The liver's unique ability among organs to regenerate itself has been little understood. Now Weill Cornell Medical College scientists have shed light on how the liver restores itself by demonstrating that endothelial cells -- the cells that form the lining of blood vessels -- play a key role.
The results of their study are published in the online edition of the journal Nature, with a companion study in the Oct. 24 issue of Nature Cell Biology describing how endothelial cells are activated to initiate organ regeneration.
It has long been known that endothelial cells passively conduct blood, passing oxygen, nutrients and metabolic waste to and from tissues through capillary walls. However, in studies published in recent years, the Weill Cornell researchers have demonstrated that endothelial cells actively influence the self-renewal of certain stem cell populations and the regeneration of tissue. Now, these scientists have uncovered the endothelial cells' "instructive role" in liver regeneration. Further, the researchers believe that in the coming years it will be possible to facilitate healing damaged livers by transplanting certain types of endothelial cells with liver cells.
"We have found that specialized blood vessel cells in the liver -- a specific type of sinusoidal endothelial cell -- initiate and sustain liver regeneration by producing growth factors that we have identified. This finding will open the door for designing new therapies to treat damaged livers," says the study's senior author, Dr. Shahin Rafii, who is the Arthur B. Belfer Professor in Genetic Medicine and co-director of the Ansary Stem Cell Institute at Weill Cornell Medical College and a Howard Hughes Medical Institute investigator.
The liver performs many physiological functions, including converting nutrients into essential blood components; storing vitamins and minerals; producing bile for digesting fats; regulating blood clotting; and metabolizing and detoxifying substances that would otherwise be harmful. When the liver malfunctions, the consequences can be grave. Liver failure, due to cirrhosis, various forms of hepatitis, and other diseases, kills some 60,000 Americans per year. But the liver's capacity for regeneration is amazing.
"Until our study, the molecular and cellular pathways that would initiate and maintain liver regeneration were not known," says Dr. Bi-Sen Ding, the study's first author and a senior postdoctoral fellow in Dr. Rafii's lab. "Attempts to transplant hepatocytes [liver cells] directly into the liver led to very limited success. But now we have identified liver sinusoidal endothelial cells (LSECs) -- that, when activated, are critical to liver regeneration and may enable proper engraftment when hepatocytes are implanted into the injured liver."
Source: www.medicalnewstoday.com
