Patients with liver failure could in future have a stopgap treatment, which slows down or even reverses disease progression, while waiting for a liver transplant.
The treatment involves injection of healthy liver cells created from human embryonic stem cells.
Researchers from the Genome Institute of Singapore, Institute of Molecular and Cellular Biology, and Stanford University's School of Medicine created large quantities of liver cells - up to billions in a single petri dish - from human embryonic stem cells during a 2½-week process.
The embryonic stem cells were harvested from unfertilised embryos donated to in-vitro fertilisation clinics. These cells are pluripotent, which means they can turn into any cell that the body needs.
The study, published in scientific journal Cell Reports on Feb 20, found that the new cells, when grafted into mice with liver injury, improved their short-term survival rate. Seven mice which were injected with the cells survived, while another eight, which were not given the cells, died.
The study began in 2013 and is ongoing. The treatment will need at least another 20 to 30 years before it can be brought to market, said Assistant Professor Kyle Loh from the Stanford University School of Medicine, who is a co-senior author of the study.
Currently, end-stage liver failure can be treated only by liver transplants. Patients suffer symptoms such as jaundice, frequent bleeding and even coma.
Due to the scarce number of liver donations, more than one million patients worldwide die every year while waiting for transplants.
"In the years before a liver transplant, patients can become very sick. Injecting them with liver cells can keep them healthy for a few years," said Prof Loh.
A similar clinical study, conducted in 1998 by other researchers, grafted actual liver cells instead of growing them from stem cells.
Other attempts by different scientists to turn embryonic stem cells into liver cells have fallen short, said Prof Loh, due to the pluripotence of stem cells.
"It is a tough process because embryonic stem cells can turn into any kind of cell in your body. That makes it difficult to turn it into liver cells specifically," he said.
The study has the potential to provide a limitless source of cells that can be used for cell-based therapy, said Associate Professor Dan Yock Young, senior consultant at the National University Hospital's Division of Gastroenterology and Hepatology. "Liver grafts for transplants are in limited supply worldwide. The ability to culture, expand and maintain functional liver cells outside the body remains a holy grail in liver disease," he said.