Direct reprogramming of somatic cells to induced pluripotent stem (iPS) cells has enormous potential to become a source of patient-specific tissue for cell replacement therapies, in vitro disease modeling, and drug screening (1). Cell therapies based on iPS technology may still be several years away. The issues of potential teratoma formation, heterogeneity of iPS cell populations, and presence of transgenes should be addressed before the technology meets the high standards that must be applied to all stem cell-based therapies (2). The requirements applied to iPS cells used in vitro could be less stringent. Therefore, disease modeling applications of iPS cells as well as pharmaceutical screening using iPS cells show immediate promise.
At a recent Stem Cells and Medicine Symposium held at the University of Wisconsin, leaders in the iPS cell field, Dr. George Daley from the Harvard Stem Cell Institute and Drs. Tim Kamp and Clive Svendsen from the University of Wisconsin, described the use of human iPS cells for disease modeling and drug testing. Drs. Daley and Svendsen both suggested that mice are not men, highlighting the necessity for human-based models of disease. This need has recently been fulfilled by the generation of iPS cells from patients with various diseases, including three major neurodegenerative diseases- amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and Parkinson's disease, and a variety of other genetic diseases (3-6). These disease-specific iPS cell lines will be distributed to the scientific community with the hope of discovering underlying disease mechanisms and potential disease therapies. Indeed, the in vitro model using iPS cells from a SMA patient has already provided proof-of-principal that human reprogrammed cells can be used to test drugs. The breakthrough offered by disease-specific iPS cells to disease modeling and drug development was highlighted by Clive Svendsen, “For disease modeling, iPS cells are very important because we can now take cells from the body, make them pluripotent, and then derive the cells that are affected by any specific disease.”
1. Yamanaka (2009) Cell
2. Hyun, et al (2008) Cell
3. Dimos, et al (2008) Science
4. Park, et al (2008) Cell
5. Ebert, et al (2009) Nature
6. Soldner, et al (2009) Cell