Be still my beating heart. Or, rather, be very, very fast, so that it can be used by science.
This is the battle cry out of the University of Toronto, where researchers are unveiling a biowire that could lead to the production of mature cardiac patches that are derived from real human cardiomyocytes (heart cells). Reporting this week in the scientific journal Nature Methods, cardiac researchers say the tech could lead to the development of mature cardiac patches in a range of sizes.
Let's back up, because when it comes to matters of the heart, things get complicated fast.
Cardiac researchers have for several years been frustrated by the inability to obtain human heart cells from human patients -- the cells simply don't proliferate in large enough numbers, so researchers have used heart cells derived from what are called reprogrammed human induced pluripotent stem cells (hiPCS). It was a big deal when this tech was invented back in 2006, but these stem cells tend to be too immature to provide much of anything for either transplants or research.
So Milica Radisic, who among her many titles is the Canada Research Chair in Functional Cardiovascular Tissue Engineering and was, in 2008, an MIT Technology Review "top Innovator Under 35," decided that it was time to figure out a way to age these cells so that they look and function more like adult heart cells. "Can we mature these cells to become more like adult cells?" she wondered.
Enter the biowire. Those stem-cells are seeded along a silk suture common in medical applications that allows the cells to grow along the length of the suture, which is similar to its natural growth pattern. They then become the object of electrical pulses -- imagine a tiny, gentle pacemaker -- that stimulate the cells enough to actually increase their size and connect and beat like real heart tissue.
With more than a hint of irony, the researchers patterned these electric pulses on a fetal heart rate -- even though they wanted the cells to ultimately look and function less like fetal cardiomyocytes. But by stimulating the cells between 180 and 360 beats per minute, they aged them fast enough to, in a short period of time, get them to resemble mature, adult cells.
"We found that pushing the cells to their limits over the course of a week derived the best effect," Radisic said in a school news release, and added that the rate of improvement in this realm of research is also astonishingly fast. "In 2006 science saw the first derivation of induced pluripotent stem cells from mice. Now we can turn stem cells into cardiac cells and make relatively mature tissue from human samples, without ethical concerns."
By using biodegradable sutures -- which is key for surgical patches that are to remain in a living body -- the biowires can be used in heart transplants and research, and could lead to more accurate drug screening.
While the tech is, in Radisic's words, a "game changer," her fellow researcher Sara Nunes from the University Health Network in Toronto is already looking ahead to the next task at hand: "One of the greatest challenges of transplanting these patches is getting the cells to survive, and for that they need the blood vessels. Our next challenge is to put the vascularization together with cardiac cells."
Do that, she says, and you just might have a viable cardiac patch.