Most of us know someone who lost their life to heart disease. Indeed, as medical science gets more sophisticated, heart disease remains the primary cause of death in the developed world. The heart is a beautifully efficient pump, with intricately arranged sheets of myofibrils producing enough force at every heart beat to propel the blood throughout the body. So what is heart disease?

When the heart’s structure, dynamics, and/or function are disrupted, the blood can no longer be efficiently pumped, which leads to a host of health complications. Finding cures is hampered by the many biophysical mysteries underpinning the efficient operation of the heart. For example, many forms of heart disease are associated with changes in cardiac myofibril organization, but how that impacts the heart’s ability to pump is unclear.

The cover image on the April 12 issue of Biophysical Journal shows a disorganized cardiac tissue that helps us understand the physical relationship between structure and function in the heart. The image is a large, 10x, view of a cardiomyocyte monolayer organized similar to a parquet floor with an arrangement of square tiles of longitudinally grained wood. To generate the sample for imaging, cardiac cells were seeded onto a parquet pattern like the one illustrated in our manuscript. The cardiomyocytes then spread out, guided by the pattern, to take on the architecture seen in the cover image. While the resultant cardiac tissue is globally disorganized, in our article, we show that such tissues produce a much higher force than disorganized tissues made from cells cultured on a uniform extracellular matrix. Using such parquet tissues, we were able to elucidate the relationship between global organization and net developed force of cardiac tissues. The discovery and experimental technique will continue to be used to understand and better design engineered cardiac tissues, including ones made from stem-cell derived cardiomyocytes.

- Meghan B. Knight, Nancy K. Drew, Linda A. McCarthy, Anna Grosberg