Three-dimensional tissues using Human pluripotent stem cell spheroids as biofabrication building blocks

A recently emerged approach for tissue engineering is tobiofabricate tissues using cellular spheroids as building blocks. Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), can becultured togenerate large numbers ofcells and can presumably be differentiated into all the cell types of the human body in vitro, thus are an ideal cell source for biofabrication. Wepreviously developed ahydrogel-based cell culture system that can economically produce large numbers of hPSC spheroids. With hPSCs and this culture system, there are two potential methods tobiofabricate adesired tissue. In Method 1, hPSC spheroids arefirst utilized tobiofabricate an hPSC tissue thatis subsequently differentiated into the desired tissue. In Method 2, hPSC spheroids are first converted into tissue spheroids in the hydrogel-based culture system and the tissue spheroids are then utilized tobiofabricate the desired tissue.Inthis paper, we systematically measured the fusion rates ofhPSC spheroids without and with differentiation toward cortical and midbrain dopaminergic neurons and found spheroids'fusion rates dropped sharply as differentiation progressed. We found Method 1 was appropriate for biofabricating neural tissues.