Biologists from the MRC Center for Regenerative Medicine at the University of Edinburgh have managed to restore liver function in mice by using stem cell transplants to regenerate them. This is the first time such a procedure has succeeded in a living animal.
If liver stem cells from human livers behave the same way as did the mouse cells in this study, then this procedure could potentially be used in place of liver transplants in human patients. This work was published by Professor Stuart Forbes and his colleagues in the journal Nature Cell Biology.
According to Forbes: “Revealing the therapeutic potential of these liver stem cells brings us a step closer to developing stem cell based treatments for patients with liver disease. It will be some time before we can turn this into reality as we will first need to test our approach using human cells. This is much needed as liver disease is a very common cause of death and disability for patients in the UK and the rest of the world.”
Liver cells are also called “hepatocytes” and even though such cells are used for liver transplants, the technology does not yet exist to easily propagate human hepatocytes in the laboratory. In this study, Forbes and his group designed a protocol that could wipe out close to 98% of the cells in the liver of laboratory mice. They genetically engineered mice whose liver cells would delete the MDM2 gene. The MDM2 gene encodes a protein called “E3 ubiquitin ligase,” which is an enzyme that tags junk proteins so that they are properly degrades and recycled. Without a functional E3 ubiquitin ligase, the vast majority of the liver cells underwent programmed cell death. Under these conditions, a group of liver-specific stem cells called hepatic progenitor cells or HPCs were transplanted from healthy mice into the adult mice with severely damaged livers. The transplanted HPCs significantly restored the structure of the liver, regenerating hepatocytes and the cells of the “biliary epithelia,” which compose the ducts that move bile into the gall bladder. This highlights the potency of these transplanted HPCs as liver regenerators. Essentially, after several months, Forbes and his coworkers discovered that major areas of the liver had regrown and these new cells significantly improved the liver’s physiological performance.
This is the first time that biologists have succeeded in regenerating an organ in a living animal by using stem cells. Even human cells have significant differences from mouse cells, if these human cells can be manipulated so that they behave in a similar manner to these mouse stem cells, transplanting stem cells or, perhaps administering drugs that activate a patient’s own liver to produce stem cells and regenerate itself, could replace liver transplants.
In a press release, Dr. Rob Buckle, director of science programs for the U.K.’s Medical Research Council, said: “This research has the potential to revolutionize patient care by finding ways of co-opting the body’s own resources to repair or replace damaged or diseased tissue. Work like this, building upon a precise understanding of the underlying human biology and supported by the UK Regenerative Medicine Platform, will give doctors powerful new tools to treat a range of diseases that have no cure, like liver failure, blindness, Parkinson’s disease and arthritis.”