Stem cells from a single cell?

A new technique plucks single cells from human embryos, generating stable embryonic stem cells lines while apparently leaving the embryo intact, scientists reported online Wednesday in Nature.

"We're able to for the first time show it's possible to create embryonic stem cells without harming the embryo's potential for life. Hopefully this will solve the most basic objection to stem cell research," coauthor Robert Lanza, of Advanced Cell Technology at Worcester, Mass., told The Scientist.

Still, scientists cautioned the technique is still in its infancy, and only time will tell if it can benefit research. For instance, additional studies need to determine how similar or different the cells produced via this technique are to conventional human embryonic stem cell lines, said James Battey, chair of the National Institutes of Health stem cell task force, who did not participate in this study. "We don't know if it's easier or harder to make dopamine-secreting neurons with them, just as an example. The only way to determine what they can and can't do is with experiments," Battey told The Scientist.

The new findings build on a previous study by Lanza and his colleagues, where they showed they could remove single cells from early stage mouse embryos and derive embryonic stem cell lines.

In their latest study, Lanza and his colleagues experimented on 16 unused embryos produced over the course of in vitro fertilization attempts. They used micropipettes to remove individual cells, known as blastomeres, from the eight-to-10-cell-stage embryos. Cells are already routinely removed from embryos during in vitro fertilization for preimplantation genetic diagnosis, a procedure that apparently does not harm the embryo.

The extracted cells were cultured together in the same medium, including mouse feeder cells. Out of 91 blastomeres, the researchers generated two stable human embryonic stem cell lines and 19 embryonic-stem-cell-like outgrowths.

The embryonic stem cell lines apparently behave like lines obtained using conventional techniques -- for instance, the lines were able to sustain undifferentiated proliferation for more than eight months. The cells also had normal chromosomes and expressed pluripotency markers such as Oct-4, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, nanog, and alkaline phosphatase. These cells readily differentiated into cells of all three germ layers in vitro, and demonstrated their pluripotency by forming teratomas containing tissues from all three germ layers when injected into immune-suppressed mice.

"This is really important work. I'm eagerly awaiting someone to reproduce the experiment to show it stands up to replication," Alberto Hayek at the Whittier Institute for Diabetes in San Diego, also not a coauthor, told The Scientist. He recommended, however, that scientists avoid exposing the embryonic lines to mouse feeder cells to sidestep issues of contamination, instead growing them with human cells or in cell-free conditions.

Arnold Kriegstein at the University of California, San Francisco, who did not participate in this study, called the research "an important advance," but cautioned that the technique remains inefficient, producing relatively few lines from the blastomeres. "The efficiency needs to be improved."

However, when scientists first tried making embryonic stem cell lines, the efficiency was very low, noted Mahendra Rao at Invitrogen, also not a co-author. This new method is not efficient, but "it is still better than how embryonic stem cell derivation started," and is therefore "impressive," he told The Scientist via Email.

Charles Q. Choi
cchoi@the-scientist.com

Links within this article

I. Klimanskaya et al. "Human embryonic stem cell lines derived from single blastomeres." Nature, August 23, 2006 (ahead of print).
http://www.nature.com

Robert Lanza
http://www.advancedcell.com/senior-executive-officers/#Robert%20Lanza,%20M.D.

James Battey
http://stemcells.nih.gov/policy/taskForce/tfMembers.asp

Y Chung, "Embryonic and extraembryonic stem cell lines derived from single mouse blastomeres," Nature, January 12, 2006.
PM_ID: 16227970.

C. Wallace. "Controversy-free stem cells?" The Scientist, October 17, 2005.
http://www.the-scientist.com/article/display/22801/

Alberto Hayek
http://www.whittier.org/pages/lab_investigators.html#Chi

D. Monroe. "Eek, No Mouse!" The Scientist, April 25, 2005.
http://www.the-scientist.com/article/display/15431/

Arnold Kriegstein
http://stemcell.medschool.ucsf.edu/Faculty/kriegstein_arnold.aspx

K Pallarito, "NIH stem cell chief resigns," The Scientist, April 21, 2006.
http://www.the-scientist.com/news/display/23340/

Correction (posted August 25): When originally posted, the story said the cells were removed from embryos more than one at a time. The cells were removed individually.