Oct. 28 (Bloomberg) -- Stem cells were changed to form the precursors of sperm and eggs in a research advance that may lead to better ways of treating the infertility affecting 10 to 15 percent of would-be parents in the U.S.

By manipulating genes, researchers were able to make germ cells, the forerunners of eggs and sperm, said Renee Reijo Pera, the Stanford University scientist who led a study published today in the journal Nature.

Infertility rarely occurs in animals besides humans, so using laboratory mice or other mammals to study the condition and test drugs isn’t useful, Reijo Pera said. The newly created germ cells can now be scrutinized to find what goes wrong in infertile people, Reijo Pera said.

“We now have a human system to examine germ cell development,” Reijo Pera said in a telephone interview on Oct. 26. “We’ve never been able to do this before, never been able to look at the genes required to make human germ cells.”

Reijo Pera, a professor of obstetrics and gynecology at Stanford, near Palo Alto, California, had discovered three genes involved in germ-cell creation that are missing or defective in infertile males. For the current research, she and her team engineered a protein that glows green when those genes are present, signifying a germ cell.

Full-Fledged Sperm

Reijo Pera said the technique would allow her to take patients’ own stem cells and make full-fledged sperm cells and, eventually, egg cells, which could be used for in vitro fertilization procedures. Her goal is to use her new methods to study infertility in a laboratory dish and hunt for drugs that could correct it.

“I’m hopeful that in two to five years we’ll be better able to understand and diagnose infertility,” providing some answers to the 30 percent of infertile couples that never find out what went wrong, she said.

“There’s a lot of expense and emotional expense caused by infertility,” she said. “It would be great to be able to reduce some of that burden and to bring down the cost of fertility treatment.”

To contact the reporter on this story: Rob Waters in San Francisco at rwaters5@bloomberg.net.

Last Updated: October 28, 2009 14:00 EDT