Characterization of self-organized osteocytic spheroids using mouse osteoblast-like cells

Osteocyte plays a central role as a commander in the bone to modulate bone remodeling processes. While the osteocyte is known to be differentiated from osteoblasts, understanding in mechanism of the osteocyte differentiation remained still poor. The aim of this study is to elucidate the osteocyte differentiation capability using three-dimensional (3D) cell culture technique. We first fabricated a self-organized spheroid reconstructed by mouse osteoblast-like cells by adjusting the number of subcultured cells in the round-bottom well. Compared to a conventional two-dimensional (2D) monolayer model, the 3D spheroid exerted greater osteocyte gene expressions in vitro within 2 days. As a result of the size-dependent experiment, there might be an appropriate cell-cell and cell-ECM interaction for osteoblast-like cells to induce the osteocytogenesis in the form of 3D spheroid culture. Moreover, the present model showed that the spheroid further exerted the prolonged osteocyte differentiation capability after a long period of incubation, 7 days. In conclusion, we characterized the self-organized osteocytic spheroids reconstructed by osteoblast-like cells and further suggested the potential application of the spheroid as a new in vitro tissue-engineered osteocytic model. an efficient model differentiation. imply that it is essential for the osteocyte differentiation of the cells to require a certain cellular where the cells encounter the appropriate cell-cell and cell-ECM interaction as in vivo processes such as unmineralized termed osteoid. Further study will be required to characterize the cellular environment in the spheroid with regard to its accumulation and also to elucidate the detailed mechanism of signal-transduction pathways for the differentiation achieved in the 3D culture system.