In a new study, Harvard researchers say they have found stem cells in women that can be used to grow new eggs. Not surprisingly, this has raised much discussion about whether a woman’s biological clock can be stopped – why worry about running out of eggs if you can just make new ones whenever you  need them?

The work described in the paper, published online Sunday by the journal Nature Medicine, is still a long way from being useful to women in need of fertility treatments. And many scientists remain skeptical that these ovarian stem cells really can mature into healthy eggs.

But as long as we’re in the pie-in-the-sky realm, let’s consider another way that the ability to grow an abundant supply of eggs would be helpful: to make human embryonic stem cell lines that would be perfectly matched to patients.

This was a hot area of research in the middle of the last decade. While many scientists studied stem cells made from embryos that were no longer needed for fertility treatments, a smaller group was pursuing a derivation method called somatic cell nuclear transfer, or SCNT. It’s better known as “therapeutic cloning.”

Here’s the idea: You take an egg and remove all the DNA in the cell nucleus. Then you replace it with DNA from a patient. You give the egg an electric shock so it starts dividing and growing into an early-stage embryo.

But instead of implanting this embryo into a uterus and producing a baby that’s a genetic copy of another person, you would use it to make a line of human embryonic stem cells. Then you can use those stem cells to make replacement parts – new cardiac cells for patients who suffered heart attacks, for instance, or nerve cells that would replace those lost after a spinal cord injury. In theory, the new cells would work perfectly because they’d be a perfect genetic match. This is the vision of regenerative medicine.

For a few months back in 2005, it looked like this vision was on the verge of reality. South Korean researcher Hwang Woo Suk published a landmark paper in the journal Science in which he claimed to have made 11 lines of stem cells that were genetic matches to patients with Type 1 diabetes, spinal cord injuries and the so-called Bubble Boy disease. Scientists rejoiced, as did doctors and patients. But a few months later, Hwang was accused of faking the results. The study was retracted, and Hwang was prosecuted for embezzling research money and violating ethics laws.

Since then, researchers at Oregon Health & Sciences University have managed to clone monkey embryos in order to create embryonic stem cells. But in a 2007 study in the journal Nature, they said they had to use 304 eggs to make just two viable cell lines.

It’s hard to imagine how scientists would ever get their hands on 304 human eggs, especially since they generally aren’t allowed to pay women who might be willing to donate eggs for research purposes. It’s also not clear that a few hundred eggs would be enough to guarantee at least one line of stem cells. South Korean investigators eventually discovered that Hwang used 2,236 eggs in his studies that failed to produce a single embryo.

This is one of the major reasons why SCNT studies fell by the wayside. (For more on that, read this story from 2006.) But if there were a relatively simple way to grow hundreds – or thousands – of eggs in the lab, some scientists are confident they could create stem cells through therapeutic cloning.

If so, that would make the research at Harvard relevant to a whole lot of people besides women who hear their biological clocks ticking.

A summary of the Nature Medicine study is online here.

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Eggs made from stem cells could treat more than just fertility