Researchers in Japan have grown functioning mouse sperm in a laboratory dish, a breakthrough that has been decades in the making and holds out new hope for millions of infertile men.
The research, reported Wednesday in the journal Nature, could help scientists understand several steps of spermatogenesis, or sperm formation, at the cellular level and ultimately lead to new treatments for male infertility.
Researcher Takehiko Ogawa of Yokohama City University not only grew healthy mouse sperm in the laboratory, but also used them to produce fertile offspring, according to the study.
The sperm were produced in a test tube from the cells taken from newborn mouse testicles, and then injected into eggs to produce to twelve healthy babies, four male and eight female, which were all fertile and able to have their own babies in adulthood.
"It's really exciting," said Mary Ann Handel, a reproductive genetics research scientist at Maine's Jackson Laboratory. "I really do think that he's really achieved a goal that a lot of people have tried over the years."
"It is a significant breakthrough," said Martin Dym, a professor of biochemistry and molecular and cellular biology at Georgetown University. Dym was part of a team that tried, and failed, to accomplish in vitro growth of functional sperm ten years ago. "We did make sperm, but could not succeed in getting the sperm to make pups. [The Japanese team] has better sperm."
The potential practical applications in humans would include treating infertility, which affects an estimated 8 to 12 percent of the male population.
"So far it's been done in mice," said Dym. "You have to show that it can work in humans."
One group in particular that stands to benefit is young boys undergoing cancer treatment. One side effect of chemotherapy is "invariably" infertility, said Dym. Adults may be able to freeze their own sperm for future use when they undergo radiation, but boys don't have that option.
By taking a biopsy of the prepubescent testicular tissue and freezing it, there may be a way to grow functioning sperm for future in vitro fertilization, Dym said.
The techique could also protect the reproductive potential of endangered animals that may die before reaching sexual maturity, according to the study.
One minor caveat that gave Dym pause was that the Japanese researchers were able to succeed in producing mouse offspring with just 100 sperm cells.
"You'd like to see millions if possible," he said. "In humans, I don't know that it would be possible to do anything with 100 cells."