Recent Stem Cell Advances: Induced Pluripotent Stem Cells for Disease Modeling and Stem Cell–Based Regeneration

Currently, the only available cure for patients with end-stage heart failure is cardiac transplantation. A number of strategies to regenerate heart tissue have been devised to resolve the shortage of available transplantation organs, including transplantation of cardiomyocytes or cardiomyogenic stem cells. Stem cell research is actively pursuing strategies to yield new cell sources for use in regenerative medicine. Stem cells are classified into 2 types of cells, somatic stem cells and pluripotent stem cells.Somatic stem cells reside in various organs such as bone marrow, brain, liver, skeletal muscle, and dermal tissue. Somatic stem cells show multipotency and a capacity for self-renewal that enable these cells to regenerate damaged tissues. However, the in vitro proliferative ability of somatic stem cells is limited. The stem cells that exhibit pluripotency are embryonic stem (ES) cells, embryonic germ cells, embryonic carcinoma cells, and induced pluripotent stem (iPS) cells. Among these pluripotent stem cells, ES cells and iPS cells are expected to be a new potential source of cells for the treatment of many different degenerative diseases, including cardiovascular diseases, as a result of their capacity for self-renewal. The therapeutic effects of human ES cell–derived progeny have been reported in animal models for several diseases.1–5 iPS cells are derived from somatic cells by introducing defined reprogramming factors, and they have the ability to differentiate into various types of somatic cells (Figure 1). Figure 1. Generation of iPS cells from somatic cells. The reprogramming factors are introduced in vitro. The established iPS cells are able to differentiate into various cell types.ES cells, which are derived from the inner cell mass of mammalian blastocysts, have the ability to proliferate robustly while maintaining both their pluripotency and the ability to differentiate into cells of all 3 germ layers.6 Human ES cells were first derived …