Induced Pluripotent Stem Cells: Their Role in Modeling Disease and Regenerative Medicine

Abstract

Although the field of induced pluripotent stem (iPS) cells is a very new, hundreds of research papers regarding them have been published over the past three years. This chapter concentrates on the medical relevance of iPS cells and where the research regarding iPS cells has reached in such a short period time. The reprogramming of cells using the “stemness” genes and the resultant populations similarity to human embryonic stem (ES) cells has allowed for another source of pluripotent stem cells to be generated which have fewer ethical ramifications then ES cells. We have compared other forms of reprogramming somatic cells to pluripotent cells and explain that even though generating iPS cell lines using the “stemness” factors is slow and inefficient it is far superior in generating pluripotent stem cells then the other methods. This relatively new technology has enabled pluripotent cell lines to be generated from various animal species such as pig, which as yet has a no counterpart in ES cell lines. One of the biggest advantages to using iPS cells is the ability to generate patient specific cells that can be used to treat patients without the complications of rejection and immunosuppression associated with using allogeneic ES cells. However, the ability to generate the correct cell type appropriate for treating the disease and, in the case of patients with genetic disorders, generating iPS cells that do not contain the mutation, are problems that must be overcome for the technology to be useful. On the other hand, using iPS cells generated from various disease types could help unfold the stages of development of the disease and enable drug testing on the diseased cells, which ultimately could be applied to treat the disease in patients. There are still some hurdles that need to be overcome; the most crucial is the safety issues associated with the generation of iPS cell lines. At the moment somatic cells are reprogrammed with vectors that integrate the DNA into the host genome in a manner not fully controlled, which could result in unfavorable insertion sites. In addition, there is the fear that the transgene might reactivate oncogenes; MYC, for instance, one of the reprogramming factors, is also known to be an oncogenes. Overall, the ability to reprogram somatic cells using stemness genes to generated iPS cells is a breakthrough whose full potential is still hard to estimate.