High-throughput fabrication of vascularized spheroids for bioprinting

• Published in: Biofabrication Vol. 10; no. 3; p. 035009
• Main Authors: De Moor, Lise, Merovci, Idriz, Baetens, Sarah, Verstraeten, Julien, Kowalska, Paulina, Krysko, Dmitri V, De Vos, Winnok H, Declercq, Heidi
• Format: Journal Article
• Language: English
• Published: England 12-06-2018
• Subjects: Bioprinting - methods; Cells, Cultured; Coculture Techniques; High-Throughput Screening Assays; Human Umbilical Vein Endothelial Cells; Humans; Neovascularization, Physiologic - physiology; Printing, Three-Dimensional; Spheroids, Cellular - cytology; Tissue Engineering - methods
• ISSN: 1758-5090
• DOI: 10.1088/1758-5090/aac7e6

Overcoming the problem of vascularization remains the main challenge in the field of tissue engineering. As three-dimensional (3D) bioprinting is the rising technique for the fabrication of large tissue constructs, small prevascularized building blocks were generated that can be incorporated throughout a printed construct, answering the need for a microvasculature within the small micron range (<10 μm). Uniform spheroids with an ideal geometry and diameter for bioprinting were formed, using a high-throughput non-adhesive agarose microwell system. Since monoculture spheroids of endothelial cells were unable to remain stable, coculture spheroids combining endothelial cells with fibroblasts and/or adipose tissue derived mesenchymal stem cells (ADSC) as supporting cells, were created. When applying the favorable coculture ratio, viable spheroids were obtained and endothelial cells spontaneously formed a capillary-like network and lumina, as shown by immunohistochemistry and transmission electron microscopy. Especially the presence of ADSC led to a higher vascularization and extracellular matrix production of the microtissue. Moreover, spheroids were able to assemble at random in suspension and in a hydrogel, creating a macrotissue. During at random assembly, cells reorganized, creating a branched capillary-network throughout the entire fused construct by inoculating with capillaries of adjacent spheroids. Combining the advantage of this natural capacity of microtissues to self-assemble and the controlled organization by bioprinting technologies, these prevascularized spheroids can be useful as building blocks for the engineering of large vascularized 3D tissues.