OBJECTIVETo investigate the development of xenografted primitive human germ cells by using fetal testicular tissues as donor tissues and an immunodeficient mouse as the recipient.

METHODSTesticular tissue fragments of a 26-week fetus were grafted under the back skin of a castrated immunodeficient mouse. Grafts were taken out after 135 days and processed for morphological and histological analyses.

RESULTSThe mass of grafts grew from about 1 mm in diameter and 5 mg in wet weight to about 3 mm and more than 20 mg 135 days after grafting. Histological observations showed a significant expansion of seminiferous tubules after grafting (80 +/- 25 microm in diameter) in comparison with seminiferous cords at the time of grafting (60 +/- 15 microm in diameter). The seminiferous cords developed into seminiferous tubules with the epithelial border and lumen. After 135 days of grafting, most of the dispersedly distributed primitive Sertoli cells and germ cells migrated to the basal part of seminiferous epithelium, located on the basement membrane and few of germ cells differentiated into spermatogonia.

CONCLUSIONHuman fetal testicular tissues could survive and continuously develop after being xenograft into castrated immunodeficient mice.