Photo/Illutration An image of a “miniature heart” created from murine ES cells by a research team primarily from the Tokyo Medical and Dental University. The organ is about 1 millimeter in diameter but has a three-dimensional structure with atrium- and ventricle-like parts. (Provided by the Tokyo Medical and Dental University)

Scientists said they used murine embryonic stem (ES) cells to create “miniature hearts” that could eventually be used to test new drugs and treatments.

The team, primarily from the Tokyo Medical and Dental University, said the hearts are about 1 millimeter in diameter but possess atrium- and ventricle-like parts and even pulsate.

The findings were published in the British scientific journal Nature Communications on Sept. 3.

ES cells are generated from fertilized eggs and can become various tissues and organs.

Many studies in Japan and abroad have tried to cultivate the cells to produce small organs. But the heart has been particularly difficult to produce because of its complicated structure.

The team added proteins--one that encourages growth and another that bonds cells together to create a three-dimensional structure--to ES cells for cultivation for 10 to 15 days to create the miniature hearts.

To enlarge organs produced through regenerative medicine, nutrients must be added for cultivation. But the procedure is technologically difficult and the results are not suitable for transplants.

For now, the miniature organs may be used to see their reactions to newly developed drugs and to understand clinical conditions.

“In the drug discovery business, it is possible that (drug) toxicities to the heart can be detected earlier and more accurately,” said Fumitoshi Ishino, a team member and developmental biology professor at the university.

The team said it is studying how to use the latest method to create miniature hearts from human induced pluripotent stem (iPS) cells.

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