RESEARCH ARTICLE Fabrication of Biomimetic Bone Tissue Using Mesenchymal Stem Cell-Derived Three- Dimensional Constructs Incorporating

The development of technologies to promote vascularization of engineered tissue would drive major developments in tissue engineering and regenerative medicine. Recently, we succeeded in fabricating three-dimensional (3D) cell constructs composed of mesenchymal stem cells (MSCs). However, the majority of cells within the constructs underwent necrosis due to a lack of nutrients and oxygen. We hypothesized that incorporation of vascular endo-thelial cells would improve the cell survival rate and aid in the fabrication of biomimetic bone tissues in vitro. The purpose of this study was to assess the impact of endothelial cells com-bined with the MSC constructs (MSC/HUVEC constructs) during short- and long-term cul-ture. When human umbilical vein endothelial cells (HUVECs) were incorporated into the cell constructs, cell viability and growth factor production were increased after 7 days. Further-more, HUVECs were observed to proliferate and self-organize into reticulate porous struc-tures by interacting with the MSCs. After long-term culture, MSC/HUVEC constructs formed abundant mineralized matrices compared with those composed of MSCs alone. Transmis-sion electron microscopy and qualitative analysis revealed that the mineralized matrices comprised porous cancellous bone-like tissues. These results demonstrate that highly bio-mimetic bone tissue can be fabricated in vitro by 3D MSC constructs incorporated with HUVECs