WASHINGTON -- Cloned cows that reach adulthood show no unusual signs of physical problems, according to a study that could have significance for the medical and commercial uses of cloning.
The study published in the journal Science found that 24 cloned Holsteins remained alive and healthy one to four years after they were born. Their immune systems were normal, they exhibited puberty at the expected age and two of the cloned cows gave birth to calves that appeared normal in all respects.
Dr. Robert Lanza of Advanced Cell Technology of Worcester, Mass., one of the participants in the study, said it was the first to study the health of cloned animals well into adulthood, and was the best evidence yet showing that cloned animals can produce healthy and functional cells.
Others in the study were the Mayo Clinic, the University of Pennsylvania School of Veterinary Medicine and two other companies involved in cell technology.
Six of the 30 cows evaluated died shortly after birth, slightly higher than the normal mortality rate for cows, but those that survived were both healthy and showed normal social interaction and behavior, according to the study.
The findings were published shortly before a National Academy of Sciences meeting next Tuesday, during which scientists will discuss cloning and animal safety issues.
Lanza said he hoped the findings would "inject a sense of reality and scientific vigor" into the cloning issue. He said his institute joins with other scientists in opposing the reproductive cloning of humans but sees great potential in the medical applications of cell cloning technology.
Pluses for cloning
He said this technology, and advances in the uses of embryonic stem cells, could be used to produce insulin-producing cells to treat diabetes or neurons to help those with Parkinson's or Alzheimer's disease.
Commercially, cloning could be used to breed animals that are free from disease, Lanza said.
Since Scottish scientists cloned the first animal, Dolly the sheep, in 1997, whole herds of cattle, sheep and pigs have been cloned.
Human cloning is opposed by most of the world's scientists, governments and religions. A bill has passed the House that would outlaw human cloning, but the Senate has yet to act.
In cloning, genes from an adult cell are implanted into an egg from which all the genetic material has been removed. The egg is then cultured into an embryo and implanted in the womb of the mother. The offspring would have only the genes from the adult cell. The result would be a genetic duplicate of the cell donor.