title: Using Del-1 to tip the angiogenic balance in endothelial cells in modular constructs.
abstract: Modular tissue engineering is a method of building vascularized tissue-engineered constructs. Submillimeter-sized collagen pieces (modules) coated with a layer of endothelial cells (EC; vascular component), and with embedded functional cells, are self-assembled into a larger, three-dimensional tissue. In this study, we examined the use of developmental endothelial locus-1 (Del-1), an extracellular matrix protein with proangiogenic properties, as a means of tipping the angiogenic balance in human umbilical vein endothelial cells incorporated in modular tissue-engineered constructs. The motivation was to enhance the vascularization of these constructs upon transplantation in vivo, in this case, without the use of exogenous mesenchymal stromal cells. EC were transduced using a lentiviral construct to overexpress Del-1. The Del-1 EC formed more sprouts in a fibrin gel sprouting assay in vitro compared with eGFP (control) transduced EC, as expected. Del-1 EC had a distinct profile of gene expression (upregulation of matrix metalloproteinase-9 [MMP-9], urokinase-type plasminogen activator [uPA/PLAU], vascular endothelial growth factor [VEGF-A], and intercellular adhesion molecule-1 [ICAM-1]; downregulation of angiopoietin-2 [Ang2]), also supporting the notion of "tipping the angiogenic balance". On the other hand, contrary to our expectations, when Del-1 EC-coated modules were implanted subcutaneously in a severe combined immunodeficient/beige animal model, the proangiogenic effect of Del-1 was less remarkable. There was only a small increase in the number of blood vessels formed in Del-1 implants compared with the eGFP implants, and only few blood vessels formed at the implant site in both cases. This was presumed due to limited EC survival after transplantation. We speculate that if we could improve EC survival in our study (for example, by adding other prosurvival factors or supporting cells), we would see a greater Del-1-induced angiogenic benefit in vivo as a consequence of increased Del-1 secretion by a higher number of surviving cells.
authors.affiliation: 1 Department of Chemical Engineering and Applied Chemistry, University of Toronto , Toronto, Canada .
authors.forename: Ema C
authors.initials: EC
authors.lastname: Ciucurel
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Vlahos
authors.forename: Michael V
authors.initials: MV
authors.lastname: Sefton
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001681:Biological Assay; D001808:Blood Vessels / Q000187:drug effects / Q000254:growth & development; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D015815:Cell Adhesion Molecules; D049109:Cell Proliferation / Q000187:drug effects; D005337:Fibrin / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D005822:Genetic Vectors / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D020007:Implants, Experimental; D036341:Intercellular Signaling Peptides and Proteins; D016086:Lentivirus / Q000235:genetics; D016513:Mice, SCID; D018919:Neovascularization, Physiologic / Q000187:drug effects; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry*; D014161:Transduction, Genetic
chemical_list: D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; C491706:Edil3 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D005337:Fibrin