Generating a sufficient blood vessel system — vascularization — is a major challenge for bioprinting and engineering 3D tissues in vitro. Present in almost all in vivo tissues, this endothelial cell-coated tubular network is needed to ensure a constant flow of oxygen and nutrients inside 3D-bioprinted constructs.
At CELLINK, we addressed this challenge by developing VasKit, a bioink designed to enable vascularization.
The need for vascularizationOne of the biggest challenges facing the bioprinting field is developing a way to supply cells with nutrients and drain their waste products. Until now, most methods didn’t involve any regulated exchange of metabolites — instead, they relied on the simple diffusion process that naturally occurs in cell culture medium.
While that can be sufficient for constructs with low-cell densities and thin geometries, dense tissues require a stable microvascular network to exchange nutrients and expel metabolic waste.
Vascular bioink functionTo establish of vascular network, a vascular bioink needs to provide a 3D environment conducive for cellular processes. It should enable live-cell imaging of endothelial cells in different stages of vascular tissue formation, including sprout formation and connection, hollow tube formation and network branching — combining to result in a functionally perfused vascular bed.
Co-culture in bioinkHuman umbilical vein endothelial cells (HUVECs) are widely used for studying angiogenesis. We bioprinted HUVECs in co-culture with human dermal fibroblasts (HDFs). The HDFs help stabilize endothelial cells and promote vascular network formation. We cultured our 3D-bioprinted constructs for 14 days in a static culture. The image shows vascular sprouts growing at the edge of the bioprinted structure and was taken on day six of cell culture.
Our tests provide strong evidence of extensive endothelial sprout formation and vascularization in constructs bioprinted using VasKit. This experiment demonstrated the benefits of VasKit and its potential to enable a functional bioprinted vascular system. The next step is implementing a new system for dynamic cell culture with VasKit as one of its main components.