Lab Cites Stem Cell Advance

In the new experiments, he and his colleagues allowed their seven-cell embryos to continue growing in laboratory dishes for as many as five days -- the longest that embryos are typically cultured in fertility clinic labs before being transferred to a woman's uterus.

Of 43 embryos biopsied, 36 (or 84 percent) developed into healthy 5-day-old embryos, as determined by various measures used by the clinics, the team reported in yesterday's online edition of the journal Cell Stem Cell.

That's a survival rate as good as or better than that of fertility clinic embryos generally, whether they are biopsied or not, according to several published reports.

"The biopsy had no effect on the embryos' development," Lanza said, adding that the effort produced five new colonies of stem cells. That is a much higher efficiency than was previously achieved. And because of improved culture conditions, the new stem cells do not need to be fed chemicals from destroyed embryos, as was previously the case.

"It is a technically impressive piece of work," said Douglas A. Melton of the Harvard Stem Cell Institute. "They've demonstrated their ability to isolate human embryonic stem cell lines without destruction of the embryos" -- something few scientists thought possible just a few years ago.

"But the fundamental ethical issue remains," said Kathy Hudson, director of the Genetics and Public Policy Center at Johns Hopkins University -- namely, how to prove that the approach is inherently harmless.

Very few studies have looked at the outcomes of fertility treatments in which biopsies had been performed, Hudson said. And those that have been done -- including a widely publicized July report that found that fertility clinic clients who had their embryos biopsied had about a 30 percent lower chance of giving birth -- are riddled with flaws, she said.

But one thing is clear, Hudson said: "Embryo biopsy is tricky and requires extraordinarily good hands and technical skills. And even in the best hands, embryos are sometimes lost."

As long as that risk is there, funding under Bush's policy will not be available, with one possible exception, Landis said.

Although the NIH will not fund Lanza's method of making stem cells, she said, the agency might fund studies on the cells themselves once they are isolated from the embryos with private money and the embryos are shown to be healthy.

Asked who would make that funding decision, Landis said it would be up to NIH officials. But pressed to say whether the White House would influence that determination, she paused.

"I'm sure they would have an interest in such a decision," she said.