More information about using telomerase to 'immortalize'
cells to treat various diseases;
http://my.netscape.com/news/TopStories/02_17_2000.rontz1412-story-bcnewsscienceliver.html?cp=aim
Immortal Cells May Be Key to Cirrhosis-Researchers
WASHINGTON (Reuters) - Helping liver cells to become a
little more immortal may be the key to treating liver
disease, two teams of researchers reported on Thursday.
One team made liver cells live longer by renewing little
caps that protect the genetic material in cells, while a
second team gave liver cells temporary immortality to help
make a grow-your-own liver transplant for rats.
This could mean that intense study aimed at understanding
the aging process might also lead to new treatments for
liver cirrhosis and other chronic diseases, the researchers
said.
The caps are called telomeres, and they are found on the
ends of the chromosomes that carry the genes. Each time a
cell divides, the telomeres become a little more frayed.
Eventually, they becomes so damaged that the cell dies.
Sometimes cells can secrete an enzyme called telomerase that
helps prevent this damage. It seems to be linked to the
out-of-control cell growth that marks cancer, but
researchers are also looking at ways to use telomerase to
reverse some aspects of the aging process.
Dr. Ron DePinho of the Dana-Farber Cancer Institute and
Harvard Medical School in Boston and colleagues showed that
telomere damage may be the cause of cirrhosis of the liver,
the world's seventh leading cause of death by disease.
``Telomerase therapy may be useful for a wide spectrum of
chronic diseases, including cirrhosis,'' he said in a
statement.
DePinho said more work needs to be done, but it offers a new
approach to treating not only cirrhosis, but a whole range
of degenerative diseases, including AIDS and leukemias.
Liver cirrhosis is caused by hepatitis, heavy drinking,
parasitic infections and other damage to the liver. It takes
years to develop because liver cells, known as hepatocytes,
can regenerate many times.
But eventually they become scarred and worn and the liver
loses its ability to filter out toxins. Fluids can build up,
causing swelling known as edema, the heart can be damaged
and even brain damage can result.
Scientists have wondered whether the telomeres in the
hepatocytes were becoming worn out as they frantically
regenerated to repair the damage caused by disease or
drinking.
``The effects of alcohol or infection create so many cycles
of cell damage and regeneration that the cells essentially
run out of telomeres,'' DePinho said.
``The cells can no longer divide and, when they die, they
stimulate the production of scar tissue.''
His team experimented with mice, damaging their livers with
chemicals and seeing how long it took the liver cells to
stop regenerating and for cirrhosis to begin.
Then they genetically engineered mice to make their liver
cells produce extra telomerase. The mice did not develop
cirrhosis when chemicals were used to damage their livers,
they reported in the journal Science.
They said they believed their findings would translate to
humans.
Currently, the only option for patients with advanced liver
disease is a transplant, but not enough livers are
available.
A second team at Harvard and Brigham and Women's Hospital in
Boston, along with a group at Okayama Medical School in
Japan, thought along similar lines.
They made human liver cancer cells ``immortal'' not with
telomerase, but with another gene taken from a virus. Taking
into account the risk of cancer, they used a second gene to
reverse this process after they had grown a lot of cells.
Transplanted into rats who had 90 percent of their livers
removed, the cells worked to keep the rats alive. One
obvious worry would be that turning on telomerase production
could cause cells to become cancerous. DePinho said more
study would be needed to answer that fear.
``It's possible that if you deliver telomerase early, before
the telomeres get too short, you may be able to prevent
cells from becoming cancerous,'' he said.
``That's because chromosomes with short telomeres are more
likely to break and rearrange themselves in abnormal ways,
resulting in a scrambling of the genetic code that can set
the stage for cancer. From that standpoint, rebuilding
telomeres may actually confer a protective cushion against
cancer. ``
-- KeelyNet - From an Art to a Science Jerry W. Decker - http://www.keelynet.com/Interact discussion list http://www.keelynet.com/discuss.htm KeelyNet - PO BOX 870716 - Mesquite, TX 75187------------------------------------------------------------- To leave this list, email <listserver@keelynet.com> with the body text: leave Interact list archives and on line subscription forms are at http://keelynet.com/interact/ -------------------------------------------------------------