Cell sheet tissue engineering: Cell sheet preparation, harvesting/manipulation, and transplantation.

Cell sheet tissue engineering is a concept for creating transplantable two-dimensional (2D) and three-dimensional (3D) tissues and organs. This review describes three elements of cell sheet tissue engineering in terms of the chemical and physical effects of material surfaces and the interfacial properties of cell sheets: preparation, harvesting/manipulation and transplantation of cell sheets. An essential technology for the preparation of cell sheets is the use of a temperature-responsive cell culture surface, where the surface of tissue culture polystyrene (TCPS) dish is modified with thin layer of temperature-responsive polymer, poly(N-isopropylacrylamide) (PIPAAm). PIPAAm-immobilized TCPS allows cultured cells to be harvested as a contiguous cell sheet with extracellular matrices (ECMs) by reducing the temperature, while chemical and physical disruption impair ECMs, cell-cell junction, and membrane proteins. Ligand-immobilized and porous hydrophilic PIPAAm-grafted surfaces are able to accelerate cell sheet preparation and harvesting, respectively. In addition, the manipulation of harvested cell sheets with the aid of cell sheet manipulator facilitates the formation of 3D tissues. Cell sheet-based tissues and their transplantation are in seven clinical settings such as heart, cornea, esophagus, periodontal, middle chamber of ear, knee cartilage, and lung. In order to create thick and large 3D tissues and organs, large production of differentiated parenchymal cells from induced pluripotent stem (iPS) cells and vascularization within 3D tissues are key issues.