Cell ' harvest' key to mend human heart.

REPAIRING a damaged heart may soon be possible.Scientists have successfully reconstructed human heart cells from stem cells extracted from mice, a breakthrough that holds out hope to repair damaged hearts without resorting to transplant surgery in the near future.

From embryonic stem cells extracted from mice, scientists at Duke University successfully grew heart muscle cells known as cardiomyocytes. Embryonic stem cells are those derived from the early stages of an embryo.

The cardiomyocytes exhibited the two most important features of heart muscle cells: an ability to contract and conduct electrical impulses essential for pumping of the heart.

But hurdles remain before the tissues can be implanted in humans. One major challenge before the scientists now is to establish blood vessels in the tissue.

Another challenge is to come out with techniques to grow human heart muscle cells fast.

The research was supported by the US's National Institute of Health, the National Heart Lung Blood Institute and Duke University's stem cell innovation programme.

Doctors in India called it an " early breakthrough" towards creating heart muscles to repair damaged hearts.

" If we are able to regenerate heart cells, it is a big thing.

Regenerating heart cells can overcome limitations of current modes of treating damaged hearts with drugs or heart transplant procedure. Conditions in which heart muscles lose elasticity such as high blood pressure can also be addressed by regenerating heart muscle cells," Dr Ravi Kasliwal, cardiologist at Apollo Hospital, said.

" Stem cells definitely have some role but it is still in experimental phase. Some studies say they have benefits, while others disagree. Even at AIIMS, stem cells have been injected in the heart's artery during bypass surgery, presuming these will go to the damaged part. Results are encouraging in some cases," Dr Rakesh Yadav, an associate professor at AIIMS's department of cardiology, said.

" If successful, it could be used in patients suffering heart attack, with weak heart muscles and other heart conditions." In the new study, the heart tissues were grown in an environment that aped natural conditions.

The cells were encapsulated in gel composed of the blood- clotting protein fibrin.

The protein allowed the tissues to grow in three dimensions.

Cells called cardiac fibroblasts were added as the tissues grew.

Cardiac fibroblasts, which make up 60 per cent of cells in a human heart, acted as helper cells.

" If you tried to grow cardiomyocytes alone, they develop into an unorganised ball of cells," Brian Liau, researcher at the biomedical engineering department at Duke's Pratt School of Engineering, said presenting the results at the annual scientific sessions of the Biomedical Engineering Society in Pittsburgh.

" We found that adding cardiac fibroblasts to the growing cardiomyocytes created a nourishing environment that stimulated the cells to grow as if they were in a developing heart," Liau said.

" When we tested the patch, we found that because the cells aligned themselves in the same direction, they were able to contract like native cells. They were also able to carry the electrical signals that make cardiomyocytes function in a coordinated fashion." The need for helper cells is known in mammalian development.

For example, nerve cells need " sheathe" cells known as glia in order to develop and function properly.

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