BREAKTHROUGH. New way to grow liver tissues outside human body

In a development that would make liver donations a passé in not-so-distant future, a team led by a scientist of Indian descent at the Massachusetts Institute of Technology (MIT), in US, has found a way to engineer complex liver tissues outside the human body.

While it may be too early to expect the technique of growing liver cells outside the body to be available in a hospital near you, it is a significant feat considering that the liver — just like the heart and kidney — one of the most complex organs to regenerate through tissue engineering.

Once it matures, the technique will not only help the patients who are waiting for a donor liver, but also those who suffer from chronic liver diseases, which otherwise do not qualify for conventional liver transplants. Such lab-bred liver tissues may benefit millions of people suffering from chronic liver diseases, including more critical cirrhosis and hepatitis.

“There are just not enough organs to go around. Our goal is that one day we could use this technology to increase the number of transplants that are done for patients, which right now is very limited,” said Sangeeta Bhatia, a professor of health sciences and technology at MIT, who led the study which appeared in the journal Science Translation Medicine on Wednesday.

Working closely with their compatriots from Rockefeller University and Boston University, Bhatia’s team developed a new way to grow human liver tissues by organising tiny subunits that contain three types of liver cells embedded into a biodegradable tissue scaffold, which is the size of a contact lens.

Subsequently, the researchers implanted the scaffold into the abdomen of a mice which had damaged liver, exploiting a technique that Bhatia’s lab developed in 2011. They had then shown that if these “seeds” of liver cells are implanted in the abdomen of a mouse with damaged liver, they would multiply by taking advantage of regenerative signals available from the surrounding environment.

Using this understanding, in the current study, the scientists implanted the scaffold into the abdomen of mice with dysfunctional livers. The signals from the surrounding environment not only stimulated the endothelial cells to form blood vessels, but also triggered the proliferation of hepatocytes (the cells that perform most of the liver’s critical functions). This led to a 50-fold expansion of the original tissue.

The scientists, however, cautioned that these implants currently contain fewer than 1 million hepatocytes. A healthy human liver has about 100 billion hepatocytes. But the scientists hoped that at least 10 to 30 per cent of that number would be necessary to help most patients.

To boost their hepatocyte population, the researchers said they can take advantage of a key trait of liver cells. “The liver is one of the only organs that can regenerate, and it’s the mature cells that divide, without an intermediate stem cell. That’s extraordinary,” Bhatia said in a statement issued by MIT.

“The idea is that it’s the seed of an organ, and you organise it in a way that it can be responsive to these regenerative signals, but it’s a minimal unit of what you eventually want to end up with,” Bhatia said.

What is exciting, according to her, is that the architecture of the tissue that emerged looked a lot like the liver architecture in the human body.