Chip Organs

Living organ-on-a-chip could soon replace animal testing

• By Sebastian Anthony on June 22, 2012 at 8:03 am
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If a team of Harvard bioengineers has its way, animal testing and experimentation could soon be replaced by organ-on-a-chip technologies. Like SoCs (system-on-a-chip), which shoehorn most of a digital computer into a single chip, an organ-on-a-chip seeks to replicate the functions of a human organ on a computer chip.

In Harvard’s case, its Wyss Institute has now created a living lung-on-a-chip, a heart-on-a-chip, and most recently a gut-on-a-chip.

We’re not talking about silicon chips simulating the functions of various human organs, either. These organs-on-a-chip contain real, living human cells. In the case of the gut-on-a-chip, a single layer of human intestinal cells is coerced into growing on a flexible, porous membrane, which is attached to the clear plastic walls of the chip. By applying a vacuum pump, the membrane stretches and recoils, just like a human gut going through the motions of peristalsis. It is so close to the real thing that the gut-on-a-chip even supports the growth of living microbes on its surface, like a real human intestine.

In another example, the Wyss Institute has built a lung-on-a-chip, which has human lung cells on the top, a membrane in the middle, and blood capillary cells beneath. Air flows over the top, while real human blood flows below. Again, a vacuum pump makes the lung-on-a-chip expand and contract, like a human lung.

These chips are also quite closely tied to the recent emergence of the lab-on-a-chip (LoC), which combines microfluidics (exact control of tiny amounts of fluid) and silicon technology to massively speed up the analysis of biological systems, such as DNA. It is thanks to LoCs that we can sequence entire genomes in just a few hours — a task that previously took weeks or months.

These human organs-on-a-chip can be tested just like a human subject — and the fact that they’re completely transparent is obviously a rather large boon for observation, too. To test a drug, the researchers simply add a solution of the compound to the chip, and see how the intestinal (or heart or lung) cells react. In the case of the lung-on-a-chip, the Wyss team is testing how the lung reacts to possible toxins and pollutants. They can also see how fast drugs (or foods) are absorbed, or test the effects of probiotics.

Perhaps more importantly, these chips could help us better understand and treat diseases. Many human diseases don’t have an animal analog. It’s very hard to find a drug that combats Crohn’s disease when you can’t effectively test out your drug on animals beforehand — a problem that could be easily solved with the gut-on-a-chip. Likewise, it is very common for drugs to pass animal testing, but then fail on humans. Removing animal testing from the equation would save money and time, and also alleviate any ethical concerns.

Moving forward, the Wyss Institute, with funding from DARPA, is currently researching a spleen-on-a-chip. This won’t be used for pharmaceutical purposes, though; instead, DARPA wants to create a “portable spleen” that can be inserted into soldiers to help battle sepsis (an infection of the blood).

And therein lies the crux: If you can create a chip that perfectly mimics the spleen or liver or intestine, then what’s to stop you from inserting those chips into humans and replacing or augmenting your current organs? Instead of getting your breasts enlarged, you might one day have your liver enlarged, to better deal with your alcoholism. Or how we connect all the organ chips together and create a complete human-on-a-chip?