Design of prevascularized three-dimensional cell-dense tissues using a cell sheet stacking manipulation technology.

To survive three-dimensional (3-D) cell-dense thick tissues after transplantation, the improvements of hypoxia, nutrient insufficiency, and accumulation of waste products are required. This study presents a strategy for the initiation of prevascular networks in a 3-D tissue construct by sandwiching endothelial cells between the cell sheets. For obtaining a stable stacked cell sheet construct, a sophisticated 3-D cell sheet manipulation system using temperature-responsive culture dishes and a cell sheet manipulator was developed. When sparsely cultured human umbilical vein endothelial cells (HUVECs) were sandwiched between two myoblast sheets, the inserted HUVECs sprouted and formed network structures in vitro. Additionally, when myoblast sheets and HUVECs were alternately sandwiched, endothelial cell connections through the layers and capillary-like structures were found in a five-layer construct. Moreover, the endothelial networks in the five-layer myoblast sheet construct were observed to connect to the host vessels after transplantation into the subcutaneous tissues of nude rats, resulted in a neovascularization that allow the graft to survive. These results indicated that the prevascularized myoblast sheet constructs could induce functional anastomosis. Consequently, our prevascularizing method using a cell sheet stacking manipulation technology provides a substantial advance for developing various types of three-dimensional tissues and contributes to regenerative medicine.