Startup: Tissue derived from iPS cells can treat heart failure

by KAZUYA GOTO
January 22, 2026

Cardiac spheroids created from human induced pluripotent stem (iPS) cells by Heartseed Inc. handout
A Tokyo-based startup said transplants of cardiac muscle cells that it engineered from induced pluripotent stem (iPS) cells have helped test subjects recover from severe heart failure.

Heartseed Inc., a Keio University spinoff, said most of the 10 patients involved in the clinical test showed improvements in cardiac function and symptoms after the implants.

“We have even confirmed some cases where patients essentially regained standard lifestyles close to those of healthy individuals,” said Heartseed CEO Keiichi Fukuda, who is also a professor emeritus of medicine at Keio University.

No complications associated with transplantation, such as an irregular pulse or tumors in the grafted cells, have been observed.

Heartseed, headquartered in Tokyo’s Minato Ward, said the safety of the therapeutic technique has been validated. It plans to apply for production and marketing approval for the treatment by the end of 2026.

The researchers used cardiac spheroids--clusters of heart muscle cells generated from iPS cells--developed by Heartseed.

Implanted cardiac spheroids are expected to help enhance heart functions in people suffering from ischemic heart disease. These patients have narrowed blood vessels and impaired cardiac function due to arterial sclerosis and other causes.

The clinical test divided the patients into two groups: a “low-dose” category receiving 50 million transplanted cells; and a “high-dose” group with 150 million grafted cells.

Cardiac spheroids were injected into areas of specifically weakened function with a specialized syringe. Coronary artery bypass surgery was simultaneously performed to restore blood flow.

Heartseed then compared pre-test conditions of the five patients of the low-dose group with their conditions one year after transplantation.

Four low-dose individuals showed improvements in indicators for subjective symptoms and cardiac function, such as their hearts’ ability to pump blood.

Three of them no longer experienced significantly troublesome health problems, such as shortness of breath when ascending slopes or stairs.

The five high-dose patients also showed either similar or improved indicators of cardiac function and subjective symptoms six months following grafting.

The cell transplant process likely exerted a distinct positive impact beyond the effect of the bypass operation, given that the patients’ cardiac function tended to markedly improve in the body areas where the cardiac spheroids were implanted, the startup said.

Referring to when the technology will become accessible to the general public, Fukuda said, “We are now doing our utmost, with the hope of delivering it to patients as early as possible.”

Heartseed plans to soon conduct a separate clinical trial to administer cardiac spheroids to patients through catheters, which place a minimal strain on their bodies.