Sympathetic neurons can modify the intrinsic structural and functional properties of human pluripotent stem cell-derived cardiomyocytes.

Summary: Have you ever wondered how your heart knows to beat faster when you’re scared? It’s thanks to the "fight or flight" nerves that connect directly to your heart muscle. In the lab, scientists often grow heart cells from stem cells, but these cells usually act like "baby" hearts—they are immature and don't beat quite right. In this study, researchers placed these lab-grown human heart cells in a dish alongside nerve cells from rats. The result? The nerve cells acted like coaches, helping the heart cells "grow up." The heart cells developed better structure and functioned more like adult heart tissue, responding properly to chemical signals. This discovery helps scientists create better heart models for testing new medicines.