Researchers at UC Davis and the University of Pennsylvania have successfully produced monkey sperm by transplanting tissue from the testicles of rhesus macaque monkeys onto the backs of mice in a study that has implications for biomedical research, human medicine and endangered-species conservation.

Stuart Meyers and Ina Dobrinski, veterinary school researchers at UC Davis and the University of Pennsylvania, have published the results of the study online in the journal Biology of Reproduction.

The researchers took small tissue fragments -- less than one millimeter in diameter -- from the testicles of sexually immature rhesus macaque monkeys and grafted the fragments onto the backs of male mice. In as little as seven months, the grafts began to produce mature sperm. The researchers gathered sperm from the grafts and used it to fertilize eggs from rhesus macaque monkeys, demonstrating that the sperm was capable of supporting embryo development.

"The transplants enabled us to produce mature sperm from immature 13-month-old rhesus monkeys in as little as seven months, whereas it would have taken nearly two more years for the monkeys to produce mature sperm," said Meyers, an associate professor in UC Davis' School of Veterinary Medicine. "This represents a significant savings in time, but also may help reduce the number of primates used in future studies of male reproduction."

Meyers and Dobrinski note that the transplant technique could also be helpful in preserving sperm from individuals from endangered primate species that might die before they reach reproductive age.

The technique also might be used in human medicine to produce and preserve sperm of pre-adolescent boys who must undergo cancer therapy that can cause them to be infertile as adults. The researchers strongly caution, however, that both ethical and safety issues would have to be resolved before the technique could be used for producing human sperm intended for human reproduction.

The transplant research was performed at the University of Pennsylvania. Funding was provided by the National Institutes of Health, the U.S. Department of Agriculture, and the Commonwealth and General Assembly of Pennsylvania.