A group of Japanese researchers says it has succeeded in creating a functional "mini heart," using embryonic stem cells from a mouse.
The group at Tokyo Medical and Dental University, led by Professor Ishino Fumitoshi, cultivated the ES cells by adding a special protein called laminin.
Embryonic stem cells have the ability to develop into all kinds of body cells and have similar characteristics to iPS cells.
The researchers say the cells formed a heart-like structure about one millimeter across after about two weeks.
The heart reportedly has an atrium and a ventricle, beats like a real heart, and has a similar structure to the heart of a mouse fetus.
The researchers say this is the first time that a heart has been successfully developed with a 3-D structure.
Ishino says his group plans to research if a miniature heart can be created in the same way from human iPS cells. He adds that artificial hearts could be used to test the safety of new drugs.