Apoptosis and spermatogenesis: physiopathological implications.

Mammalian spermatogenesis is a dinamic and rather complex process which provides mature spermatozoa starting from staminal spermatogonia. However, not all the proliferating germ cells will complete the differentiation program and the presence of apoptotic germ cells in the testis of healthy and fertile individuals is a common observation. Although the causes for this physiological cell death are still largely unknown, the apoptosis of germ cells appears to accomplish two important functions: a) adeguate the number of proliferating germ cells to that of the supporting Sertoli cells; b) remove those germ cells affected by differentiation problems. In addition, germ cell apoptosis may be induced by a variety of pathological conditions or in response to noxious environmental stimuli, able to interfere with the germ cell differentiation program. Thus, germ cell apoptosis may be considered as the final step of a quality control system which identifies unfit germ cells and eliminates them. Up to date, our informations regarding the cellular mechanisms responsible for the activation of the apoptotic pathways in germ cells are still very poor. However, the renewed interest in this field, by many reproductive biologist and andrologist, should rapidly increase our knowledge on germ cell apoptosis. This will be of undoubt clinical relevance in man to understand all those cases of reduced fertility still unexplained.