One of the more intriguing promises of regenerative medicine is the thought that one day stem cells could be used to grow replacement organs. That day is still a way off but may be just a little bit closer after researchers in Japan showed that they could grow functioning human liver tissue in mice.
In the study, which appears in the journal Nature, the researchers explain how they mixed together three forms of stem cells to try and re-create the environment of early liver development. They took induced pluripotent or iPS cells (the kind that can be created by reprogramming an adult cell, such as a piece of skin, into behaving like an embryonic stem cell capable of becoming any other cell in the body) and turned those into cells capable of expressing liver genes. They then added cells that line blood vessels and cells that can make bone and cartilage.
In a briefing for reporters, the lead researcher, Takanori Takebe of the Yokohama City University Graduate School of Medicine explained what happened:
“They unexpectedly self-organized to form a three-dimensional liver bud — this is a rudimentary liver. The liver bud is formed at the very early stage of development — normally in humans, maybe around five or six weeks. We basically mimicked this very early transition process of the liver-bud-forming process”
The researchers then transplanted the cells into mice and found that they developed blood vessels and took on some of the normal functions of a liver. When the researchers induced a form of liver failure in the mice, those given the liver buds survived.
Impressive as that is the researchers caution it’s a long way from this to being able to reproduce these kinds of results in humans, and to be able to do it safely and efficiently. For a start they point out that while the liver buds demonstrated some of a normal liver’s function, there were other things they were unable to do – such as produce cells that help clear toxins from the blood. They also say it will be important to monitor the buds for several more months to see if they continue to thrive and grow, or if they produce tumors.
There is a great need for this kind of work. There are more than 16,000 people on the waiting list for a liver transplant and in any given year only around one third of those get a transplant. Every year thousands of people die waiting for an available organ.
We have a number of researchers working in this area, including one team that is trying to develop a human liver cell line that can be employed in liver cell transplantation or in a bio-artificial liver. You can read about their work here
One of our latest Stories of Hope also features that research and you can read about their work and watch videos of the researcher and his patient here.