Engineered heart tissue reveals fibroblast-cardiomyocyte crosstalk in hypertrophic cardiomyopathy

In a laboratory at the intersection of tissue engineering and cardiac disease, researchers have watched something unexpected unfold in miniature heart tissue grown from human cells. The tissue carried a genetic mutation known to cause hypertrophic cardiomyopathy—a condition where the heart's walls thicken abnormally, restricting blood flow and triggering chest pain, breathlessness, and sometimes sudden heart failure. But the mutation alone did not fully explain what the researchers saw. When they added a second cell type—connective tissue cells called fibroblasts—the disease signature became unmistakable. The two cell types were talking to each other in ways that amplified the damage.

Hypertrophic cardiomyopathy, or HCM, typically arises from mutations in genes that build the sarcomere, the fundamental contractile unit of muscle. Two genes in particular, MYH7 and MYBPC3, have been repeatedly implicated in the disease. For years, researchers focused on what these mutations did to the heart muscle cells themselves—the cardiomyocytes. But the new work, led by Nathaniel Huebsch and colleagues, suggests that understanding HCM requires looking beyond a single cell type.

The team engineered human micro-heart tissue in the laboratory, a three-dimensional structure that mimics the architecture of real cardiac tissue far more faithfully than flat cell cultures. They introduced the MYBPC3 mutation and then manipulated a key variable: the stiffness of the tissue scaffold. As they increased mechanical stiffness—simulating the stiffer environment of a diseased heart—something shifted. The fibroblasts and cardiomyocytes began communicating differently. The cardiomyocytes' sarcomere structures, already compromised by the mutation, began to break down more severely. The disease phenotype, in other words, became visible only when all the pieces were present together.

Huebsch explained the reasoning behind the approach: prior work had shown that mechanical stress could trigger the HCM disease state in tissue models. But to see that state fully expressed, the tissue needed to be structurally sophisticated enough to mature properly. A simple two-dimensional culture of mutant cells would not suffice. "By using something that's structurally more like a real heart, we could push the tissue to be mature enough to see a disease phenotype," he said. The engineered tissue provided that maturity.

The critical finding was the crosstalk itself. When fibroblasts were absent, the mutant cardiomyocytes showed less severe disease markers. When fibroblasts were present, the damage accelerated. The researchers observed that as tissue stiffness increased, the communication between the two cell types changed—a shift that appeared to drive further deterioration of the cardiomyocyte structure. This suggested the team was not simply observing a disease state but capturing distinct stages of disease progression, each dependent on the interaction between cell types.

The implications challenge how researchers think about cardiac disease modeling. Most studies focus on the cell carrying the mutation—what it produces, how it behaves in isolation. But HCM, like many diseases, unfolds in a tissue context. Fibroblasts secrete molecules that influence cardiomyocytes; cardiomyocytes release signals that shape fibroblast behavior. This paracrine crosstalk—the real-time chemical conversation between neighboring cells—appears to be essential to how the disease actually develops. A model that includes only mutant cardiomyocytes will miss this conversation entirely.

Huebsch posed the question directly: how sophisticated do disease models need to be? The answer, his team's work suggests, is more sophisticated than we have typically assumed. The crosstalk between fibroblasts and cardiomyocytes is not a detail to be added later. It is fundamental to understanding how HCM progresses from a genetic mutation to a life-threatening condition. Future research into treatments will need to account for this cellular dialogue, not just the behavior of individual cell types in isolation.