Rats produced by interspecies spermatogonial transplantation in mice and in vitro microinsemination.

Spermatogonial transplantation has demonstrated a unique opportunity for studying spermatogenesis and provided an assay for spermatogonial stem cells. However, it has remained unknown whether germ cells that matured in a xenogeneic environment are functionally normal. In this investigation, we demonstrate the successful production of xenogeneic offspring by using spermatogonial transplantation. Rat spermatogonial stem cells were collected from immature testis and transplanted into the seminiferous tubules of busulfan-treated nude mouse testis. Using rat spermatids or spermatozoa that developed in xenogeneic surrogate mice, rat offspring were born from fresh and cryopreserved donor cells after microinsemination with rat oocytes. These offspring were fertile and had a normal imprinting pattern. The xenogeneic offspring production by interspecies germ cell transplantation and in vitro microinsemination will become a powerful tool in animal transgenesis and species conservation.