A research on the character and the specific gene expression of spermatogonial stem cells

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Male germ cells were isolated from donor mice, and successfully transplanted in mice devoid of germ cells. By using GFP transgenic mice as donors, transplanted germline stem cells could be distinguished from the cells of recipients, and their mode of expansion were traced under a fluorscent microscope. Three weeks after transplantation, most of the transplanted cells were undifferentiated spermatogoniae megative to c-Kit antibody, and formed distinct colonies. Later, more differentiated cells such as differentiated spermatogoniae and spermatocytes appeared in the colony.With this transplantation system, we ingestigated the effect of a gonadotropin antagonist, leuprorelin, which suppresses the secretion of gonadotropin from the pituitary and thus raise the intratesticular production of testosterone.When leuprorelin was adiministered, donor-derived colonies increased in size, showing the activation of growth of spermatogonial stem cells by leuprorelin. This indicates the inhibitory effect of testosterone in the process of spermatogonial growth, which is in contrast to the widely-accepted notion that testosterone is necessary for the survival and differentiation of germ cells after the meiotic stage.In search for the mechanism of leuprorelin inhibition, we hypothesized that stem cell factor/c-Kit signalling system has the highest possibility, and investigated the effect of leuprorelin in Sl/Sl mutant mice which do not express stem cell factor. The donor derived colonies, however, were formed in the Sl/Sl recipeint testes without any detrimental effect. We concluded that leuprorelin showed its effect on spermatogoniae through signalling mechanisms other than SCF/c-Kit.