Over the past few years, there have been almost daily reports about stem cells and their miraculous medical benefits. There are countless reports of stem cells being used to treat patients with various illnesses. But what exactly are stem cells?

Stem cells are a group of undifferentiated cells that have the potential to differentiate into almost any type of specialized cell. In general stem cells can be derived from the embryo or adult tissues.  Adult stem cells can be found in almost any tissue but unlike the embryo their numbers are limited. The adult stem cells are usually in a non-dividing state and only become activated if there is tissue injury or a need for repair.

The adult stem cells have the ability to self renew indefinitely enabling them to generate several types of cells types or even regenerate an entire organ. It was initially believed that adult stem cells had a limited ability to differentiate only into the tissues of their origin but now evidence indicates that they can also differentiate into other cell types.

Embryonic stem cells have the potential to differentiate into any cell or an organ-for example you can theoretically create a clone human. The embryonic stem cells are those that are derived from a 4-5 day old embryo.

When stem cells are isolated they are placed in a controlled environment that prevents them from specializing or differentiating but permits them to divide and replicate. This process allows for having a large number of stem cells when needed.

The potential to differentiate into other cell types further classifies stem cells. Embryonic cells are the most potent as they have the ability to differentiate into any cell type.

So how can stem cell help?
For many years, researchers have been studying stem cells for treatment of many medical disorders. Because these cells have the potential to differentiate into any cell type, their potential is unlimited. One of the major uses of stem cells has been to regenerate tissues. At the moment there is a serious shortage of organs for transplantation. Stem cells could potentially be used to grow a new organ. For example after a major burn to the skin, stem cells could be used to replace the burnt skin. In China, eye surgeons recently used stem cells to grow a new lens after removal of cataracts. Scientists are also studying stems cells for the treatment of diabetes.
Other studies involve using stem cells to replace brain tissues in people with Alzheimer and Parkinson disease.
There are currently studies using stem cells to replaced damaged heart tissue. Further studies are being conducted to treat several types of blood disorders (eg sickle cell anemia, leukemia and certain cancers of the bone marrow) with stem cells.
While the potential for stem cell is enormous, there are legal issues surrounding their use. In many countries, the production of embryonic stem cells is illegal, particularly in Europe and the US. In the USA, one can do research on stem cells but any type of human study requires permission. Further, in the USA one cannot use federal funds to do research on stem cells. At the moment, the use of stem cells to treat medical disease is restricted in the US. Until the ethical and legal challenges are sorted out, stem cell therapy will be limited to the lab the potential for abuse of these cells is enormous and this is the reason why there is caution. One does not want a crazy scientist or government to create a clone of humans for any sinister reasons.