Molecular mechanisms of the induction of spermatogenic cell apoptosis through mitochondria

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In mammalian spermatogenesis, germ cell apoptosis is very common. The mechanism to be rescued from the apoptosis seems to be essential to understand the reset of life program. Since redistribution of mitochondria derived apoptosis-related proteins, Bax and cytochrome C (cytC), in the cytoplasm was implicated in the induction of germ cell apoptosis, in the present study we investigated the distribution of mitochondria in relation with the redistribution of Bax and cytC in apoptotic germ cells in adult male mice. During the study, we also attempted to establish the method of gene transfection by electroporation in to testis in vivo and the conditions of primary culture of testicular germ cells. When the distribution of mitochondria and their proteins in apoptotic germ cells was examined by immuno-electron microscopy, the redistribution of Bax and cytC was not accompanied with a change in mitochondrial distribution. In fact, in the testis transfected with pEYFP-Mito DNA by electroporation, the fluorescence signal of YFP was co-localized with Bax and cytC, but not with SP-22 protein, which is another marker of mitochondria. These results indicate that the redistribution of apoptosis-related proteins derived from mitochondria may be triggered by loss of their ability to anchor those mitochondrial proteins. In addition, we examined various culture conditions for a long term primary culture of isolated germ cells from adult mouse testes and now can maintain the cells for several weeks in vitro, but the overall characteristics were variable among batches depending upon the quality of Sertoli cell feeder layer.