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>Sperm Grown In A Dish From Scratch?


Sperm grown in a test tube

Immature mouse testicles yield fully developed sperm in culture.
By Janelle Weaver
Researchers in Japan have made fertile mammalian sperm in a culture dish, a feat long thought to be impossible. The technique, reported March 23 in Nature, could help to reveal the molecular steps involved in sperm formation and might even lead to treatments for male infertility.
Biologists have been trying to make sperm outside the body for almost a century. Failure has often struck at the stage of meiosis, a type of cell division during which paired chromosomes swap DNA and the number of chromosomes per cell is halved. The result of this process is sperm cells ready to fuse with an egg.
Takehiko Ogawa and colleagues at Yokohama City University discovered that the key to getting sperm through meiosis lay in a simple change to standard culture conditions.
“The report is quite exciting because it represents the fulfilment of a goal held by many reproductive biologists over many years,” says Mary Ann Handel, an expert in reproductive genetics at the Jackson Laboratory in Bar Harbor, Maine.
Culture shock
By trial and error, Ogawa’s team worked out which culture methods allowed sperm in tissue fragments from neonatal mouse testes to mature. To track sperm development, they used a fluorescent protein that marked cells undergoing–or that had undergone–meiosis.
Initially, the researchers placed the fragments on a gel and soaked them in fetal bovine serum, a typical ingredient of cell cultures. But nothing they added to this mix worked, not even factors known to stimulate sperm maturation.
The authors’ success came when they replaced the fetal bovine serum with a serum-free medium, KnockOut Serum Replacement, which is often used to grow embryonicstem cells.