Even people with a modest knowledge of the human body know the liver is one tough organ. In scientific parlance, it has a high capacity to regenerate – a far higher capacity than other organs.
Why this is the case has been a mystery. Scientists used to believe that a group of adult stem cells called oval cells were responsible for the liver’s renowned regenerative properties, but this has been disproved. Now comes a study out of the University of California-San Diego School of Medicine that identifies a different group of cells that can regenerate liver tissue – importantly, without forming tumors.
Dr. Gregory MacKay, a gastroenterologist affiliated with Indian River Medical Center, is familiar with the study; he says, “This is an area that’s really important. More study needs to be done, but knowing that there are liver cells that can maintain growth and regeneration without causing cancer is very exciting.”
The discovery could lead to breakthrough treatments for hepatitis, cirrhosis and other liver maladies.
The liver sits on the right side of the belly, protected by the rib cage. It’s a large organ, weighing about 3 pounds. (To put that in perspective, the heart weighs about three-quarters of a pound, a kidney weighs less than a third of a pound, and the gallbladder weighs about 2 ounces.)
The liver’s main function is to filter blood coming from the digestive tract and pass it along to the rest of the body. It also metabolizes drugs, breaking down and converting medication into active chemical substances.
The most common conditions of the liver include:
Hepatitis, which is inflammation of the liver, usually caused by viruses like hepatitis A, B, and C. Hepatitis can also be caused by heavy drinking, drugs, allergic reactions, or obesity. Dr. MacKay shared some good news about hepatitis C; saying, “Although cases remain at epidemic levels, there are remarkable new treatments available which offer a cure, by taking one pill a day for only 12 weeks.”
Hemochromatosis is a condition that allows iron to deposit in the liver, which damages it. In hemochromatosis, the iron is also deposited in other places throughout the body, causing multiple health problems, including (potentially) to the heart, joints, and endocrine glands. Dr. MacKay says hemochromatosis is a hereditary disorder affecting about 1 percent of the population; people who have it absorb iron very efficiently, which was an advantage hundreds or thousands of years ago, when our diets lacked iron; this uber-efficiency is no longer a good thing.
Cirrhosis. While laymen usually associate cirrhosis with excessive alcohol use, which is a main cause of the condition, long-term damage to the liver from any cause can lead to permanent scarring, which is what cirrhosis is. This scarring negatively affects the liver’s ability to function.
Liver cancer. The most common type of liver cancer, hepatocellular carcinoma, almost always occurs after cirrhosis is present.
Liver failure. Causes include infection, genetic diseases, and excessive use of alcohol.
The researchers found that cells called “hybrid hepatocytes” are the reason for the liver’s capacity for regeneration. These unique cells, discovered in an area of the liver known as the portal triad, proliferate extensively and replenish liver tissue. They are so vigorous they can rescue a diseased liver from complete failure. While the majority of the research was conducted using mouse models, the researchers were able to identify similar cells in human livers.
There has been research using other types of cells to repair damaged livers. Those cells did have a therapeutic effect, but it was hard to stop them from proliferating – giving rise to cancer. The University of California-San Diego School of Medicine study showed that hybrid hepatocytes regenerate the liver without causing tumor growth – a very encouraging outcome of this study.
Experts hope that cell-based therapies will one day replace transplants as a treatment for severely damaged livers. Dr. MacKay agrees, saying, “Now that we know what area of the liver these hybrid hepatocytes cells come from, we may be able to find a way to use them to boost liver function and avoid a transplant.” He says that liver transplantation is generally successful, with a 3-year survival rate well over 90 percent, but the problem is there are more people on the waiting list than there are available organs.
Dr. MacKay says that people in Florida are very generous in donating their organs. He encourages everyone who drives to check their license and look for the “Organ Donor” designation, saying, “It’s a fabulous, wonderful gift; you can save a life.”
If you are not an organ donor and would like to become one, you can register on-line at https://www.donatelifeflorida.org/register. To have the designation appear on your driver’s license, you can visit one of three local administrative offices: 1800 27th St, Building B in Vero; 1860 82nd Ave, Suite 102 in Vero; or 11610 U.S. 1 in Sebastian.
Dr. MacKay’s office is located at 3745 11th Circle, #101 in Vero Beach; the office phone is 772-299-3511.