Research suggests that injecting some types of stem cells into damaged tissues like the brain or heart causes the cells to differentiate according to the host environment into the appropriate tissues of that environment, sometimes repairing the damage.
One of the major obstacles to using stem cells to treat injury or disease has been obtaining the stem cells. They exist in adults but are rare and difficult to identify. They are plentiful in embryos, but harvesting embryos to get stem cells has obvious ethical difficulties. Moreover, stem cells obtained this way, like any foreign transplant tissue, may be rejected by the host.
Several technologies are coming to the rescue, however:- The development of nondestructive tests to identify stem cells in the person with the tissue damage: Once found, these stem cells be transplanted back into the person with no immune response problem.
- Pharmacological techniques that can reverse the differentiation of any adult cell, such as a skin cell, and turn it into a particular type of stem cell, such as a neural stem cell: Neural stem cells transplanted into a brain area where the patient's own cells have died, such as the subtantia nigra in Parkinson's disease, may produce replacement cells as the stem cells sense their local environment and differentiate into the needed neural types.
In addition to the stem cell treatments for Parkinson's disease mentioned here, a number of laboratories are attempting to restore vision caused by photoreceptor death by using stem cells to replace the photoreceptors; others are inserting DNA to rescue photoreceptors or turn other cells into photoreceptive cells. Choosing the right stem cells and manipulating their state may be necessary to ensure the proper integration of stem cells into the host such that they restore function properly.
