2009 年 30 巻 4 号 p. 190-192
The stem cell is defined in terms of pluripotency and self-renewability. However, the fact is that the cell population called “stem cells” is gathering of the cells with various differentiation stages of various lineages. The authentic stem cells are just small parts of the cells in the population. Since the stem cells differentiate into many kinds of cells, it is difficult to strict the lineage toward the necessary cells. We have developed a method for differentiation of embryonic stem cells into the retinal cells. However, a lot of cells differentiate into other cells. Therefore, it is necessary to select required cells and to purify them. Moreover, ES cell transplantation is allogenic transplantation and may cause immune rejection. It is the iPS cell that might solves the problem.