Embryonic stem cells are surely having important advantages over adult stem cells.

Firstly, embryonic stem cells are pluripotent, that is, they can form any adult tissue except placenta or fetus; adult stem cells can form only the parent tissue or very few others.

Secondly, embryonic stem cells can be cultured in vitro to generate millions of stem cells needed for replacement therapy. Adult stem cells are rare in number, difficult to isolate and cannot be cultured.

Finally, unlike embryonic stem cells, adult stem cells can accumulate genetic abnormalities.

However, there is a chance that, embryonic stem cells may be rejected by the recipient’s immune system. This problem could be circumvented through therapeutic cloning in which the nuclear DNA from a patient’s cell is transferred into an egg cell which has had its nucleus removed. This process generates a perfect genetic match of the patient.

Animal experiments have led to encouraging results. For example, Parkinson’s, which afflicts 2 percent of people over 65, is a progressively degenerative disease leading to loss of muscle. It is caused by a deficiency in dopamine production in the brain. Embryonic stem cells can be transformed into dopamine-producing neurons.

Early studies showed that mouse embryonic stem cells could replace neurons and other cells of damaged nervous tissues and improve locomotion. Promising results with other organ systems include heart and blood vessels, kidney tubules and pancreatic islet cells which produce insulin.

It appears that, many technical hurdles must be overcome before embryonic stem cells will be available for human therapies, but the potential rewards are enormous.

Link [www.pww.org/article/articleview/9582/1/332]