffold (2 mm in diameter) with a microstructure of nonwoven fibers was produced by electrospinning of poly (propylene carbonate) (PPC). Rat MSCs obtained from bone marrow were expanded in culture and modified with vasculoprotective gene endothelial nitric oxide synthase (eNOS) or marker gene green fluorescent protein (GFP). These MSCs were seeded onto the electrospun fibrous grafts (internal diameter = 2 mm), and cultured in 5% CO(2) at 37 degrees C. The growth of MSCs in the scaffold was analyzed with scanning electron microscopy (SEM) and hematoxylin and eosin (H&E) staining. The gene transfer and transgenic gene expression were examined with fluorescence-activated cell sorting (FACS), immunochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR), and western blot. The production of nitric oxide (NO) by the engineered vessels was measured with an NO detection kit. Our data showed that the seeded cells integrated with the microfibers of the scaffold to form a three-dimensional cellular network, indicating a favorable interaction between this synthetic PPC scaffold with MSCs. High transduction efficiency was obtained with the use of concentrated retrovirus in the gene transfection of MSCs. The eNOS gene transcripts and protein were detected in the grafts seeded with eNOS-modified MSCs by RT-PCR and immunochemical staining. The amount of NO produced by grafts seeded with eNOS-modified MSCs was comparable to that produced by native blood vessels, and it was significantly higher than that in the grafts seeded with nonmodified MSCs. In summary, the vascular graft produced by culture of eNOS gene-modified MSCs onto the electrospun tubular scaffolds shows promising results in terms of function. The use of MSCs and therapeutic genes in tissue engineering of blood vessels could be helpful in improving vessel regeneration and patency.
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Affiliation(s)
- Jun Zhang
- The Key Laboratory of Bioactive Materials, Ministry of Education, College of Life Science, Nankai University, Tianjin. China
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Noh I, Choi YJ, Son Y, Kim CH, Hong SH, Hong CM, Shin IS, Park SN, Park BY. Diffusion of bioactive molecules through the walls of the medial tissue-engineered hybrid ePTFE grafts for applications in designs of vascular tissue regeneration. J Biomed Mater Res A 2006; 79:943-53. [PMID: 16941597 DOI: 10.1002/jbm.a.30872] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Strategies of better vascular tissue engineering may require delivery of soluble bioactive signals in cell culture medium to the cells in tissue-regenerating constructs. We measured the diffusivity and permeability of model tissue-engineering bioactive molecules such as water and heparin through the walls of both a hybrid ePTFE graft and a porcine carotid artery, a model vascular tissue. While diffusivities of H(3)-water and H(3)-heparin were measured as 3.9 x 10(-) (6) and 1.6 x 10(-) (6) cm(2)/s in the artery, respectively, under diffusional circulation of cell culture medium through the lumens of the carotid arteries, their corresponding permeabilities were 4.7 x 10(-) (5) and 2.0 x 10(-) (5) cm/s. On the other hand, diffusivities of H(3)-water and H(3)-heparin were also measured as 5.1 x 10(-) (6) and 4.7 x 10(-) (6) cm(2)/s, respectively, in the tissue-engineered hybrid ePTFE grafts; their corresponding permeabilities were 5.1 x 10(-) (5) and 3.7 x 10(-) (5) cm/s. The hybrid graft tissues were engineered by replacing the biodegradable, porous poly(lactide-co-glycolide) layers coated on the ePTFE surfaces with smooth muscle cell-derived tissues for 6 weeks. We analyzed the morphologies of the artery and the engineered hybrid ePTFE tissues with scanning electron microscopy and H&E stains. While the artery had its typical structure properties with layers of intima, media and adventitia, the tissue-engineered ePTFE hybrid graft had two layers of engineered tissues on the inner and outer surfaces of the ePTFE. There were no significant differences among the luminal tissue morphologies of the test samples from the effects of diffusion flow applications, with minor changes on their luminal surfaces. The results of water and heparin diffusion experiments indicated that these bioactive molecules were well transported from the cell culture medium to the tissue-engineering cells, enough to support tissue regeneration. We hope that these transport results may elucidate the transport behaviors of soluble nutrient molecules and biological signals through the vascular constructs under tissue engineering processes.
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Affiliation(s)
- Insup Noh
- Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung 2-Dong, Nowon-Gu, Seoul 139-743, Korea.
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Kuzuya A, Matsushita M, Oda K, Kobayashi M, Nishikimi N, Sakurai T, Komori K. Healing of Implanted Expanded Polytetrafluoroethylene Vascular Access Grafts with Different Internodal Distances: A Histologic Study in Dogs. Eur J Vasc Endovasc Surg 2004; 28:404-9. [PMID: 15350564 DOI: 10.1016/j.ejvs.2004.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2004] [Indexed: 11/20/2022]
Abstract
OBJECTIVE We assessed characteristics of healing, over time, of two types of expanded polytetrafluoroethylene grafts. STUDY DESIGN An experimental histological study in dogs. METHODS The graft types studied had the same internal diameter (5 mm) but different internodal distances. In one, the internodal distance was 60 microm in the external surface and 20 microm in the luminal surface. In the other, the internodal distance was 30 microm throughout the material. Sixteen grafts of each type were implanted between the femoral artery and vein in 16 dogs; explanted 1, 2, 4 or 12 weeks later; and examined histologically. RESULTS In both graft types, infiltrating-cell density and maximum cell-penetration depth increased significantly between 1 and 2 weeks after implantation, but no significant increases occurred after 2 weeks. The number of inflammatory cells peaked 1 week after implantation and decreased significantly by 2 weeks. Subsequently, there were no significant changes in inflammatory cell numbers, suggesting that the inflammatory phase was over by 2 weeks after implantation and the grafts had become attached to surrounding tissue. There were no significant differences between the two graft types in cell density, cell-penetration depth, or number of inflammatory cells at any assessment time. CONCLUSION Our results provide histologic support for guidelines recommending that synthetic vascular grafts for hemodialysis access should not be cannulated until 2 weeks after implantation. Since increasing the internodal distance to 60 microm in the external surface had no effect on graft healing, methods other than manipulation of internodal distance should be used in developing a graft suitable for early cannulation.
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Affiliation(s)
- A Kuzuya
- Division of Vascular Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Zhang Z, Wang Z, Liu S, Kodama M. Pore size, tissue ingrowth, and endothelialization of small-diameter microporous polyurethane vascular prostheses. Biomaterials 2004; 25:177-87. [PMID: 14580921 DOI: 10.1016/s0142-9612(03)00478-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Small-diameter microporous polyurethane vascular prostheses with an average pore size of between 5 and 30mum at the outer surfaces and 30mum at the luminal surface were prepared. Thirty-two PU and 8 expanded polytetrafluoroethylene (ePTFE) prostheses were implanted into the abdominal aorta of rats for periods ranging from 1 to 8 weeks. Harvested prostheses were analysed histologically and morphologically. The progress of endothelial-like cells and the extent of infiltration of perigraft tissues were quantified. All of the prostheses showed fast growth of endothelial-like cells in the second week, with the PU prostheses having an external pore size of 30mum producing the highest rate. It was also during the second week that perigraft tissue grew most significantly into the prosthetic structure. This coincident may suggest the importance of rapid tissue regeneration for the early endothelial healing. The role of the ingrowth perigraft tissues is likely to support and stabilize the neointima. The thickening of neointima was mainly located at the vicinity of the proximal anastomoses of some of the PU prostheses and was unrelated with the extent of perigraft tissue infiltration. In the PU prostheses, a complete lining of endothelial-like cells was achieved by the end of 4 weeks. Expanded PTFE prostheses displayed smooth, thin intima, very limited tissue ingrowth, and incomplete coverage of endothelial-like cells.
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Affiliation(s)
- Ze Zhang
- Département de chirurgie, Faculté de Médecine, Université Laval; Centre recherche de Hôpital Pavillon Saint-François d'Assise, CHUQ, 10, rue de l'Espinay, Local E0-165, Québec (QC), Canada G1V 3L5.
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Wang C, Zhang Q, Uchida S, Kodama M. A new vascular prosthesis coated with polyamino-acid urethane copolymer (PAU) to enhance endothelialization. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2002; 62:315-22. [PMID: 12209916 DOI: 10.1002/jbm.10137] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Clinically available synthetic ePTFE vascular grafts frequently fail when used for small-diameter arterial substitution. The lower long-term patency of ePTFE grafts is due mainly to thrombogenicity and poor healing. We developed a new small-diameter (1.5-mm) ePTFE vascular prosthesis coated with polyamino-acid urethane copolymer (PAU) to enhance endothelialization. Coating with PAU made the hydrophobic ePTFE vascular graft hydrophilic. Scanning electron microscopy (SEM) observation showed that PAU was homogeneously coated on the ePTFE graft while maintaining the graft's porous structure. Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectra showed PAU was present on graft inner surfaces. Noncoated and PAU-coated ePTFE vascular grafts were implanted into the rat abdominal aorta and evaluated within 1 week and at 8 weeks after implantation. We evaluated the extent of neoendothelialization by SEM, light microscopy, and immunohistochemical staining. Noncoated grafts showed partial endothelialization at proximal and distal areas of grafts but none at midsection. One-percent PAU-coated grafts showed incomplete neoendothelialization, but endothelial cells were observed in the midsection of grafts. Three-percent PAU-coated ePTFE grafts showed complete endothelialization with typical endothelial cell layers under SEM and histologic observation. Immunohistochemical staining also showed that an endothelial cell lining positively reacted with anti-von Willebrand factor (endothelial cell marker) antibody. We conclude that PAU-coated ePTFE vascular grafts enhance endothelialization.
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Affiliation(s)
- Chunren Wang
- 3-Dimensional Cell & Tissue Engineering Group, National Institute for Advanced Interdisciplinary Research, Agency of Industrial Science and Technology, 1-1-4 Higashi, Tsukuba, Ibaraki 305-8562, Japan
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Wong P, Hopkins S, Vincente D, Williams K, Macri N, Berguer R. Differences in neointima formation between impervious and porous polytetrafluoroethylene vascular patch material. Ann Vasc Surg 2002; 16:407-12. [PMID: 12132026 DOI: 10.1007/s10016-001-0163-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The aim of this study was to compare the neointima formation and blood loss of an impervious ePTFE with those of the porous ePTFE patch. Ten mongrel dogs were selected for the study. Both the impervious and porous ePTFE patches were implanted into the common iliac arteries in each dog. The blood loss of each patch was recorded and the patches were explanted 30-60 days later for microscopic analysis. The arteries with either the impervious or the porous ePTFE patch were all patent at the end of the study. The impervious ePTFE patch had a significant reduction in blood loss when compared with the porous ePTFE patch (p = 0.04). The neointima covering both patches showed no statistically significant difference in its thickness or in its cellular composition. It has been speculated that wall porosity is essential for tissue ingrowth, endothelial cell proliferation, and neointima formation. In this study, the impervious ePTFE patch did not inhibit neointima formation. Our study shows that graft porosity does not improve neointima formation or patency. Neointimization of the impervious ePTFE patch is the result of pannus ingrowth and deposition of circulating blood elements. There is a statistically significant reduction in blood loss (p = 0.04) with impervious ePTFE patch, compared with that of the porous ePTFE patch.
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Affiliation(s)
- Peter Wong
- Division of Vascular Surgery, Harper University Hospital, Wayne State University, Detroit, MI 48201, USA
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Abstract
Tissue engineering, using either polymer or biological based scaffolds, represents the newest approach to overcoming limitations of small diameter prosthetic vascular grafts. Their disadvantages include thromboembolism and thrombosis, anticoagulant related haemorrhage, compliance mismatch, neointimal hyperplasia, as well as aneurysm formation. This current review represents an overview about previous and contemporary studies in the field of artificial vascular conduits development regarding arterial and venous autografts, allografts, xenografts, alloplastic prostheses, and tissue engineering.
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Affiliation(s)
- Omke E Teebken
- Leibniz Research Laboratories for Biotechnology & Artificial Organs, LEBAO, Thoracic & Cardiovascular Surgery, Hannover Medical School, Hannover, Germany
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Catanese J, Cooke D, Maas C, Pruitt L. Mechanical properties of medical grade expanded polytetrafluoroethylene: the effects of internodal distance, density, and displacement rate. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2000; 48:187-92. [PMID: 10331912 DOI: 10.1002/(sici)1097-4636(1999)48:2<187::aid-jbm13>3.0.co;2-m] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Expanded polytetrafluoroethylene (e-PTFE) is used successfully in a multitude of biomedical and clinical applications. The success of this biomaterial is due to its microporous structure that allows biointegration for fixation, as well as overall mechanical integrity. The mechanical properties and degree of tissue ingrowth depend on the microstructure of the expanded polymer foam, yet little is known about the correlation of the internodal distance and other microstructural features with the monotonic tensile properties. Complete structure-property correlation can be used to provide invaluable knowledge for the design of biomedical devices. The purpose of this study was to investigate the monotonic tensile properties of e-PTFE over a range of medically relevant microstructural features and manufacturing parameters. The microstructural and manufacturing parameters considered were internodal distance, linear density, volumetric density, and reduction ratio. Additionally, the effect of displacement rate on mechanical properties was studied. We found that the ultimate stress and strain increased linearly with linear density (R2 = 0.88 and 0.67, respectively). Surprisingly, elastic modulus did not correlate with any parameter measured and only weak correlations were found between all properties and internodal distance. The yield and ultimate stresses increased with increasing displacement rate (R2 = 0.88 and 0.57, respectively). The findings from this study indicate that linear density is a better predictor of mechanical properties than internodal distance and may be the preferred parameter to control when specifying a material for implantation in load bearing situations.
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Affiliation(s)
- J Catanese
- Joint Bioengineering Graduate Group, University of California, Berkeley, USA
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Teebken OE, Bader A, Steinhoff G, Haverich A. Tissue engineering of vascular grafts: human cell seeding of decellularised porcine matrix. Eur J Vasc Endovasc Surg 2000; 19:381-6. [PMID: 10801371 DOI: 10.1053/ejvs.1999.1004] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVES To develop a biocompatible and mechanically stable vascular graft combining human cells and a xenogenic acellular matrix. DESIGN/MATERIALS: Decellularised matrix tubes were obtained by enzymatic cell extraction of native porcine aortas. Endothelial cells and myofibroblasts were isolated from human saphenous veins and grown in cell cultures. The inner surface of the tubes was seeded with endothelial cells or myofibroblasts and exposed to pulsatile flow. RESULTS After cell extraction, the absence of cellular components, as well as the maintenance of matrix integrity, was demonstrated by means of light microscopy and scanning electron microscopy. Furthermore, the porcine matrix was successfully seeded with human endothelial cells, which grew to a monolayer under flow conditions. Stable biomechanical properties were achieved at physiological perfusion pressures in vitro. CONCLUSIONS Cellular components can be extracted from native porcine blood vessels. Vascular grafts can be generated in vitro of animal acellular matrix and human cells.
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Affiliation(s)
- O E Teebken
- Leibniz Research Laboratories for Biotechnology and Artificial Organs, LEBAO, Hannover Medical School, Hannover, Germany
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Abstract
Experimental studies have reported that complete healing of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts occurs only if the porosity of the graft is increased, thereby allowing ingrowth of perigraft capillaries yielding endothelial cells. This study investigates the effects of varied graft porosity on the healing characteristics of 2-mm internal diameter (ID) ePTFE grafts interposed in the rabbit common carotid artery. Four groups were evaluated: Group A (n = 8) standard (30-microm pores) ePTFE grafts; Group B (n = 8) increased porosity (60-microm pores) ePTFE grafts; Group C (n = 8) standard ePTFE; and Group D (n = 8) 60-microm ePTFE external graft surface was externally coated with an impermeable layer of polyurethane. Patency was 100% for all groups at 8 weeks. At explantation, the neointima was composed of primarily modified smooth muscle cells. Endothelial cells were only identified at the perianastomotic region using the endothelial cell-specific antibody CD31. The impermeable external polyurethane coating of ePTFE grafts had no effect on neointima formation, regardless of porosity.
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Affiliation(s)
- M A Contreras
- Division of Vascular Surgery, Department of Cardiac Surgery, Beth Israel Deaconess Hospital / Childrens Hospital, Harvard Medical School, Boston, MA, USA.
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37
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Vermette P, Thibault J, Lévesque S, Laroche G. Lipid uptake across the wall of an expanded polytetrafluoroethylene vascular graft. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1999; 48:660-8. [PMID: 10490679 DOI: 10.1002/(sici)1097-4636(1999)48:5<660::aid-jbm9>3.0.co;2-p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Previous studies have shown that vascular grafts were prone to inducing an atherosclerosis-like phenomenon, thus possibly jeopardizing their performance. Furthermore, lipid retention, observed in most synthetic arterial prostheses explanted from humans, appears to have an important role in the progression of this atherosclerotic process, therefore hindering the healing process and neo-intima formation of these synthetic conduits. The current study examined lipid concentration profiles across prosthesis membranes exposed to lipid dispersion under various transmural pressures, flow rates, and durations of exposure. It was demonstrated that the lipids rapidly permeated the prosthesis membrane, as lipid advection increased to a maximum, then steadily decreased until the membrane became completely impermeable to the fluid. The concentration of lipids within the grafts was monitored using FT-IR microspectroscopy, then correlated as a function of time in order to evaluate the mass transfer coefficients and lipid saturation concentration. Lipid sorption, as a function of time, was described by a mechanism taking into account two first-order kinetic models. The lipids were first rapidly adsorbed onto the Teflon(R), potentially influenced by the strong affinity of these lipids for the highly hydrophobic polytetrafluoroethylene polymer. This affinity then enhanced the germination of the lipid deposits that filled in the prosthesis wall. For lipid retention as a function of the transmural pressure and flow rate, no clear tendency was established.
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Affiliation(s)
- P Vermette
- Department of Chemical Engineering, Laval University, Sainte-Foy, Québec, Canada, G1K 7P4
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38
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Müller-Mai CM, Gross UM. Histological and ultrastructural observations at the interface of expanded polytetrafluorethylene anterior cruciate ligament implants. JOURNAL OF APPLIED BIOMATERIALS : AN OFFICIAL JOURNAL OF THE SOCIETY FOR BIOMATERIALS 1999; 2:29-35. [PMID: 10149062 DOI: 10.1002/jab.770020105] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Anterior cruciate ligament (ACL) grafts made from expanded polytetrafluorethylene (ePTFE) were examined after failure (n = 7; 3 instabilities, 2 partial ruptures, and 2 complete ruptures) to provide information about secondary fixation mechanisms via ingrowth of the different tissues. The ultrastructural evaluation clearly evidenced the existence of two main interface areas of ePTFE ACL-replacement: First, in areas without a dense cellular infiltrate there was interdigitating collagen producing a dense ePTFE-collagen network. Additionally, in a few areas of the graft/bone-tunnel interface a fibrous cartilage or bone regenerate could be demonstrated to be in contact with the prosthesis. Second, there was a dense infiltration of macrophages and multinuclear giant cells, partially containing birefringent material of implant origin, with and without a neosynovia-like reaction product, indicating a disturbance of tissue integration of the prosthesis. In areas of inflammation there was no bone development and only few collagen interdigitation with the graft material. This study provides further knowledge about mechanisms of secondary graft fixation due to tissue ingrowth. The interdigitation of collagen fibers and ePTFE filaments provides interfaces which should be at least partially resistant against load.
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Affiliation(s)
- C M Müller-Mai
- Institute of Pathology, Free University of Berlin, Germany
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39
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Affiliation(s)
- D N Tatakis
- Department of Periodontics, School of Dentistry, Loma Linda University, California, USA
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40
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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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41
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Nishibe T, Manase H, Miyazaki K, Ohkashiwa H, Satoh Y, Watanabe S, Takahashi T, Katoh H, Okuda Y, Tanabe T. Portal vein reconstruction with conventional polytetrafluoroethylene grafts: an experimental study in dogs. Surg Today 1998; 28:391-5. [PMID: 9590703 DOI: 10.1007/s005950050147] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The purpose of this study was to examine the short- and long-term performance of conventional polytetrafluoroethylene (PTFE) grafts for portal vein reconstruction. The grafts were placed as a portal vein replacement in 11 mongrel dogs. At 1 month and 6 months, the grafts were then retrieved and examined for patency, while also undergoing a pathological analysis. During the observation period (at 55 days), one dog died of an unknown cause with a patent graft. The patency rates of the other 10 grafts were 83% (5/6) at 1 month and 100% (4/4) at 6 months. However, the neointima formation was incomplete even 6 months after implantation. In conclusion, although conventional PTFE grafts may be used as a synthetic alternative to autogenous vein grafts, every effort should be made to use autogenous vein grafts before considering conventional PTFE grafts.
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Affiliation(s)
- T Nishibe
- Second Department of Surgery, Hokkaido University School of Medicine, Sapporo, Japan
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42
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Dolmatch BL, Dong YH, Trerotola SO, Hunter DW, Brennecke LH, LaBounty R. Tissue response to covered Wallstents. J Vasc Interv Radiol 1998; 9:471-8. [PMID: 9618109 DOI: 10.1016/s1051-0443(98)70302-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
PURPOSE To evaluate and compare the healing response related to two types of graft-covered Wallstents (WSs) and an uncovered WS in the canine iliac artery. MATERIALS AND METHODS Eight bare mesh WSs, 10 polyethylene terephthalate interbraided WSs (PET-WSs), and six polytetrafluoroethylene covered WSs (ePTFE-WSs) were placed in the iliac arteries of 12 dogs. Arteriograms were obtained before and after implantation and at explantation. Devices were explanted at 1 month (n = 8), 3 months (n = 6), and 6 months (n = 10) and sent for histologic study. RESULTS One ePTFE-covered stent-graft was found to be thrombosed at 3 months; the remaining 23 of 24 implants remained patent to the time of explantation. The WS and ePTFE-WS both generated a uniform myointimal cell response without inflammation. The PET-WS induced a fibrous luminal response with substantial foreign body-type inflammatory reaction around the PET fibers. Although neointima associated with the PET-WS appeared thicker than that associated with either the ePTFE-WS or the bare WS, none of the patent implants developed greater than 50% angiographic narrowing. CONCLUSION The PET-WS induced chronic inflammation, a response not seen with either the WS or ePTFE-WS. This may explain the occurrence of pain and/or fever in human studies of arterial PET endoluminal stent-grafts. Patency for all three implants was excellent in this model.
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Affiliation(s)
- B L Dolmatch
- Department of Radiology, Cleveland Clinic Foundation, OH 44195, USA
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43
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Jakobsen HL, Baekgaard N, Christoffersen JK. Below-knee popliteal and distal bypass with PTFE and vein cuff. Eur J Vasc Endovasc Surg 1998; 15:327-30. [PMID: 9610345 DOI: 10.1016/s1078-5884(98)80036-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVES To determine the value of PTFE grafts with a distal vein cuff as a conduit for below-knee (BK) popliteal and distal bypass in the absence of autologous vein. DESIGN Retrospective study. MATERIALS AND METHODS Forty below BK popliteal and distal bypass procedures in 39 patients with PTFE and distal vein cuff (Miller cuff n = 31, Wolfe cuff and adjuvant arteriovenous fistula n = 9). Nineteen primary and 21 secondary reconstruction procedures. RESULTS The primary patency rate was 62.5% at 1 year falling to 50% at 2 years. The secondary patency rates were very similar owing to poor outcome of thrombectomy. Ten cases (25%) resulted in major amputation postoperatively. There was a tendency towards better outcome for primary procedures compared to secondary/redo procedures. CONCLUSIONS BK popliteal and distal bypass with PTFE and distal vein cuff is a worthwhile procedure in the absence of autologous vein. The value of thrombectomy following thrombosis of a secondary bypass procedure with PTFE and distal vein cuff is questionable.
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Affiliation(s)
- H L Jakobsen
- Vascular Section, Gentofte University Hospital, Denmark
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44
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Ariyoshi H, Okuyama M, Okahara K, Kawasaki T, Kambayashi J, Sakon M, Monden M. Expanded polytetrafluoroethylene (ePTFE) vascular graft loses its thrombogenicity six months after implantation. Thromb Res 1997; 88:427-33. [PMID: 9556231 DOI: 10.1016/s0049-3848(97)00278-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Although expanded polytetrafluoroethylene (ePTFE) has been believed to be an inert material for vascular prosthesis, it shows less tendency of graft maturation by means of endothelialization. The aim of this study is to evaluate long-term alteration in thrombogenicity of ePTFE grafts after implantation. Serial levels of thrombin-antithrombin III complex (TAT), D-dimer, C-reactive protein (CRP), and prothrombin time (PT) were examined in 77 patients following ePTFE Y-graft implantation for up to five years. TAT showed biphasic elevation after implantation; TAT increased from 16.4+/-8.6 ng/ml to 27.4+/-10.5 ng/ml at one day, decreased to 18.5+/-4.5 ng/ml at one week, and increased again to 25.3+/-8.5 ng/ml at two weeks. Elevated TAT gradually decreased after the second peak to reach a lower level than that before surgery after six months. There was no significant difference in TAT level after six months due to the difference in diagnosis or anti-thrombotic therapy. We suggest that ePTFE grafts lose their thrombogenicity six months after implantation, after which anti-thrombotic therapy might be unnecessary.
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Affiliation(s)
- H Ariyoshi
- Department of Surgery II, Osaka University Medical School, Suita, Japan
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45
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Bacourt F. Prospective randomized study of carbon-impregnated polytetrafluoroethylene grafts for below-knee popliteal and distal bypass: results at 2 years. The Association Universitaire de Recherche en Chirurgie. Ann Vasc Surg 1997; 11:596-603. [PMID: 9363305 DOI: 10.1007/s100169900097] [Citation(s) in RCA: 27] [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
The purpose of this prospective randomized multicenter study is to compare patency for a new carbon-impregnated polytetrafluoroethylene (PTFE) graft and standard PTFE grafts. One hundred and sixty patients presenting severe chronic ischemia of the lower extremity were recruited at 17 centers of the French Association Universitaire de Recherche en Chirurgie. Eighty-one carbon-impregnated graft and 79 standard grafts were implanted. The procedure consisted of below-knee femoropopliteal bypass in 83 cases and femorodistal bypass in 77 cases. The minimum duration of the follow-up period was 2 years. Twenty-four patients died during the study. The actuarial primary patency rate, actuarial secondary patency rate, and limb salvage rate were 45%, 53%, and 57% respectively in the carbon-impregnated PTFE group and 35%, 36%, and 47% respectively in the standard PTFE group. The carbon-impregnated graft appeared to achieve better patency than the standard graft but the difference was not statistically significant. Since there was no difference up to 12 months, the study will be continued to determine if further follow-up confirms these findings. In this study we also assessed factors contributing to patency of below-knee prosthetic bypass grafts. Only two factors had a significant influence on patency, i.e., ankle/arm pressure difference greater than 0.25 as opposed to ankle/arm pressure difference less than 0.25 (p < 0.01) and below-knee femoropopliteal bypass as opposed to femorodistal bypass (p < 0.001).
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Affiliation(s)
- F Bacourt
- Département de Chirurgie Vasculaire, Hôpital Américain, Neuilly-sur-Seine, France
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46
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Nishibe T, Satoh Y, Iwashiro N, Hirano S, Ohtake S, Ohkashiwa H, Watanabe S, Katoh H, Okuda Y, Tanabe T. Expanded polytetrafluoroethylene grafts for portal vein replacement: use of omentum wrap to promote graft healing. Surg Today 1997; 27:149-53. [PMID: 9017993 DOI: 10.1007/bf02385905] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This study was designed to reexamine the healing process of expanded polytetrafluoroethylene (EPTFE) grafts with standard porosity (30 microm) and high porosity (60 microm) in portal vein replacement, and to evaluate the effect of an omentum wrap, which has certain functions that promote healing, on graft healing. These grafts, either wrapped by the omentum or not, were placed as portal vein replacements in 24 mongrel dogs. After 1 month, the grafts were retrieved and examined for patency, thrombus-free areas, thickness of the pseudointima, and the total number of cells growing into the graft wall. There were no statistical differences in the patency rates. The high-porosity grafts had a significantly larger thrombus-free area, a thicker pseudointima, and a larger growth of cells than the standard-porosity grafts. The omentum wrap significantly increased the thrombus-free area and stimulated a larger growth of cells in both grafts. The high-porosity grafts plus omentum demonstrated a thrombus-free area of 82.2% vs 27.3% in the standard-porosity grafts. In addition, the migration of fibroblasts and macrophages was most evident in the high-porosity grafts wrapped by the omentum. In conclusion, graft healing enhancement was observed in the high-porosity EPTFE grafts wrapped by the omentum. It is thus suggested that transmural cellular migration plays an important role in the process of graft healing.
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Affiliation(s)
- T Nishibe
- Second Department of Surgery, Hokkaido University School of Medicine, Chuo-ku, Sapporo, Japan
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47
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Sabanegh ES, Downey JR, Sago AL. Long-segment ureteral replacement with expanded polytetrafluoroethylene grafts. Urology 1996; 48:312-6. [PMID: 8753750 DOI: 10.1016/s0090-4295(96)00185-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Traumatic loss of significant lengths of ureter all too often results in nephrectomy when vascularized pedicles of bowel or bladder fail or are not available for substitution. Historically, alloplastic replacement of ureters has failed due to obstruction, bioincompatibility, or graft migration. This study was undertaken to test the performance of ringed expanded polytetrafluoroethylene (PTFE) tube grafts as ureteral replacements in a canine model. METHODS Eight female dogs underwent partial ureteral replacement with ringed PTFE tube grafts. An involuting anastomosis was used to anchor the graft to the bladder. The dogs were followed with intravenous urograms and Whitaker infusion pressure tests for up to 12 months. RESULTS Six of 8 animals (75%) had preservation of excellent renal function with normal intravenous urograms and low Whitaker infusion pressures. One animal had mild hydronephrosis with an elevated infusion pressure. One animal died of spontaneous renal rupture secondary to obstruction at the ureteral-graft anastomosis. All other grafts were patent by histologic examination without encrustation or infection. CONCLUSIONS Although not suggested as first-line therapy after ureteral loss, expanded PTFE may have a use as a prosthetic ureteral replacement in situations where conventional surgical therapies are unsuccessful. This material appears to be biocompatible, and the technique of bladder anastomosis described here prevented migration of the prosthesis.
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Affiliation(s)
- E S Sabanegh
- Department of Urology, Wilford Hall Medical Center, Lackland Air Force Base, TX 78236-5300, USA
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48
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Matsuda T, Nakayama Y. Surface microarchitectural design in biomedical applications: in vitro transmural endothelialization on microporous segmented polyurethane films fabricated using an excimer laser. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1996; 31:235-42. [PMID: 8731212 DOI: 10.1002/(sici)1097-4636(199606)31:2<235::aid-jbm10>3.0.co;2-k] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We describe the preparation of segmented polyurethane (SPU) films with round micropores and present a quantitative assay method of endothelial cell (EC) migration through micropores of and growth on microprocessed SPU films as an in vitro model of transmural endothelialization in open-cell-structured small-diameter vascular grafts. The micropored films, pores of which ranged from 9 to 100 microns in diameter, were microfabricated using an excimer laser. Time-dependent processes of EC ingrowth through micropores of SPU films with different pore sizes, which have a confluent monolayer sheet on one face and are cell free on the other, and subsequent endothelialization were quantitatively studied. The circular cellular sheet centered at the micropores expanded as incubation proceeded. Markedly retarded migration was found for the smallest pore size (9 microns in diameter). The larger the pore, the higher was the endothelialization rate. The endothelialization characteristics were studied on multiply microspored films of different pore sizes and densities, each of which was prepared so as to provide a fixed total pore area per unit area (0.01 mm2 per mm2). The highest endothelialization rates in an early incubation period were found on films with microspores between 18 and 50 microns in diameter.
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Affiliation(s)
- T Matsuda
- Department of Bioengineering, National Cardiovascular Center Research Institute, Osaka, Japan
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49
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Renard G, Cetinel B, Legeais JM, Savoldelli M, Durand J, Pouliquen Y. Incorporation of a fluorocarbon polymer implanted at the posterior surface of the rabbit cornea. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1996; 31:193-9. [PMID: 8731207 DOI: 10.1002/(sici)1097-4636(199606)31:2<193::aid-jbm5>3.0.co;2-i] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
An implant of porous expanded polytetrafluoroethylene (PTFE) in the corneal stroma allows fast cell colonization and can become translucent. We studied the behavior of the same polymer implanted in the anterior chamber of the rabbit eye and sutured to the posterior surface of the cornea. The expanded tetrafluoroethylene was provided as 200-micron thick sheets in 3 pore diameters (20, 50 and 80 microns). Disks (5 mm) were implanted in the anterior chambers of 20 rabbits and sutured to the posterior surface of the cornea. Histological and ultrastructural studies were performed after 3 and 4 months. Quantimetry was done on TEM images to analyze the fibrillar structure of the intercellular matrix inside and around the implanted polymer. The material was well tolerated. In all cases there was mild central corneal edema, which disappeared after 1 month. Mild neovascularization occurred in five cases, decreasing after 1 month. The polymer became translucent after 8 days. Keratocytes from the corneal stroma colonized the implant via breaks in the Descemet's membrane along the sutures. Quantimetry showed three types of fibrils inside and beside the polymer. Corneal endothelial cells regenerated over the fibroblasts and the polymer. This fluorocarbon polymer implanted in the anterior chamber and sutured to the posterior surface of the cornea was well tolerated, and there was real incorporation, with keratocytes producing collagen fibrils inside the polymer and endothelial cells forming a posterior cell monolayer. This is promising for the development of a keratoprothesis with posterior fixation.
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Affiliation(s)
- G Renard
- Service d' Ophtalmologie, Hôtel Dieu, Paris, France
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50
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Shibuya T, Kambayashi J, Kim DI, Kawasaki T, Shiba E, Sakon M, Mori T. Pseudointimal hyperplasia of ridged outer wall polytetrafluoroethylene vascular prostheses. Surg Today 1996; 26:333-9. [PMID: 8726618 DOI: 10.1007/bf00311602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In addition to the polytetrafluoroethylene (PTFE) vascular graft (G) with its conventionally smooth surface, a unique PTFE graft with a ridged outer wall (T) is now also currently available for clinical use. Although an excellent antikinking property is provided by this unique outer structure, the possible influence of the structure on the formation of pseudointima has not yet been investigated in detail. Four kinds of T grafts (3 mm inner diameter, 3 cm long) with various fibril lengths (FL, T-15, T-30, T-60, T-90) and a G graft with 30 microns FL (G-30) were implanted into the inferior vena cava of rabbits. The patency of the grafts at 4 weeks were as follows: 6/8(T-15), 6/8(T-30), 5/8(T-60), 0/8(T-90) and 4/6 (G-30). Pseudointimal hyperplasia (PH) of the T grafts advanced as the FL increased, judging by the thickness of the pseudointima, cellular density, and maturity of fibroblasts. In addition, the maturity of endothelial-like cells on the luminal surface increased as the FL increased. The degree of pseudointimal hyperplasia in G-30 was comparable to that of T-15, although the maturity of the endothelial-like cells was similar to that of T-60. Microscopically, there was a micro-heterogeneity of cellular density in T grafts probably due to the uneven outer structure. In conclusion, not only FL but also the outer structure of PTFE may thus influence the formation of the pseudointima.
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Affiliation(s)
- T Shibuya
- Second Department of Surgery, Osaka University Medical School, Japan
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