Many heart patients are forced to wear pacemakers, which can be uncomfortable and difficult. But now a group of researchers say they have an amazing new fix for this problem. They conducted a study where they used pigs’ hearts to test gene therapy as a replacement for pacemakers. Scientists and doctors in the cardiology field are thrilled with the results.
This gene therapy procedure could replace bulky implanted electronic pacemakers. A group of scientists have found a way to turn ordinary pig heart muscles into specialized ones that act as a biological pacemaker. These specialized muscles offer a steady heartbeat using gene therapy. The authors of the study hope that this procedure will replace pacemakers in the near future.
How was the study conducted?
Scientists used pigs with a condition called heart block that makes their hearts beat at an extremely slow rate. The researchers injected a human gene into a small region of the heart's pumping chambers; it was almost the size of a peppercorn. Then the researchers reprogrammed heart muscle cells into a type of cell that gives off electrical impulses to drive the beating heart. By doing this, cardiologists at Cedars-Sinai Heart Institute in Los Angeles created ‘biological pacemaker’ cells that restored a normal heart rate in the pigs used in the study. The procedure was able to get the same result as implanting an electronic pacemaker (which sends electrical pulses to the heart, if it beats too slowly or skips a beat) would have gotten.
Dr. Marban, from Mount Sinai, led the study, and issued a statement saying,
“This development heralds a new era of gene therapy where genes are used not only to correct a deficiency disorder but actually to convert one type of cell into another to treat disease. About 2 percent of pacemakers lead to an infection requiring treatment. In the United States alone, about 300,000 people get pacemakers annually. The biological pacemaker also appeared to function as well as an original sino-atrial node and better than typical electronic pacemakers.”
How do researchers know that their results are accurate and applicable to human hearts? Pig hearts are actually quite similar to human hearts as they are around the same size, so researchers were able to substitute them in for humans and still get an accurate result.
“The key to the new procedure is a gene called TBX18, which converts ordinary heart cells into specialized sino-atrial node cells, Marban said. The heart's sino-atrial node initiates the heartbeat like a metronome, using electric impulses to time the contractions that send blood flowing through people's arteries and veins, the scientists explained. People with abnormal heart rhythms suffer from a defective sino-atrial node,” according to CBS news.
Dr. Marban also explained how he proceeded, “In essence, we create a new sino-atrial node in a part of the heart that ordinarily spreads the impulse, but does not originate it. The newly created node then takes over as the functional pacemaker bypassing the need for implanted electronics and hardware. When we exercise, our hearts go faster. When we rest, our hearts slow down. The pigs with the biological pacemaker faithfully reproduced these responses, which were absent in 'control' pigs that had been treated only with an electronic pacemaker.”
What were the effects on the pigs later? After just two days of getting the injection pigs that took it had much stronger heartbeats than pigs that did not receive the gene. This effect lasted for the entire period of the two week study. By the end of the fourteen days, the treated pigs' heart rates began to stall to some extent, but still generally stayed stronger than that of the pigs who did not receive the treatment of the gene injection.
How do researchers plan to use the procedure now? Will it be truly beneficial to pacemaker patients?
Scientists and physicians have set out to use the procedure to help people with heart rhythm disorders who cannot use a pacemaker because of device-related complications (such as an infection or in fetuses in the womb with congenital heart block). Fetuses with such issues cannot have a pacemaker implanted and are at risk for severe heart failure, which many times results in stillbirth. Doctors find that gene therapy will probably be beneficial to them as well.
The scientists hope to create an injection-based treatment to offer the gene therapy to these babies, as they get bigger. Doctors from Mount Sinai said they hope that later the procedure will be utilized in a broader patient population as a real alternative option to the uncomfortable pacemaker. Gene therapy could be utilized as a link to help patients, especially those patients whose electronic pacemaker has to be removed or changed.
Dr. David Friedman, chief of heart failure services at North Shore-LIJ's Franklin Hospital in Valley Stream, N.Y., told CBS,
“Many people with electronic pacemakers that help maintain normal heart rhythm experience short periods when their pacemaker is compromised due to infection or other problems that render it non-functional, Friedman explained. This gene therapy may someday fill that gap, expanding the arsenal of currently experimental gene and stem cell therapies that symbolize the 'holy grail' of treatments for a wide array of heart conditions.”
Many experts are excited about the new development. Dr. Cingolani from Mount Sinai Hospital told Reuters, “Rather than having to undergo implantation with a metallic device that needs to be replaced regularly and can fail or become infected, patients may someday be able to undergo a single gene injection and be cured of the slow heart rhythm forever.”