Generation of functional vascular channels using 3D bio-printing technology

Abstract

3D bio-printing technology capable of dispensing live cells, soluble factors, and phase-changing hydrogel in a desired pattern, has great potential in creating 3D tissue. However, maintaining the viability of a thick tissue structure during tissue growth and maturation is challenging due to inadequate vascular perfusion.

As a next step, we developed a 3D printing method to construct larger (lumen size of ~1mm) fluidic vascular channels and to create adjacent capillary network through a maturation process, thus providing a method to connect the capillary network to the large perfused vascular channels. We developed functional in vitro vascular channels with adjacent capillary network. Our bio-printing technology allows the embedding of various components involved in the capillary formation (e.g. supporting cells, soluble factors, and ECMs); therefore, it has a great potential in engineering vascularized thick tissues and vascular niches, as the vascular channels are simultaneously created while cells and matrices are printed around the channels in desired 3D patterns. It can also serve as a unique experimental tool for investigating fundamental mechanisms of vascular function and maturation process under 3D flow conditions.

In order to address the vascularization issue, we first created dynamically-perfused vasculatures within 3D matrix using bio-printing technology, and characterized the structural and functional aspects of the fabricated vascular channels. The channels (~1mm in diameter) presented appropriate vascular structures and barrier functions, and showed a capability to support cell viability in a simple tissue model with 5 million cells/mL of cell density. Although the engineered vasculature achieved adequate perfusion in the simple tissue model with limited number of cells and scaffold types, complex and dense tissue requires a capillary network to actively regulate gas, nutrient, and waste exchanges between vasculature and surrounding tissues. Therefore, creating a functional vascular network during the bio-printing process is critical for thick tissue fabrication using this technology. However, construction of a complete capillary network (~10µm in diameter) at single cell level using existing technology is nearly impossible due to limitations in time and spatial resolution.