Human pluripotent stem cells are a unique scientific and medical resource. In 1998, scientists at the University of Wisconsin and at Johns Hopkins University isolated and successfully cultured human pluripotent stem cells. The pluripotent stem cells were derived using non-Federal funds from early-stage embryos donated voluntarily by couples undergoing fertility treatment in an in vitro fertilization (IVF) clinic or from non-living fetuses obtained from terminated first trimester pregnancies. Informed consent was obtained from the donors in both cases. Women voluntarily donating fetal tissue for research did so only after making the decision to terminate the pregnancy.
Because pluripotent stem cells give rise to almost all of the cells types of the body, such as muscle, nerve, heart, and blood, they hold great promise for both research and health care. This advance in human biology continues to generate enthusiasm among scientists, patients suffering from a broad range of diseases, including cancer, heart disease and diabetes, and their families. For example, further research using human pluripotent stem cells may help:
- Generate cells and tissue for transplantation. Pluripotent stem cells have the potential to develop into specialized cells that could be used as replacement cells and tissues to treat many diseases and conditions, including Parkinson's disease, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis.
- Improve our understanding of the complex events that occur during normal human development and also help us understand what causes birth defects and cancer.
- Change the way we develop drugs and test them for safety. Rather than evaluating the safety of candidate drugs in an animal model, drugs might be initially tested on cells developed from pluripotent stem cells and only the safest candidate drugs would advance to animal and then human testing.
The Potential of Adult Stem Cell Research
Questions have been raised about the usefulness of adult stem cells in research and treatment, especially as compared to pluripotent stem cells derived from embryos or fetal tissue. Indeed, there is enormous potential for research using such cells. Human adult stem cells have been isolated from tissues such as blood, brain, intestine, skin, and muscle. Furthermore, some adult stem cells have been shown to be more "plastic" than first thought — that is, some of these stem cells appear to be capable of developing into different kinds of cells than first predicted.
There is, however, considerable evidence that adult stem cells may have limited potential compared to pluripotent stem cells derived from embryos or fetal tissue. Human adult stem cells have not yet been isolated from all cell and tissue types, and they have not been shown to be capable of developing into all of the different cell and tissue types of the body. Furthermore, adult stem cells are difficult to obtain, since they are often present in only minute quantities. They are difficult to isolate and purify, and their numbers appear to decrease with age. Moreover, adult stem cells may have more DNA damage, and they appear to have a shorter life span than pluripotent stem cells. For all of these reasons, and because of the enormous potential of stem cell approaches to research and treatment, it is vitally important that scientists study and compare both pluripotent and adult stem cells.