[Show abstract][Hide abstract] ABSTRACT: We sought to fabricate a compliant engineered vascular graft (inner diameter of approximately 4.5 mm and length of 6 cm) lined with endothelial progenitor cells derived from circulating peripheral canine blood and to verify its nonthrombogenicity potential in vivo.
Autologous circulating endothelial progenitor cells derived from the peripheral veins of 6 adult mongrel dogs were isolated by using a density gradient method. The cells were proliferated in vitro in EGM-2 culture medium, prelined on the luminal surface of in situ-formed collagen type I meshes as an extracellular matrix, and wrapped with a segmented polyurethane thin film with multiple micropores as a compliant scaffold. After canine carotid arteries were bilaterally implanted with these grafts for 1 and 3 months, microscopic observation, histologic staining, and immunochemical staining were performed to evaluate morphogenesis.
After 33.3 +/- 10.5 days of culture in vitro, 4.2 +/- 1.2 x 10(6) endothelial progenitor cells were obtained. Eleven of the 12 engineered vascular grafts were patent. The grafts possessed smooth, glistening, and ivory-colored luminal surfaces at the predetermined observation period up to 3 months. The intimal layer was covered with confluent, cobblestone-like monolayered cells that were positively stained with factor VIIIB-related antigen. The thickness of the neoarterial walls was approximately 300 microm at 3 months after implantation. A few smooth muscle cells were observed in the medial tissue, and fibroblasts dominated the adventitial tissue.
Circulating endothelial progenitor cells could be a substitute source of endothelial cells for endothelialization on small-diameter-vessel prostheses to ensure nonthrombogenicity.
Preview · Article · Sep 2003 · Journal of Thoracic and Cardiovascular Surgery
[Show abstract][Hide abstract] ABSTRACT: In this article, we show that human endothelial progenitor cells (EPCs) in circulating peripheral blood may be a novel cell source for a cell-incorporated engineered vascular graft. Cultures of human peripheral blood mononuclear cells collected by the density gradient technique developed highly proliferative EPC colonies, which expanded with culture time. The production rates of antiplatelet substances such as endothelial-type nitric oxide synthase and 6-keto-prostaglandin-F(1)-alpha were approximately one-third and approximately one-half of those of mature endothelial cells (ECs), respectively. On the other hand, the tissue-type plasminogen activator production rate of EPCs was almost the same as that of ECs. EPCs were seeded and cultured on a small-diameter compliant graft (inner diameter, 1.5 mm) made of microporous segmented polyurethane film coated with a photo-reactive gelatin layer, and subsequently subjected to hydrodynamic shear stress by ex vivo circulation. EPCs fully covering the graft elongated and aligned themselves with the direction of the flow, resulting in the production of an integrated EPC-engineered graft. These results indicate that EPCs, which have high proliferative potential and high antithrombogenic potential, comparable to those of ECs, are a suitable cell source for cardiovascular tissue engineering.
No preview · Article · Mar 2003 · Tissue Engineering
[Show abstract][Hide abstract] ABSTRACT: Two types of hybrid vascular grafts were hierarchically structured with an autologous smooth muscle cell (SMC)-inoculated collagen gel layer and an endothelial cell (EC) monolayer, and wrapped with different elasomeric scaffolds. Type A graft was wrapped with poly(urethane)-nylon mesh, and type B graft was wrapped with an excimer laser-directed microporous segmented polyurethane (SPU) film as the scaffold. Type A graft was more compliant than canine carotid arteries, whereas compliance of type B graft was close to that of native arteries. After implantation into canine carotid arteries for 1 month, all type A grafts were dilated due to loosening of the mesh, resulting in loss of prelined ECs and thrombus formation. In contrast, type B grafts developed a well-organized neoarterial wall composed of a confluent EC monolayer and SMC-resided medial tissue, resulting in only slightly appreciable thrombus and minimal tissue ingrowth 6 months after implantation. Compliance of type B graft was reduced at 6 month's implantation, which is mostly due to encapsulated connective tissue formed around the graft.
No preview · Article · May 2002 · Tissue Engineering
[Show abstract][Hide abstract] ABSTRACT: The object of this study was to develop a compliant hybrid vascular graft minimally supported by an elastomeric scaffold for arterial replacement. The hybrid vascular grafts designed were composed of three layers: an inner surface lined with endothelial cells (ECs); a hybrid medial tissue composed of a collagenous gel embedded with smooth muscle cells (SMCs); and an outer layer made of a laser-processed micropored segmented polyurethane (SPU) film with the circular pore size (diameter 150 microm) but different film thickness (50-200 microm) and different pore-to-pore distances (1 or 4 mm). The approximate dimensions of the hybrid vascular graft without the SPU film were as follows: inner diameter, 5 mm; length, 5 cm; thickness, 50 microm. The intraluminal pressure-external diameter relationship was measured by infusion of a phosphate buffer solution into the hybrid vascular graft. Canine carotid arteries and commercially available ePTFE grafts served as controls. Decrease in the thickness of the SPU film and increase in the pore density of the SPU film increased the pressure-dependent distensibility of the hybrid vascular grafts. The thinner the film and higher the pore density, the more compliant was the hybrid graft. The pressure-induced distensibility of the designed hybrid graft was found to be close to that of native carotid arteries.
No preview · Article · Feb 2002 · Cell Transplantation
[Show abstract][Hide abstract] ABSTRACT: Hierarchic structured hybrid tubular vascular media composed of endothelial cells (ECs), which covered the luminal surface, and smooth muscle cells (SMCs), which resided in the tubular collagen gel, were wrapped with thin segmented polyurethane elastomeric films designed to provide compliance matching with native arteries and transmural tissue permeability using a laser-directed ablation technique to provide different pore densities. Two hybrid grafts with high and low pore densities (inner diameter: 150 microm and length: 4 cm), and exhibiting pressure-dependent distensibility in response to pulsatile pressure, were bilaterally implanted into canine common arteries for up to 6 months. Irrespective of the pore density, high patency was achieved and no dilation and bursting occurred. Maintenance of full endothelialization during the entire course of implantation period was observed for the graft wrapped with the film with higher pore density. On the other hand, the graft wrapped with the film with lower pore density exhibited markedly reduced endothelialization at a later period of implantation, probably due to delamination of neoarterial tissue from the segmented polyurethane (SPU) surface. There were some differences in transmural tissue ingrowth between the two grafts. At anastomotic sites, neoarterial thickness for type A graft was smaller than that for type B graft regardless of the implantation period. Slightly reduced compliance was observed for both types of grafts at the sixth month of the implantation period. This study indicates that a hybrid vascular graft minimally supported with a thin elastomeric film can be used to replace diseased arteries if micropores are well designed for tissue permeability and anchoring.
No preview · Article · Feb 2002 · Cell Transplantation