Growth medium based on human plasma rewires cell metabolism

CAMBRIDGE, Mass. – Human cells grown in Petri dishes are the foundation for disease research and drug testing.  Yet the basic culture media recipes used to nourish human cells growing in the lab have not greatly changed since Eisenhower was in office. Now Whitehead Institute researchers have designed a growth medium that more closely resembles the cells’ environment in the body. In the process, they demonstrated that it significantly alters the cells’ inner workings, relative to established media.

Cells proliferating in a dish depend on growth medium for their nutrients. Older synthetic formulations were designed to be easily produced in large batches, and with the primary objectives of enabling cell survival and proliferation or even exploiting cells as biomolecular factories. Recently, scientists have tweaked the media levels of one or a few nutrient components in isolation to more closely resemble human plasma.  But with technological advances, scientists have now been afforded the ability to analyze human plasma at a much deeper level. With this data in hand, Jason Cantor, a postdoctoral researcher in Whitehead Member David Sabatini’s lab, decided to overhaul how culture media are designed.

“If you’re studying a human disease, you’re not interested in how a cell behaves in a dish.  You want to know how they act in the body,” says Cantor, who is the lead author of a paper in the journal Cell that describes the revamped medium. “Media composition absolutely affects cell metabolism. It’s very unclear, besides keeping cells ‘happy’, what the original media do to a cell, but we do know now that it’s affecting their metabolism in substantial ways. Hopefully, our recipe is taking a step in the right direction to better reflect these cells’ natural environment.”

Once Cantor finished designing his recipe, he determined how closely it mimics the plasma that nourishes cells within the body.  First, he compared it to a sample of plasma from Sabatini, and found that it largely reflected that of the human sample.  Cantor then explored how the metabolism of human cells was affected in his medium relative to one of the otherwise established workhorse formulations.  Cells in both types of media grew at similar rates, but strikingly, the new recipe has a profound effect across the cells’ metabolic landscape, including on the metabolism of pyrimidine nucleotides (the C’s, T’s, and U’s in DNA and RNA).

Cantor determined that the level of uric acid in his formula is responsible for the profound effects on pyrimidine metabolism—his formulation contains approximately 40 times more uric acid than the established medium to which he made his comparisons. Interestingly, due to a genetic event in higher primate evolution, uric acid levels in human plasma are indeed also 5 to 10 times greater than in most mammals, including mice. In fact, uric acid at concentrations resembling those of human plasma acts as an endogenous inhibitor of a key enzyme in the creation of pyrimidines. Such a metabolic change is not trivial.  Cantor found that one consequence of this action by uric acid makes cancer cells less sensitive to the common cancer drug 5-fluorouracil.

According to Sabatini, the significant changes in cell function caused by growth media underscore that media do more than simply keep cells alive.

“I think given the appreciation that we now have for the impact of environmental factors on human cell metabolism and human cell biology in general, taking steps toward better reflecting physiologic conditions in culture, like we have done with this new reagent, could open the door to not only potentially shifting our understanding of known phenomena, but perhaps as interestingly, could lead to new discoveries as well,” says Sabatini, who is also a Howard Hughes Medical Institute investigator and a professor of biology at Massachusetts Institute of Technology.

This work was supported by the National Institutes of Health (R01 CA103866 and R37 AI047389), the Koch Institute, the Department of Defense (W81XWH-15-1-0337), the American Cancer Society (PF-12-099-01-TBG), EMBO (ALTF 1-2014 and ALTF 350-2012), and the American Association for Cancer Research (16-40-38-KANA).

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David Sabatini's primary affiliation is with Whitehead Institute for Biomedical Research, where his laboratory is located and all his research is conducted. He is also a Howard Hughes Medical Institute investigator and a professor of biology at Massachusetts Institute of Technology.

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Cantor, J. et al. “Physiologic medium rewires cellular metabolism and reveals uric acid as an endogenous inhibitor of UMP synthase." Cell, April 6, 2017.