Fabrication of PCL/keratin composite scaffolds for vascular tissue engineering with catalytic generation of nitric oxide potential

Tissue-engineered vascular grafts (TEVGs) have been proposed as a promising solution to fulfill the need for small-diameter blood vessel substitutes.

A Novel Strategy for Creating Tissue-Engineered Biomimetic Blood Vessels Using 3D Bioprinting Technology

In this work, a novel strategy was developed to fabricate prevascularized cell-layer blood vessels in thick tissues and small-diameter blood vessel substitutes using three-dimensional (3D) bioprinting technology. These thick vascularized tissues were comprised of cells, a decellularized extracellular matrix (dECM), and a vasculature of multilevel sizes and multibranch architectures. Pluronic F127 (PF 127) was used as a sacrificial material for the formation of the vasculature through a multi-nozzle 3D bioprinting system. After printing, Pluronic F127 was removed to obtain multilevel hollow channels for the attachment of human umbilical vein endothelial cells (HUVECs). To reconstruct functional small-diameter blood vessel substitutes, a supporting scaffold (SE1700) with a double-layer circular structure was first bioprinted. Human aortic vascular smooth muscle cells (HA-VSMCs), HUVECs, and human dermal fibroblasts–neonatal (HDF-n) were separately used to form the media, intima, and adventitia through perfusion into the corresponding location of the supporting scaffold. In particular, the dECM was used as the matrix of the small-diameter blood vessel substitutes. After culture in vitro for 48 h, fluorescent images revealed that cells maintained their viability and that the samples maintained structural integrity. In addition, we analyzed the mechanical properties of the printed scaffold and found that its elastic modulus approximated that of the natural aorta. These findings demonstrate the feasibility of fabricating different kinds of vessels to imitate the structure and function of the human vascular system using 3D bioprinting technology.

Oligonucleotide and Parylene Surface Coating of Polystyrene and ePTFE for Improved Endothelial Cell Attachment and Hemocompatibility

In vivoself-endothelialization by endothelial cell adhesion on cardiovascular implants is highly desirable. DNA-oligonucleotides are an intriguing coating material with nonimmunogenic characteristics and the feasibility of easy and rapid chemical fabrication. The objective of this study was the creation of cell adhesive DNA-oligonucleotide coatings on vascular implant surfaces. DNA-oligonucleotides immobilized by adsorption on parylene (poly(monoaminomethyl-para-xylene)) coated polystyrene and ePTFE were resistant to high shear stress (9.5 N/m2) and human blood serum for up to 96 h. Adhesion of murine endothelial progenitor cells, HUVECs and endothelial cells from human adult saphenous veins as well as viability over a period of 14 days of HUVECs on oligonucleotide coated samples under dynamic culture conditions was significantly enhanced (P<0.05). Oligonucleotide-coated surfaces revealed low thrombogenicity and excellent hemocompatibility after incubation with human blood. These properties suggest the suitability of immobilization of DNA-oligonucleotides for biofunctionalization of blood vessel substitutes for improvedin vivoendothelialization.

Stem Cells and Vascular Regenerative Medicine

Vascular applications in regenerative medicine include blood vessel substitutes and vasculogenesis in ischemic or engineered tissues. For these repair processes to be successful, there is a need for a stable supply of endothelial and smooth muscle cells. For blood vessel substitutes, the immediate goal is to enable blood flow, but vasoactivity is necessary for long term success. In engineered vessels, it is thought that endothelial cells will serve as an anti-thrombogenic lumenal layer, while smooth muscle cells contribute to vessel contractility. In other clinical applications, what is needed is not a vessel substitute but the promotion of new vessel formation (vasculogenesis). A simplified account of vasculogenesis is that endothelial cells assemble to form vessel-like structures that can then be stabilized by smooth muscle cells. Overall, the need for new vasculature to transfer oxygen and nutrients is important to reperfuse not only ischemic tissue in vivo, but also dense, structurally complex engineered tissue. The impact of these vascular therapies, however, is limited in part by the low yield and inadequate in vitro proliferation potential of primary endothelial and smooth muscle cells. Thus, there is a need to address the cell sourcing issue for vascular cell-based therapies, potentially using stem cells.