Stem cell hopes double 

Embryonic and adult stem-cell findings may re-fuel cloning debates. 
 21 June 2002 

HELEN PEARSON 




Catherine Verfaillie has isolated a stem cell from adult human bone marrow 
that can produce all tissue types.


source: Nature




US scientists have reversed the symptoms of Parkinson's disease in rats using 
stem cells from mouse embryos1. Another team has compelling evidence that 
they have isolated a stem cell from adult human bone marrow that can produce 
all the tissue types in the body, from blood to muscle to nerve2. 


Stem cells from embryos were known to give rise to every type of cell. Those 
from adults were thought to have a more limited repertoire. 


Researchers hope to use stem cells to repair or replace diseased or damaged 
organs, leading to new treatments for human disorders that are currently 
incurable, including diabetes, spinal-cord injury and brain diseases.

 

The new reports may re-fuel the debate in the US Senate over whether to permit 
the cloning of human embryos for medical research, which stalled earlier this 
week. US scientists are fighting to be able to harvest stem cells from human 
embryos. Opponents, such as anti-abortion groups, claim that such studies are 
unnecessary because adult stem cells are an equally versatile alternative.

 

Today's papers do not settle the adult-versus-embryo dispute: they suggest 
that both could yield promising therapies. Ultimately, different cell types 
might best treat different diseases, so most scientists advocate continued 
research on both types. "Parallel work is the efficient way to go," says 
stem-cell researcher Neil Theise of New York University.

 

Embryonic cells

 

Parkinson's disease affects up to 5 million people worldwide. It comes about 
when nerve cells in the brain that produce a chemical called dopamine die, 
causing movement and walking difficulties. 


Scientists have previously struggled to make sufficient dopamine-producing 
cells for a transplant. "We nail that," says Ron McKay of the National 
Institutes of Health in Bethesda, Maryland. His team engineered a gene into 
embryonic stem cells that keeps them churning out the correct type of nerve 
cell. 


The researchers transplanted the cells into the brains of rats with 
Parkinson's symptoms. The animals stopped running in circles and survived for 
2-3 months - "the equivalent of forever", says McKay. 







Ron McKay has reversed the symptoms of Parkinson's disease in rats using stem 
cells from mouse embryos.


source: Nature




This is one of the first demonstrations that embryonic stem cells can help 
animals recover from disease. But the research has a long way to go before it 
can be tested in humans. 


McKay is now trying the technique on monkey and human embryonic stem cells. In 
earlier efforts to treat Parkinson's, transplanted fetal nerve cells had 
trouble making the correct level of dopamine - this problem will also have to 
be tackled. 


If it pans out, stem-cell transplants might be used to repair Parkinson's 
brain damage alongside drugs that prevent nerve cells from degenerating in 
the first place, predicts Ole Isacson of McLean Hospital and Harvard Medical 
School in Belmont, Massachusetts, who is carrying out similar studies: "I 
can't wait for it". 


And the technique - using gene therapy to repair or alter stem cells - could 
be applied to treat many other diseases. Researchers are already working on 
treating diabetes by transplanting cells that secrete insulin into the 
pancreas. "It's a very exciting way to engineer cells that are 
therapeutically useful," says Isacson. 


Adult cells

 

But embryonic stem cells still have disadvantages. First, transplanted cells 
sometimes grow into tumours. Second, the human embryonic stem cells that are 
available for research would be rejected by a patient's immune system. 


Tissue-matched transplants could be made by either creating a bank of stem 
cells from more human embryos, or by 'cloning' a patient's DNA into exisiting 
stem cells to customize them. This is laborious and ethically contentious. 


These problems could be overcome by using adult stem cells, taken from a 
patient, that are treated to repair problems and then put back. But until now 
some researchers were not convinced that adult stem cells could, like 
embryonic ones, make every tissue type.

 




It's very exciting that we can now compare the two
 


Austin Smith, Centre for Genome Research Edinburgh, UK
 




Catherine Verfaillie of the University of Minnesota Medical School in 
Minneapolis and her team have all but settled that debate by identifying an 
adult cell that can grow into any other cell type. "It's an extraordinary 
thing," says stem-cell expert Austin Smith of the Centre for Genome Research 
in Edinburgh, UK, who has criticized some earlier studies.

 

Verfaillie's findings were first revealed in the press in January this year. 
Now they have undergone scrutiny by other scientists and the details have 
been published. The team isolated a rare cell in bone marrow from mouse, rat 
and human. They injected the mouse cells into mouse embryos. 


The cells' descendants turned up in almost every tissue including blood, 
brain, muscle, lung and liver. "People didn't think such cells could be 
generated," says Stuart Orkin of Harvard Medical School in Boston, 
Massachusetts.

 

Groups arguing against human cloning have already quoted Verfaillie's results 
as evidence that there is no need to clone humans to make embryonic stem 
cells. But scientists suspect that there may be some subtle differences 
between the newly discovered adult cells and embryonic stem cells, which 
could affect how they act therapeutically. 


"It's very exciting that we can now compare the two," says Smith. "Politicians 
and lobbyists can say what they like, but it's clear you have to investigate 
both. Nobody serious has ever suggested anything other than that." 





References
 
McKay, R. et al. Dopamine neurons derived from embryonic stem cells function 
in an animal model of Parkinson's disease. Nature 417, published online 20 
June; doi:10.1038/nature00900, (2002). |Article| 
Verfaille, C.M. et al. Pluripotency of mesenchymal stem cells derived from 
adult marrow . Nature 417, published online 20 June; doi:10.1038/nature00870 
(2002). |Article| 




© Nature News Service / Macmillan Magazines Ltd 2003

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