Inside a 7-tesla MRI scanner in Donostia-San Sebastián, lab-grown human heart tissue gave researchers a clear signal: a new iron-based agent gathered in scarred areas, and the signal grew stronger as the scarring became more severe.
The work, led by Ikerbasque research professor Aitziber L. Cortajarena at CIC biomaGUNE, could point toward a different way to image cardiac fibrosis. This condition develops when the heart keeps producing collagen after damage or strain, such as a heart attack or long-term high blood pressure. The buildup can stiffen the heart and make it harder to fill and pump blood. Fibrosis is a major factor in heart failure, which affects millions of people worldwide, and there is currently no approved treatment made specifically to slow it.
Doctors often use magnetic resonance imaging, or MRI, to look for heart scarring. Most MRI contrast agents are based on gadolinium, a metal that helps damaged areas stand out in images. But gadolinium can remain in body tissues for years, and its use is restricted for people with kidney failure. The concerns matter especially for patients who need repeated scans to follow their condition.
The new agent uses a specially designed protein to hold tiny clusters of iron atoms. Each cluster measures about 1.4 nanometers—around 50,000 times thinner than a human hair. Iron is a metal the body already knows how to store and remove. Earlier iron-based agents had a drawback: they darkened damaged tissue instead of making it easier to see. The CIC biomaGUNE team says its protein design overcomes that problem.
In tests, the agent accumulated in fibrotic tissue, and its MRI signal became more intense as disease severity increased. The researchers also found that it slowed the progression of fibrosis in the lab-grown tissue. The heart models were made with human heart cells using three-dimensional tissue engineering. They were developed by Ana Villar’s group at the Institute of Biomedicine and Biotechnology of Cantabria, in collaboration with Cortajarena’s team. These models reproduce features such as collagen buildup and increased stiffness, offering a more lifelike setting for testing approaches than ordinary cell cultures.
Lead author Lydia Martínez Parra said the compound was stable, released very little iron and showed low toxicity to cells. It can also be made in water without toxic reagents or extreme conditions, which the researchers describe as a simpler and more sustainable process.
The findings, published in Advanced Functional Materials, are an early step rather than proof that the agent is ready for use in patients. The study was carried out in engineered heart tissue, not in people. Still, combining clearer imaging with a slowing effect in the same agent gives researchers a promising direction to investigate. Further work will be needed to learn whether it can safely and reliably help patients who need heart scans over time.