As a graduate student, I first learned the story of Henrietta Lacks from a professor of mine. She is a woman that forever changed biological research without being a scientist, physician, or high-level researcher. As told in The Immortal Life of Henrietta Lacks, she was a patient suffering from an aggressive form of cervical cancer. While receiving medical treatment, her tumor was biopsied and researchers tried growing her cells in a petri dish. They discovered that her cells possessed the unique ability to grow almost as aggressively outside of her body as they did inside. As Henrietta’s cells continued to grow in the lab, they were named using the first two letters of her first and last name. And with that the world’s first immortal cell line, would be called HeLa. Today, HeLa cells are still growing in research labs around the world, nearly 60 years after Henrietta’s passing.
HeLa cells became workhorses for biomedical advancement by being used to determine the amount of DNA in human cells, discover new effective cancer treatments, and develop the polio vaccine. Each of these research breakthroughs was possible because of the extraordinary ability of HeLa cells to be kept alive outside of the body. Thanks to a greater understanding of proper cell culture conditions, there are now thousands of cell lines in existence from all kinds of different species.
An unparalleled collection of animal cell lines lives within the Frozen Zoo® as part of the San Diego Zoo Institute for Conservation Research. Currently there are cells, called fibroblasts, from approximately 900 species represented by over 9,000 individuals. It is the largest “zoo” of its kind, harboring samples from some of the world’s most endangered animals. There are even fibroblasts in there from extinct species.
The ability to work with cells growing in culture opens the door to many research possibilities. For example, our Reproductive Physiology lab is interested in testing the effects of environmental chemicals on endangered species reproduction. Let’s say you wanted to conduct this work in mice. All you would need to do is simply get a colony of mice, expose them to whichever chemicals you were interested in testing, and measure how reproduction was affected. But we don’t work with mice. We work with animals like rhinos. We will never have, nor would we ever want, an experimental rhino colony. However, we do take advantage of cell lines to determine how environmental chemicals might affect rhino reproduction.
To do this we take copies of rhino DNA and stick them into primate cells in petri dishes so that they make the rhino proteins that regulate reproduction. Then we expose those rhino proteins to different chemicals and measure how the two interact by measuring the production of a “reporter,” which (are you ready for this?) happens to be an insect enzyme. It sounds absolutely bizarre, but believe it or not, this is a well-accepted, common approach. The problem is, we can’t help but also ask, “How well does what is happening in this petri dish reflect what happens in a 5,000-pound rhino?” An answer to that question may lie in the Frozen Zoo.
In collaboration with the Institute’s Genetics Division, we are exploring new ways to use Frozen Zoo fibroblast lines to get a more accurate idea of how environmental chemicals may affect endangered species reproduction. This idea all started with our interesting discovery that many fibroblasts in the Frozen Zoo make proteins that regulate reproduction, even though they are usually taken from nonreproductive tissues. We have also found that, like HeLa cells, individual fibroblast lines possess their own unique qualities, and we can take advantage of this to address specific research questions. So instead of the science fiction-sounding rhino/primate/insect system, we can treat rhino cells directly with chemicals to which rhinos may be exposed. Everything about those cells, from the membrane to the DNA to protein, is made in the same way it would be in a rhino. In other words, we think what happens in those rhino cells paints a much more accurate picture of what happens in a whole animal. Sure, they are still cells growing in a dish, but cells alone can be extremely powerful tools. Just look at what Henrietta and her cells have accomplished.
Christopher Tubbs is a scientist in the Reproductive Physiology Division of the San Diego Zoo Institute for Conservation Research.