Transplantation of germ cells from fertile donor mice to the testes of infertile recipient mice results in donor-derived spermatogenesis and transmission of the donor's genetic material to the offspring of recipient animals. Germ cell
transplantation provides a bioassay to study the biology of male germ line stem cells, develop systems to isolate and culture spermatogonial stem cells, examine defects in spermatogenesis and treat
male infertility. Although most widely studied in rodents, germ cell
transplantation has been applied to larger mammals. In domestic animals including pigs, goats and cattle, as well as in primates, germ cells can be transplanted to a recipient testis by ultrasonographic-guided cannulation of the rete testis. Germ cell
transplantation was successful between unrelated, immuno-competent pigs and goats, whereas
transplantation in rodents requires syngeneic or immuno-compromised recipients. Genetic manipulation of isolated germ line stem cells and subsequent
transplantation will result in the production of transgenic sperm. Transgenesis through the male germ line has tremendous potential in domestic animal species where embryonic stem cell technology is not available and current options to generate transgenic animals are inefficient. As an alternative to
transplantation of isolated germ cells to a recipient testis, ectopic grafting of testis tissue from diverse mammalian donor species, including horses and primates, into a mouse host represents a novel possibility to study spermatogenesis, to investigate the effects of drugs with the potential to enhance or suppress male fertility, and to produce fertile sperm from immature donors. Therefore,
transplantation of germ cells or
xenografting of testis tissue are uniquely valuable approaches for the study, preservation and manipulation of male fertility in domestic animals.