June 26, 2000 -- Cells from your bone marrow routinely turn into new liver cells, travel to the liver, and help the liver rebuild itself -- an amazing new finding that may lead to new treatments for all kinds of liver disease.
Animal studies show that a type of cells -- called stem cells -- from the brain and bone marrow can grow up to be cells for other organs, something that was previously thought to be impossible. The new study, published this week in a medical journal for liver specialists, shows that this not only happens in humans but that it appears to be an important way for the body to repair damage caused by injury or disease.
"I'm not making any assumptions about what is possible any more, because this was supposed to be impossible, and there it is," lead author of the study, Neil D. Theise, MD, tells WebMD. "We now find cells from two organs streaming between each other. The concept that organs are separate from one another maybe has to be reexamined. This is not like anything they taught me in medical school."
Theise and co-workers knew from animal studies that bone marrow cells could turn into liver cells. They hit on a way to see whether this happens in humans. First they found two women who had bone marrow transplants from male donors. Using a dye that stains the male Y chromosome in the DNA of a cell, they found that male cells had taken root in the liver of each woman. These cells could only have come from the bone-marrow transplants.
Next, the researchers looked at the livers of four men who received liver transplants from female donors. Using the same dye, they found that the livers had been repopulated with male cells; that is, their new female livers had some male cells, which could only have come from somewhere else in their own bodies -- in one case, nearly half of the female donor liver's cells had been replaced by male cells.
"What is different and quite exciting with this new paper is that it sounds like the level of replacement or proliferation of bone marrow cells is quite significant," liver-regeneration expert Neville Fausto, MD, tells WebMD. "Production of [liver cells] of up to 40% -- that is really significant." Fausto, chair of the pathology department at the University of Washington in Seattle, was not a participant in the new study.
The liver's amazing ability to grow back even after most of it has been cut away has been known for a long time. In ancient Greek mythology the titan Prometheus was punished by forever being chained to a rock where an eagle each day ate his liver. Every night, his liver grew back. A similar process occurs in people who undergo liver surgery: Even when more than half of the organ has to be removed, it is able to grow back.
Sometimes disease or injury is so severe that the liver cannot regenerate fast enough. Theise says that the new findings may one day allow doctors to use bone-marrow cells -- from a donor or even from the same patient -- to keep the liver functioning until it has a chance to repair itself.
Theise speculates that the findings may lead to other, even more exciting treatments. These are based on the fact that marrow cells are much easier to harvest and grow outside the body than liver cells. People whose livers don?t work because of genetic defects might be cured by receiving transplants of genetically engineered marrow cells. And the new cells also might be used to build an artificial liver for patients waiting for a liver transplant.
"This opens up the possibility of a personalized artificial liver using a person's own cells," Theise says.