Transcripts of aromatase and estrogen receptors and significance of other RNAs in human spermatozoa.

Abstract

The existence of a complex population of mRNAs in human sperm is well documented but their role is not completely elucidated. Evidence for a latent transcriptional capacity and/or a potential translation de novo in mature spermatozoa from fertile men has been provided and is helpful in understanding the final steps of sperm maturation (capacitation and/or the acrosome reaction). Spermatogenesis is controlled by gonadotrophins and testosterone, their effects are modulated by locally-produced factors that include estrogens derived from the irreversible transformation of androgens by aromatase. The data demonstrating an additional source of estrogens in rat germ cells along with several studies showing a decreased sperm motility in men deficient in aromatase has led to the further explanation of the expression of aromatase in ejaculated spermatozoa from fertile men. A significant decrease in the amount of aromatase transcripts in the immotile sperm fraction was recorded. In addition, the levels of transcripts encoding for proteins involved in either nuclear condensation protamines 1 and 2 (Prm1 and Prm2) or in capacitation endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide sythase (nNOS) and c-myc were compared in low and high motile sperm prepared from the same sample. No significant change in the ratio of c-myc/Prm2 between the two populations of spermatozoa was observed. Conversely the amount of Prm1 mRNA was significantly higher in the low motile fraction than in the high motile fraction; in most of the high motile sperm samples analyzed, eNOS and nNOS transcripts were undetectable, whereas they were observed in low motile sperm. Moreover, a partial or complete disappearance of c-myc transcripts was observed after capacitation. Analysis of the mRNA profile in human ejaculated sperm could be helpful either as a diagnostic tool to evaluate the male gamete quality and/or as a prognostic value for fertilization and embryo development.