Transplantation of germ cells and testis tissue for the study and preservation of fertility.

The germ line stem cells in the mammalian testis form the basis of male fertility. When these stem cells are transplanted from the testis of a fertile donor animal to the testis of an infertile recipient they can establish donor-derived spermatogenesis in the recipient testis, and the resulting sperm can transmit the genotype of the donor to the offspring of the recipient. Germ cell transplantation provides a system to study the biology of germ line stem cells, to explore stem cell isolation and culture, to examine defects in spermatogenesis and to overcome male infertility. Although most widely studied in rodents, germ cell transplantation is now applied to larger mammals, including primates. Germ cell transplantation can preserve fertility from valuable animals and potentially restore fertility in patients that underwent cytotoxic treatments for cancer. In addition, genetic manipulation of germ cells prior to transplantation provides a new approach to germ line modification and transgenesis. As an alternative to transplantation of isolated germ cells to a recipient testis, ectopic grafting of testis tissue from diverse mammalian donor species, including primates, into a mouse host represents a model to study spermatogenesis, to investigate the effects of substances with the potential to enhance or suppress male fertility, and to produce fertile sperm from immature donors. Therefore, transplantation of germ cells or testis tissue are uniquely valuable approaches for the study, preservation and manipulation of male fertility in mammalian species.