The effect of FSH on male germ cell survival and differentiation in vitro is mimicked by pentoxifylline but not insulin

High concentrations of FSH have been shown to boost in-vitro differentiatio n of germ cells from men with normal spermatogenesis and from some patients with in-vivo maturation arrest. This study shows that the differentiation- promoting effect of FSH is connected to protection against germ cell apopto sis and that both effects can be mimicked by the intracellular cyclic AMP ( cAMP)-elevating drug pentoxifylline. On the other hand, a high concentratio n of insulin, supposed to act at the insulin-like growth factor I receptor did not exert any effect either on differentiation or apoptosis of germ cel ls in vitro. These data show that the in-vitro effects of supraphysiologica l concentrations of FSH on human spermatogenesis are mediated by the classi cal FSH signal transduction pathway involving cAMP as a second messenger. P entoxifylline may thus be useful as an alternative means for intracellular cAMP elevation in men with high circulating FSH concentrations leading to d esensitization of the FSH receptor.