WASHINGTON - RESEARCHERS have identified the early master cells that make up the human heart and said on Wednesday they could someday be used to make patches to fix damaged hearts.

'This cell that we describe is probably not going to be used directly as cell-based therapy because it has the possibility of going into too many different cell types,' said Mr Kenneth Chien of the Harvard Stem Cell Institute and Massachusetts General Hospital.

But Mr Chien said his team is now looking for intermediate cells that are on their way to becoming beating heart muscle, the cells that line the arteries, and other heart cell types.

More immediately, it helps in understanding what causes heart disease, Mr Chien told reporters in a telephone briefing.

'The study provides a new way of understanding heart disease as it appears in children and in adults,' Mr Chien said.

Mr Chien's team worked entirely with human cells and found the human heart develops differently from hearts in mice - a surprising finding.

'The human heart at birth is more than a thousand times bigger than the adult mouse heart, yet the size of the initial embryos are close in size. Humans are just a heck of a lot bigger than mice, and every organ is bigger. How is that achieved?' Mr Chien asked.

In mice, the progenitor cells that Mr Chien's team found exist for just 48 hours. But a mouse develops from conception to birth in just three weeks, while humans gestate for nine months.

And it turns out the human heart develops from patches of these early heart stem cells. Another surprise - these patches of stem cells tend to congregate in areas linked with congenital heart disease, including the heart valves and pumping chambers. -- Reuters