Insulin cells are self-renewing, US study finds

1.00pm

WASHINGTON - The cells in the pancreas that make insulin can create copies of themselves, a finding that shows potential new ways to treat juvenile or type-1 diabetes, US researchers said on Wednesday.

The research, published in this week's journal Nature, also boosts arguments that controversial research using embryonic stem cells may be the best way to pursue a cure for the disease, experts said.

Dr Douglas Melton of Harvard University and the Howard Hughes Medical Institute and colleagues found the self-renewing pancreatic cells in mice.

These cells, called beta cells, make insulin. However, in type-1 diabetes, which affects between 1 million and 2 million people in the United States alone, the immune system mistakenly destroys these cells.

Patients must inject themselves with insulin daily to stay alive, and they risk blindness, limb loss and stroke.

Scientists are working to find new sources of these cells, but there are not enough donors for transplants.

Another potential source is master cells called stem cells, which give rise to new cells. So-called adult stem cells exist in various tissues and blood but have not been found in the pancreas.

Then there are embryonic stem cells. These cells have the ability to produce cells that make any kind of tissue at all, and the hope is to train them to produce tissues and organs on demand.

However, their origin is controversial to some people, because they are taken from tiny embryos left over from IVF or test tube fertilisation attempts. They can also be made using cloning technology.

Opponents, including President George W Bush and some members of the US Congress, find both approaches ethically unacceptable, although there is wider acceptance of the use of IVF embryos.

Melton and colleagues looked for evidence of adult stem cells in the pancreases of the mice.

They gave the cancer drug tamoxifen to the mice, using it as a tracer in cells. It persists in the mature beta cells.

All the new beta cells they could find contained tamoxifen, showing they were generated from pre-existing beta cells, Melton reported.

"If ... people have residual beta cells, these findings suggest that a useful clinical direction would be to find a way to boost the proliferative capacity of those beta cells, to restore insulin production in such patients," Melton said in a statement.


"On the other hand, if type 1 diabetics don't have any beta cells left, then these findings suggest that the only source of new beta cells is probably going to be embryonic stem cells, because there don't appear to be adult stem cells involved in regeneration."

Dr Ken Zaret of the Fox Chase Cancer Centre in Philadelphia said the study did not prove there are no adult stem cells in the pancreas. "But it does shine light on a resource for insulin-producing cells that has been there all along: the beta-cell itself," Zaret wrote in a commentary.

Dr Robert Goldstein of the Juvenile Diabetes Research Foundation said the study supported his organisation's argument that the federal government should lift restrictions on funding embryonic stem cell research.

"Some people say you don't need embryonic stem cells because adult stem cells do everything. This would suggest that is not correct," Goldstein said in a telephone interview.

His organisation is offering funding to researchers who want to find out if beta cells can regenerate themselves.

- REUTERS