Gene therapy to replace pacemakers?

A team of Australian researchers has developed a gene therapy treatment that they say could one day replace electronic pacemakers in people with heart damage. The scientists, based at the Children's Medical Research Institute in Sydney, have managed to electrically excite fibroblast cells growing in the laboratory. The treated cells are able to 'twitch' again, like healthy heart muscle cells responding to electrical signals.

The heart's 'natural pacemaker', which makes the electrical signals that cause the heart to beat,  is a mass of cells at the top of the right upper chamber. For the heart to beat properly, these signals must travel across the heart to reach the lower chambers, which pump the blood around the body. Damage to the heart, like that caused by a heart attack, can interfere with ability of heart cells to generate or respond to these electrical signals. Artificial pacemakers are small, battery operated devices that can replace a defective natural pacemaker or blocked pathway.

In the latest study, published in the journal Circulation, the researchers used a virus to deliver two genes to fibroblast cells - the cell type that makes up scar tissue. The first gene, called MyoD, reprogrammed the cells to behave like muscle cells, which enabled them to respond to electrical signals. The second, called connexin43, allowed the cells to communicate with other cells, making them capable of passing on electrical signals. The study shows that gene therapy could potentially be used instead of an artificial pacemaker. 'We can take scar tissue cells and we can, using gene transfer, make them behave as though they were a heart cell', said team leader Ian Alexander.

Alexander said that a single injection of the genes had the potential to repair thousands of scarred heart cells. He hopes that animal experiments and eventually human trials will begin soon. 'What we envisage is you might have a patient with damage to those electrical pathways caused by scarring from a heart attack, an operation or even in childhood with a congenital heart problem - we could go and genetically reprogram them to be a useful cell type that restores function of the heart', he said.