Getting It Right on Stem Cells

Why hundreds of embryonic stem cell lines aren't enough

Join Our Community of Science Lovers!

This fall funding for embryonic stem cell research once again faces uncertainty. In August a federal district court judge blocked the use of federal funds for any project that would destroy embryos. In September a higher court restored funding temporarily, while it considers an appeal by the Justice Department. We offer a guide to the facts behind the controversy:

Where do the embryos used for stem cell lines come from?
All stem cell lines come from discarded IVF embryos. Currently there are around 400,000 embryos stored at fertility clinics around the country.

How many stem cell lines are there?
A stem cell line is a family of constantly dividing cells produced from a group of parent cells that were harvested from a single embryo. M. William Lensch, a scientist at the Harvard Stem Cell Institute, estimates there are 800 lines around the world.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Why isn’t this enough?
In theory, one stem cell line can supply an infinite number of researchers indefinitely. But despite their omnipotent potential, embryonic stem cells are a finicky lot. Some have a tendency to grow into liver cells, others into blood, and others into nerve, pancreas or heart tissue. Sometimes the differences are caused by known factors, such as embryo age or protein contamination, but more frequently they are not understood. “For some projects, existing lines work very well, but for others, not at all,” Lensch says.

Why aren’t more unused embryos made into cell lines?
Whereas some 60 percent of infertility patients would like to donate their unused embryos to research, a dearth of funding and an uncertain regulatory environment have muddied the process. “Everything is at a standstill right now,” says Elena Gates, director of the IVF tissue bank at the University of California, San Francisco.

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American