Scientists believe they've discovered stem cells in the lung that can make a wide variety of the organ's tissues, a finding that might open new doors for treating emphysema and other diseases.
When these human cells were injected into mice, they showed their versatility by rebuilding airways, air sacs and blood vessels within two weeks. One expert called that "amazing."
While stem cells have been found in bone marrow and some other parts of the body, it hasn't been clear whether such a versatile cell existed in the lung.
Experts not involved in the study stressed that the work must be confirmed by further research and that it's too soon to make any promises about therapies. But they said it could be a significant advance in a difficult field of research.
"These are remarkable findings and they have extraordinary implications," said Dr. Alan Fine of Boston University, who called the mouse results amazing. "But it has to be replicated."
Stem cells can produce a wide variety of specialized kinds of cells. Scientists are working to harness them as repair kits for fixing damage from diseases like Parkinson's and diabetes. Most people have heard about embryonic stem cells, which have caused controversy because embryos must be destroyed to recover them.
In contrast, the new lung cell would be an "adult" stem cell, like others found in the body. Adult stem cells maintain and repair the tissues where they're found. The bone marrow cells, for example, give rise to various kinds of blood cells, and they've been used for years in transplants to treat leukemia and other blood diseases.
The lung work is reported in Thursday's issue of the New England Journal of Medicine by Drs. Piero Anversa and Joseph Loscalzo and colleagues at Brigham and Women's Hospital in Boston. In a telephone interview, Anversa said it's not clear what the lung stem cell normally does but that he thinks it's involved in replacing other lung cells lost throughout life.
Loscalzo said it's too early to tell what lung diseases might be treated someday by using the cells. He said researchers are initially looking at emphysema and high blood pressure in the arteries of the lungs, called pulmonary hypertension. Emphysema is a progressive disease that destroys key parts of the lung, leaving large cavities that interfere with the lung's function.
Anversa said the cells may also prove useful to build up lungs after lung cancer surgery. It's not clear whether they could be used in treating asthma, he said.
While a lung stem cell theoretically could be used to grow a lung in a lab for transplant, Loscalzo said that would be very difficult because the lung is so complex. Instead, he said, scientists will first look at isolating the cells from a patient, multiplying them in the laboratory, and then injecting them back into the patient's lung.
The mouse experiments showed "the cells are smarter than we are," able to build normal lung structures in an injured lung, he said.
The researchers found the cells in donated surgical samples of adult tissue. The same cells appeared in tissue donated from nine fetuses that had died, giving evidence that the cells are present before birth and perhaps participate in lung development. To study the cells' behavior, researchers injured lungs of mice and then injected six doses of about 20,000 cells apiece.
Within 10 to 14 days, the injected cells had formed airways, blood vessels and air sacs. "We had a very large amount of regeneration" involving millions of new cells, Anversa said.
The new tissue showed "seamless" connection to the rest of the lung, and researchers believe it would work, although that wasn't tested, Loscalzo said. The results appeared in all 29 mice tested.
Dr. Brigitte Gomperts at the Broad Stem Cell Research Center at the University of California, Los Angeles, said scientists have been hotly debating whether a single stem cell type could give rise to the more than 40 cell types in the lung __ cells that do such different jobs as protecting the body from inhaled germs and exchanging oxygen for carbon dioxide. It's a technically difficult question to study, said Gomperts, who was not involved in the new work.
If the new results can be confirmed, "it's a significant advance" that will help in understanding normal lung repair and abnormal repair found in disease, she said.
The work was supported by the National Institutes of Health and a Swiss foundation.
New England Journal: http://www.nejm.org