Biological heart pacemakers made from human embryo cells have been successfully tested in pigs, raising the possibility that tissue transplants could replace electronic pacemakers.

Because they would be natural, the cell implants would need no power source and, over time, would integrate naturally with the heart. They could even be genetically engineered or manipulated to enhance or alter their function, say scientists.

Although many obstacles need to be overcome before biological pacemaker cells can be used in practice – such as ensuring they cannot form tumours – the proof-of-principle research, carried out by a team in Israel, is a landmark.

The pacemaker cells were derived from stem cells extracted from early-stage donated human embryos.

Such embryonic stem (ES) cells are unprogrammed “mother” cells able to become any type of body tissue, including nerves, organs, skin and heart muscle.

Although some find their use controversial, many scientists believe they hold the promise of revolutionary new cures and treatments for diseases ranging from Parkinson’s to diabetes.

In the new study, scientists from Israel and the United States grew ES cells in the laboratory and chemically coaxed them into becoming cardiomyocytes, the standard muscle cells of the heart. The cells formed three-dimensional clusters called embryoid bodies, parts of which were seen to beat spontaneously in the same way as a normal heart muscle.

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