McGill researchers develop 'mini-heart' from patient blood cells to study heart disease

A team at McGill University's Research Institute has built a working model of a diseased human heart no larger than a microchip, grown from the blood cells of a patient living with dilated cardiomyopathy. The miniature organ beats on its own, contracts in response to stimuli, and exhibits the same structural and functional abnormalities that characterize the disease in the patient whose cells gave it life. It is, in essence, a window into one person's heart disease, engineered in a laboratory.

Dilated cardiomyopathy is a condition in which the heart muscle weakens and the organ enlarges, losing its ability to pump blood efficiently. It is one of the leading reasons people require heart transplants. The disease is serious and often progressive, and treatment options remain limited. Understanding why it develops and how different therapies might slow or reverse it has been constrained by the tools available to researchers—animal models do not perfectly mirror human disease, and studying actual patient tissue is difficult and limited in scope.

The McGill team, led by Dr. Renzo Cecere and postdoctoral fellow Ali Mousavi, approached the problem differently. They took blood cells from a patient with dilated cardiomyopathy and reprogrammed them into induced pluripotent stem cells, a type of cell capable of becoming almost any tissue in the human body. From those stem cells, they coaxed the development of cardiomyocytes—the specialized muscle cells that make up the heart. These cells were then organized into three-dimensional cardiac tissue on a chip, where they self-assembled into a functioning miniature heart that beats and contracts without external prompting.

To validate their model, the researchers created a second version using blood cells from a healthy volunteer and compared the two side by side. The differences were striking. The patient-derived mini-heart showed distinct variations in its structure, the pattern and force of its contractions, the rhythm of its beating, the movement of calcium through its cells, and the molecular signatures that underlie its function. In other words, the lab-grown tissue faithfully reproduced the hallmarks of dilated cardiomyopathy.

The implications are significant. A model like this could accelerate the search for new treatments by allowing researchers to test drug candidates directly on tissue that carries a patient's specific disease signature. It could also open the door to personalized medicine—the possibility that doctors might one day grow a mini-heart from a patient's own cells, test multiple therapies on it, and identify which treatment is most likely to work for that individual before administering it in the body. This kind of precision could improve outcomes and reduce the number of people who ultimately need a transplant.

Cecere, a cardiac surgeon at the McGill University Health Centre and an associate professor of surgery at McGill, emphasized that the model more closely mimics actual human heart behavior than traditional research approaches. The work represents a meaningful step forward in how scientists can study disease and develop interventions. What remains to be seen is how quickly this technology can move from proof of concept to clinical application—whether the insights gained from mini-hearts grown in dishes can translate into therapies that change how dilated cardiomyopathy is treated in living patients.