Heroic three-year study reveals safe methods for growing clinical-grade stem cells

Imagine seeking out the ideal pancake recipe: should you include sugar or no sugar? How about bleached vs. unbleached flour? Baking power or baking soda? When to flip the pancake on the skillet? You really have to test out many parameters to get that perfectly delicious light and fluffy pancake.

Essentially that’s what a CIRM-funded research team from both The Scripps Research Institute (TSRI) and UC San Diego accomplished but instead of making pancakes they were growing stem cells in the lab. In a heroic effect, they spent nearly three years systematically testing out different recipes and found conditions that should be safest for stem cell-based therapies in people. Their findings were reported today in PLOS ONE.

stem cells 2

Pluripotent stem cells. Courtesy of Andres Bratt-Leal from Jeanne Loring’s laboratory.

Let’s step back a bit in this story. If you’re a frequent reader of The Stem Cellar you know that one of the reasons stem cells are such an exciting field of biology is their pluripotency. That is, these nondescript cells have the capacity to become any type of cell in the body (pluri= many; potency = potential). This is true for embryonic stem cells and induced pluripotent cells (iPS). Several clinical trials underway or in development aim to harness this shape-shifting property to return insulin producing cells to people living with diabetes or to restore damaged nerves in victims of spinal cord injury, to name just two examples.

The other defining feature of pluripotent stem cell is their ability to make copies of themselves and grow indefinitely on petri dishes in the laboratory. As they multiply, the cells eventually take up all the real estate on the petri dish. If left alone the cells exhaust their liquid nutrients and die. So the cells must regularly be “passaged”; that is, removed from the dish and split into more dishes to provide new space to grow. This is also necessary for growing up enough quantities of cells for transplantation in people.

Previous small scale studies have observed that particular recipes for growing pluripotent cells can lead to genetic instability, such as deletion or duplication of DNA, that is linked with cancerous growth and tumor formation. This is perhaps the biggest worry about stem cell-based transplantation treatments: that they may cure disease but also cause cancer.

To find the conditions that minimize this genetic instability, the research team embarked on the first large-scale systematic study of the effects of various combinations of cell growth methods. One of the senior authors Louise Laurent, assistant professor at UC San Diego, explained in a press release the importance of this meticulous, quality control study:

“The processes used to maintain and expand stem cell cultures for cell replacement therapies needs to be improved, and the resulting cells carefully tested before use.”

To seek the ideal recipe, the team tested several parameters. For example, they grew some cells on top of so-called “feeder cells”, which help the stem cells grow while other cells used feeder-free conditions. Two different passaging methods were examined: one uses an enzyme solution to strip the cells off the petri dish while in the other method the cells are manually removed. Different liquid nutrients for the cell were included in the study as well. The different combinations of cells were grown continuously through 100 passages and changes in their genetic stability were periodically analyzed along the way.

loring_jeanne

Jeanne Loring (above) is professor of developmental neurobiology at TSRI and senior author of the study with Louise Laurent of the University of California, San Diego.

The long-term experiment paid off: the team found that the stem cells grown on feeder free petri dishes and passaged using the enzyme solution accumulated more genetic abnormalities than cells grown on feeder cells and passaged manually. The team also observed genetic changes after many cells passages. In particular, a recurring deletion of a gene called TP53. This gene is responsible for making a protein that acts to suppress cancers. So without this suppressor, later cell passages have the danger of becoming cancerous.

Based on these results, the other senior author, Jeanne Loring, a professor of developmental neurobiology at TSRI, gave this succinct advice:

“If you want to preserve the integrity of the genome, then grow your cells under those conditions with feeder cells and manual passaging. Also, analyze your cells—it’s really easy.”

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7 thoughts on “Heroic three-year study reveals safe methods for growing clinical-grade stem cells

  1. Hi Todd- thanks for talking about our work. My quote is a bit too succinct, though. We do grow our hESCs and iPSCs on feeder layers with manual passaging when they are first derived, up until the time that we make our first cell banks. After that, we transfer the cells to feeder-free conditions for differentiation. But we can always go back to the bank if we see unacceptable genomic changes in the expanded population. We want to do this in the safest possible way.
    Jeanne

  2. Well written article and i enjoyed the intro/explainer video you produced for CIRM last year also. Hopefully we will get to see more of your work soon Todd. Congratulations to Jeanne, Louise and everyone involved, it’s a great start to 2015.

    • Thanks so much for the feedback. If you’re referring to last year’s “Stem Cells in Your Face: Disease in a Dish” video, we do indeed have another one in the works. Cheers, Todd.

  3. You are welcome and i don’t think CIRM get enough exposure or international recognition.
    The videos are very informative and i actually started with the Video Production Demo Reel on Vimeo and then i found your Grantee Elevator Pitch Challenge on http://www.youtube.com/user/CIRMTV
    I would definitely recommend the Youtube channel to anyone that is not familiar with the great work that CIRM is involved in and the fantastic results they have achieved so far.

  4. To reversibly suppress the effects of p53 on stem cell growth and increase iPSC production efficiency, apply Asymmetrex’s SACK technology. Just add xanthine.

    See:

    Paré, J.-F., and Sherley, J. L. (2011) “Culture Environment-Induced Pluripotency of SACK-Expanded Tissue Stem Cells,” J. Biomed. and Biotechnol. vol. 2011, Article ID 312457, 12 pp., 2011. doi:10.1155/2011/312457.

    and

    J. L. Sherley and J.-F. Paré, “Method for Cloning Pluripotent Stem Cells,” U.S. Provisional No. 61/266,602, Filed December 4, 2009. Approved April, 2014. USPTO No. 8,759,098 B2.

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