If reliable techniques can be developed, pluripotent stem cells could someday allow doctors to create customized, rejection-proof transplants to patch a scarred heart, reawaken damaged nerves or reboot an immune system incapable of fighting infection.
There would then be four critical steps:
- Grow the pluripotent stem cells in culture to create a large quantity of stable, healthy cells.
- Repair faulty genes. This step would be needed if the cells carry a genetic disorder, such as sickle cell anemia.
- Turn the stem cells into a specific cell type or tissue. Once a stable, genetically healthy line of pluripotent cells is established, they must be coaxed into creating specialized types of cells. This process is called differentiation. In nature, it happens through a complex mix of physical and chemical signals, and researchers are learning how to copy these signals in the laboratory.
- Transplant the cells or tissue to the diseased/damaged organ or tissue. The cells will need to reach the right part of the body, take hold, and begin to function. Scientists know how to deliver blood stem cells—through bone marrow transplant, for example—but they still need to develop effective delivery methods for other cell types.
Getting the pluripotent stem cells:
Right now, it’s not clear what will ultimately be the source of pluripotent stem cells used to create treatments, because none of the techniques currently being studied have yet moved into the clinic. The cells can be made in one of several ways:
- Nuclear transfer—using a patient’s skin cell, transferred into an egg (possibly the patient’s own, or that of an egg donor)
- Genetic reprogramming—transforming a skin cell, blood cell or other cell from the patient into a pluripotent stem cell
- Parthenogenesis—using unfertilized eggs. A woman might be able to donate her own eggs to create stem cells that match her genetically, or draw on master banks of stem cells made from eggs (see Off-the-shelf stem cells?).
For more on these techniques, click on the link at right, How do we get pluripotent stem cells?