Stem cells taken from human fat can be transformed into smooth muscle cells, offering a way to treat many kinds of heart disease, gastrointestinal and bladder ills, US researchers reported on Monday.

A microscopic view of undifferentiated human embryonic stem cells. California Gov. Arnold Schwarzenegger moved on Thursday to provide his state's voter approved stem-cell research institute with a loan of up to $150 million. [Reuters]

While the experiment does not quite offer a way to turn a pot belly into a flat stomach, the researchers said the transformed cells contracted and relaxed just like smooth muscle cells.

These cells help the heart beat and blood flow, push food through the digestive system and make bladders fill and empty, the researchers reported.

Their study, published in the Proceedings of the National Academy of Sciences, is the latest to show that fat can be a rich source of the body's master cells.

"Fat tissue may prove a reliable source of smooth muscle cells that we can use to regenerate and repair damaged organs," said Dr. Larissa Rodriguez, an assistant professor in the Department of Urology at the University of California Los Angeles medical school.

And almost any American has plenty of spare fat cells.

Rodriguez and colleagues incubated adipose-derived stem cells in a nourishing mixture of growth factors, human proteins that encouraged the cells to become smooth muscle cells.

The researchers said scientists have been looking for sources of smooth muscle for organ repair and treating heart disease, gastrointestinal diseases and bladder dysfunction.

"A major obstacle for such an approach has been finding a reliable source of healthy smooth muscle cells that can be safely harvested and that requires minimal manipulation," they wrote.

Clean, Healthy Fat

One approach has been to take a patient's own cells from an organ. But studies have shown that stem cells taken from a diseased organ are also damaged and do not work well when scientists try to grow them in the lab for a transplant.

Transplants grown from a patient's own fat could be used with no need for anti-rejection drugs, Rodriguez said. Smooth muscle cells have been produced from stem cells found in the brain and bone marrow, but acquiring stem cells from fat is much easier, she added.

The stem cells found in fat are known as multipotent stem cells. They can produce a variety of cell and tissue types, but are not as flexible as embryonic stem cells.

Last week, President George W. Bush vetoed a bill that would have broadened federal funding of human embryonic stem cell research, saying he preferred that researchers pursue so-called adult stem cells, such as those used at UCLA.

Many groups have been looking to fat as a source of stem cells. In April, Cytori Therapeutics Inc. said it was starting a clinical trial to test whether stem cells derived from fat can be used to regenerate breast tissue.

Other researchers have been trying to get stem cells from liposuction specimens.

In a second study published in the same journal, British researchers said they found one important protein that keeps stem cells in a quiescent and non-dividing stage.

Fiona Watt of Cancer Research UK and colleagues studied stem cells from human skin and found a protein known as Lrig1 kept the skin cells from proliferating. When Lrig1 production was silenced, the stem cells began growing and dividing.

The finding may not only offer important information to stem cell researchers, but may also offer insights into cancer, Watt's team said. In cancer, cells ignore the normal signals from the body and proliferate uncontrollably.

The protein is also involved in psoriasis.