"Furthermore, we're talking about significant amounts of functional liver tissue -- up to 40 percent in one case we studied," said Dr. Neil Theise, first author of the cover report for HEPATOLOGY's July issue. HEPATOLOGY is the monthly peer-reviewed journal of the American Association for the Study of Liver Diseases (AASLD). "The whole notion of a bone-marrow cell traveling around, becoming anything it wanted, is the first time I've had an idea that I couldn't see the limits of."
The discovery has implications for organ transplants, artificial livers, gene therapy and more, explained Theise, who is an associate professor of pathology at New York University School of Medicine.
Only in the last year have scientists in the field agreed that some animals, such as mice, can transform bone marrow into new liver tissue. Whether humans have liver stem cells at all has been a decades-old debate.
"The liver is an incredibly regenerative organ using its own cells," said Theise. "So some people have argued why invoke stem cells? A couple of studies have looked for them in humans but the data have never been definitive until now."
Theise and his team, which also includes investigators at Yale University School of Medicine and at Memorial-Sloan Kettering Cancer Center, started with a deceptively simple approach: only male cells carry the Y chromosome.
The researchers first examined samples of liver tissue from two women who had received bone-marrow transplants from male donors. They prepared the tissues and then stained them with chromosome-specific dye (Y chromosomes fluoresced as light green dots, X chromosomes as red). Between 5 and 20 percent of the women's liver cells (hepatocytes) and bile-duct cells (
Contact: Kirk Monroe