Control of the formation of vascular networks in 3D tissue engineered constructs.

Construction of bio-mimetic well-organized three-dimensional (3D) tissue with various cells in vitro is one of the ultimate goals of tissue engineering. In particular, fabrication of vasculature in 3D tissue is one of the most important tasks in tissue engineering, because a vascular network is indispensable for almost every tissue in our body. Here, we sandwiched stripe patterned endothelial cells by randomly cultured fibroblast sheets to control the formation of vasculature in the tissue. The endothelial cells left the original pattern and formed a random network between the two sheets, but, where fibroblasts were focally oriented, some endothelial cells changed their orientation to the same direction as the surrounding fibroblasts. Based on this phenomenon, we sandwiched stripe-patterned endothelial cells between parallel-oriented fibroblast sheets to construct a continuous pre-vascular structure. In the tissue, endothelial cells maintained the shape of their original pattern. On the other hand, stripe-patterned endothelial cells that were vertically sandwiched between oriented fibroblast sheets diverged from the original pattern at right angles, so that they were aligned with the surrounding fibroblasts. These data indicates that, 3D design with consideration of cell-to-cell interaction is critical to fabricate a specific 3D tissue structure. The 3D-designed tissue will become a powerful tool for the study of pharmacology and biology, the substitution of animal models and the fabrication of vascularized tissue grafts.