Altered microRNA expression in patients with non-obstructive azoospermia

In this study, the miRNA expression profiles of testes of patients with non-obstructive azoospermia (NOA) and normal controls were performed by using microarray technologies.Altered microRNA expression in NOA patients was found, with 154 differentially down-regulated and 19 up-regulated miRNAs. These findings have been confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) assays on select miRNAs, including miR-302a, miR-491-3p, miR-520d-3p and miR-383. Several down-regulated miRNA clusters in patients with NOA were identified, such as the oncogenic potential of the mir-17-92 cluster and mir-371,2,3 cluster.This is the first report that the expression of miRNAs is altered in testicular tissues of patients with NOA, suggesting a role of miRNAs in regulating spermatogenesis in human males.Infertility is a worldwide reproductive health problem which affects 10%–15% of couples. Half of the cases are due to male factors, and about 60–75% of male infertility cases are idiopathic, since the molecular mechanisms underlying the defects remain unknown [1]. A significant proportion of idiopathic male infertility is accompanied by severe oligozoospermia or azoospermia. Spermatogenic cells are characterized with stringently regulated spatiotemporal gene expression and strongly repressed translation in meiotic and haploid male germ cells. For example, impaired chromosome synapsis (marked by synaptonemal complex protein 3 (SCP3) and SCP1) and decreased meiotic recombination (marked by human mutL homologue 1, MLH1, an ortholog of the Escherichia coli Mut L mismatch repair protein) [2-4], were identified in infertile individuals with non-obstructive azoospermia (NOA). Such meiotic errors make these cells susceptible to spermatogenetic arrest and the production of aneuploid gametes. However, the molecular pathways of genetic defects in spermatogenesis are not known. Recently, the mouse maelstrom homolog (MAEL) protein was found in unsynapsed chromosomes of th