Experimental induction of testicular teratomas in dissociated-reaggregated chimaeric gonads

Testicular teratomas can be experimentally induced in some strains of mice by grafting 12.5-day male genital ridges to the testes of adults. The grafts develop into testes and most of them have teratomas. The cells of 12.5-day foetal gonads were dissociated and the germ cells and somatic cells were separated. When germ cells were reaggregated with somatic cells and implanted in adult testes, they formed seminiferous tubules with teratomas. The somatic cell populations were contaminated with about 1% germ cells, and when they were implanted in adult testes, they formed testes with a comparatively low incidence of teratomas. When germ cells of a highly susceptible strain were combined with somatic cells from a resistant strain, they formed chimaeric testes with a high incidence of teratomas. When germ cells from a resistant strain were combined with somatic cells from a susceptible strain they formed chimaeric gonads and the incidence of teratomas was low. This indicates that at 12.5 days the genotype of the germ cells is responsible for susceptibility. When germ cells from older foetal gonads were combined with somatic cells of 12.5-day gonads, the incidence of teratomas was low. This showed that 12.5-day somatic cells cannot 'rejuvenate' older germ cells in a way to regain their susceptibility. When 12.5-day germ cells of highly susceptible strains were combined with older somatic cells the incidence of tumours was low indicating that the age of the somatic cells influences susceptibility to teratocarcinogenesis.