| Research Abstract |
Germ cell death is very common in mammalian testes during developmental as well as adult period. In mouse testis, it was known that a small, but significant number of germ cells are spontaneously degenerated during adult life and in fact 25-75% of the expected sperm yield are thought to be lost in the mature spermatogenesis. Also, in artificial cryptorchidism and estrogen-treated (i.p.injection of 30 mu g beta-estradiol-3-benzoate/head, every 5 day for 60 days) mice, the degeneration of germ cells are much more prominent. However, we are not sure wether the germ cell death is of apoptotic nature or necrotic nature, and moreover our knowledge on the underlying mechanism to induce the germ cell death is only limited. Therefore, in this study, we attempted to clarify the type of cell death, which occurs in normal as well as the damaged mouse testes, by both electron microscopy and in situ nick translation and/or TUNEL.As a result, we found that most of the degenerating germ cells were of apoptotic nature in normal and damaged testes, and that in the normal testis apoptosis of spermatogonia and spermatocytes was most abundant in the stage XII of seminiferous epithelium cycle. To elucidate the induction mechanism of germ cell apoptosis, we investigated the spatial and temporal relationship of the expression of Fas/Fas ligand with the appearance of apoptosis molecular-histochemically. Then we did not find any positive correlation between them in normal testis, whereas in estrogen-treated mouse testis both expressions of Fas and Fas ligand were markedly increased in germ cells and Sertoli cells, respectively, and seemed to be closely associated with the apoptotic germ cells. Consequently, these results indicate that the Fas/Fas ligand system may be involved in the induction of germ cell apoptosis in damaged testis, but not in normal spermatogenesis.
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