A new device that uses a rigorous training regimen to grow small amounts of cardiac tissue and measure how strongly it beats has been developed by the researchers at the University of Toronto (UniToronto). The platform is ideal for testing the effects of potential drug molecules and could help bring personalized medicine closer to reality. Many potential new drugs fail because of toxicity issues, and cardiac toxicity is a major challenge. The researchers build devices that enable lab-grown cells and tissues to develop into 3-D forms that more closely resemble those in the human body. Five years ago, they created the Biowire, a platform in which heart cells grow around a silk suture. By pulsing electricity through the cells, the device causes them to elongate and become more like mature human heart cells.

The work describes a new platform dubbed Biowire II. It contains two wires made of elastic polymers and positioned three millimeters apart, with heart cells forming a small band of tissue between them. Each time the cells contract, they bend the wires. By measuring the amount of deflection in the wires, the researchers can determine the force of the contraction. The advantage of this system is that it tells the researchers how a given drug molecule is affecting the cardiac output by examining forces of contraction and other key functional readouts.

As with the original Biowire, electrical pulses are used to simulate exercise and 'train' the heart cells. The team has refined the training regimen to create tissue that is even more life-like than what was possible with the previous device, all in just six weeks. The scientists have created both atrial and ventricular heart tissues, and they can even grow a heteropolar tissue, one with both atrial and ventricular ends. 

One of the most impressive tests of the system came when the device was seeded with six different cell lines. Three came from patients with a condition called left ventricular hypertrophy, while the other three came from patients without the condition. The researchers could clearly identify the tissues from patients with the condition by the loss of contractility, which is one of the hallmarks of the disease. 

The ability to accurately replicate the heart condition of a real patient opens the door to new applications in personalized medicine. In addition to studying the progression of disease in a particular patient, the model heart could also be used to screen several potential treatments simultaneously, narrowing in on the ones most likely to be effective for that individual. Ultimately, lab-grown tissues may one day be implanted back into humans to repair damaged organs. The researchers are pursuing separate technologies to address that challenge, but she says that the fact that Biowire II is already having an impact is very gratifying.