Embryonic stem cells still gold standard
Posted by Andrea Gawrylewski
[Entry posted at 13th June 2008 09:53 PM GMT]
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The technical challenges of using retroviruses to reprogram cells to a 
pluripotent state could be worked out within the year, researchers said 
today in a press conference at the annual meeting of the International 
Society for Stem Cell Research in Philadelphia. However, they stressed, 
human embryonic stem cells are still, and will continue to be, the gold 
standard for research on pluripotency and differentiation.

The speakers, including George Daley of the Harvard Stem Cell Institute, 
Shinya Yamanaka from Kyoto University, and Rudolph Jaenisch from the 
Whitehead Institute, agreed that while differentiated cells reprogrammed for 
pluripotency hold massive promise, continued research on human embryonic 
stem cells is essential. Indeed, noted Yamanaka, whose group first published 
on reprogramming somatic cells into stem cell-like cells last November, 
without earlier research on how human embryonic stem cells maintain 
pluripotency and differentiate, the reprogramming studies could never have 
been done.

"We need new human embryonic stem cells," said Jaenisch. "They differ 
enormously from iPS cells," and understanding the reprogrammed cells will be 
impossible without good human embryonic stem cells. In particular, these two 
types of cells are derived in completely different ways and therefore, a 
clear understanding of how safe iPS cells are, or how they may behave in 
therapies, is still a long way off.

To move away from using retroviruses, some groups are experimenting with 
adenoviruses, chemicals, and proteins to transfect cells without genetically 
altering them. The panelists agreed that, thanks to the dozens of labs 
working on this problem, an alternative to using retroviruses will be 
revealed within a year.

At this time embryonic stem cells are the only appropriate cells to be 
considered for therapies in the clinic, said Ian Wilmut from the University 
of Edinburgh, who was also at the conference. Even so, Jaenisch added that 
some clinical trials will have to proceed without full knowledge of what 
controls pluripotency and differentiation. And right now, just how 
reprogramming works in iPS cells, in nuclear transfer, and in oocytes is 
still a big black box.

Rayilyn Brown
Director AZNPF
Arizona Chapter National Parkinson Foundation
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