Using a technology previously developed by Chien’s collaborator, Kevin “Kit” Parker, a bioengineer at Harvard, researchers then grew the cells on a thin polymer film that had been patterned with molecules typically found outside of cells, such as collagen. “The cells recognize the geometric cues on the film and reorganize themselves to spontaneously form a piece of cardiac tissue,” says Parker. The cells can contract, and they express the same genes as those expressed by normal heart muscle. (See a video of the muscle cells contracting.) “We can use them to test new drugs, as well as the safety of different drugs, chemicals, and nanomaterials,” says Parker. “We can also graft them onto the heart and restore contractility of that injured region of the heart.”
The researchers still have several steps to surmount before they can test how well the patches will repair the heart. They must find ways to isolate human versions of these cells. To make patches that are therapeutically useful, they must create three-dimensional versions of the two-dimensional patches of muscle cells. That will require the addition of blood vessels to feed the muscle. “We are working on additional technology to template in a vascular system within the cardiac tissue,” says Parker. “Once we’re comfortable with that, we will take it into animals.”
Ultimately, scientists would like to generate these heart-muscle-producing cells from induced pluripotent stem cells, a type of adult stem cell that can be made from a patient’s skin cell. This would allow physicians to take a skin biopsy from a heart-attack patient, generate a heart patch that is genetically matched to the patient, and implant it over the damaged heart tissue.