Theranostics 2022; 12(12):5404-5417. doi:10.7150/thno.74852 This issue

Research Paper

Bone tissue engineering supported by bioprinted cell constructs with endothelial cell spheroids

WonJin Kim1*, Chul Ho Jang2*, GeunHyung Kim1,3✉

1. Department of Biomechatronic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University (SKKU), Suwon 16419, South Korea.
2. Department of Otolaryngology, Chonnam National University Medical School, Gwangju 61469, South Korea.
3. Biomedical Institute for Convergence at SKKU (BICS), Sungkyunkwan University, Suwon 16419, South Korea.
*These authors contributed equally to this work.

This is an open access article distributed under the terms of the Creative Commons Attribution License ( See for full terms and conditions.
Kim W, Jang CH, Kim G. Bone tissue engineering supported by bioprinted cell constructs with endothelial cell spheroids. Theranostics 2022; 12(12):5404-5417. doi:10.7150/thno.74852. Available from

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Graphic abstract

In bone tissue engineering, efficient formation of vascularized bone tissue is a challenging issue. Here, we introduce a new strategy for effectively using multiple cells laden in a hybrid structure, such as endothelial cell (EC) spheroids and homogeneously distributed human adipose stem cells (hASCs) for bone regeneration.

Methods: To fabricate the EC spheroids, cell-mixed mineral oil was used, and microscale droplets of the cell mixture were interlayered between the bioprinted hASC-laden struts. In vitro cellular responses of spheroid-laden multiple-cell constructs have been evaluated by comparing with the cell constructs bioprinted with the mixture of hASCs and ECs. In addition, mastoid obliterated rat model has been used to observe in vivo bone formation of those cell constructs.

Results: The spheroid-laden multiple-cell constructs induced outstanding angiogenesis and osteogenic activities compared to a conventionally bioprinted multiple-cell construct. The enhanced biological results were clearly due to the EC spheroids, which triggered highly cooperative crosstalk between ECs and stem cells. The co-culture of the hASC constructs with the EC spheroids exhibited enhanced osteogenic- and angiogenic-related gene expression in vitro. In addition, in a rat obliterated mastoid model, considerably greater new bone formation and more competent development of new blood vessels were observed compared to those achieved with the normally bioprinted multiple cell-loaded structure.

Conclusion: In vitro and in vivo results demonstrated that the bioprinted spheroid-laden multiple-cell construct is a potential candidate for use in bone tissue engineering.

Keywords: Tissue engineering, bone, bioprinting, spheroids, multiple cells