title: Prolonged presence of VEGF promotes vascularization in 3D bioprinted scaffolds with defined architecture.
abstract: Timely vascularization is essential for optimal performance of bone regenerative constructs. Vascularization is efficiently stimulated by vascular endothelial growth factor (VEGF), a substance with a short half-life time. This study investigates the controlled release of VEGF from gelatin microparticles (GMPs) as a means to prolong VEGF activity at the preferred location within 3D bioprinted scaffolds, and the effects on subsequent vascularization. The release of VEGF from GMPs was continuous for 3 weeks during in vitro studies, and bioactivity was confirmed using human endothelial progenitor cells (EPCs) in migration assays. Traditional and real-time migration assays showed immediate and efficient EPC migration in the presence of GMP-released VEGF, indistinguishable from VEGF-solution that was added to the medium. Matrigel scaffolds containing EPCs and VEGF, which was released either in a fast or sustained fashion by application of GMPs, were investigated for their in vivo vasculogenic capacity. Implantation in subcutaneous pockets in nude mice for one week demonstrated that vessel formation was significantly higher in the VEGF sustained-release group compared to the fast release group. In addition, regional differences with respect to VEGF release were introduced in 3D bioprinted EPC-laden scaffolds and their influence on vasculogenesis was investigated in vivo. The different regions were retained and vessel formation occurred analogous with the results seen in the Matrigel plugs. We conclude that GMPs are suitable to generate sustained release profiles of bioactive VEGF, and that they can be used to create defined differentiation regions in 3D bioprinted heterogeneous constructs, allowing a new generation of smart scaffold design. The prolonged presence of VEGF led to a significant increase in scaffold vascularization when applied in vivo.
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, G05.228, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: m.poldervaart@umcutrecht.nl.
authors.forename: Michelle T
authors.initials: MT
authors.lastname: Poldervaart
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, F03.227, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: h.gremmels@umcutrecht.nl.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Gremmels
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, G05.228, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: k.v.deventer@hotmail.com.
authors.forename: Kelly
authors.initials: K
authors.lastname: van Deventer
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, F03.227, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: j.o.fledderus@umcutrecht.nl.
authors.forename: Joost O
authors.initials: JO
authors.lastname: Fledderus
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, G05.228, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: f.c.oner@umcutrecht.nl.
authors.forename: F Cumhur
authors.initials: FC
authors.lastname: Oner
authors.affiliation: Department of Nephrology and Hypertension, University Medical Center Utrecht, F03.227, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: m.c.verhaar@umcutrecht.nl.
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Verhaar
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, G05.228, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80163, 3508 TD Utrecht, The Netherlands. Electronic address: w.dhert@umcutrecht.nl.
authors.forename: Wouter J A
authors.initials: WJ
authors.lastname: Dhert
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, G05.228, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: j.alblas@umcutrecht.nl.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Alblas
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000187:drug effects; D066026:Endothelial Progenitor Cells / Q000187:drug effects / Q000502:physiology; D005260:Female; D005780:Gelatin / Q000737:chemistry; D006801:Humans; D008819:Mice, Nude; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D066330:Printing, Three-Dimensional; D054457:Tissue Scaffolds; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage* / Q000737:chemistry
chemical_list: D042461:Vascular Endothelial Growth Factor A; D005780:Gelatin
keywords: 3D printing; Bioprinting; Gelatin microparticles; Regenerative medicine; VEGF; Vascularization