Rapid Perfusion and Network Remodeling in a Microvascular Construct After Implantation

Abstract

Objective-We have previously demonstrated the ability to construct 3-dimensional microvascular beds in vitro via angiogenesis from isolated, intact, microvessel fragments that retain endothelial cells and perivascular cells. Our objective was to develop and characterize an experimental model of tissue vascularization, based on the implantation of this microvascular construct, which recapitulated angiogenesis, vessel differentiation, and network maturation. Methods and Results-On implantation in a severe combined-immunodeficient mouse model, vessels in the microvascular constructs rapidly inosculated with the recipient host circulation. Ink perfusion of implants via the left ventricle of the host demonstrated that vessel inosculation begins within the first day after implantation. Evaluation of explanted constructs over the course of 28 days revealed the presence of a mature functional microvascular bed. Using a probe specific for the original microvessel source, 91.7%Ϯ11% and 88.6%Ϯ19% of the vessels by day 5 and day 28 after implantation, respectively, were derived from the original microvessel isolate. Similar results were obtained when human-derived microvessels were used to build the microvascular construct. Key Words: vascularization Ⅲ microcirculation Ⅲ angiogenesis Ⅲ human Ⅲ vascular remodeling V ascularization is the process by which perfusion pathway length and vessel segment number are increased and organized into a functional vascular bed. In normal situations, this effective increase in vessel density delivers more blood to the tissue, facilitating tissue growth and/or increased tissue activity. 1,2 Consequently, vascularization is a primary component of tissue growth and repair, such as occurs during development, 3 after an upstream occlusive event leading to tissue ischemia, 4 or during proliferative events, as seen in tissue healing 5,6 and tumor growth. 7 Although we know of many factors and signals that initiate or terminate the vascularization process, little is known about the rules that govern vascularization as an integrated process that includes angiogenesis, 3 arteriogenesis, 8 vascular remodeling, 9 vessel adaptation, 10 and arterio-venous polarization. 11 We have previously shown that isolated intact microvessel fragments retain angiogenic potential and are capable of forming a simple microvascular bed when cultured in a 3-dimensional collagen I gel. 12 In this microvascular construct, the vessel fragments undergo stereotypical angiogenesis, forming neovessels that maintain patent lumen and perivascular cell associations. Furthermore, the vessel fragments within this culture system are responsive to proangiogenic conditions. 12,13 All of this occurs in the absence of blood flow and relatively few nonvascular cells. Conclusions-WithHere we report the development and characterization of an experimental model of tissue vascularization based on the implantation of this microvascular construct. Precultured or freshly formed microvascular constructs implanted subcutaneously inosculate with the...

Engineered vascularized bone grafts

“…The ability to precisely control in vitro experimental conditions directly led to identifying the mechanisms of many fundamental aspects of this process over the past several decades (5)(6)(7)(10)(11)(12)(13)(14). Several groups have recently shown that microvascular structures that are preformed in vitro by using endothelial and smooth muscle progenitor cells can anastomose with the host vasculature when implanted in a nude mouse model (15)(16)(17)(18)(19)(20). In this study we demonstrate that human mesenchymal stem cells (hMSCs) coimplanted with endothelial cells (ECs) in a fibronectin-containing collagen gel act as a source of perivascular cells and generate a stable functional vasculature within a porous scaffold.…”

Interaction of angiogenic microvessels with the extracellular matrix

“…3). The resulting microvessel networks, characterized previously (16,33), have a collagen IV basement membrane, stain for von Willebrand factor, and integrate with host vessels after in vivo implantation (33).…”

Chimeric Vessel Tissue Engineering Driven by Endothelialized Modules in Immunosuppressed Sprague-Dawley Rats

“…18 A recent report describes the use of the rat omentum to prevascularize a cardiac patch, although no mention was made of immune suppression, and there was no tracking of the transplanted cells. 19 There are also several reports of EC transplantation in immune-compromised animals [20][21][22] (see below). Here we report that native, unmodified EC develop over 21-60 days into mature blood vessels in an allogeneic transplant model.…”