Liver Regeneration May Be Simpler Than Previously Thought

  The way the liver renews itself may be simpler than what scientists had been assuming. A new study, appearing in the April 13 issue of The Journal of Biological Chemistry, provides new information on the inner workings of cells from regenerating livers that could significantly affect the way physicians make livers regrow in patients with liver diseases such as cirrhosis, hepatitis, or cancer.

     "The human liver is one of the few organs in the body that can regenerate from as little as 25 percent of its tissue," says Seth Karp, assistant professor of surgery at Harvard Medical School, Boston, and main author of the study. "It is not known how the liver does it, but our results provide some details of what makes the liver so unique."

     To investigate how the liver regenerates, Karp and his colleagues set out to determine which proteins are involved in the regenerating cells. The scientists were also interested in testing whether regenerating cells behave like embryonic ones, as is commonly assumed for other organs.

     Karp's team considered two samples of mice. The first consisted of embryonic mice at various stages of development while the second was composed of adult mice to which two-thirds of their livers were removed. Using techniques such as DNA microarrays -- which determine which genes are active in a cells -- and software programs that analyze the collected information, the scientists listed all the proteins that help the cells grow and proliferate in both samples.

     It was originally assumed that the same types of proteins were involved in both embryonic development of the liver as well as regeneration of the liver after injury or partial hepatectomy ( removal of a portion of the liver). But the results were unexpected. The researchers noticed that only a few proteins were common to both processes. Specialized proteins known as 'transcription' proteins (those that transfer genetic information from the DNA into RNA in the cell) were highly involved in the development of the embryo liver, but not in adult liver regeneration.  Instead, proteins that help cells proliferate were active in the regenerating livers.

WHAT DOES THIS ALL MEAN ?

     These findings showed that a regenerating liver does not behave as a developing embryo. Instead, regeneration could actually be only due to an increase in cells that multiply through regular cell divisions, a process called hyperplasia.

     "We think that the liver regrows through a relatively simple process, which could explain its prodigious ability to repair itself," Karp says.

MEDICAL IMPLICATIONS FOR HEPATITIS AND CIRRHOSIS PATIENTS

     Transcription proteins are known to be more difficult to manipulate than the other identified proteins. Since the transcription factors were not present in regenerating livers, it might be easier to stimulate liver regeneration by only activating the other identified proteins.  If regrowing livers are simply a matter of stimulating a few proteins, then regrowing livers this way would be especially useful for patients whose livers have been damaged by tumors or viruses (i.e. hepatitis c virus)

THE NEXT STEP:

     The next step will be for scientists to understand whether the regenerating cells are stem cells. Studies have shown that adult stem cells are involved in the repair of many  organs, but in the case of the liver, the cells repairing it through regeneration may simply be regular cells, not stem cells.

     Adapted from: Article: "Restoration of Liver Mass after Injury Requires Proliferative and Not Embryonic Transcriptional Patterns" by Hasan H. Otu, Kamila Naxerova, Karen Ho, Handan Can, Nicole Nesbitt, Towia A. Libermann, and Seth J. Karp, 2007

NOTE:  We find this research very fascinating and extremely promising.  A number of people have late stage cirrhosis for which no medication, no herbal preparation and no treatment other than liver transplantation is helpful.  For these people, it might soon be possible for scientists to regrow the damaged portions of their livers simply by stimulating the proteins involved in liver regeneration.

[orphanedhawk]

   Doctors don't make livers regrow. Livers do this all on thier own ! Of course anything we learn to help, is great. On a  forum I used before finding this one, there was a Brithish man who had HCV w/stage  4 cirrhosis. He was told to put his things in order, nothing could be done for him. Instead he did tx. 8 years later he is stil SVR and his liver has renewed itself.

[GoofyDad]

Whenever I hear about how well the liver will regenerate when chunks are removed - I wonder why I don't just have a chunk of mine taken out so it will growback all spiffy and new. Like pruning the roses for fresh blooms.  

OH - That's a remarkable story - especially since I think 9 yrs ago it was mono therapy with unpegalated IFN. Very fortunate for someone in his condition to clear with that tx.