PHILADELPHIA -- With pinhead-sized grafts of testicular tissue from newborn mammals, scientists at the University of Pennsylvania have induced mice to produce fully functional sperm from evolutionarily distant species. The result has important implications for preserving the germ lines of critically endangered species as well as prized livestock.

The study, in which male mice produced functional gametes first from other mice and then from pigs and goats, is reported in the Aug. 15 issue of the journal Nature.

"This is the first report of complete spermatogenesis from tissue grafted across species," said Ina Dobrinski, assistant professor of large animal reproduction in Penn's School of Veterinary Medicine. "The production of functionally competent sperm from three different mammals indicates that testis tissue grafting may be applicable to a wide variety of species."

The work also yielded the first functional sperm from immature reproductive tissue, meaning sperm could be derived even from individuals that have not reached sexual maturity. Unlike cryonic approaches to preservation, testis tissue grafting offers a potentially inexhaustible supply of male gametes.

Mice with the testis grafts could aid studies of the effects of drugs -- including potential male contraceptives -- on sperm production. The mice also give scientists a valuable model to better understand testicular function, many aspects of which remain murky.

Dobrinski and colleagues grafted as much as one cubic millimeter of tissue from the testes of newborn mice, goats and pigs onto the backs of mice. As many as eight miniature testes developed, and in vitro fertilization revealed that the sperm produced by those testis grafts were functional.

"At least 60 percent of grafts grew into functional testis tissue under the skin," Dobrinski said, "and those grafts produced as much sperm, gram for gram, as testes in the donor species. Some grafts grew more
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Contact: Steve Bradt
bradt@pobox.upenn.edu
215-573-6604
University of Pennsylvania
14-Aug-2002

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