In vivo study of a model tissue‐engineered small‐diameter vascular bypass graft

Abstract

Conventionally used vascular grafts such as polyester (Dacron) or expanded polytetrafluoroethylene perform inadequately as small-diameter vascular bypass grafts (SDBGs). SDBGs, which can maintain long-term patency and those that could potentially evolve with the somatic growth, are highly desirable in vascular surgery and thus research into tissue-engineered blood vessels (TEBVs) is of keen interest. A TEBV was developed by seeding endothelial cells onto a collagen matrix that was cross-linked and contracted by smooth muscle cells (SMCs). A polyester graft served as a scaffold. Recovery studies (12 TEBVs and seven controls) were carried out to assess in vivo endothelialization and long-term patency of TEBVs. Hemodynamic observations indicated para-anastomotic turbulences and high shear stress at anastomosis. Recovery studies demonstrated confluent endothelialization, thrombus-free surfaces, and patent TEBVs in all cases. Graft incorporation and neovascularization of the scaffold occurred in both hybrid and control grafts. However, thickened neointima formation occurred in TEBV grafts, which was most likely caused by the rigidity of polyester scaffold. Significant perigraft inflammatory changes could be observed in both TEBVs and control grafts at 1, 4, and 8 weeks. In conclusion, the TEBVs demonstrated satisfactory performance as an infra-renal-aortic graft in a porcine model. The TEBV serves as a promising model and facilitates the development of a TEBV in a clinical setting, potentially with human stem cells and with more biocompatible, biodegradable scaffolds that are mechanically more compliant with natural vessels.

Effect of fibroin sponge coating on in vivo performance of knitted silk small diameter vascular grafts

“…They are serious problems especially for small diameter artificial vascular grafts. [22][23][24][25][26] To improve graft patency, thrombus formation and neointimal hyperplasia should be controlled. Early stage endothelialisation offers a potential solution.…”

Physiologically Modeled Pulse Dynamics to Improve Function inIn Vitro-Endothelialized Small-Diameter Vascular Grafts

“…Specifically, EC denudation at reperfusion, and an inappropriate ''wound'' state are characterized by EC upregulation of pro-inflammatory or thrombotic genes, leading to an increased potential for graft occlusion. [37][38][39] Our working hypothesis is that through exposure to appropriate fluid pulse and shear conditioning in vitro, EC will adopt a functional state that is more resilient to arterial hemodynamics and with reduced potential for early inflammatory and thrombotic events. 31 Whether engineering fully cellular constructs or seeding EC alone, denudation of EC-seeded grafts due to shear exposure has been a significant problem limiting the success of in vitro endothelialization, and the outcomes of the two-stage seeding method would likely be improved by increasing the resistance of seeded cells to hemodynamic stresses.…”

Stem cells for tissue engineered vascular bypass grafts

“…Bovine vessels were then cultured under pulsatile conditions, which had rupture strengths greater than 2000 millimeters of mercury, high suture retention strengths and collagen content (Niklason et al 1999). Another type of TEVGs were generated by the contraction and compaction of collagen type I by porcine aortic SMCs onto a compliant polyester graft scaffold (Baguneid et al 2004(Baguneid et al , 2011. Furthermore, ECs attachment and resistance to shear stress was enhanced by incorporating a period of shear stress preconditioning at 10-20 lN/cm 2 , as well as by surface modification with fibronectin (FN) and collagen to mimic endogenous ECM (Baguneid et al 2004).…”