Experimental validation of seminal miR-31-5p as biomarker for azoospermia and evaluation of the effect of preanalytical variables

Background and objectives Predicting the origin of azoospermia with non-invasive biomarkers is clinically relevant for determining the chance of successful sperm retrieval from the testes before attempting assisted reproduction treatment. Here, the semen small extracellular vesicle microRNA miR-31-5p-based biomarker test to distinguish obstructive azoospermia from secretory azoospermia (previously described by our group) is validated for clinical use, and additionally, the sample source (seminal small extracellular vesicles vs. total seminal plasma) as a preanalytical variable is considered to optimize the procedure. Results and Discussion Our results provide evidence that altered miR-31-5p expression can be determined both from extracellular vesicles and from the whole seminal plasma to discriminate obstructive from secretory azoospermic samples. Not only have we validated this microRNA-based molecular model as a clinically useful test for predicting the origin of azoospermia in a sample from azoospermic individuals, but additionally, and more interestingly for the clinicians, we have evidenced its usefulness for predicting the presence of spermatogenic failure in azoospermic patients with follicle-stimulating hormone values <10 IU/L as a sensitive and specific biomarker (area under the receiver operating characteristic curve >0.88; p-value < 0.006). The use of total seminal plasma as an analytical sample would facilitate the use of a simplified technical procedure for miR-31-5p quantification and would represent a great improvement in reproductive treatment decision protocols for azoospermia in clinical practice.