Stem-cell breakthrough

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Stem-cell breakthrough

By Helen Tobler

18jun02

SCIENTISTS have succeeded in rebuilding an organ crucial to the human immune

system entirely from stem cells, opening the way for the treatment of HIV

and cancer.

Stem cell researcher Boyd. Photo Craig Borrow

More national news Stem cells in the thymus - the organ that is crucial to

the normal functioning of the immune system - have been identified by a team

at Monash University in Melbourne. T-cells, the cells that fight infection,

are only created in the thymus.

In an article, published today in the international journal Nature

Immunology, research scientists Boyd and Gill reveal they were

able to rejuvenate a damaged thymus and then regenerate the immune system in

mice.

Associate professor Boyd, who led the research, said the discovery

had opened an opportunity to rebuild a patient's thymus after it had been

destroyed. But the real significance of the research was the ability to

create T-cells, Dr Boyd said.

The research, which took 15 years and was funded by the federal Government,

could lead to treatments for conditions in which the T-cells have been

severely depleted, such as AIDS, and after radiation therapy or

chemotherapy.

" It will also be useful in controlling organ transplantation and correcting

auto-immune diseases. We know these diseases are caused by abnormal

T-cells, " Dr Boyd said.

In auto-immune diseases, such as diabetes, multiple sclerosis and lupus, a

malfunctioning thymus is symptomatic.

Dr Gill said the studies on mice enabled them to generate a fully functional

organ from stem cells.

" It's the first time people have generated a fully functional organ that has

been shown to conduct every function exactly the same from very few starting

stem cells.

" We haven't effectively shown that the cells we're looking at are able to

give rise to themselves, which is an issue we bring up in the paper. But

we've clearly shown that these cells are able to give rise to all the other

cells within the thymus, and that these cells are able to attract other

various cells in, and make a fully functioning organ. "

The thymus normally was fully functional before puberty and replenished the

blood with T-cells, Dr Gill said.

" But after puberty, when the sex steroids come out, the thymus drastically

decreases its function. Normally it's not a big issue but when you have to

replenish the immune system, say in diseased states, it can be a problem.

" So we're looking at therapies to be able to activate these stem cells and

give rise to a fully functional thymus in the adult situation. "

If the epithelial cells -- cells in the thymus that are essential to the

immune response -- can be stimulated to produce a thymus, this will

regenerate the T-cell pool.

Dr Gill said human trials were still some way off.

The Australian