Tiny ‘Mini-Hearts’ Offer Hope for New A-Fib Treatments After 30-Year Drought
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A groundbreaking advance in cardiac research offers a beacon of hope for the estimated 60 million people worldwide living with atrial fibrillation (A-fib). After three decades without the development of new treatments for this common heart rhythm disorder, scientists at Michigan State University (MSU) have created remarkably accurate, three-dimensional heart organoids – often referred to as “mini-hearts” – that promise to accelerate drug discovery and improve patient outcomes.
The challenge in developing new A-fib therapies has long been the lack of reliable human models to study the condition. Existing treatments primarily address symptoms rather than the underlying causes, and animal models have proven inadequate in replicating the complexities of the human heart. This new technology directly addresses that critical gap.
Replicating the Human Heart in Miniature
The research, initiated in 2020, centers around these organoids – tiny, lentil-sized models of the human heart constructed from donated human stem cells. These cells, crucial for growth and tissue repair, are guided to develop into the various components of a functioning heart, complete with chamber-like structures and a network of arteries, veins, and capillaries. Remarkably, the organoids beat rhythmically, with the pulsations visible to the naked eye.
“Our new model allows us to study living human heart tissue directly, something that hasn’t been possible before,” explained a researcher involved in the study.
A key milestone came with the addition of immune cells, or macrophages, to the organoids by Colin O’Hern, an osteopathic medicine physician-scientist student at MSU. These cells play a vital role in heart development and formation, and their inclusion significantly enhances the physiological accuracy of the models.
Mimicking A-Fib and Testing Therapies
Researchers were able to induce inflammation within the organoids, triggering an irregular heartbeat that closely mimics A-fib. This allowed them to test the efficacy of an anti-inflammatory drug, which, as predicted, partially restored the heart’s normal rhythm. The findings, published in Cell Stem Cell, demonstrate the potential of these organoids to accelerate the development of targeted therapies.
“This new model can replicate a condition that is at the core of many people’s medical problems,” stated Aitor Aguirre, associate professor of biomedical engineering and chief of the division of developmental and stem cell biology at MSU’s Institute for Quantitative Health Science and Engineering. “It’s going to enable a lot of medical advances so patients can expect to see accelerated therapeutic developments, more drugs moving into the market, safer drugs and cheaper drugs, too, because companies are going to be able to develop more options.”
Unveiling the Role of the Immune System
The study also shed light on the role of long-lived immune cells in guiding heart development and rhythm. This insight extends beyond A-fib, offering potential understanding into the origins of congenital heart disorders, the most common type of birth defect. By “aging” the organoids through controlled inflammation, researchers were able to simulate the conditions that lead to A-fib in adult hearts.
Aguirre emphasized the importance of the immune cell addition, noting, “We’re now seeing how the heart’s own immune system contributes to both health and disease. This gives us an unprecedented view of how inflammation can drive arrhythmias and how drugs might stop that process.”
A New Era for Cardiac Research
The development of these human heart organoids represents a significant leap forward in cardiac research, poised to overcome the 30-year stagnation in A-fib treatment. The technology directly supports the National Institutes of Health’s mission to modernize translational research and improve preclinical testing.
MSU researchers are already collaborating with pharmaceutical and biotech companies to screen potential compounds, ensuring they don’t cause heart damage while effectively preventing arrhythmia. The team has established MSU as a global leader in human heart organoid research, with further advancements anticipated.
Looking ahead, Aguirre’s team envisions developing personalized heart models derived from individual patient cells for precision medicine, and ultimately, generating transplant-ready heart tissues.
Significant contributors to this research include Christopher Contag, Nureddin Ashammakhi, and Sangbum Park from the MSU Institute for Quantitative Health Science and Engineering; Nagib Chalfoun from Corewell Health; and Chao Zhou from Washington University. The research was supported by MSU, the National Institutes of Health, National Science Foundation, the Corewell Heath-MSU Alliance Foundation, Corewell Health, Alternatives Research and Development Foundation, the Saving tiny Hearts Society and the American Heart Association.
