Tail stem cells used to cure sickle cell anemia in mice

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CHICAGO (AFP) - Stem cell research took another major step forward

Thursday when scientists announced they had cured sickle cell anemia

in mice using stem cells derived from adult skin.

It was the first study to prove that stem cells derived from skin

rather than embryos can be used for therapeutic purposes, something

scientists have hailed as the Holy Grail of genetic research.

It came barely a year after Japanese scientists demonstrated they

could generate stem cells from the skin of mice, a discovery which led

to researchers do the same with human skin in ground-breaking research

announced just over two weeks ago.

Stem cells offer enormous potential for curing and treating disease

because they can be transformed into any cell in the body and then

used to replace damaged or diseased cells, tissues and organs.

In this experiment according to the study published online in Science

Express, researchers reprogrammed skin cells from the tails of mice

with sickle cell anemia into stem cells and then manipulated them into

bone marrow cells.

They then replaced the damaged gene in these bone marrow cells which

caused sickle cell anemia, a chronic, debilitating and mostly

hereditary disease which affects tens of millions of people worldwide

and is especially prevalent in people of African descent.

Then they destroyed most of the defective bone marrow cells using

radiation therapy and replaced them with the healthy bone marrow cells

grown out of the mouse's stem cells.

These healthy cells then replicated themselves and took over the

production of blood cells, curing the mice.

Perhaps most significantly, there was no need for dangerous

immuno-suppressant drugs to prevent rejection of the new cells,

because the stem cells were genetically identical to the treated mice

since they came from the mice's own skin cells.

Scientists had previously only managed to make these customized cells

by replacing the nucleus of an embryonic stem cell with the DNA of the

animal or human they wanted to clone.

This was an incredibly complex process that very few labs were capable

of doing.

It was also hampered by the limited availability of donated human

embryos and the controversy and ethical dilemma surrounding cloning

and the need to destroy a potentially viable embryo in order to access

the stem cells.

But deriving the stem cell from an adult skin cell is a simple process

that can be performed in just about any standard biological lab.

" This demonstrates that (stem cells derived from adult skin) have the

same potential for therapy as embryonic stem cells, without the

ethical and practical issues raised in creating embryonic stem cells, "

said study co-author Rudolf Jaenisch of the Whitehead Institute for

Biomedical Research.

The technique is still far from being ready for use in treating

humans, the researchers cautioned.

" The transplants have been successful now for over four months, but of

course we'll have to monitor the animals to see if this will provide

(healthy blood) cells for the lifetime of the animal, " said study

co-author Tim Townes of the University of Alabama at Birmingham.

Researchers also have to find a better way to transform the skin cells

into stem cells.

That is currently done by using a retrovirus to deliver four genes to

the cell which cause it to revert to its original stem cell form.

But retroviruses can bring other genetic changes such as cancer that

are potentially deadly and hard to control.

" We need a delivery system that doesn't integrate itself into the

genome, " said lead author Hanna also of the Whitehead Institute,

which is associated with the Massachusetts Institute of Technology.

" Retroviruses can disrupt genes that should not be disrupted or

activate genes that should not be activated. "