2007); however, the full therapeutic and scientific potential of these induced pluripotent stem (iPS) cells requires continued exploration (Robinton and Daley, 2012). Both hES and iPS cells are often referred to as pluripotent stem cells because they have, in principle, the capability to give rise to all adult tissues.
The ability of these different types of stem cells to self-renew and differentiate into more mature cell types is the foundation of the regenerative medicine field, providing hope for repairing or supplementing a patient’s damaged tissue (Robinton and Daley, 2012). Furthermore, stem cell therapy, if successfully developed, could potentially treat diseases, such as Parkinson’s disease, type 1 diabetes, and spinal cord injury, for which current forms of therapy are less than adequate, and although even more challenging, could potentially be used in treatment of other serious diseases that historically have had poor outcomes, such as Alzheimer’s disease, stroke, and some types of cancer. Another use of stem cells is to help test and develop new drugs (Grskovic et al., 2011). Because pluripotent stem cells can differentiate into a variety of differentiated cell types, drug testing can be performed on these cells before clinical trials are conducted on human subjects, making it possible to test the drugs’ effectiveness and adverse effects more efficiently, particularly in patient-specific stem cell lines (Yu and Thomson, 2010). Pluripotent stem cells (both hES and iPS) derived from patients with specific diseases have also proved useful in studying disease pathogenesis. This has been clearly demonstrated for “cell-autonomous” diseases such as long QT syndrome, in which cardiomyocytes differentiated from patient-specific pluripotent stem cells display the abnormal electrophysiologic phenotype characteristic of the disease. Regenerative medicine can be defined as the process of creating living, functional tissues to repair or replace tissue or organ function lost due to age, disease, damage, or congenital defects. This can be done through a variety of approaches including the replacement of tissue function with synthetic constructs (artificial organs) and using cellular therapies such as stem cells or genetically modified cells to generate new tissues and organs (ESF, 2012).
Because the derivation of hES cells involves the destruction of human embryos, the scientific community and others immediately recognized that the use of these cells raises important ethical questions regarding the moral status of the embryo; whether research that involves the destruction of embryos is morally acceptable; and if so, whether such research should be funded by federal or state governments. Given the continuing and sharply different perspectives on these key ethical issues, the controversy regarding the appropriateness of public funding for research that requires creat-