Stem Cell Discovery Could Put Cloning on the Fast Track

Bioethics   |   Rebecca Taylor   |   Mar 5, 2012   |   11:07AM   |   Washington, DC

Researchers at Massachusetts General Hospital have announced they have found stem cells in ovaries that may be able to generate egg cells. It was previously thought that women are born with all the eggs they will ever have in a lifetime. But this research suggests that more eggs can be made by extracting these stem cells from ovaries.

The scientists first found these stem cells in mice and were able to generate mouse eggs. They then turned to ovaries donated by Japanese women undergoing a sex-change. The reproductive stem cells were isolated and coaxed to differentiate into follicles and mature eggs. From the New York Times:

The new research, by a team led by the biologist Jonathan L. Tilly, depends on a special protein found to mark the surface of reproductive cells like eggs and sperm. Using a cell-sorting machine that can separate out the marked cells, the team obtained reproductive cells from mouse ovaries and showed that the cells would generate viable egg cells that could be fertilized and produce embryos.

They then applied the same method to human ovaries donated by women at the Saitama Medical Center in Japan who were undergoing sex reassignment because of a gender identity disorder. As with the mice, the team was able to retrieve reproductive cells that produced immature egg cells when grown in the laboratory. The egg cells, when injected into mice, generated follicles, the ovarian structure in which eggs are formed, as well as mature eggs, some of which had a single set of chromosomes, a signature of eggs and sperm. The results were published online Sunday by the journal Nature Medicine.

Dr. Tilly and colleagues wrote that their work opens up “a new field in human reproductive biology that was inconceivable less than 10 years ago,” and that access to the new cells will make possible novel forms of fertility preservation.

This discovery is being hailed as a game-changer for the fertility industry where eggs are a hot commodity. The specter of a greater supply has everyone talking.

But I want to talk about a few realities. First, the reality of using eggs grown in the lab to make embryos in a lab. Starting out life in a dish with naturally made eggs is already a dangerous prospect. Children conceived with IVF are are 9 times more likely to have the genetic disorder Beckwith-Wiedemann’s Syndrome. Some recent studies are suggesting that people conceived with IVF have different patterns of gene expression that those conceived naturally and so are at greater risk for major disease like obesity and diabetes later in life. And it is estimated that 90% of IVF embryos have chromosomal abnormalities.

How much greater will the genetic risks be with eggs grown artificially? What does that mean for the offspring? Does anyone care? I have not seen a single commentary questioning the safety for the children that would be produced. Are we all too busy simply wondering if it can be done to wonder if it should be done?

I also fear that the “new field in human reproductive biology that was inconceivable less than 10 years ago” that Dr. Tilly mentions goes far beyond simple IVF. Back in the 1990’s the world was all a buzz with the “hope” of therapeutic cloning. In therapeutic cloning, also known as somatic cell nuclear transfer (SCNT), a patient would be cloned using a human egg creating a cloned embryo. That embryo would then be destroyed for embryonic stem cells that would be a genetic match to the patient. This technique was hyped as the “most promising” way to make patient-specific embryonic stem cells which in turn would cure a multitude of disease.

We don’t hear much about therapeutic cloning these days for a couple of reasons. First, the amount of eggs needed to make even one cloned embryo is at best in the hundreds, at worst in the thousands. The reality is that therapeutic cloning was never really a viable option for widespread patient-specific embryonic stem cells because there were just not enough women with enough eggs to make it happen.

The second reason therapeutic cloning has fallen out of favor, even with cloning pioneer Ian Wilmut, is that there is a better alternative for making patient-specific embryonic-like stem cells without cloning and without eggs. The stem cells are called induced pluripotent stem cells and they are made by reprogramming the patient’s adult cells back to a pluripotent (embryonic-like) state using various methods that do not require human eggs. Induced pluripotent stem cells are now being called “Biology’s New Supermodel.” And there are no ethical objections to this approach because no women need be exploited for their eggs and no human embryos need be created and destroyed.

And yet there are those that want to continue with cloning research. The promise of a greater supply of eggs using these stem cells found in ovaries has people talking about therapeutic cloning again. And as many experts believe, therapeutic cloning, cloning embryos for research, is only a stop on the road to reproductive cloning, cloning embryos to produce children. Gregory Pence, philosophy professor at the University of Alabama at Birmingham and cloning advocate, rightly observed in his book, Cloning After Dolly: Who’s Still Afraid?, “Scientists are naive to think they can ban reproductive cloning and go ahead studying embryonic [therapeutic] cloning.”

So this discovering has much greater ramifications than simply slowing a woman’s biological clock. If successful, this technique may put the push for cloning back on the fast track.