THURSDAY, Sept. 12, 2002 (HealthDayNews) -- With the help of gene therapy, researchers have re-programmed guinea pig heart cells to do a pacemaker's job, and they hope to one day be able to do the same for humans.
A team from the Johns Hopkins School of Medicine got the rodents' hearts beating properly by changing the function of less than 1 percent of their heart cells. The researchers report on what they call the first "biopacemaker" in today's issue of Nature.
Dr. Eduardo Marbán, the lead researcher, says scientists can envision a day when doctors can recreate a human's pacemaker cells rather than having to implant an electronic pacemaker. He adds, though, that such a possibility is years away.
Normally, the heart's pacemaker cells, which are found in the blood-receiving chamber called the atrium, generate electrical impulses that spread through the organ and make it contract. With age or illness, natural human pacemaker cells die off, making a pacemaker necessary.
More than 600,000 pacemakers are implanted every year, according to the American Heart Association. These battery-operated devices work by artificially replacing the heart's natural electrical impulses.
Most heart cells are set to maintain a level of potassium that makes it difficult for them to send electrical signals, or "fire." That means they can't generate an electrical signal on their own; they must wait to be triggered by pacemaker cells.
The Hopkins researchers suspected that if they could alter the potassium balance in the heart cells, the cells might be able to fire without being triggered. To do so, they needed to block the usual potassium "channel" that keeps potassium levels in check.
They did this by altering the gene that controls the potassium channel, inserting it into a virus, and then injecting it directly into the guinea pig heart cells. Three to four days later, the animals' heart cells started producing the defective potassium channel, according to the study. Then, those cells started firing electrical impulses on their own.
Marbán says the researchers saw no evidence of adverse effects from the gene therapy.
He says the researchers plan on testing the gene therapy on larger animals and, if all goes well, they hope to start human trials in as little as four years.
"This is exciting work," says Dr. Freddy Abi-Samra, director of the electrophysiology lab at Ochsner Clinic Foundation in New Orleans. However, he cautions that many steps have to occur before these findings will be useful to humans, and further warns that while guinea pigs provide a good model for human heart function, they are not exactly the same.
Plus, he says the researchers changed only ventricle cells in the heart into pacemaking cells, but would need to be able to change atrial cells for the finding to be of use. Marbán says he suspects that atrial cells will show a similar pacemaking ability once the potassium channel is blocked in those cells.
What To Do
To learn more about the anatomy of the heart and how it works, go to HowStuffWorks. For more information on pacemakers, visit the American Heart Association.
