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A San Francisco company announced Tuesday that they would be the first to offer IVF patients the option of growing, freezing and banking their own embryonic stem cells. Until now, couples undergoing in vitro fertilization could not earmark stem cells derived from their embryos for their own future use; they could only donate them to the nationwide pool of embryos used for stem cell research.

Somewhere between 400,000 and 500,000 such embryos lie in frozen animation in IVF clinics across the U.S. Couples have the option of keeping these embryos frozen, discarding them, donating them to other infertile couples, or making them available for study. Because President Bush has forbidden federal funds to be used to study human embryonic stem cells, only privately supported programs can ask couples with excess embryos to donate them for stem cell research. Given the high cost of each IVF cycle, however, more and more couples expressed a desire to keep their stem cells from themselves, to use whenever stem cell therapies became a reality for treating diseases from diabetes to Parkinson's.

"When I was doing research on stem cells, my team got a lot of inquiries from IVF patients and professionals asking if they could donate embryos to generate stem cells that they could have access to," says Anna Krtolica, a biochemist and CEO of StemLifeLine, the California company offering the service. "Until now, there wasn't that option."

Stem cell lines are not easy to generate, however, so StemLifeLine requests that interested couples donate at least 10 embryos if they want to take advantage of the service. Those frozen embryos will be shipped from the IVF center to the company's San Francisco facility at a cost of several thousand dollars (Krtolica declined to provide an exact figure, citing ongoing talks with a few IVF clinics). There scientists thaw and nurture the embryos to generate stem cells. These are then removed, cultured and allowed to grow. The surviving colonies are then frozen and kept cryopreserved in liquid nitrogen in StemLifeLine's own freezers on the premises. (The company charges about $350 per year to keep the cells in deep freeze.)

Not everyone is convinced that banking stem cells this way would be providing a truly valuable medical service. "Given the current status of the research and the many innovations that are likely down the road," says Dr. Renee Reijo Pera, director of Stanford University's Human Embryonic Stem Cell Research Center, "the value of this service is minimal, especially in light of the the difficulties with cryopreservation."

Krtolica maintains that the frozen embryos StemLifeLine starts out with are only slightly less viable than fresh ones in generating stem cells lines, and that freezing cells is a routine and well understood process. So far, she says, there is no evidence that frozen stem cell lines are any less active or viable when thawed — but scientists don't yet have a lot of experience in manipulating and storing human stem cells. The most harmful part of the process, says Krtolica, is the freezing itself; "the freezing process has the biggest harm in killing cells," she says. "The number of cells you freeze is not the number of cells you recover. However, the cells that survive the freezing process don't carry any genetic change due to the freezing process."

One thing to remember about these embryos is that they are not genetic matches to either parent — they are embryos, which means they are as genetically different from mom and dad as children are. So if a parent needs a precisely genetically matched tissue type, these stem cells may not be of much use. Krtolica points out, however, that many organs, including livers and kidneys, are routinely donated today by relatives, and that such organ donations could be made easier by utilizing banked stem cells.

There's no telling when the potential of stem cells will actually be realized in a safe and reliable way. Krtolica tells patients that taking part in the service is an "insurance for the future," warning them that there are currently no therapies available, although dozens of treatments are being tested today. No telling yet when that investment, will pay off.

• Alice Park
• A California company now offers IVF patients the option of creating and storing their own stem cells