Right beat

Stem cells can replace pacemaker

Published: Monday 31 January 2005

New rhythm from human stem cel (Credit: John Hopkings)Researchers from Johns Hopkins Medical Institutions have successfully implanted genetically engineered human embryonic stem (ES) cells into the hearts of guinea pigs (Circulation, Vol 432, No 7015).

If replicated in humans, the technique could replace electronic pacemakers used by hundreds of thousands of people worldwide. These devices are used to rectify certain heart conditions that interfere with a normal heartbeat. But they can't react the way the heart's own pacemaker does -- for example, raising the heart rate to help us climb stairs.

The scientists engineered ES cells to produce a green protein so that the human cells would be easy to tell apart from animal cells. They then injected them into the heart muscles of the rodents. A few days later, the researchers destroyed each animal's own pacemaking cells located near the point of injection by freezing them. Careful monitoring revealed a new beat originating from the green ES cells and slower than the animal's heart rate -- likely reflecting the lower human rate.

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