In Vitro Multitissue Interface Model Supports Rapid Vasculogenesis and Mechanistic Study of Vascularization across Tissue Compartments

Abstract

A significant challenge facing tissue engineers is the design and development of complex multitissue systems, including vascularized tissue–tissue interfaces. While conventional in vitro models focus on either vasculogenesis (de novo formation of blood vessels) or angiogenesis (vessels sprouting from existing vessels or endothelial monolayers), successful therapeutic vascularization strategies will likely rely on coordinated integration of both processes. To address this challenge, we developed a novel in vitro multitissue interface model in which human endothelial colony forming cell (ECFC)-encapsulated tissue spheres are embedded within a surrounding tissue microenvironment. This highly reproducible approach exploits biphilic surfaces (nanostructured surfaces with distinct superhydrophobic and hydrophilic regions) to (i) support tissue compartments with user-specified matrix composition and physical properties as well as cell type and density and (ii) introduce boundary conditions that prevent the cell-mediated tissue contraction routinely observed with conventional three-dimensional monodispersion cultures. This multitissue interface model was applied to test the hypothesis that independent control of cell–extracellular matrix (ECM) and cell–cell interactions would affect vascularization within the tissue sphere as well as across the tissue–tissue interface. We found that high-cell-density tissue spheres containing 5 × 106 ECFCs/mL exhibit rapid and robust vasculogenesis, forming highly interconnected, stable (as indicated by type IV collagen deposition) vessel networks within only 3 days. Addition of adipose-derived stromal cells (ASCs) in the surrounding tissue further enhanced vasculogenesis within the sphere as well as angiogenic vessel elongation across the tissue–tissue boundary, with both effects being dependent on the ASC density. Overall, results show that the ECFC density and ECFC–ASC crosstalk, in terms of paracrine and mechanophysical signaling, are critical determinants of vascularization within a given tissue compartment and across tissue interfaces. This new in vitro multitissue interface model and the associated mechanistic insights it yields provide guiding principles for the design and optimization of multitissue vascularization strategies for research and clinical applications.

Tissue regeneration using endothelial colony-forming cells: promising cells for vascular repair

“…Much effort has been devoted to determining which cells or reagents can enhance the neoangiogenic potential of ECFCs. A combination treatment of ECFCs with mesenchymal stem/ progenitor cells (61)(62)(63)(64)(65), adipose tissue-derived stromal cells (66), or host myeloid cells (61,67) has been reported to synergistically enhance neovascularization compared with use of either cell population alone. Although some of these beneficial effects were implicated with the known immunosuppressive potency of mesenchymal stem cells (64) or priming ECFCs by Notch signaling (65), the exact underlying mechanism of interaction among these cells that promotes neovascularization still needs further investigation.…”

Fabrication of centimeter-scale and geometrically arbitrary vascular networks using in vitro self-assembly

“…For self-assembly models, vascular endothelial cells or progenitor cells are initially seeded within or adjacent to a three-dimensional biological or synthetic polymer matrix that supports invasion and proliferation of cells arbitrarily throughout the bulk. Typical materials include alginate [16], fibrin [17-23], collagen [24-34], collagen/fibrin [35,36], or modified PEG gels [37]. The cells then invade the surrounding matrix, create lumens through vacuole formation/coalescence, and sprout into the matrix to form an interconnected network of endothelialized tubes [38,39].…”

Development of a Novel 3D Tumor-tissue Invasion Model for High-throughput, High-content Phenotypic Drug Screening

“…The proposed 3D tumor-tissue invasion model (Fig. 1a ) was inspired, in part, by a “multi-tissue interface” model developed for vasculogenesis/angiogenesis studies and involved creation of two adjacent, independently tunable tissue compartments 29 . The use of standardized self-assembling oligomeric type I collagen (Oligomer) for creation of the interstitial ECM supports definition, customization, and standardization of relevant physicochemical parameters, including molecular composition, intermolecular crosslink content, fibril architecture, and matrix stiffness.…”