Today I took a break from my reading and research and traveled to one of the neighboring labs here in the National Toxicology Program. I ventured out of the pathology group and instead joined Dr. Michael DeVito, leader of the Predictive Toxicology and Screening Group, for the day. For a few trying hours in the morning, we attended a mandatory NTP meeting focused on statistics, citations, and publication format; I may have been the only high school student in the room, but I was not the only one that struggled to remain attentive. Later, though, I had the much more exciting opportunity to join Dr. DeVito and his lab staff. One of their current projects is focused on creating a predictive model of the liver that can be used to efficiently test various chemicals for toxicity. While traditional in vitro, or outside of an organism, hepatocyte (liver cells) cultures are grown in two dimensions, Dr. DeVito has found a method to grow these cells in sphere culture systems, similar to stem cells. This three-dimensional innovation has allowed in vitro toxicology and carcinogenic testing to more accurately model the biological effects on human organs than the effects measured in cells grown in two dimensions. More accurate in vitro testing also allows for a decreased reliance on in vivo, or inside of an organism, testing. I also learned about some of the equipment used in Dr. DeVito’s lab, such as a mass spectrometer (MS) and liquid chromatographer. The MS is used to finely quantitate the mass of molecules down to a couple of decimal places, and the liquid chromatographer is used to identify the different chemicals in a mixture.
While in Dr. DeVito’s lab, I also learned about how toxicology testing works in a real-world context. When a company finds a new chemical compound to use in their products, they must first gain approval from the FDA (Food and Drug Administration) or the EPA (Environmental Protection Agency), which nominates the chemical to the NIEHS or NTP. The National Toxicology Program is then responsible for finding if the chemical has negative effects, and if so, at what dosage. Here is a very elementary description of this process:
Dr. DeVito and his lab grow cell cultures in wells, then splash them with a fluorescent dye that sticks to the nucleus of each cell; next, using a handy motorized pipette, they dissolve the dye with dimethyl sulfoxide (DMSO), a universal solvent; next, they wash the cells with a phosphate-buffered saline solution a couple of times (I was allowed to complete this); finally, they splash the cells with whichever chemical they are testing for toxicology.
After a period of incubation, they take the cells out and insert them into a fluorescence microplate reader, which reads the fluorescence signature from each well and compiles the measurements into a document, so at the end of reading there are 384 measurements (one for each well) compiled. The premise of the test is that the less fluorescence emitted by a well, the fewer nuclei in the well, which means fewer cells, which means more cell death. So, Dr. DeVito and his lab can predict at what dosage cell death begins to take place by measuring the dosage at which the fluorescence begins to decrease. This test, however, is simply to find out whether or not chemicals are harmful at any reasonable dosage. The real challenge, which is far beyond my understanding, is identifying how the chemicals harm the cells and what these damages translate to in terms of humans.
If there was one thing that I took away from my time in Dr. DeVito’s lab, though, it was not their intriguing projects nor their complicated machines: it was that collaboration is an essential part of their research. No one person is an expert in everything or even more than one thing, and everyone relies on each other to complete the work.