Induced "pacemaker" heart cells could take the place of man-made pacemakers
By Ben Coxworth
December 19, 2012
Scientists at the Cedars-Sinai Heart Institute have successfully reprogrammed ordinary heart cells to become exact replicas of so-called “pacemaker” heart cells. Such replica cells could conceivably one day be used instead of electronic pacemakers, in patients with heart disease.
Also known as SAN cells, pacemaker cells constitute about 10,000 of the human heart’s approximately 10 billion total cells. They generate coordinated electrical impulses that result in rhythmic contractions of the heart muscle – in other words, they allow the heart to beat. If something goes wrong with them, the implantation of an electronic pacemaker is often required ... for now.
The scientists reprogrammed regular, non-SAN guinea pig heart cells by injecting them with a gene known as Tbx18. The resulting induced SAN cells – or iSAN cells – reportedly had all the key features and functionality of native SAN cells. Even after the effects of the Tbx18 injection faded, those characteristics remained intact.
Previous studies have also succeeded in modifying regular heart cells to behave in a pacemaker-like fashion, although those cells were reportedly still more like regular heart cells than SAN cells. Pacemaker cells have also been created from embryonic stem cells, although using such cells could introduce a risk of cancer.
“Although we and others have created primitive biological pacemakers before, this study is the first to show that a single gene can direct the conversion of heart muscle cells to genuine pacemaker cells,” said team member Dr. Hee Cheol Cho. “The new cells generated electrical impulses spontaneously and were indistinguishable from native pacemaker cells.”
Additional studies into the safety and effectiveness of the technique must be conducted before human trials can begin. Ultimately, however, it is hoped that heart disease patients could be treated with an injection of Tbx18, or with a transplant of lab-grown iSAN cells.
A paper on the research is about to be published in the journal Nature Biotechnology, and is already posted on its website.