Influence of fibril length upon ePTFE graft healing and host modification of the implant

Hirabayashi, Kunihiko; Saitoh, Eiichi; Ijima, H; Takenawa, T.; Kodama, Makoto; Hori, Motokazu

doi:10.1002/jbm.820261104

Cited by 55 publications

(43 citation statements)

References 11 publications

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“…Since Wesolowski et al described porosity as a primary determinant of the ultimate fate of synthetic grafts more than three decades ago, 15 many studies have been directed at elucidating the significant role of porosity in neoarterial regeneration and intimal hyperplasia. It has been reported that an increase in pore size or internodal distance increased the degree of transmural tissue ingrowth, resulting in an increase in neoarterial wall thickness, 17 hydroxyproline content (as a measure of collagen production), 18 endothelial coverage, 19 and patency rate. 15 It also has been reported that transmural tissue ingrowth often is accompanied by capillaries or microvessels from which ECs are recruited.…”

Section: Discussionmentioning

confidence: 99%

Significance of porosity and compliance of microporous, polyurethane-based microarterial vessel on neoarterial wall regeneration

Doi

Matsuda

1997

J. Biomed. Mater. Res.

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The microporous structure of artificial vascular grafts, which increases compliance and porosity simultaneously, may enhance neoarterial regeneration. In order to differentiate these effects, three models of segmented polyurethane grafts (inner diameter, 1.5 mm; wall thickness, 100 microns) with or without micropores fabricated using an excimer laser ablation technique, were prepared, and their neoarterial regenerative potentials were studied upon implantation: Model I (microporous, permeable, compliant); Model II (smooth-surfaced, impermeable, compliant); and Model III (smooth-surfaced, impermeable, noncompliant). In Models I and II, the pore or groove size (diameter, 100 microns) and pore or groove arrangement were fixed, and consequently their compliances were almost identical. Irrespective of model, the luminal surfaces were coated with benzophenone-derivatized gelatin and subsequently photocured. Twenty grafts (length, 20 mm) of each model were implanted in the aortas of rats. Predetermined implantation periods were 4, 12, and 24 weeks. Total patency rate decreased in the order Model I (100%), II (87%), and III (59%) grafts. All patent grafts were completely endothelialized after 12 weeks of implantation, irrespective of model. After 12- and 24-week implantations, in Model I grafts, the neoarterial wall was thin, and smooth muscle cells (SMCs) were of the contractile phenotype. In Model II grafts, the neoarterial wall exhibited considerable thickening. In Model III grafts, the neoarterial wall exhibited marked thickening, and SMCs were of the synthetic phenotype. The neoarterial wall thickness at the midportion of the grafts after 24 weeks of implantation increased in the order Model I (48 +/- 8 microns), II (146 +/- 87 microns), and III (385 +/- 21 microns) grafts. These results strongly suggest that compliance matching and porosity synergistically resulted in neoarterial wall restoration without appreciable thickening.

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Section: Discussionmentioning

confidence: 99%

Significance of porosity and compliance of microporous, polyurethane-based microarterial vessel on neoarterial wall regeneration

Doi

Matsuda

1997

J. Biomed. Mater. Res.

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“…[11][12][13][14][15] With expanded polytetrafluoroethylene (ePTFE), the internodal distance is considered the measure of porosity and is thought to be a major factor influencing cell invasion. However, this internodal space is filled with fibers, which could be even more important in the determination of cellular migration through the polymer.…”

Section: Introductionmentioning

confidence: 99%

The effects of porosity on endothelialization of ePTFE implanted in subcutaneous and adipose tissue

Salzmann

Kleinert

Berman

et al. 1997

J. Biomed. Mater. Res.

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Healing of biomaterial implants varies depending on the type and structure of material and the tissue surrounding the implant. In this study we examined structural differences of 30 microm, 60 microm, and 100 microm expanded polytetrafluoroethylene (ePTFE) using scanning electron microscopy, and we also investigated differences in healing for these three different porosity ePTFE grafts implanted within subcutaneous tissue and adipose tissue. Scanning electron microscopic examination of 30 microm, 60 microm, and 100 microm ePTFE revealed structural differences and differences in fiber density within the internodal space. Circular patches (6 mm in diameter) of 30 microm ePTFE were implanted within subcutaneous tissue and epididymal fat pads of male Sprague-Dawley rats. After 5 weeks, the implants were removed and analyzed for fibrous capsule formation, endothelialization, and for activated monocytes and macrophages in association with the material. Histological evaluation revealed dense fibrous capsule formation surrounding only the 30 microm ePTFE subcutaneous implants. From immunohistochemistry data obtained, we generated an Endothelialization Index (measure of neovascularization) and a Monocyte/Macrophage Index (measure of inflammatory response) for each sample. Consistently, 60 microm ePTFE had the greatest Endothelialization Index at both implant sites while 100 microm ePTFE generally had the largest values for the Monocyte/Macrophage Index. These data indicate that both the structure of the material and the site of implant influence the healing characteristics of ePTFE and suggest that activated monocytes and/or macrophages associated with the implant may inhibit endothelialization of ePTFE.

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“…They observed the highest, second highest, and third highest patency rates in the 90-, 120-, and 60-Ìm grafts, respectively. Thereafter, several laboratories including ours revisited the relationship of internodal distance to graft healing [9][10][11][12]. They reported that ePTFE vascular grafts with a greater internodal distance resulted in better graft healing as compared to conventional ePTFE vascular grafts.…”

Section: Discussionmentioning

confidence: 99%

“…They suggested that there appeared to be an optimal internodal distance near 60 Ìm, since the 10-to 30-Ìm grafts failed to achieve luminal endothelial cell coverage and the 90-Ìm grafts exhibited instability of the pseudointima with focal endothelial cell loss. In 1992 Hirabayashi et al [10] determined the dependence of neoendothelial healing, cellular response, and biocompatibility on the internodal distance of ePTFE vascular grafts in rats. They suggested that the 60-Ìm grafts were the best choice out of 20-, 40-, 60-, and 90-Ìm grafts in terms of endothelial healing, collagenesis, and cellular ingrowth.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Node-Fibril Morphology on Healing of High-Porosity Expanded Polytetrafluoroethylene Grafts

Miura

Nishibe²,

Yasuda³

et al. 2002

Eur Surg Res

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Purpose: To manufacture high-porosity expanded polytetrafluoroethylene (ePTFE) vascular grafts with the same internodal distance but different node-fibril morphology, and to evaluate their biologic behaviors in a canine carotid artery implantation model. Materials and Methods: Several types of high-porosity ePTFE vascular grafts with the same inside diameter (4 mm) and wall thickness (650 µm) were manufactured under different heating, stretching conditions. The luminal surface and cross section of the grafts were photographed by scanning electron microscopy and the node-fibril structure was examined. Two typical types of high-porosity ePTFE vascular grafts were then selected and proceeded to an animal study. The test grafts were explanted after an interval of 12 weeks and subjected to histomorphometric analyses. Results: The following two types of high-porosity ePTFE vascular grafts were selected; one had a through-pore structure extending from the outer to the inner surface and the other had a random-node architecture with tortuous path channels extending from the outer to the inner surface. The histomorphometric analyses of thrombus-free surface, thickness of pseudointima, cellular ingrowth, capillary ingrowth, and cellular proliferation revealed no significant differences between the grafts. Conclusion: In high-porosity ePTFE vascular grafts, graft healing enhanced by transmural tissue ingrowth may be not largely dependent on node-fibril morphology. This knowledge will be helpful to design a new type of high-porosity ePTFE vascular grafts available for clinical use.

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Influence of fibril length upon ePTFE graft healing and host modification of the implant

Cited by 55 publications

References 11 publications

Significance of porosity and compliance of microporous, polyurethane-based microarterial vessel on neoarterial wall regeneration

Significance of porosity and compliance of microporous, polyurethane-based microarterial vessel on neoarterial wall regeneration

The effects of porosity on endothelialization of ePTFE implanted in subcutaneous and adipose tissue

The Influence of Node-Fibril Morphology on Healing of High-Porosity Expanded Polytetrafluoroethylene Grafts

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