Mice are a boon to biomedical research; they can often predict how humans will react to certain conditions, and not too many people get upset if they die from an overdose of toxic chemicals. But mice aren't as useful in pharmaceutical research because their livers react to drugs differently than human livers. That means a drug can make it all the way to human trials before scientists realize that it may be toxic to the liver. And so over 90% of drugs fail in clinical testing, often because of toxicities that weren't spotted earlier.
But now researchers at MIT have figured out how to grow "humanized" livers inside of mice--so the little critters could soon accurately predict how human livers will respond to drugs.
The discovery comes from graduate student Alice Chen, who has figured out how to grow human liver tissue inside of mice. This was not an easy task--liver cells lose functionality quickly after being removed from the human body, and until now, generating human-like livers in the animals required using only mice with compromised immune systems, limiting their use in drug testing.
The model, in which human liver cells are suspended on "scaffolds" inside mice, is proving to work. Chen and her team found that the implanted human liver tissue can integrate into a mouse's circulation system--meaning that drugs can reach the implanted tissue, and proteins generated by the humanized liver can go into the bloodstream.
Next up: studying how the humanized mouse livers react to drugs whose effects on human livers are well known. Researchers have already confirmed that mice with liver implants who are given coumarin and debrisoquine (an anticoagulant and an antihypertensive drug, respectively) generate byproducts normally only found in human livers.
If Chen's research continues to pan out, the implanted livers could eventually be used by pharmaceutical companies on untested drugs. Not only could that save these companies cash and time (which could be used to develop better drugs), it could also save untold numbers of human lives--and livers.