The rapamycin-sensitive complex of mammalian target of rapamycin is essential to maintain male fertility
10.12.2015 Schell C, Kretz O, Liang W, Kiefer B, Schneider S, Sellung D, Bork T, Leiber C, Rüegg MA, Mallidis C, Schlatt S, Mayerhofer A, Huber TB, Grahammer F. Am J Pathol. 2016;186(2):324-336 The mammalian target of rapamycin (mTOR) complex 1 inhibitor rapamycin and its analogs are being increasingly used in solid-organ transplantation. A commonly reported side effect is male subfertility to infertility, yet the precise mechanisms of mTOR interference with male fertility remain obscure. With the use of a conditional mouse genetic approach we demonstrate that deficiency of mTOR complex 1 in the epithelial derivatives of the Wolffian duct is sufficient to cause male infertility. Analysis of spermatozoa from Raptor fl/fl*KspCre mice revealed an overall decreased motility pattern. Both epididymis and seminal vesicles displayed extensive organ regression with increasing age. Histologic and ultrastructural analyses demonstrated increased amounts of destroyed and absorbed spermatozoa in different segments of the epididymis. Mechanistically, genetic and pharmacologic mTOR inhibition was associated with an impaired cellular metabolism and a disturbed protein secretion of epididymal epithelial cells. Collectively, our data highlight the role of mTOR complex 1 to preserve the function of the epididymis, ductus deferens, and the seminal vesicles. We thus reveal unexpected new insights into the frequently observed mTOR complex 1 1 inhibitor side effect of male infertility in transplant recipients. 