Scientists develop new method to create stem cells for human liver

A new method for creating stem cells for the human liver and pancreas, which could enable both cell types to be grown in sufficient quantities for clinical use, has been developed by scientists.

Using the technique, researchers have for the first time been able to grow a pure, self-renewing population of stem cells specific to the human foregut, the upper section of the human digestive system.

These so-called "Foregut stem cells" could then be developed further to produce liver or pancreatic cells. The method significantly improves on existing techniques for cultivating this type of stem cell, and raises the possibility that, with further work, they could be grown in large numbers in bioreactors. That would make it possible to use them for regenerative therapies, repairing damaged organs or tissues in the body, and treating conditions such as type I diabetes or liver disease. The scientists have developed a cell culture system which allows them to specifically isolate foregut stem cells in the lab.

These cells have huge implications for regenerative medicine, because they are the precursors to the thyroid upper airways, lungs, liver, pancreas, stomach and biliary systems. The scientists now have a system where they may be able to create all these cell types from the same starting population.

The approach marks a breakthrough because it overcomes some of the problems which currently limit scientists' abilities to grow cells associated with the liver, pancreas, and other parts of the foregut in sufficiently large numbers for clinical use. The scientists were also able to show that these human foregut stem cells do not form tumours, which means that they can be safely injected for therapeutic purposes, without having adverse side effects. Although the procedure does not improve scientists' ability to produce pancreatic or liver cells specifically, it does provide a much purer source population for doing so. The researchers are now building on the research by studying the mechanisms to further improve the production of these cell types for regenerative medicine.

A big breakthrough in creating human liver through stem cells

Scientists have for the first time created a functional human liver from stem cells derived from skin and blood and say their success points to a future where much-needed livers and other transplant organs could be made in a laboratory.

While it may take another 10 years before lab-grown livers could be used to treat patients, the Japanese scientists say they now have important proof of concept that paves the way for more ambitious organ-growing experiments. The promise of an off-the-shelf liver seems much closer than one could hope even a year ago. Even though there is still much unknown and it will take years before it could be applied in regenerative medicine.

Researchers around the world have been studying stem cells from various sources for more than a decade, hoping to capitalise on their ability to transform into a wide variety of other kinds of cell to treat a range of health conditions.

There are two main forms of stem cells - embryonic stem cells, which are harvested from embryos, and reprogrammed "induced pluripotent stem cells" (iPS cells), often taken from skin or blood.

Countries across the world have a critical shortage of donor organs for treating patients with liver, kidney, heart and other organ failure. Scientists are keenly aware of the need to find other ways of obtaining organs for transplant.

The Japanese team, based at the Yokohama City University Graduate School of Medicine in Japan, used iPS cells to make three different cell types that would normally combine in the natural formation of a human liver in a developing embryo - hepatic endoderm cells, mesenchymal stem cells and endothelial cells - and mixed them together to see if they would grow.

They found the cells did grow and began to form three-dimensional structures called "liver buds" - a collection of liver cells with the potential to develop into a full organ.

When they transplanted them into mice, the researchers found the human liver buds matured, the human blood vessels connected to the mouse host's blood vessels and they began to perform many of the functions of mature human liver cells. The results offered the distinct possibility of being able to create mini livers from the skin cells of a patient dying of liver failure and transplant them to boost the failing organ. That livers and other organs may one day be made from iPS cells is an "exciting" prospect and holds out real promise for a viable alternative approach to human organ transplants.