New insights about the evaluation of human sperm quality: the aromatase example.

Abstract

Male contribution to the couple's infertility is at first evaluated by the routine examination of semen parameters upon optical microscopy providing valuable information for a rational initial diagnosis and for a clinical management of infertility. But the different forms of infertility defined according to the WHO criteria especially teratozoospermia are not always related to the chromatin structure or to the fertilization capacity. New investigations at the molecular level (transcript and protein) could be developed in order to understand the nature of sperm malformation responsible of human infertility and thus to evaluate the sperm quality. The profile analysis of spermatozoal transcripts could be considered as a fingerprint of the past spermatogenic events. The selection of representative transcripts of normal spermatozoa remains complex because a differential expression (increased, decreased or not modified levels) of specific transcripts has been revealed between immotile and motile sperm fractions issued from normozoospermic donors. Microarrays tests or real-time quantitative PCR could be helpful for the identification of factors involved in the male infertility. Differences in the expression of specific transcripts have been reported between normal and abnormal semen samples. With the aromatase example, we have noted a negative strong correlation between the amount of transcript and the percentage of abnormal forms especially in presence of head defects. Immunocytochemical procedures using fluorescent probes associated with either confocal microscopy or flow cytometry can be also helpful to proceed with further investigations about the localization of proteins in the compartmentalized spermatozoa or the acrosome reaction. The dual location of aromatase both in the equatorial segment, the mid-piece and the tail could explain the double role of this enzyme in acrosome reaction and motility.

Tissue physiology and pathology of aromatase

“…Decreased sperm motility is common in aromatase-deficient men and in aromatase knockout mice [42]. Additionally, spermatozoa of asthenospermic, teratospermic and asthenoteratospermic patients exhibit decreased aromatase expression [43]. In aromatase-deficient adult men, spermatogenesis varies from normal to highly reduced (hypospermatogenesis) [44].…”

“…In aromatase-deficient adult men, spermatogenesis varies from normal to highly reduced (hypospermatogenesis) [44]. In fact, it has been proposed that the quantification of aromatase in ejaculated sperm could be used as an indicative parameter of sperm function and spermiogenesis to evaluate male infertility [37, 43]. More strikingly, in ejaculated spermatozoa, aromatase localises to the midpiece, the tail, and the annular region located at the limit between the acrosomal membrane and the nucleus [38, 43].…”

“…In fact, it has been proposed that the quantification of aromatase in ejaculated sperm could be used as an indicative parameter of sperm function and spermiogenesis to evaluate male infertility [37, 43]. More strikingly, in ejaculated spermatozoa, aromatase localises to the midpiece, the tail, and the annular region located at the limit between the acrosomal membrane and the nucleus [38, 43]. More importantly, aromatase in human spermatozoa is still active after ejaculation [45].…”