MSU researchers have developed the world’s first human heart organoids capable of faithfully modeling atrial fibrillation (A-fib), offering a powerful new platform to study heart development, disease, and drug responses. These tiny, functioning heart-like tissues are about the size of a lentil and include chamber-like structures and vascular networks, enabling experiments that were previously impossible with traditional models.
Why this matters: roughly 60 million people globally live with arrhythmias, including A-fib, and there has not been a major drug breakthrough for this condition in over three decades. By providing a living, human-based model of the heart, MSU scientists hope to accelerate therapeutic discovery and improve drug safety assessments.
The Aguirre lab at Michigan State University leads this cutting-edge work in heart organoids. The team starts with donated human stem cells, which can differentiate into various cardiac cell types, to build mini-hearts complete with internal chambers and networks of arteries, veins, and capillaries. A key recent advance came from Colin O’Hern, a physician-scientist in MSU’s osteopathic medicine program, who introduced immune cells—specifically macrophages—into the organoids. In developmental experiments, these immune cells help guide proper heart formation.
Using this enhanced model, researchers induced inflammation within the organoids, triggering irregular heart rhythms that mirror A-fib. Remarkably, applying an anti-inflammatory treatment partially restored normal rhythm, demonstrating the model’s potential for testing therapies aimed at inflammation-driven arrhythmias. The study detailing these findings appears in Cell Stem Cell.
As Aguirre notes, this living human tissue model provides direct insight into heart physiology that hasn’t been accessible before. By surfacing how inflammation can drive arrhythmias and how drugs might interrupt that process, the model could shorten the timeline for developing safer, more effective A-fib treatments and broaden the range of therapeutic options for patients.
Beyond drug discovery, the researchers used their system to age the organoids toward adult-like hearts by exposing them to inflammatory conditions associated with A-fib. This aging approach helps model age-related changes in heart rhythm and disease progression, offering a more relevant testbed for potential interventions.
Aguirre emphasizes that integrating the heart’s own immune components yields a more accurate representation of human physiology, which strengthens our understanding of both health and disease. The absence of reliable human heart models has long hindered progress in arrhythmia research, but this new approach opens doors to faster, more reliable translational advances—and potentially lower costs through better preclinical screening.
MSU is actively collaborating with pharmaceutical and biotech partners to screen compounds for safety and efficacy in preventing arrhythmias, while avoiding cardiac damage. The lab’s ongoing work positions Michigan State University at the forefront of human heart organoid research, with plans to expand toward personalized organoids derived from patient cells and, ultimately, transplant-ready heart tissues.
Contributors to this milestone include researchers from MSU’s Institute for Quantitative Health Science and Engineering and partners at Corewell Health and Washington University, among others. Funders include the National Institutes of Health, the National Science Foundation, Corewell Health–MSU Alliance Foundation, and several foundations dedicated to heart research. This line of work aligns with NIH’s New Approach Methodologies initiative to modernize translational research and improve how preclinical testing predicts human outcomes.
What’s next? Expect broader adoption of patient-specific organoids for precision medicine, expanded drug screening pipelines, and continued refinement of immune-cell–inclusive heart models to capture more facets of heart disease and therapy response. Do you think organoid-based models will redefine how we test cardiovascular drugs in the next decade, or will traditional models still hold sway for certain questions? Share your thoughts in the comments.
