Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan.
Tissue Eng Part A. 2021 Aug;27(15-16):1037-1043. doi: 10.1089/ten.TEA.2020.0228. Epub 2020 Nov 19.
Bone-related studies have been widely carried out by culturing cells on two-dimensional (2D) culture system because of its easiness of handling, but these 2D achievements may imply a distinct outcome compared with the situation. On the contrary, three-dimensional (3D) culture system has been suggested as a better biomimetic model by providing an appropriate cell-cell or cell-matrix interaction. In this study, we successfully reconstructed a 3D disk type of scaffold-free tissue (SFT) using mouse osteoblast-like cells, which evoked an osteocyte differentiation within 2 days. Particularly, the SFT was also utilized as an osteocytic model to elucidate the effect of hypoxia on cellular differentiation capability. As a result, the hypoxia upregulated a matured osteocyte marker, , in the SFT, whereas both osteoblast and osteocyte markers were significantly downregulated by hypoxia in the 2D conventional monolayer model. The results imply that the hypoxia may enhance the initiation of osteocyte differentiation and retain the osteocyte differentiation in the 3D culture system. Of note, we reported the significance of 3D culture system that might represent the situation regarding cellular response to stimuli. Hence, our study suggests wide applications of SFT using osteoblast cells as a novel osteocyte model for the osteocyte-related studies. Impact statement In this study, we fabricated a three-dimensional (3D) disk type of scaffold-free osteocytic tissue, termed scaffold-free tissue (SFT), reconstructed by mouse osteoblast-like cells. It induced an osteocyte differentiation of osteoblast-like cells in the SFT within 2 days. Moreover, we first showed that a matured osteocyte marker, , was modulated by hypoxia in the SFT in a different manner compared with the two-dimensional (2D) monolayer. These results highlighted the significance of 3D culture system that might represent the situation regarding cellular response to stimuli. Of note, our model can be utilized as a new osteocyte model for the osteocyte-related studies.
骨相关研究已经通过在二维（2D）培养系统上培养细胞广泛开展，因为其易于操作，但这些 2D 研究结果可能与实际情况存在显著差异。相比之下，三维（3D）培养系统通过提供适当的细胞-细胞或细胞-基质相互作用，被认为是更好的仿生模型。在本研究中，我们成功地使用鼠成骨样细胞构建了 3D 盘状无支架组织（SFT），该组织在 2 天内诱导了成骨细胞向成骨细胞分化。特别地，该 SFT 还被用作成骨细胞模型，以阐明缺氧对细胞分化能力的影响。结果表明，缺氧上调了 SFT 中的成熟成骨细胞标志物 ，而缺氧在 2D 传统单层模型中显著下调了成骨细胞和成骨细胞标志物。这些结果表明，缺氧可能增强成骨细胞分化的启动，并在 3D 培养系统中保留成骨细胞分化。值得注意的是，我们报告了 3D 培养系统的重要性，它可能代表了细胞对刺激的实际反应情况。因此，我们的研究表明，使用成骨细胞作为新型成骨细胞模型的 SFT 在成骨细胞相关研究中有广泛的应用。
