Acta Biomater. 2019 Sep 19. pii: S1742-7061(19)30640-3. doi: 10.1016/j.actbio.2019.09.028. [Epub ahead of print]

Fabrication of core-shell spheroids as building blocks for engineering 3D complex vascularized tissue.

Kim EM¹, Lee YB¹, Kim SJ¹, Park J¹, Lee J¹, Kim SW², Park H³, Shin H⁴.

Abstract

Cell spheroids as building blocks for engineering micro-tissue should be able to mimic the complex structure of natural tissue. However, control of the distribution of multiple cell populations within cell spheroids is difficult to achieve with current spheroid-harvest methods such as hanging-drop and with the use of microwell plates. In this study, we report the fabrication of core-shell spheroids with the ultimate goal to form 3D complex micro-tissue. We used endothelial cells and two types of stem cells (human turbinate mesenchymal stem cells (hTMSCs)/adipose-derived stem cells (ADSCs)). The stem cells and endothelial cells formed layered micro-sized cell sheets (μCSs) on polydopamine micro-patterned temperature-responsive hydrogel surfaces by a sequential seeding method, and these layered μCSs self-assembled to form core-shell spheroids by expansion of the hydrogels. The co-cultured spheroids formed a core-shell structure irrespective of stem cell type. In addition, the size of the core-shell spheroids was controlled from 90 ± 1 to 144 ± 3 μm by changing pattern sizes (200, 300, and 400 μm). The shell thickness gradually increased from 12 ± 3 to 30 ± 6 μm by adjusting the endothelial cell seeding density. Finally, we fabricated the micro-tissue by fusion of the co-cultured spheroids, and the spheroids with the core-shell structure rapidly induced in vitro vessel-like network in 3 days. Thus, the position of endothelial cells in co-cultured spheroids may be an important factor for the modulation of the vascularization process, which can be useful for the production of 3D complex micro-tissues using spheroids as building blocks.