Oct. 29, 2010 – For the first time, human cells have been used to create a lab-grown liver.
It's a milestone on the way to creating a new source of livers for transplant, Wake Forest University (WFU) researchers say.
Last June, a different research team reported growing a liver from animal cells. But if the goal is human transplants, fully human livers are likely to be safer and more effective, suggests project director Shay Soker, PhD, professor of regenerative medicine at WFU.
"We have focused on the clinical aspect of this by using human cells," Soker tells WebMD. "We believe that the use of human cells will provide patients with the best solution for liver disease, compared with those that have used animal cells which are less safe."
In 2006, similar experiments at WFU's Institute for Regenerative Medicine paid off in lab-grown bladders that were successfully transplanted into human patients.
The organs are grown on "scaffolds" created from cadaver organs. By pumping a harsh detergent through the harvested organs, the researchers remove all cellular materials. What's left behind is a collagen matrix that's a perfect scaffold for a new organ.
When fetal cells from the appropriate organ are pumped into the scaffold, they hone in on the appropriate location and begin to grow. When supplied with oxygen and nutrients in the lab's "bioreactor," the cells create a new organ on the scaffold.
Creating a lab grown bladder was a major achievement. But creating more complex organs is a challenge that still has not been fully solved.
In their current work, Soker, Pedro Baptista, PhD, PharmD, and colleagues used fetal liver and blood-vessel precursor cells to reconstitute a scaffold made from a ferret liver. In the lab, at least, the livers appear to function.
"We have been testing them profusely in the laboratory, not only to see if they resemble normal liver tissues but also to see if they are expressing the proper cell markers and proteins" Baptista tells WebMD. "We are able to find most of these markers."
The next step will be to transplant the livers back into animals to see if they work. The final test will be to grow livers large enough for humans -- but the technology hasn't yet advanced that far.
"The adult organ has 100 billion liver cells," Baptista says. "The number we seeded is 100 million. We are quite far away from required number. But our aim is to reconstitute only 30% of the full-size adult liver, because that is the bare minimum needed to sustain a person."
Work is also underway to create other lab-grown organs, including the pancreas, kidney, and even the heart.
"The kidney has 20 types of cells. The pancreas has complex structures such as islets," Soker says. "However, the concept of creating a scaffold that exactly mimics the natural tissue has the potential to overcome the problem of engineering a three-dimensional tissue vs. the two-dimensional tissues like skin that are already available."
Baptista and Soker reported the findings at this week's annual meeting of the American Association for the Study of Liver Diseases in Boston.