Rather than hoping that an animal will respond like a human, in vitro research is conducted in an external, controlled environment, such as a test tube or a petri dish. Because most illnesses do their work at a microscopic level, these experiments make ideal test beds for studying the course of human disease. Not only are in vitro tests more humane than killing animals by exposing them to experiments, but they have been shown to produce more accurate results which correlate from the laboratory to real life as well.
Toxicity tests using human cell cultures are two to three times more accurate than tests on rats and mice.
Penicillin and streptomycin are historical examples of in vitro discovery, and there have been thousands since. Today’s in vitro technology enables researchers to receive accurate information from as many as 100,000 compounds per day.
The major criticism of cell cultures, especially in toxicology but elsewhere as well, is that they are oversimplifications.
That’s where the cell culture analog comes in. A cell culture analog, also known as an “animal-on-a-chip” or a “human-on-a-chip”, is a silicon wafer with reservoirs that represent organs and canals that act as vasculature. Once the reservoirs and canals are lined with cells of the appropriate type, then fluid is pumped through the system so that it flows through the organs in the proper physiological sequence. The method enables an accurate approximation of the physiology of the whole human body.
The applications of CCAs go beyond simple toxicology – they can be used to study drug-drug and organ-organ interactions, as well as to predict disease progression and treatment outcomes. The scientist credited with inventing the CCA concept, Dr. Michael Shuler at Cornell University, is currently pursuing a three-dimensional model as well as a CCA that uses human stem cells. These could be the first steps towards a personalized CCA – a replica of a patient’s unique physiological profile – which would be a crucial tool for personalized medicine.
“Currently, nine out of ten experimental drugs fail in clinical studies because we cannot accurately predict how they will behave in people based on laboratory and animal studies”
Mike Leavitt, Secretary of Health and Human Services, U.S. Department of Health and Human Services (Food and Drug Administration press release, FDA Issues Advice to Make Earliest Stages of Clinical Drug Development More Efficient, January 12, 2006)