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Blood cells regenerate liver, scientists find

By Maggie Fox, Health and Science Correspondent

WASHINGTON, July 26 (Reuters) - People's livers can regenerate using

stem

cells from blood -- a discovery that means patients may be able to grow

their own liver transplants using bone marrow, scientists said on

Wednesday.

They found strong evidence that people who received bone marrow

transplants used some of the cells in their livers.

This adds to a growing body of evidence that stem cells, known as

``master

cells'' because they can produce a variety of different kinds of cells,

might one day be manipulated to create custom-grown organ transplants.

More than 68,000 people are waiting for organ transplants in the United

States alone -- most of them for livers. An average of 10 people die

every

day waiting.

Liver failure can be caused by alcoholism, drug overdoses, hepatitis

infection or other problems. Sometimes, with care, the liver can repair

itself.

``The liver is an incredibly regenerative organ using its own cells,''

Dr.

Neil Theise of the New York University School of Medicine, who led the

study, said in a statement.

So his team decided to look and see if other cells might get drafted in

to

help with this process.

Writing in the journal Hepatology, they said they examined the livers of

two women who had received bone marrow transplants from men.

Bone marrow is rich in stem cells and is routinely used to help patients

with leukaemia, a blood cancer treated by destroying the bone marrow and

replacing it with healthy bone marrow.

Various studies are just starting to suggest that at least some of these

stem cells have the power, under the right circumstances, to give rise

not

only to the various kinds of blood cells but also to cells from other

organs.

Because only men have a Y chromosome, Theise's team looked for cells in

liver samples from the women that carried a Y -- and found them.

``They were women who received bone marrow transplants from men, so we

know they had to have come from bone marrow,'' Theise, a pathologist,

said

in a telephone interview.

He said he did not know why the cells appeared in the livers of the

women,

because their livers were, apparently, healthy. ``It seems that

regeneration and repopulation of the liver with or without injury seems

to

be part of a very complex web of interactions,'' he said.

``It must be putting out some factor which calls them in.''

If scientists could identify this factor, he said, it might be possible

to

give the compound to people suffering from liver disease to help their

bodies repair themselves.

He said other studies suggest that the brain, skeleton and lungs also

call

in stem cells from elsewhere.

Theise's team also looked at men who got liver transplants from women.

Their livers should contain no Y chromosomes, as they came from women.

But

Theise said in one patient, 40 percent of his liver and bile duct cells

had the male chromosome, suggesting they originated from elsewhere in

his

body.

``This isn't a minor process -- this is a major operation,'' he said.

The study suggests other ways to treat liver disease using stem cells.

``You could take cells from the circulation, get them to turn into

hepatocytes (liver cells), and re-inject then into the patient to give

them enough functioning liver mass to get them through the acute

process,'' Theise said.

Teams of scientists are studying just what the factors are that induce

stem cells to produce nerve cells, muscle cells, blood cells and so on.

``The second possibility is to use such cells to populate an artificial

liver assist device ... that could work sort of like kidney dialysis

does.''

Last week British scientists, basing part of their work on Theise's

studies, said they had also managed to derive human liver cells from

bone

marrow stem cells.

14:10 07-26-00

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