Inhibition of mammalian target of rapamycin signaling pathway decreases retinoic acid stimulated gene 8 expression in adult mouse testis.

To evaluate the expression of mammalian target of rapamycin (mTOR) pathway molecules in mouse spermatogenesis and as well as its role during proliferation and meiotic initiation of spermatogenic cells. Experimental animal study. University. C57Balb-C adult male mice. Expressions of mTOR signaling pathway proteins in adult testis were evaluated. Then the effect of inhibition of this pathway on proliferation and differentiation of spermatogonial stem cells was investigated using seminiferous tubule culture. Immunohistochemistry was performed to evaluate the expressions of mTOR signaling pathway proteins. To inhibit mTOR signaling pathway by rapamycin, seminiferous tubule culture was done. Viability assay and terminal deoxynucleotidyl transferase dUTP nick end labeling was performed to evaluate the culture conditions and to examine cell death, respectively. Western blot was used to determine the expressions of the PCNA, STRA8, and VASA proteins. Our results showed that spermatogonial stem cells and preleptotene spermatocytes express total mTOR, p-mTOR, total p70S6K, p-p70S6K, and p-4EBP1. Expressions of p-p70S6K, p-4EBP1, PCNA, and STRA8 decreased significantly in the rapamycin-treated group, where no difference was observed in VASA expression. Cell viability and the number of apoptotic cells were similar for all groups. Our findings suggest that the mTOR signaling pathway may have role in the proliferation and stimulation of meiotic initiation of spermatogonial stem cells. To the best of our knowledge, this is the first ex vivo study that reports the function of the mTOR pathway in adult mouse spermatogenesis.