Imagine a therapy that could cure diseases, repair organs, grow replacement body parts and reverse many of the unwanted effects of ageing. These are just some of the hopes for stem-cell therapy, an area in which the list of potential uses in medicine grows longer almost by the day.

Like a blank microchip that can be programmed to perform particular jobs, stem cells can be primed to do just about anything. So in theory, at least, any tissue that has degenerated is a potential candidate for stem-cell therapies, raising the possibility of new treatments for spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis, rheumatoid arthritis, vision disorders, motor neuron disease and liver diseases.

Although stem-cell therapy is seen as an exciting new technology, blood stem cells have been used in bone marrow transplantations for more than 40 years to treat leukaemia, cancer, immune system disorders and other conditions.

What has pushed expectations of stem-cell therapy into the stratosphere, is the notion that the potential of stem cells to develop into many different cell types means that they can be used as a body-repair system for many diseases and disorders. One of the areas that holds some of the greatest promise is therapies in which stem cells are triggered to develop into the specific cell type required to repair damaged or destroyed cells or tissues.

According to the US National Institutes of Health, stem cells, directed to develop into specific cell types, offer the possibility of a renewable source of replacement cells and tissues to treat conditions including Parkinson’s and Alzheimer’s diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis. Potential treatments include replacing the dopamine-producing cells in the brains of Parkinson’s patients, developing insulin-producing cells for type I diabetes and repairing heart muscle damaged by a heart attack with cardiac muscle cells.

Instead of transplanting whole organs, such as hearts or kidneys, it may become possible to inject a few stem cells and allow nature to do the rest. In heart disease, for example, one of the goals is to grow healthy heart muscle cells in the laboratory and then transplant them into patients with chronic heart disease. Research in animals suggests that bone marrow stem cells can generate heart muscle cells.

Several clinical trials worldwide are looking at the impact of stem cells on stopping the cascade of events that follow a heart attack. The idea is that injections or infusions of stem cells after a heart attack will help to limit the damage, grow new heart muscle and increase the efficiency of the heart.

Blindness, caused by diseases such as age-related macular degeneration, is also a target for stem-cell therapy: "Retinal regeneration with stem cells isolated from the eyes can lead to a possible cure for damaged or diseased eyes and may one day help reverse blindness," says the International Society for Stem Cell Research.

The use of stem cells in dentistry is also being investigated, raising the prospect of adults growing replacement teeth, instead of wearing dentures.

There is still much work to be done but the potential of stem-cell therapies is giving hope to millions.