The research team, headed by Dr. Ina Dobrinksi of the Center for Animal Transgenesis and Germ Cell Research in the School of Veterinary Medicine, University of Pennsylvania, believes that this method could be used to preserve genetic material from endangered nonhuman primates that might die before reproducing. It could also offer reproductive options to men rendered infertile by cancer treatments before they reach puberty.
The authors of the report warn, however, that ethical and safety issues will need to be resolved before work on this method proceeds to the production of human sperm for assisted fertilization.
The grafting technique has been successfully used to produce fertile sperm of farm animals such as pigs, but the period before sexual maturity is considerably shorter for farm animals than for primates. Because mice only live about 1.5 years and male rhesus monkeys typically do not reach sexual maturity until around 4 years old, the researchers were not sure that the entire process, from grafting immature testicular tissue to producing mature sperm, could occur during the life span of the host mice. Mature sperm, though, were produced in the grafts in as little as 7 months.
In the experiment, donor tissue from the testes of two 13-month-old rhesus monkeys was grafted under the back skin of specially prepared mice. Sperm taken from the grafts at various times were analyzed to see if they would lead to viable rhesus embryos. When injected with sperm taken from grafts after more than 8 months, 9 of 16 rhesus oocytes began to divide normally. This is similar to the fertilization rate for naturally produced rhesus sperm.
Biology of Reproduction, published by the Society for the Study of Reproduction, is the top-rated peer-reviewed journal in the field of reproductive biology.