Gene expression in the epididymis of normal and vasectomized men: what can we learn about human sperm maturation?

Anatomically, the human epididymis is unusual when compared with the excurrent duct of other eutherian mammals. Furthermore, clinical observations suggest that it may not be as important for sperm maturation as is the case for laboratory animals. In contrast, hierarchical clustering of microarray data of epididymides from normal men revealed 2274 modulated qualifiers between the epididymal segments, 1184, 713, and 269 of them being highly expressed in the caput, corpus, and cauda, respectively. The organization of qualifiers according to their similarities by gene ontology indicated that caput transcripts are dedicated to cell-cell adhesion, whereas the corpus is characterized by genes involved in response to other organisms (ie, defense mechanisms) and the cauda transcriptome is specialized in muscle contraction and establishment of localization. A region-specific gene expression pattern thus characterizes the human epididymis as in animal models. In humans, vasectomies have consequences on the epididymal transcriptome. Cluster analysis revealed that 1363 genes are expressed in both normal and vasectomized epididymides, whereas 911 and 660 of them are specifically expressed in normal and vasectomized epididymides, respectively. Three of the affected genes are particularly interesting because of their involvement in sperm biochemical remodeling during epididymal transit: dicarbonyl/l-xylulose reductase, Niemann-Pick disease, type C2, and cysteine-rich secretory protein 1. In some vasovasostomized men, these modifications in gene expression induced by vasectomy are irreversible, thus affecting the biochemical parameters, and potentially, the function of their ejaculated sperm. This may explain the discrepancies between a surgically successful vasovasostomy and fertility recovery.