"Our study offers positive and direct evidence in living models that bioengineered cells can replace the electronic pacemaker," said Ronald Li, who leads the research team and is an associate professor of cell biology and human anatomy at the UC Davis School of Medicine.
In the current study, the researchers delivered a gene encoding a bio engineered cell-surface protein to heart muscle cells of pigs. This protein mimics the combined action of several proteins called HCN ion channels, which play a critical role in maintaining a normal, evenly paced heartbeat. These channels control the flow of sodium and potassium ions in and out of cells that regulate the electrical impulses of the heart.
"These channels are critical to normal heart function. We were able to make one protein that codes for a single channel that does the work normally required by several," Li explained. By getting heart muscle cells to produce bioengineered HCN channels, Li and his colleagues were able to reconstruct the SA node of the heart in pigs with implanted electronic pacemakers. The SA node is normally located on the right atrium, the upper right chamber of the heart that receives deoxygenated blood from the body. "We were even able to create new pacemaker regions on the left atrium," Li said.
The researchers first removed the SA nodes in pigs' hearts. To restore the SA node function and evaluate the bioengineered cells, Li's team then implanted electronic cardiac pacemakers like those used in humans and injected an adenovirus carrying a gene encoding for the engineered HCN protein into the heart muscle. In a matter of days following the gene transfer, the pigs' hearts had generated bioartificial nodes at the injection sites. Studies done two weeks after the injections showed the new nodes were able to take over pacemaking function from the electronic devices.
MEDICA.de; Source: University of California, Davis