Baby Rats Born From Mice

August 30, 2006

Rat sperm cells grown in mouse testicles have been used to successfully produce healthy baby rats, scientists say.

The research proves a concept first envisioned a decade ago: that functional sperm cells from many types of animals can be produced in small surrogate fathers of a different species.

The finding has implications for species conservation as well as farming and agriculture.

"If you use a surrogate father, you can reduce the space for keeping animals and the amount of food [required]," Takashi Shinohara, a molecular geneticist at Kyoto University in Japan, said in an email.

Frozen sperm stem cells could be used to fertilize eggs of endangered species or to create genetically modified organisms more easily.

And cattle producers could save space and food by growing bull sperm in mice. (Related: "Mice Used as Sperm Factories for Pigs, Goats" [August 2002].)

Shinohara is lead author of the study, published yesterday in the journal Proceedings of the National Academy of Sciences (PNAS).

Rats and Mice

Sperm stem cells are incapable of fertilizing eggs themselves but give rise to cells that develop into sperm.

Scientists have known since 1996 that rat sperm stem cells transplanted into mouse testicles produced what appeared to be viable rat sperm.

However, the technology to show that these rat sperm actually worked as advertised was lacking until now.

Shinohara and his colleagues used a recently developed technique called in vitro microinsemination to fertilize rat eggs with mouse-grown rat sperm.

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