Serum miR-155 as a potential biomarker of male fertility.
OBJECTIVE
Are serum levels of micro-RNAs miR-155 and miR-146a associated with male fertility, low-grade systemic inflammation (LGSI) and androgens?


CONCLUSIONS
miR-155 was associated with male subfertility independent of LGSI or androgens while miR-146a was only weakly associated with subfertility and LGSI.


BACKGROUND
Male subfertility has been associated with LGSI as well as with androgen deficiency. miR-155 and miR-146a are central regulators of inflammation and their level in cells and in the serum has been associated with several inflammatory conditions.


METHODS
In this case-control study, two independent groups of 60 subjects each (exploratory and confirmatory cohort) were randomly selected from an ongoing study on subfertile men (in total: hypogonadal; n = 40, eugonadal; n = 40 and control group n = 39) at a University Hospital Reproductive Medicine Centre. Individuals were matched for age.


METHODS
Total RNA was isolated from cell-free serum. As internal control a synthetic miRNA, UniSp6, was added to each sample prior to extraction. miRNA expression levels were measured by real-time RT-PCR and presented as fold difference (arbitrary units, U) from control. Sera from these individuals had been previously analyzed for hormone and cytokine levels.


RESULTS
Serum levels of miR-155 were associated with levels of miR-146a (P < 0.0001), but only miR-146a was associated with inflammatory markers. miR-155 was strongly associated with subfertility (for subfertile group 1.88 U, 95% confidence interval (CI) 1.6-2.1 U versus 1.15, 95% CI 1.0-1.2 U in controls; P = 0.001). Receiver operating characteristic curve analysis indicated that miR-155 but not miR-146a can be used as a marker of subfertility. MiR-155 with a cutoff value of 1.77 had 47% sensitivity and 95% specificity for identifying subfertility and a positive predictive value (PPV) and negative predictive value (NPV) of 95 and 47%, respectively. When used in combination with FSH, sensitivity and specificity were 80 and 100%, respectively, while PPV and NPV were 100 and 71%, respectively, those values being higher than for the FSH alone. Repeating the results obtained in the exploratory cohort in an independent confirmatory cohort reduced the risk of a chance finding.


CONCLUSIONS
Although the results from the exploratory cohort were confirmed in the confirmatory cohort, studies from other centers are needed to establish the role of miR-155 as a new biomarker of male fertility. Furthermore, the role of this marker in distinguishing between different groups of male subfertility is to be elucidated.


CONCLUSIONS
Association of the inflammatory miRNA miR-155 with male fertility contributes to our understanding of the pathophysiology of subfertility and suggests a novel biomarker. Serum miR-155 in combination with FSH has higher diagnostic specificity and sensitivity compared with FSH alone.


BACKGROUND
This work was supported by grants from Swedish Governmental Grant (ALF), Skane county council research and development foundation, Skane University Hospital Fonds and by the EU and Greek funds under the action 'Education and lifelong learning' program THALIS-FAT-VESSEL (No 379527). The authors have no competing interests to disclose.
Molecular Reproductive Research Group, Department of Translational Medicine, Lund University, Malmö, Sweden Department of Clinical Chemistry, School of Medicine, University of Crete, Heraklion, Crete, Greece tsatsani@med.uoc.gr.
Christos
C
Tsatsanis
Molecular Reproductive Research Group, Department of Translational Medicine, Lund University, Malmö, Sweden Reproductive Medicine Centre, Skåne University Hospital Malmö, Malmö, Sweden.
Johannes
J
Bobjer
Molecular Genetic Reproductive Medicine, Department of Translational Medicine, Lund University, Malmö, Sweden.
Hamideh
H
Rastkhani
Department of Clinical Chemistry, School of Medicine, University of Crete, Heraklion, Crete, Greece.
Erini
E
Dermitzaki
Department of Clinical Chemistry, School of Medicine, University of Crete, Heraklion, Crete, Greece.
Marianna
M
Katrinaki
Department of Clinical Chemistry, School of Medicine, University of Crete, Heraklion, Crete, Greece.
Andrew N
AN
Margioris
Molecular Genetic Reproductive Medicine, Department of Translational Medicine, Lund University, Malmö, Sweden.
Yvonne Lundberg
YL
Giwercman
Molecular Reproductive Research Group, Department of Translational Medicine, Lund University, Malmö, Sweden Reproductive Medicine Centre, Skåne University Hospital Malmö, Malmö, Sweden.
Aleksander
A
Giwercman
D000293:Adolescent; D000328:Adult; D000728:Androgens / Q000378:metabolism; D015415:Biomarkers / Q000097:blood*; D016022:Case-Control Studies; D002474:Cell-Free System; D015331:Cohort Studies; D005298:Fertility; D005640:Follicle Stimulating Hormone / Q000097:blood; D005786:Gene Expression Regulation; D006801:Humans; D007248:Infertility, Male / Q000097:blood*; D007249:Inflammation; D008297:Male; D035683:MicroRNAs / Q000097:blood*; D008875:Middle Aged; D012372:ROC Curve; D055815:Young Adult
D000728:Androgens; D015415:Biomarkers; C542542:MIRN146 microRNA, human; C524942:MIRN155 microRNA, human; D035683:MicroRNAs; D005640:Follicle Stimulating Hormone
FSH; inflammation; male fertility; micro-RNA; testosterone