Identification of microRNAs predominately derived from testis and epididymis in human seminal plasma

Abstract

Objectives: Aiming to develop potential noninvasive biomarkers for male infertility, the present study is designed to identify cell-free seminal piRNAs (PIWI-interacting RNA), and microRNAs predominately derived from testis and epididymis in human semen, which is secreted from the male accessory reproductive organs.

Design and methods: The ejaculate of successfully vasectomized men does not contain any secretion from the testis or epididymis. We screened cell-free seminal piRNAs, and microRNAs that predominately derived from testis/epididymis by comparing Solexa sequencing of seminal RNA of normozoospermic donors and vasectomized men, followed by quantitative PCR validation in individuals.

Results: Totally 84 seminal microRNAs exhibited levels >4-fold higher in normozoospermic donors than in vasectomized men. Subsequent quantitative PCR validation in individuals confirmed 61 microRNAs predominately secreted from testis/epididymis. Of these miRNAs, the lowest level in normozoospermic donors is ≥2-fold (24 miRNAs) or 0-2-fold (37 miRNAs) more than the highest level in vasectomized men. Interestingly, 28 microRNAs, which contain 5 microRNA clusters (18 microRNAs), reside on the X-chromosome. Some microRNAs have been shown or predicted to target important genes in spermatogenesis or sperm maturation. At least 995 seminal piRNAs were identified in normozoospermic donors while were absent in vasectomized men.

Conclusions: The present study identified cell-free seminal piRNAs, and microRNAs that predominately derived from testis and epididymis. These small noncoding RNAs might be useful noninvasive epigenetic markers for human male infertility researches on revealing the etiology and physiopathological status of impaired sperm production and maturation.

Keywords: Epididymis; Human seminal plasma; Male infertility; MicroRNA; Noninvasive biomarker; Testis.