There's a new recipe in the embryonic stem cell cookbook. Scientists have announced the creation of a human master heart cell, able to transform into all the different cells that make up a beating heart.

Though the cells can repair a damaged mouse heart, it's too soon to say whether they will help treat humans who have suffered a heart attack, says Gordon Keller, a cell biologist at McEwen Centre for Regenerative Medicine in Toronto.

Embryonic stem cells are an exciting technology because, in the right environment, they transform into any human tissue. But the human heart, made of three different kinds of tissue, has thus far proved elusive.

By tweaking an existing recipe that makes one kind of heart cell, Keller's team coaxed stem cells into forming all three types: cardiac muscle cells that pump blood, smooth muscle cells that form blood vessels, and endothelial cells that line coronary blood vessels.

Beating cells

Beginning with human embryonic stem cells grown in the lab, Keller's team added proteins important to cell growth and differentiation. After two weeks, the researchers had created a culture that included all three kinds of heart cells, and Ð importantly Ð no others. Even in a Petri dish, the cells beat.

"I think it's fascinating to think you can take a cell, put it in a dish and 12 to 14 days later you get populations that are contracting human heart cells," Keller says.
When implanted into mice, the cells improved their damaged hearts. Just as importantly, the cells did not form teratomas, tumours that are a common problem with stem cell therapies.

"It's extremely interesting to think about having one cell that could do it all," says Chuck Murry, a cell biologist at the University of Washington in Seattle, whose lab converted embryonic stem cells into heart muscle cells last year. (New Scientist, 23 April 08)