Study question: What is the profile of miRNAs in seminal plasma of patients with non-obstructive azoospermia (NOA)?
Summary answer: miR-141, miR-429 and miR-7-1-3p are significantly increased in seminal plasma of patients with NOA compared with fertile controls.
What is known already: There is currently an urgent need to develop a noninvasive diagnostic test for NOA. Altered microRNA (miRNA) profiles have been proposed as potential biomarkers for the diagnosis of disease states.
Study design, size, duration: A total of 200 subjects (n = 100 for NOA, n = 100 for fertile control) were recruited to participate in this study. Recruitment took place from May 2008 to June 2010.
Participants/materials, setting, methods: We employed a strategy consisting of initial screening by TaqMan Low Density Array then further validation with a TaqMan quantitative RT-PCR assay. Validation of the profiling results was conducted in two independent phases. In addition, the expression of the three validated seminal plasma miRNAs (sp-miRNAs) was examined in testicular tissues of patients with NOA and of fertile controls. Methylation status and functional analyses were also performed for the identified sp-miRNAs.
Main results and the role of chance: miR-141, miR-429 and miR-7-1-3p were significantly increased in seminal plasma of patients with NOA compared with fertile controls. As sensitive and specific biomarkers, the profiling of these three identified sp-miRNAs provides a novel noninvasive, semen-based test for NOA diagnosis. The methylation status of these sp-miRNAs was inversely associated with their expression patterns. Additionally, we found that Cbl and Tgfβ2 were down-regulated by miR-141, while Rb1 and Pik3r3 were down-regulated by miR-7-1-3p.
Limitations, reasons for caution: miRNA expression profile was investigated in seminal plasma samples from only a small number of NOA patients. In future investigations, a larger sample size should be adopted and the functional role of the three sp-miRNAs should be further characterized in animal models.
Wider implications of the findings: Given that sp-miRNAs show reproducible and stable expression levels, they are potentially novel noninvasive biomarkers for the diagnosis of NOA. We propose that the three sp-miRNAs described above may participate in a methylation-miRNA-gene network related to NOA development. This work provides a foundation for interpretation of miRNA changes associated with pathogenesis of NOA and extends the current understanding of human NOA pathogenesis.
Keywords: DNA methylation; male infertility; microRNA; non-obstructive azoospermia; seminal plasma.