P-012 Investigating the potential role of microRNAs as biomarkers in idiopathic non-obstructive azoospermia: A systematic review and in-silico analysis of the affected pathways
Authors: Pantou A , Grigoriadis S , Karagkouni D , Pantos K , Maziotis E , Tomara P , Hatzigeorgiou A , Agarwal A , Sfakianoudis K , Simopoulou M 
Published: June 2022

Abstract

Study question
Is there an association between microRNA profiles in seminal plasma and microRNAs profiles in testicular tissue samples obtained from idiopathic non-obstructive azoospermia (NOA) patients?

Summary answer
This study identified common alterations in microRNA profiles and gene expression patterns between seminal plasma and testicular tissue samples obtained from NOA patients.

What is known already
Despite the significant advances in the field of reproductive medicine the exact infertility aetiology remains unidentified regarding 30-40% of infertile men. This fact highlights the need for more accurate and sensitive diagnostic tools and biomarkers, especially regarding the most severe cases of male infertility, such as idiopathic NOA patients. It has been voiced that microRNA profiling of seminal plasma and testicular tissue samples obtained from idiopathic NOA patients could be a powerful tool towards better understanding the underlined pathogenesis and towards developing novel diagnostic and individualized biomarkers. However, a collective analysis of these data has not been performed hitherto.

Study design, size, duration
A systematic review was performed in PubMed/Medline and Embase up to November 2020. Search strategy included a combination of keywords, namely non-coding RNA OR small non-coding RNA OR microRNA AND non-obstructive azoospermia. Following study selection, original data on altered microRNAs were analyzed aiming to underline differences between microRNA expression profiles in seminal plasma and testicular tissue samples of idiopathic NOA cases. Following this, in-silico analysis was performed to detect commonly affected gene expression pathways.

Participants/materials, setting, methods
Only full-length original retrospective or prospective human studies were included. Strict inclusion-exclusion criteria were applied. The studied population consisted of idiopathic NOA patients, while the control groups consisted of men with normal semen analysis. In-silico analysis was performed employing a combination of bioinformatic tools, namely the DIANA-TarBase, microT-CDS, the GTEx repository and the KEGG database. Statistical analysis was performed using the R-package-limma. The statistically significant threshold indicating altered gene pathways was set at 0.01 P-value.

Main results and the role of chance
Five studies were considered eligible, including 382 NOA cases and 412 controls (Finocchi et al., 2020; Song et al., 2017; Wu et al., 2013; Wu et al., 2012; Wang et al., 2011). Two studies co-evaluated the profile of microRNAs in both seminal plasma and testicular tissue samples (Wu et al., 2013; Wu et al., 2012), one study evaluated only testicular tissue (Song et al., 2017) and the other two only seminal plasma (Finocchi et al., 2020 and Wang et al., 2011). Data extraction revealed a total of 14 differentially expressed microRNAs between NOA patients and controls. The following microRNAs were found to be up-regulated in both seminal plasma and testicular tissue samples of NOA cases: hsa-miR-141-3p, hsa-miR-429, hsa-miR-7-1-3p, hsa-miR-19b-3p and hsa-let-7a-5p. The hsa-miR-188-3p was found to be down-regulated in testicular tissue samples. Finally, the following microRNAs were also downregulated only in seminal plasma: hsa-miR-34c-5p, hsa-miR-122-5p, hsa-miR-181a-5p, hsa-miR-146b-5p, hsa-miR-374b-5p, hsa-miR-509-5p, hsa-miR-513a-5p and hsa-miR-34b-3p. Despite the limited number of common microRNAs between seminal plasma and testicular tissue samples, in-silico analysis revealed 34 statistically significant dysregulated gene pathways, regarding both seminal plasma and testicular tissue samples, indicating that idiopathic NOA patients are sharing several common altered molecular mechanisms involved in NOA pathogenesis.

Limitations, reasons for caution
The limited number of the included studies as well as the small size population characterizing the great majority of them, constitute the main limitations of this systematic review. Moreover, great heterogeneity was observed among the studies regarding the molecular methods employed for microRNA profiling.

Wider implications of the findings
These collective findings indicate that microRNA profiling in seminal plasma could indeed be raised as a powerful non-invasive tool towards better understanding and diagnosing idiopathic NOA. Larger well-controlled studies employing state-of-the-art microRNAome techniques are needed to validate these conclusions. Moreover, the molecular network of targeted gene pathways also merits investigation.

Trial registration number
Not Applicable