"Regardless of all the strife in this field and our complaining incessantly about our national policy and some recent events that cast a shadow on this work, there is a great deal of excitement," said Dr. John Gearhart of Johns Hopkins University in Baltimore.
"I am still excited about this. It is robust ... it is vibrant," Gearhart told a news conference after a symposium on stem cell research at a meeting of the American Association for the Advancement of Science in St. Louis.
As they met, the independent National Academy of Sciences said it was setting up a new committee to provide updated guidelines on how best to ethically conduct human embryonic stem cell research.
Dr. Lawrence Goldstein of the University of California San Diego and Howard Hughes Medical Institute said researchers will be working on the use of cloning technology to make stem cells -- valued because they would perfectly match the patient and perfectly model an individual's disease.
"I am personally optimistic that with enough skilled people working on this problem in the United States and other countries it is workable," Goldstein told the news conference.
Goldstein said there is no reason to believe humans cannot be cloned, as sheep, dogs, cats, mice and other animals have been. "While it is possible that humans somehow will pose unusual difficulties, I don't think it is likely," he said.
The bigger problem, Goldstein said, is a lack of human eggs to work with. Therapeutic cloning or nuclear transfer is done by hollowing out an egg cell and inserting the nucleus of a cell from the animal, or the tissue, to be cloned.