Patching Hearts

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Frederick Schoen, a professor of pathology at Harvard Medical School who was not involved in the study, says that the MIT research offers a solution to a problem that has only recently been addressed by cardiac tissue engineers. Schoen says that, just as rowers line up in one direction to propel a boat forward, "all the heart muscle cells in a given region have to be lined up and contracting in the same direction" in order for the heart to beat efficiently. The honeycomb-like scaffold described by the MIT group represents a "substantial jump" toward that goal, Schoen says.

Ultimately, the goal is to create patches of tissue that can repair damaged areas of the heart better than current patches, which are made out of synthetic materials. Richard Weisel, a cardiac surgeon from University of Toronto, says that such patches are used during heart surgery in two major ways: to restore heart tissue in patients who have had damaged tissue removed after a heart attack, and to repair congenital heart defects in infants and children. But inert materials, while helpful, can't act as part of the living heart and can lead to scarring over time. "If we had a biodegradable biomaterial, which had beating heart cells, we might be able to return function to that part of the heart," he says.

But a major hurdle still must be crossed before heart tissue engineering becomes a reality: finding a reliable source of cells. While Weisel and other researchers have had luck coaxing adult stem cells from bone marrow and other tissues to turn into heart muscle cells, Lisa Freed, senior author of the Nature Materials paper, says that finding enough stem cells to generate tissue is still a practical problem. Another challenge is to expand this honeycomb scaffold to create thicker, larger pieces of tissue, which would be necessary to have practical uses in the clinic.

In the meantime, Freed believes that the technology could have a more immediate use as a better way to screen for heart drugs. She says that a three-dimensional scaffold of aligned cells offers a more true-to-life model for testing how drugs affect the beating heart than current methods that rely on cells cultured in a single layer.