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Scientists have bioengineered miniature human livers – possibly for the first time. The livers were created by University of Pittsburgh researchers in an effort to move away from less reliable experiments on mouse livers. 

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Fluid passing through a bioengineered “mini liver,” made from human stem cells and a rat liver stripped of its own genetic material. (Courtesy of UPMC)

The livers will be used to study non-alcoholic fatty liver disease, a condition connected to obesity that can lead to liver failure.

“We can use these systems to capture the progression of the disease to evaluate new drugs before we move into actual patients,” said the study’s lead author Dr. Alejandro Soto.

The livers are created using human stem cells, which are transformed into liver cells. Those cells are then transplanted into a rat liver that has been stripped of everything but the collagen structure: effectively making them a vehicle for the newly engineered livers.

Medical research often uses mice, but results from those studies are not always applicable to humans.

“If you look at the genome sequences [between humans and mice], only around 85 percent are similar, so there are a lot of differences that make us humans and that make mice, mice,” said Santhosh Girirajan, professor of genomics at Penn State University. “That accounts for changes in a lot of things, for example the level of metabolism that occurs in mice and in humans.”

Soto said these livers aren’t perfect: they can mimic real human livers about 80 percent, so not all functions are present. But still, Soto said this opens up a lot of possibilities for research.

“We could basically derive livers for each patient with a different background and genetic variations to test drugs, for example,” Soto said.  

Soto said it will likely be years before bioengineered livers will be used for transplantation. 

This story originally appeared on WESA, which receives funding from the University of Pittsburgh.