Expectations for umbilical-cord stem cells may be too high
5 February 2003
Parents paying to freeze their child's umbilical-cord blood in the hope of fighting future disease, may be over-optimistic, suggests new research. The banked cells appear unlikely to repair the brain.
A growing number of parents are attempting to insure their child's future health by storing a vial of blood drained from its umbilical cord at birth. According to the medical companies offering the service, the stem cells this contains could cure conditions from leukaemia to dementia.
Some of these claims are overblown, warns Evan Snyder of Harvard Medical School in Boston. He has preliminary evidence that cord blood cells cannot generate new brain cells easily - which would be needed to treat a stroke, or Parkinson's or Alzheimer's disease. "I object to [the practice of] giving false hope," he says.
Snyder's group examined the autopsied brain of a deceased 20-month-old girl who, at nine months of age, had received an experimental transfusion of a male's cord blood to treat her rare brain disease. They looked for nerve cells derived from the blood - and found none.
Other scientists echo Snyder's concerns. "[Blood] cells banked as they are will not be very useful except for a bone-marrow transplant," argues Juan Sanchez-Ramos of the University of South Florida in Tampa.
Sanchez-Ramos carried out some of the first promising studies that suggest that, in the lab at least, stem cells from cord blood can generate nerve-like cells spontaneously. Two years down the line, he now believes that perhaps only one in a million cells can do this. "I wouldn't want the public to be misled," he says.
For banking, blood left in the umbilical cord and placenta is syringed out minutes after a baby's birth and the cord has been cut. Vials are shipped to the storage lab, where the valuable blood cells and stem cells are filtered out and kept in liquid nitrogen.
These stockpiled cells can save lives. But so far, doctors have mainly used stores in public banks to treat unrelated people with rare blood cancers or genetic diseases. The young cells are often better tolerated than are adult bone-marrow transplants.
Parents who use private banks hope that the cells could save their child if they develop such a disease. This likelihood is very slim, warns Joanne Kurtzberg, director of the paediatric stem-cell transplant programme at Duke University in Durham, North Carolina. "I think [banks] are playing on people's fears," she says.
According to the website of the Cord Blood Registry, the biggest private US bank, "many doctors and scientists believe that in the future, stem cells may be used to repair brain or spinal cord damage". For $1,385 - plus $95 a year for storage - the bank freezes a vial of cord blood.
David Harris, scientific director of the Cord Blood Registry, argues that his company's information is not misleading because it portrays the science as work in progress. "We try to present it even-handedly," he says.
In the United States private cord-blood banks voluntarily submit to inspection by the US Food and Drug Administration. In the majority of European countries (including UK, Netherlands, Belgium, Austria) there is no regulation; in France it is banned.
Despite their concerns, scientists admit that future research on cord blood cells could reveal new medical uses. For example, Sanchez-Ramos has found (but not published) evidence that a few special stem cells can be isolated from cord blood in the laboratory. Treating them with specific growth factors seems to help them produce new nerve cells, he says.
"In 20-50 years these cells might be a life-saver," he says, "but I'd
be reluctant to give a guarantee."
© Nature News Service