We tend to think of a pacemaker as a man made device, a piece of metal surgically implanted in a damaged heart to help redirect the rhythm of the heartbeat. But the heart has its own “pacemaker” cells that occur naturally, and an electronic pacemaker device is only inserted to assist the heart in pumping when the cells can’t do it on their own anymore.
Instead of implanting an electronic pacemaker device, why don’t scientists just replenish the heart’s stock of pacemaker cells by creating their own healthy cells in the lab? Answering this question is the mission of a group of scientists from the McEwen Centre for Regenerative Medicine in Canada.
Sinoatrial node pacemaker cells are naturally produced by the body to be the heart’s primary source of pacemaking. Without these cells, the heartbeat would not consist of the infamous “lub dub” characterized by diastole and systole. Defects in the pacemaker cells cause common heart rhythm disorders, which is where the electronic pacemaker devices come into play.
Electronic pacemakers are commonly implanted to help the heart keep the beat, but they are also associated with negative side effects like a lack of hormonal responsiveness, and for young pacemaker recipients, an electronic device is incapable of adapting to changes in the size of the heart.
Another concern is Pacemaker Syndrome, a condition where affected patients with implanted pacemakers experience fatigue, dizziness, and hypotension in association with simultaneous atrial and ventricular contractions.
Using pluripotent stem cells, flexible cells that are capable of becoming more than 200 different cell types from every tissue and organ in the body, researchers are investigating the specific parameters that need to be met to successfully “encourage” these stem cells into becoming biological pacemaker cells reflective of the body’s own cells that are naturally produced. With the right push, scientists could provide an alternative fix for heart rhythm disorders to bypass the use of electronic pacemaker devices.
Scientists from the McEwen Centre for Regenerative Medicine have been vigorously studying the developmental pathway they would have to accurately and precisely navigate to successfully transform stem cells into functional pacemaker cells.
The video above shows an in-vitro visualization of pacemaker heart cells created from pluripotent stem cells, specifically a cluster of human pacemaker cells on top of a sheet of human cardiomyocytes. The pacemaker cells initiate and regulate the heartbeat.
The process is tricky, first author Dr. Stephanie Protze said, because "you have to determine the right signaling molecules, at the right concentration, at the right time to stimulate the stem cells." Once they developed the proper formula, researchers tested the biological pacemaker cells in rats, where the pacemaker cells successfully initiated and regulated the heartbeat.
"We are replicating nature's way of making the pacemaker cell," said senior author and Director of the McEwen Centre, Dr. Gordon Keller.
Human clinical trials to run the same tests are still five to ten years away, as researchers must first ensure safety and reliability. Currently, electronic pacemakers last an average of seven years in the human body, but biological pacemaker cells derived from stem cells could last a lifetime.
The present study was recently published in the journal Nature Biotechnology.