Characterization of the model for experimental testicular teratoma in 129/SvJ-mice

An animal model of experimental testicular teratoma has been established to study how a teratoma affects the host testis and how the host testis react s against the teratoma. 129/SvJ-mice were used as experimental animals. To induce the experimental testicular teratoma, male gonadal ridges from 12-da y-old 129/SvJ-mouse fetuses were grafted into the testes of adult mice for 1-12 weeks. The developing tumour was analysed by light and electron micros copy and by immunocytochemical localization of transcription factors SOX9 a nd c-kit, glial fibrillary acidic protein (GFAP) and type IV collagen. Test icular teratoma was observed in 36 out of 124 testes with implanted fetal g onadal ridges (frequency 29%), One spontaneous testicular teratoma was obse rved in this material from 70 male mice (1.5%), One week after implantation intracordal clusters of cells were seen in embryonic testicular cords of t he graft as the first sign of testicular teratomas. Four weeks after implan tation the embryonic testicular cords had totally disappeared from grafts w ith teratomas, and the tumour tissue had enlarged the testis and invaded th e interstitium of the host testis, It consisted of solitary pieces of immat ure cartilage as well as of glial cells and of primitive neuroepithelium. S ix to eight weeks after implantation the tumour tissue had expanded so that the enlarged testis could be detected by macroscopic enlargement of the sc rotum. The testicular tissue of the host had practically disappeared, and o nly solitary disrupted seminiferous tubules of the host were seen surroundi ng the teratoma. Neuroepithelial structures of some teratomas cultured for 8 weeks had cells with a granular nucleus as a sign of obvious apoptosis. E leven to 12 weeks after implantation the growth of the teratoma had stopped , and the histology corresponded to that of a mature cystic teratoma, GFAP, SOX9 and type IV collagen were strongly positive in some parts of the tumo urs cultured for 4 and 8 weeks, white only occasional c-kit-positive areas were observed in tumours cultured for 8 weeks. As conclusions: (1) the meta stasizing capacity of the experimental testicular teratoma is very low duri ng 12 weeks, but the behaviour of the tumour in the testicular tissue of th e graft is invasive; (2) the growth of experimental testicular teratomas ce ase 6-8 weeks after implantation of the fetal gonadal ridges with the obvio us apoptosis of the immature tissue components; (3) the model of experiment al testicular teratoma in the mouse is suitable for studying how the terato ma affects the host testis and how the host testis reacts to teratoma.