Scientists: Stem Cells Made Without Harming Embryos

WASHINGTON — Scientists in Massachusetts said yesterday they had created several colonies of human embryonic stem cells without harming the embryos from which they were derived, the latest in a series of recent advances that could speed development of stem cell-based treatments for a variety of diseases.

In June, scientists in Japan and Wisconsin said they had made cells very similar to embryonic stem cells from adult skin cells, without involving embryos. But that technique so far requires the use of gene-altered viruses that contaminate the cells and limit their biomedical potential.

By contrast, the new work shows for the first time that healthy, normal embryonic stem cells can be cultivated directly from embryos without destroying them.

The new technique involves the careful removal of a single cell from a newly formed eight-cell embryo and coaxing that cell to divide repeatedly until it forms a self-replenishing colony of embryonic stem cells.

Fertility doctors perform such "single-cell biopsies" thousands of times every year to test the genetic health of embryos conceived by in vitro fertilization, with little or no apparent effect on the remaining seven cells' ability to form a normal baby. The idea is to check the removed cell for DNA defects and transfer to the woman's womb only embryos whose cells test normal.

Mr. Lanza's team first reported growing stem cells from individual embryo cells in 2006. But that work was criticized for not showing plainly that the plucked embryos could develop normally, relying instead on evidence from the nation's many fertility clinics that embryos can survive the process.

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

Of 43 embryos biopsied, 36 (or 83%) developed into healthy five-day-old embryos, as determined by various measures used by the clinics, the team reports in yesterday's online edition of the journal Cell Stem Cell.

That's a survival rate as good as or better than occurs with fertility clinic embryos generally, whether they are biopsied or not, according to several published reports. "It is a technically impressive piece of work," Douglas Melton of the Harvard Stem Cell Institute said. "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 .