[Development and regulations of testicular functions in the human foetus]

Two major functions are assumed by the testis: the production of male gametes (that is, spermatozoa) and the production of steroid hormones. Both two functions are established during fetal life and are essential to the adult fertility and the masculinization of the internal tract and genitalia. For many years, our laboratory has been interested in the ontogeny of those two functions in rodents and, since 2003, in collaboration with gynecology and obstetrics service of professor R. Frydman in Antoine-Béclère hospital, we have studied them in human. The first aim of this work was to improve the global knowledge of the human fetal testis development by using both our experimental data and the literature. Then, we focused on the different defects that can occur during the fetal testis development. Indeed, male reproductive abnormalities have been steadily increasing since the last decades and are thought to be related to the concomitant increase of the concentration of contaminants and particularly of endocrine disruptors in the environment. Thus, we decided to study the effect of endocrine disruptors on human fetal testis and, more particularly, the effect of phthalates, by using an organ culture system developed for human. In contrast to the data obtained in rat, mono (ethylhexyl)-phthalate (MEHP), an active metabolite of the most widespread phthalate in the environment, does not disturb the steroidogenic function. On the other hand, it has a negative effect on the male germ cells number. This study is the first experimental demonstration of a negative effect of phthalates directly on human fetal testis.