Mise en évidence des transcrits du cytochrome P450 aromatase dans les spermatozoïdes humains éjaculés

Estrogens in males: what have we learned in the last 10 years?

This review focuses on the role of estrogen in men, mainly in male reproduction. The continuing increase in data obtained, and recent discoveries in this area will enable a better understanding of male physiology; these, in turn, will have important clinical implications.

Reproductive system: aromatase and estrogens

The cytochrome P450 aromatase (P450arom) is the terminal enzyme responsible for the formation of estrogens from androgens. In the rat testis we have immunolocalized the P450arom not only in Leydig cells but also in germ cells and especially in elongated spermatids. Related to the stage of germ cell maturation, we have shown that the level of P450arom transcripts decreases, it is much more abundant in pachytene spermatocytes (PS) than in mature germ cells whereas the aromatase activity is two- to fourfold greater in spermatozoa when compared to younger germ cell preparations. In rat germ cells, the aromatase gene expression is not only under androgen and cyclic AMP control but also subjected to cytokine (TNFalpha) and growth factor (TGFbeta) regulation. In the bank-vole testis we have evidenced a positive correlation between a fully developed spermatogenesis and a strong immunoreactivity for both P450arom and estrogen receptor (ERbeta) not only in Sertoli cells but also in PS and round spermatids (RS). Therefore, the aromatase gene expression and its translation in a fully active protein in rodent germ cells evidence an additional site for estrogen production within the testis. Our recent data showing that human ejaculated spermatozoa expressed specific transcripts for P450arom reinforced the observations reported in germ cells of other mammalian species. Together with the widespread distribution of ERs in testicular cells these data bring enlightenment on the hormonal regulation of spermatogenesis.

Increased testicular steroid concentrations in patients with idiopathic infertility and normal FSH levels

In 10 men with idiopathic infertility, the authors evaluate hypophyso-gonadal axis by measuring the intratesticular concentrations of several steroids in relation with the serum hormonal status. The data are compared with those from men (n = 20) after cerebral death (stage IV coma), taken as a control group. There was no difference between the two groups. The histological studies of the testes revealed no significant differences between control and infertile men both in the development of the interstitial tissue and in the spermatogenic score. Conversely, the testicular concentrations of pregnenolone, dehydroepiandrosterone, progesterone, androstenedione, testosterone, and estradiol were higher in infertile men compared to control. Therefore, it is difficult to evoke a specific parameter involved in that peculiar pathology, but the large amounts of endogenous estradiol may account for the impairment of fertility.