Stem cells repair heart attack damage

Heart attacks kill thousands in the UK each year

Stem cells taken from adult animals can start rebuilding tissues damaged by heart attacks, say US scientists.

Stem cells are the body's "master cells", which can develop into a wide variety of different cells types to replace those which die or are damaged.

However, controlling this development could potentially provide a source of cell types for transplant.

This study offers hope that we might one day be able to actually reverse the damage caused by a heart attack

Professor Francis Collins, National Genome Research Institute

If, during a heart attack, more than about 40% of the principal pumping chamber of the organ is damaged, very little can be done to save the patient.

A ready supply of replacement cells could save some of these patients, doctors believe. In this experiment, carried out on mice, the stem cells were taken from the bone marrow, where they normally help produce replacement blood cells.

However, when injected into the damaged mouse hearts, remarkably, the stem cells began to develop into replacement cardiac muscle cells.

Not only this, but the cells actually migrated into the damaged areas of the hearts, and also produced cells to produce the blood vessels needed to supply the new muscle with blood.

Function improved

After an average of nine days, the new heart muscle cells were present in 68% of the damaged portions of the mouse hearts.

Dr Donald Orlic, from the National Human Genome Research Institute, said: "Initially, I thought if there was a little regeneration - some heart muscle cells forming - then that would be considered successful.

"Instead, our expectations were far exceeded in terms of seeing not just heart muscle cells, but blood vessels and functional measurements showing that the repair actually improved cardiac output. It was a wonderful surprise."

His colleague, Professor Francis Collins, added: "This study offers hope that we might one day be able to actually reverse the damage caused by a heart attack."

Not everything was good news though. The treatment only worked in 12 out of 30 cases - about 40%. This was thought to be caused by the difficulty of achieving an accurate injection of a tiny heart that beats 600 times a minute.

Nonetheless, clinical trials in humans could begin within three years.

The success also provides encouragement that useable stem cells can be found from other sources apart from the human embryo, which remains controversial.

In fact, other researchers have already managed to persuade adult bone marrow stem cells to develop into brain neurons.