Future Technology of Cell Therapies: Bioengineering of the Human Myocardium
Decellularization of the Heart
The complex heart tissue is difficult to reconstitute with regenerative cardiomyo- cytes in vitro. In order to reconstitute three-dimensional (3-D) tissues, cells need a scaffold. As a cardiac tissue scaffold, a cytoskeleton was developed from decellular- ized heart tissue (Ott et al. 2008). The hearts of humans or pigs may be useful for clinical application. As mentioned above, the critical issue is the preparation of a large number of cardiomyocytes, which can fill up the whole or part of the cardiac tissue. In addition, inclusion of components other than cardiomyocytes, such as endothelial cells and smooth muscle cells, will be necessary. If the cardiac cells are stably supplied, human iPSC-derived cardiomyocytes and a decellularized cytoskel- eton will enable preparation of a functional human myocardial-like tissue (Guyette et al. 2016). Therefore, it may become possible to transplant constructed heart tissue using a mixture of human iPSC-derived cardiomyocytes and a decellularized cyto- skeleton in the near future.
Recent developments in printing technologies have made it possible to print anything in three dimensions (Nakamura et al. 2010). Organs and tissues in animals can also be printed as a 3-D mass. This technology is also utilized in regenerative medicine. Blood vessels, bones, cartilage, and skeletal muscles have been printed in 3-D using differentiated cells (Kang et al. 2016; Norotte et al. 2009). It is also considered that heart tissues will be able to be printed as a 3-D tissue. However, because there are many types of cells in the heart tissue that are connected to each other in complex manners, the ability to transplant 3-D-printed working heart tissue will likely take more time; however, we expect that this will be possible in the future.