title: Cell-demanded liberation of VEGF121 from fibrin implants induces local and controlled blood vessel growth.
abstract: Although vascular endothelial growth factor (VEGF) has been described as a potent angiogenic stimulus, its application in therapy remains difficult: blood vessels formed by exposure to VEGF tend to be malformed and leaky. In nature, the principal form of VEGF possesses a binding site for ECM components that maintain it in the immobilized state until released by local cellular enzymatic activity. In this study, we present an engineered variant form of VEGF, alpha2PI1-8-VEGF121, that mimics this concept of matrix-binding and cell-mediated release by local cell-associated enzymatic activity, working in the surgically-relevant biological matrix fibrin. We show that matrix-conjugated alpha2PI1-8-VEGF121 is protected from clearance, contrary to native VEGF121 mixed into fibrin, which was completely released as a passive diffusive burst. Grafting studies on the embryonic chicken chorioallantoic membrane (CAM) and in adult mice were performed to assess and compare the quantity and quality of neovasculature induced in response to fibrin implants formulated with matrix-bound alpha2PI1-8-VEGF121 or native diffusible VEGF121. Our CAM measurements demonstrated that cell-demanded release of alpha2PI1-8-VEGF121 increases the formation of new arterial and venous branches, whereas exposure to passively released wild-type VEGF121 primarily induced chaotic changes within the capillary plexus. Specifically, our analyses at several levels, from endothelial cell morphology and endothelial interactions with periendothelial cells, to vessel branching and network organization, revealed that alpha2PI1-8-VEGF121 induces vessel formation more potently than native VEGF121 and that those vessels possess more normal morphologies at the light microscopic and ultrastructural level. Permeability studies in mice validated that vessels induced by alpha2PI1-8-VEGF121 do not leak. In conclusion, cell-demanded release of engineered VEGF121 from fibrin implants may present a therapeutically safe and practical modality to induce local angiogenesis.
authors.affiliation: Institute for Biomedical Engineering, and University of Zurich, Zurich, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Ehrbar
authors.forename: Valentin G
authors.initials: VG
authors.lastname: Djonov
authors.forename: Christian
authors.initials: C
authors.lastname: Schnell
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Tschanz
authors.forename: Georg
authors.initials: G
authors.lastname: Martiny-Baron
authors.forename: Ursula
authors.initials: U
authors.lastname: Schenk
authors.forename: Jeanette
authors.initials: J
authors.lastname: Wood
authors.forename: Peter H
authors.initials: PH
authors.lastname: Burri
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hubbell
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Zisch
mesh_terms: D000482:Allantois / Q000098:blood supply / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002199:Capillary Permeability / Q000187:drug effects; D002642:Chick Embryo; D002823:Chorion / Q000098:blood supply / Q000187:drug effects; D004058:Diffusion; D004343:Drug Implants; D042783:Endothelial Cells / Q000187:drug effects / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000166:cytology; D016326:Extracellular Matrix Proteins / Q000032:analysis; D005337:Fibrin / Q000008:administration & dosage / Q000378:metabolism*; D005782:Gels; D006801:Humans; D051379:Mice; D009024:Morphogenesis / Q000187:drug effects; D018995:Myosin Heavy Chains; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D024501:Nonmuscle Myosin Type IIB; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015202:Protein Engineering; D017434:Protein Structure, Tertiary; D042787:Receptor, TIE-2 / Q000032:analysis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000032:analysis; D000979:alpha-2-Antiplasmin / Q000737:chemistry / Q000235:genetics
chemical_list: D004343:Drug Implants; D016326:Extracellular Matrix Proteins; D005782:Gels; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D000979:alpha-2-Antiplasmin; D005337:Fibrin; D042787:Receptor, TIE-2; D040301:Vascular Endothelial Growth Factor Receptor-2; D024501:Nonmuscle Myosin Type IIB; C103815:nonmuscle myosin type IIB heavy chain; D018995:Myosin Heavy Chains