Edited by Robert Langer, Massachusetts Institute of Technology, Cambridge, MA, and approved January 3, 2019 (received for review August 23, 2018)
Rapid graft revascularization, while critical for graft survival, is often not seen in current grafts due to poor basal vascularization. In the present work, we assessed the effect of engineered vessel network assembly and maturation in pre-vascularized constructs prior to implantation on the dynamics of graft integration and perfusion. Grafts bearing highly complex and mature vessel networks were rapidly invaded by host vasculature, which anastomosed with the engineered vessels, promoting their perfusion and reducing blood clot accumulation in the graft. The implantation of grafts with highly mature engineered vessels promises to improve graft integration with the host vasculature and its overall survival.
Graft vascularization remains one of the most critical challenges facing tissue-engineering experts in their attempt to create thick transplantable tissues and organs. In vitro prevascularization of engineered tissues has been suggested to promote rapid anastomosis between the graft and host vasculatures; however, thrombotic events have been reported upon graft implantation. Here, we aimed to determine whether in vitro vessel maturation in transplantable grafts can accelerate vascular integration and graft perfusion and prevent thrombotic events in the grafts. To this end, endothelial cells and fibroblasts were cocultured on 3D scaffolds for 1, 7, or 14 d to form vasculature with different maturation degrees. Monitoring graft–host interactions postimplantation demonstrated that the 14-d in vitro-cultured grafts, bearing more mature and complex vessel networks as indicated by elongated and branched vessel structures, had increased graft–host vessel anastomosis; host vessel penetration into the graft increased approximately eightfold, and graft perfusion increased sixfold. The presence of developed vessel networks prevented clot accumulation in the grafts. Conversely, short-term cultured constructs demonstrated poor vascularization and increased thrombus formation. Elevated expression levels of coagulation factors, von Willebrand factor (vWF), and tissue factor (TF), were demonstrated in constructs bearing less mature vasculature. To conclude, these findings demonstrate the importance of establishing mature and complex vessel networks in engineered tissues before implantation to promote anastomosis with the host and accelerate graft perfusion.
Author contributions: S.B.-S. and S. Levenberg designed research; S.B.-S. performed research; S.B.-S., S. Landau, and U.M. analyzed data; S.B.-S. and S. Levenberg wrote the paper; and S. Levenberg supervised the research.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1814238116/-/DCSupplemental.
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