Evaluation of Tissue-Engineered Blood Vessels as Three-Dimensional In Vitro Testing System in Cardiovascular Research and Device Approval

BackgroundDisturbed crosstalk between endothelial cells (ECs) and vascular smooth muscle cells (SMCs) has an important role in atherosclerosis and restenosis after vascular intervention, however, the exact pathomechanisms are incompletely understood. Current preclinical testing models do not adequately recapitulate the complexity of human arteries. Here, we present tissue-engineered blood vessels (TEBVs) as a novel in vitro model and validate it for intimal hyperplasia. MethodsTEBVs fabricated from SMC suspended in fibrin gel, supported by a textile mesh, were seeded with ECs at various concentrations and subjected to arterial flow conditions in a bioreactor. In addition, TEBVs underwent plain old balloon angioplasty (POBA) and implantation of bare metal stents (BMS) and drug-eluting stents (DES) at day 7 after fabrication. TEBVs were dynamically conditioned in a bioreactor for 21 days in total and monitored by optical coherence tomography. ResultsTEBVs with absent or incomplete endothelial layer exhibited thicker vessel walls, more disorganized and misaligned collagen, and increased cellular proliferation compared with completely endothelialized TEBVs. POBA and stent implantation were feasible 7 days after TEBV fabrication. At 14 days post-intervention, POBA-treated TEBVs exhibited significantly thicker vessel walls than untreated controls and stented TEBVs, whereas stented TEBVs showed greater lumen diameters than unstented TEBVs. Endothelial strut coverage was significantly higher in BMS-treated compared with DES-treated TEBVs. Over the course of the conditioning period, levels of IL-6, IL-8, and MCP-1 were highest in medium samples from BMS-treated TEBVs compared to DES-treated TEBVs and compared to untreated controls. ConclusionsTEBVs are a promising approach towards an in vitro system for the study of intimal hyperplasia. Due to their similarity in size and wall thickness to human coronary arteries, TEBVs may also serve as a platform for testing new stent designs. Graphical AbstractTissue-engineered blood vessels (TEBV) fabricated from smooth muscle cell /fibroblast mixtures suspended in fibrin gel, supported by a textile mesh, were seeded with endothelial cells and conditioned in a bioreactor system for 21 days. Different endothelialization strategies resulted in differences in wall thickness. In addition, TEBVs underwent plain old balloon angioplasty (POBA) and stent implantation. POBA-treated TEBVs exhibited thicker vessel walls compared with non-treated TEBV controls and compared with stented TEBVs. We also observed significantly higher stent strut coverage with endothelial cells after implantation of bare metal stents (BMS) compared to drug-eluting stents (DES). TEBVs are a promising approach towards an in-vitro system for the study of intimal hyperplasia. Due to their similarity in size and wall thickness to human coronary arteries, TEBVs may also serve as a platform for testing new stent designs.