Spermatogenesis and spermatogenic control: a state of the art

In this short overview we summarize recent progress made in some areas of fundamental research related to spermatogenesis and its control. After a brief reminder of the main characteristics of the spermatogenic process we focus on the determinants of sperm output. Particular attention is paid to factors controlling the number of Sertoli cells, to the role of germ cell apoptosis, and to factors rendering human spermatogenesis relatively inefficient. Thereafter, we summarize recent insights on the relative role of testosterone and FSH in the endocrine control of human spermatogenesis. The potential contribution of testosterone metabolites such as 5alpha-dihydrotestosterone and 17beta-estradiol is discussed in the light of novel experimental paradigms. The contribution of cell-cell interactions to spermatogenic control is illustrated on the hand of the kit-ligand-c-kit-receptor system and the scientific and potential therapeutic potential of germ cell transplantation techniques underlined. Finally we focus on clinical and fundamental approaches which contribute to our understanding of specific genes involved in spermatogenesis. It is concluded that research in the field of spermatogenesis is rapidly expanding and that several recent findings will lead to diagnostic and therapeutic applications in the near future.