Human Heart Regeneration, Lab-Grown Pacemaker, and Heart-on-a-Chip Mark Cardiac Breakthroughs

Researchers have shown for the first time that human heart muscle cells can regrow after a heart attack, created the world's first lab-grown sinoatrial node, and developed a beating 'heart-on-a-chip' that can track cardiac activity at the cellular level. The advances could lead to new ways to treat and study cardiovascular disease, the leading cause of death worldwide.

In a study published in Circulation Research, scientists from the University of Sydney, the Baird Institute, and the Royal Prince Alfred Hospital found that heart muscle cells can regrow after a heart attack, a process previously observed only in mice. Increased mitosis, a process in which cells divide and reproduce, was confirmed in human heart tissue for the first time. The study analyzed tissue collected from living patients during bypass surgery, using samples from both diseased and healthy areas of the heart. A heart attack can destroy up to one-third of the cells in the human heart, and although survival rates have improved, many patients develop heart failure, a condition that can only be cured through transplantation. In Australia, around 144,000 people live with heart failure, yet only about 115 heart transplants are performed each year. The research identified several proteins previously shown to be involved in heart regeneration in mice, with the goal of developing therapies that amplify the heart's natural ability to produce new cells.

Separately, scientists in Shanghai have engineered the world's first laboratory-grown sinoatrial node, the tiny structure that acts as the heart's natural pacemaker. Using human pluripotent stem cells, the team constructed a 3D organoid capable of beating autonomously. The sinoatrial node, nestled inside the right atrial chamber, continuously sends electrical signals that dictate when the atria and ventricles should contract. If it fails, the heartbeat can slow to dangerous levels or pause entirely. The organoid could transform cardiac disease research and drug screening, according to the researchers.

In another advance, scientists from multiple Canadian institutions have created a three-dimensional 'heart-on-a-chip' (HOC) that beats on its own and responds predictably to common drugs. It is the first to incorporate a dual-sensing platform providing real-time tracking of activity throughout the heart tissue down to the cellular level. The researchers harvested cardiac muscle cells and connective tissue cells from rats, seeded them on silicon chips within a gel-like matrix, and embedded two types of sensors: elastic pillars that deform with each heartbeat to measure contractile strength, and hydrogel microsensors averaging 50 micrometers that capture local mechanical stresses at the cellular level. Tests with norepinephrine, which increases heart activity, and blebbistatin, an inhibitor of muscle activity, worked as predicted, demonstrating the HOC's potential for drug screening. The team next plans to simulate disorders using cells from patients with dilated cardiomyopathy and arrhythmias, with the long-term goal of using HOCs to identify the most effective medication for each patient before treatment is administered. The research was published in the journal Nano Micro Small.