WASHINGTON (AP) _ Human umbilical cord blood frozen for 15 years was revived and able to grow and expand in laboratory mice, suggesting that specimens preserved for that long could restore the bone marrow in cancer patients, experts say.
Researchers at the Indiana University School of Medicine said Monday that human cord blood frozen in 1985 and 1986 was able to grow in laboratory cultures with the same vigor as fresh cord blood.
Hal E. Broxmeyer, a professor of microbiology and immunology and a pioneer in the freezing of cord blood, said the experiment suggests strongly that such cells frozen for a decade and a half can be used successfully to treat patients. Earlier studies had suggested that five years was about the limit, he said.
``We showed we could take the cells after defrosting and have them expand extremely well _ as well as if we had used fresh cord blood,'' said Broxmeyer. He is the first author of a study appearing this week in the Proceedings of the National Academy of Sciences.
Blood extracted from the umbilical cord after birth contains stem cells that can develop into bone marrow cells. Since 1989, cord blood has been used to restore the bone marrow of cancer and leukemia patients whose natural bone marrow was destroyed by radiation and chemotherapy treatments.
When compatible bone marrow transplants are available, doctors can use stronger drugs and radiation to attack the cancer and are, thus, more likely to arrest the disease. Restoring bone marrow using cord blood transplant has been performed more than 2,000 times worldwide and experts say the success rate is comparable to compatible bone marrow transplants.
Dr. Celso Bianco of America's Blood Centers, an organization of blood and bone marrow banking companies, said the research finding by Broxmeyer ``is very important'' for expanding the availability of material for bone marrow transplants.
``Only in recent years have institutions started collecting cord blood to restore the bone marrow of patients,'' Bianco said. ``As these repositories grow, you'll have more chances of finding a match'' for patients.
Expanding the time when frozen cord blood can be used from five years to about 15, he said, would substantially expand the inventory of transplantable cells.
But Bianco said the Broxmeyer study is still experimental and 15-year-old cells will have to prove themselves in actual clinical use before such a lengthy cryopreservation is accepted by other experts in the field.
Bianco, however, said the new study may prompt doctors to use long-frozen cells for patients who are in dire need and have no other matching alternative.
In the study, Broxmeyer's team along with two researchers from the National Institutes of Health thawed 15-year-old frozen cord blood and tested it for viability. They found the cells could be grown in laboratory culture, and specimens removed from that culture and grown into a new colony. This procedure, called replating, is considered a key test for the viability of frozen stem cells.
The researchers also put thawed cells into laboratory mice bred to have a flawed bone marrow system and no immune system. Broxmeyer said the long-frozen human cord blood cells thrived in the mice and grew bone marrow cells.
``We were able to get engraftment in those mice as good as we get from fresh cord blood samples,'' he said.
The cells also matched up well with fresh samples when compared in a series of experiments testing whether the cells could grow and expand in number in the laboratory.
``It looks really good that these cells can be cryopreserved for 15 years,'' said Broxmeyer.
Asked if he could recommend that human cord blood frozen for such a long time be used for patients in need, he said, ``Yes, I could.''