Control of Cell-Cell Distance and Cell Densities in Millimeter-Sized 3D Tissues Constructed by Collagen Nanofiber Coating Techniques.

In the field of tissue engineering, fabrication of millimeter- or centimeter-sized three-dimensional (3D) human tissues with controlled 3D cell density, 3D cell components, and 3D cell locations has been a goal of researchers. In this study, we fabricated collagen nanofiber layers of varying thicknesses on cell surfaces by previously reported collagen-coating techniques and then constructed millimeter-sized 3D human tissues, controlling the 3D cell-cell distance. In these 3D tissues, cells in the constructed 3D tissues kept a constant cell-cell distance after 24 h of incubation. Thickness of the obtained 3D tissues was controlled successfully by altering the number of cells seeded and coating times. The maximum thickness was over 2 mm when coating was carried out three times. Cell-cell distance was also controllable from approximately 15-30 μm. When cells coated once and twice with collagen nanofibers were used for the continuous construction of 3D tissues, millimeter-sized 3D tissues with areas of different cell density were obtained. The interfaces between higher and lower cell density areas were slightly mixed, but more than 80% viability was maintained after 4 days of incubation. The results suggested that stable millimeter-sized 3D tissues can be achieved using collagen nanofiber-coated cells. In addition, 3D tissues constructed by collagen-coated iPS-CM and human cardiac fibroblast were also successful.