Defying dogma

When Massachusetts General Hospital's Dr. Jonathan Tilly was rooting around in fertility research during the 1990s, he kept running into "the dogma." It was something he'd learned in medical school, something he took for granted.

The dogma, as fertility scientists still call it, was that a woman's egg supplies decrease with age until none of the hundreds of thousands of eggs she had at birth are left. That's why women face difficulties conceiving from their mid-30s on. Several important papers over the years asserted this, and medical textbooks to this day state it as fact.

"When I got my PhD, that's what I was taught," says Tilly, a boyish-looking researcher who works out of Mass. General's new labs in the Charlestown Navy Yard. "The dogma was so strong, no one thought to challenge it."

Tilly was an expert in how cells die. A few years ago, he wanted to study the way egg cells die as females age. So he began to map out the process -- and was stunned at what he found.

Eggs in the test mice were dying at an unexpectedly rapid clip. At that speed, they should run out much earlier in life. But they don't. The implication was clear: Somehow, while some eggs were dying off, new eggs were simultaneously being manufactured -- a direct contradiction of the dogma.

"We were floored," Tilly says. "Even when I think about it now, I get goose bumps."

Tilly and his small team of researchers decided to keep the finding to themselves, until they could muster more proof. But Tilly immediately saw the implications: Methods could be devised to stimulate egg production for women later in life. Childbearing was something he'd come to deeply appreciate. In 1996, his son Ryan was born.

"Up to that point, my whole life revolved around my research. And then I went through this miracle," he says. "I realized it was something that no person should be robbed of."

There was a second implication that also struck close to home. Women with cancer often got radiation treatments that killed their eggs and chances at motherhood. Four years ago, Tilly himself was diagnosed with testicular cancer. It has since cleared, but he remains wary, saying, "I lived it; I experienced it."

His lab performed a battery of creative experiments. It appears that females have stem cells, the plastic-like cells that give rise to all bodily organs, in their reproductive tract that produce new eggs well into life.

Last March Tilly's research was released, generating worldwide headlines. The dogma began crumbling. Now, his lab is racing to find the DNA signature of the egg stem cells. With it, researchers may soon be able to pluck out women's stem cells for freezing and use later in life.

"The turning point in my life will be when a woman shows me her baby that was born through the work I did," Tilly says.