Vascular tissue construction on poly(ε-caprolactone) scaffolds by dynamic endothelial cell seeding: effect of pore size

Abstract

In vitro tissue engineering for fabrication of small diameter vascular grafts probably undergoes a sequence of events similar to the in vivo angiogenesis process. In both cases endothelial cells (ECs) play the crucial role in generating a non-thrombogenic vessel lumen and stabilization of ECs in the lumen of new vessels requires the deposition of collagen IV and elastin. Shear stress is an important in vivo signal for inducing synthesis of extracellular matrix (ECM) components, collagen IV and elastin, which form the basement membrane in the case of new blood vessels. Stimulation of ECs may therefore produce collagen and elastin in the lumen of a polymeric scaffold during the vascular tissue-engineering process if appropriate biochemical and mechanical signals are presented. However, the morphology and physicochemical characteristics of polymer scaffolds may also be crucial for EC monolayer formation and ECM deposition. In this study, tubular scaffolds made of biodegradable poly(ε-caprolactone) (PCL) with biomimetic fibrin-based coating were evaluated to compare the effects of pore sizes on surface coverage of ECs and synthesis of ECM under dynamic culture conditions. Actin was stained for identification of cells, while specific antibodies were used for locating collagen IV and elastin deposition on the scaffolds. It was found that dynamic seeding of ECs in the lumen stabilized the cells and aligned them along the direction of flow, with better deposition of insoluble elastin and collagen IV when ∼75% of pores were < 24 µm in diameter. In addition, monolayer on the ε-PCL scaffolds with lower pore sizes was found to produce nitric oxide (NO), indicating a non-thrombogenic EC layer in the lumen.

A Biomimetic Heparinized Composite Silk-Based Vascular Scaffold with sustained Antithrombogenicity

“…1a). It was demonstrated that smaller pores in scaffolds could improve ECs proliferation 25 . Conversely, larger pores (60–150 μm) in the outer layer could aid SMCs cultivation, infiltration and proliferation 24 .…”

“…Therefore, the best hemocompatibility is obtained when the luminal surface is coated with healthy endothelial cells that facilitate blood flow and prevent thrombosis 22, 23 , while the presence of functional SMC within the medial layer of vascular wall facilitates certain functions such as vasoconstriction and relaxation as well as secretion of vasoactive regulators 21, 24 . Smaller pores are more suitable for ECs to create a monolayer on the luminal surface of the scaffold while SMCs require interconnected pores above 60 micrometers in diameter to proliferate and build a muscular media 24, 25 . Therefore, an ideal vascular scaffold must provide the suitable requirements for the growth of both cell types.…”

Elastin-Coated Biodegradable Photopolymer Scaffolds for Tissue Engineering Applications

“…In the perspective of biodegradable 3D stent, the mask-projection excimer laser stereolithography allows not only fabricating stents with the proper macrogeometry (diameter, length/height, and meshed shape), but also controlling the morphology on the microscale. The selection of appropriate scaffold architecture with suitable pore mesh has long been recognized as the key factor that may influence the mechanical strength and determine tissue remodelling [18]. …”

“…In addition, it was reported that elastin promotes in vivo endothelial cells adhesion and proliferation [27], which are responsible for all those mechanisms that regulate the platelet and smooth muscular cells overgrowth [28]. In particular, elastin displays a natural antithrombotic effect, which prevents the new obstruction of blood vessels [2, 18, 29]. …”

“…As for the perspective of biodegradable stents, the mask-projection excimer laser stereolithography allows the fabrication through the layer-by-layer approach of 3D scaffolds (i.e., stents) not only with the proper macrogeometry (diameter, length, and meshed shape), but also with the optimal morphology on the microscale. This allows achieving a better and more stable elastin coating by tuning the pore and groove dimensions on the micrometer scale [18]. In general, diethyl fumarate (DEF, the monomer used for the synthesis of PPF) is blended to the polymer to reduce the viscosity that is necessary for the production.…”