Context: Germ cells formed during human fetal life are essential for fertility of the adult, and several studies have described an increasing frequency of male reproductive disorders, which may have a common origin in fetal life and which are hypothesized to be caused by endocrine disruptors. However factors inducing a genotoxic stress may also be implicated.

Objectives: We investigated the effect of irradiation on the functions of human fetal testis during the first trimester of gestation by using an organ culture system. Then we focused on the role of the p53 pathway in the observed effects.

Results: Germ cells were highly sensitive to irradiation even at doses as low as 0.1 and 0.2 Gy. Indeed, for these doses a third of germ cells died by apoptosis. Other germ cells were blocked in their cycle, but no repair seemed to occur, and longer culture with the highest dose used, showed that they were destined to die. Sertoli cells were less affected although their proliferation and the level of AMH were reduced. Irradiation had no effect on testosterone secretion or on the expression of steroidogenic enzymes by Leydig cells. After irradiation, p53 phosphorylated on serine 15 was detected from 1 h to 24 h, in all cells types. This activation of p53 was accompanied by an increase in mRNA levels of pro-apoptotic factors Bax and Puma, whereas that of anti-apoptotic Bcl-2 remained unchanged. P21, which is responsible for cell cycle arrest, was also upregulated 6, 30 and 72 h after irradiation. Finally, when we added pifithrin , a specific inhibitor of p53 functions, a significant decrease in irradiation-induced apoptosis in both germ and Sertoli cells was observed, indicating the involvement of p53 pathway in irradiation-induced apoptosis.

Conclusions: This study demonstrated here for the first time, the great sensitivity of human fetal germ cells to genotoxic stress caused by ionizing radiation.