Heart muscle cells grown from patient stem cells offer a promising way to repair damage caused by heart attacks and heart failure. However, once transplanted, these cells often struggle to synchronize with native heart tissue, increasing the risk of dangerous arrhythmias. A major obstacle has been the inability to directly monitor how transplanted cells mature and electrically integrate inside the living heart. Now, a flexible electronic platform offers real-time monitoring of stem cell integration.

Researchers from Harvard University (Cambridge, MA, USA) have developed the first platform capable of continuously tracking the maturation and electrical behavior of transplanted heart cells in vivo. The platform is based on “cyborg organoids,” which combine cardiac tissue with stretchable nanoelectronics embedded throughout their three-dimensional structure.

Using this approach, researchers grew human induced pluripotent stem cell–derived cardiomyocytes with integrated mesh nanoelectronics and implanted them into living hearts. The embedded sensors enabled real-time, cellular-resolution recording of electrical activity over extended periods. This allowed the team to distinguish signals from transplanted cells against the much stronger electrical activity of the native heart and identify cells that fell out of rhythm.

With the monitoring system in place, the researchers tested strategies to improve graft maturation and integration, including a self-assembling peptide known as RADA16. RADA16, which is already approved as a hemostatic agent, forms supportive fibers that mimic the heart’s natural environment. When mixed with stem cell–derived cardiomyocytes before transplantation, the peptide significantly improved electrical coupling and reduced arrhythmia-like activity, according to the findings published in Science.

Long-term monitoring showed that RADA16-treated cardiac patches developed more mature structural organization and remained largely synchronized with the host heart over months. Instead of firing independently, the transplanted cells beat in step with native tissue, indicating safer and more effective integration. The researchers believe the platform could serve as a powerful tool for evaluating safety and efficacy in heart regeneration and other cell-based therapies where precise tissue integration is critical.

“This work demonstrates how flexible bioelectronics and cyborg organoids together can form a powerful framework for assessing the safety and efficacy of regenerative medicine,” said Assistant Professor Jia Liu, who led the research. “Like all new therapies, safety is a big issue for human heart cell therapy. We think this approach may help the field identify the safest approach."

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