In Vitro

In Vitro (cell culture) Research

In vitro research examines cells and biological molecules outside the living body, in a contained environment, typically a solution or a culture medium, often known as a Petri dish. The term “in vitro” is derived from Latin meaning “in glass,” hence the popular term “test tube.”

One of the most profound discoveries in the history of medicine arose from in vitro work in 1928, when microbiologist Alexander Fleming noticed by chance that mold inhibited the growth of bacteria in his culture dishes. The mold turned out to contain a powerful antibiotic, penicillin, a discovery that would alter the course of medicine. Before and since then, in vitro work has proven to be an immensely powerful technology for isolating and studying cellular processes.

The information we have today about the biochemistry of cholesterol synthesis in the human body came through modern in vitro techniques. Researchers Michael Brown and Joseph Goldstein won the Nobel Prize in 1985 for their work studying human epidemiology coupled with human tissue, enabling them to discover the LDL receptor, which has revolutionized our understanding of cholesterol biochemistry. This led to the development of anti-cholesterol medications used by millions of people today.[1]

In 1990, after frustrating attempts to use mouse tumors to screen compounds for potential efficacy in fighting cancer, the National Cancer Institute (NCI) established a system to utilize human tumor cells to screen for potential effectiveness of new drugs. [2] This extensive cell line, maintained by the NCI, is referred to as NCI-60, because it is made up of 60 different types of human cancer cells including leukemia, melanoma and cancers of the lung, colon, ovary, breast, prostate and kidney. NCI-60 has proven to be more effective, cheaper and faster than using the mouse tumor cells. 

Cell Culture Analogs or Organ-chips 

One of the major obstacles of cell culture technology is that isolated cells can behave differently when they are in a living organism, where they are surrounded by and connected to other cells, tissues, and organs.  

Today’s in vitro research has evolved to overcome many of the obstacles of cellular isolation. By utilizing the full complement of genetic and biotechnological techniques available, current in vitro research is quite refined and advanced. 

The development of the cell culture analog, also known as an “organ-on-a-chip,” is a marvel of modern bioengineering that has enabled the sophisticated study of interconnected cells that more closely resemble the living body. [3] 

The chip, about the size of a computer memory stick, is made up of a silicon wafer with several chambers that represent “organs,” such as the brain, liver, heart and bone marrow, which are then connected by miniaturized canals that mimic the circulatory system. 

The chambers and canals are lined with cells of the appropriate type, i.e. liver cells, heart cells, so that the analog can be used as a test bed to evaluate the drug or therapy, simulating the way the drug would naturally be metabolized by the body.

The applications of cell culture analogs go beyond simply understanding drug metabolism – they can be used to study complex physiological interactions, as well as to predict disease progression and treatment outcomes.

Cell culture chips are also utilized in the emerging field of personalized medicine, which employs an individual’s cells to create a unique cell culture analog known as “You-on-a-chip.” [4] Personalized cell culture analogs would essentially be miniature replicas of a person’s unique physiology. One proposed application would be pretesting chemotherapy on a patient’s healthy cells as well as their tumor biopsy, in order to determine which drugs would be most appropriate for that patient. 

Body-on-a-chip

Perhaps the most advanced version of the cell culture analog has been realized by the “body-on-a-chip” model, which uses a 3D printer and “ink” comprised of living human cells, which are multi-layered on a gel surface to print out miniature organs. These “organs,” are connected by a blood-simulating fluid, enabling transport between the cells and organs, mimicking the functions of the heart, liver, lung and blood vessels.

The U.S. Department of Defense invested $24 million in this technology in September 2013 to enable the development of simulated miniature human organs that would be used to develop countermeasures against bio-threats, such as chemical weapons or infectious disease outbreaks.[5]

The resulting “body-on-a-chip” can act as a testing platform for evaluating how the human body might respond to chemical agents, like ricin and sarin, or diseases like Ebola virus, and also develop vaccines and therapeutics to counteract them.

Industry leaders

A growing number of bio-technology companies are investing their resources and efforts into the exciting field of cell culture work.

One of the leading companies in developing organ-chips is the Wyss (pronounced “Veese”) Institute for Biologically Inspired Engineering, affiliated with Harvard University. (http://wyss.harvard.edu/). In 2010, the Institute pioneered the creation of a lung-on-a-chip which mimicked the living, breathing human lung. 

By placing two adjacent layers of tissues from the lining of the lung and surrounding blood vessels, the chip demonstrates the flow of air across a porous boundary. Researchers also incorporated a vacuum effect into the chip’s workings to simulate the natural expansion and contracting of the chest during breathing.

According to Donald Ingber, founding director of the Wyss Institute:

"The ability of the lung-on-a-chip device to predict absorption of airborne nanoparticles and mimic the inflammatory response triggered by microbial pathogens provides proof-of-principle for the concept that organs-on-chips could replace many animal studies in the future." [6]

Since developing the lung-on-a-chip, the Wyss Institute has manufactured a whole range of organs-on-chips, including those that simulate the workings of kidney, liver, gastrointestinal tissue and bone marrow.

In July 2014, the Wyss Institute announced that it has formed a private company, Emulate, Inc, to commercialize its organ-on-chips technology “to accelerate development of pharmaceutical, chemical, cosmetic, and personalized medicine products.”[7]

Another prominent company in the cell culture industry is the HuRel Corporation, (http://hurelcorp.com) whose company name is a derivation of the phrase “Human-Relevant.” HuRel produces a range of biochips which they make available to other companies for research. On their website they explain that their biochips

“produce unrivaled levels of physiologically relevant predictive sensitivity - ‘human relevance’- that define the current state of the art of hepatic [liver] and multi-tissue cell-based assays.” [8]

RegeneMed, (http://www.regenemed.com) specializing in tissue engineering, has developed a variety of in vitro models including liver, gastrointestinal, bone marrow, cardiovascular and neuronal.

RegeneMed’s 3D liver model, launched in 2007, offers greater cell longevity than traditional flat cell cultures and a closer approximation to human physiology for evaluating chronic toxicity and drug-drug interactions. The longer lifespan of the 3D culture allows scientists to get a picture of long-term, and more normal, dose response, while the 3D, interconnecting porous structure allows the cultured cells to migrate, and interact with adjacent cells, the way they would in a living body.[9]

As described on the company’s website:

“The first and critical application of these tissue-based in vitro model systems is to replace cell-based assays and animal testing to debottleneck ADME/Tox [toxicolgical] evaluation, the leading cause of drug failures facing the pharmaceutical industry.”

New directions

So powerful and effective are the new generation of cell culture techniques that, in 2007, the U.S. Environmental Protection Agency, in conjunction with four other major regulatory agencies, announced that it would pursue a new non-animal based system for screening chemicals to “dramatically reduce the need for animal testing because the new tests would be based on human cells and cell components.” [10]

These innovations in cell culture technology demonstrate not only how new methodologies far exceed the capabilities of animal-based testing, but also how the decades-long failure of animal testing is increasingly being acknowledged by scientists, government and industry.

As Dr. D. Lansing Taylor, Director of the University of Pittsburgh Drug Discovery Institute and author of more than 150 scientific papers has stated: “The vision to reduce, refine and ultimately replace animal testing is within our grasp.”[11]