Minor DNA methylation changes are observed in spermatozoa prepared using different protocols

Association between Sperm Morphology and Altered Sperm microRNA Expression

Simple Summary

Sperm morphology is usually determined subjectively, and studies focused exclusively on sperm morphology are scarce. There is a global tendency to find objective markers of spermatozoa quality, including sperm morphology, as this will allow for a more personalized approach to managing and treating male infertility. MicroRNAs (miRNAs) are widely recognized as promising putative and objective biomarkers. In our study, we included 15 patients with normal sperm morphology and 13 patients with abnormal sperm morphology. We determined the expression profiles of 13 different miRNAs in the sperm of these participants and revealed that 9 miRNAs could serve as potential biomarkers of sperm morphology in spermatozoa.

Abstract

Evaluation of male infertility has been based on semen analysis for years. As this method can be subjective at times, there is a scientific tendency to discover stable and quantifiable biomarkers. This study included 28 couples who underwent an in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycle. The couples were assigned into two groups, according to sperm morphology. Couples where the males were normozoospermic were placed in the control group (15 participants), while couples where males had teratozoospermia were placed in the study group (13 participants). Thirteen candidate miRNAs were selected for qPCR analysis, based on our literature search. We determined significant under-expression of nine miRNAs (miR-10a-5p/-15b-5p/-26a-5p/-34b-3p/-122-5p/-125b-5p/-191-5p/-296-5p and let-7a-5p) in spermatozoa from patients with teratozoospermia compared to the controls, whereas expression levels of four miRNAs (miR-92a-3p/-93-3p/-99b-5p/-328-3p) did not significantly differ between the study and control groups. The expression levels of all 13 included miRNAs were significantly positively correlated with each other and significantly positively associated with spermatozoa morphology, excluding miR-99b-5p. There were no other significant associations between miRNA expression and sperm quality parameters. Only expression levels of miR-99b-5p were significantly positively correlated with good-quality day 3 embryo rate (ρ = 0.546; p = 0.003), while other variables of the IVF/ICSI cycle outcome showed no significant associations with miRNA expression profiles. This is one of the rare studies providing an insight directly into miRNA profiles in regard to sperm morphology. We identified nine miRNAs that could serve as biomarkers of spermatozoa quality in regard to teratozoospermia.

Global 5mC and 5hmC DNA Levels in Human Sperm Subpopulations with Differentially Protaminated Chromatin in Normo- and Oligoasthenozoospermic Males

Epigenetic modifications play a special role in the male infertility aetiology. Published data indicate the link between sperm quality and sperm chromatin protamination. This study aimed to determine the relationship between methylation (5mC) and hydroxymethylation (5hmC) in sperm DNA, with respect to sperm chromatin protamination in three subpopulations of fertile normozoospermic controls and infertile patients with oligo-/oligoasthenozoospermia. For the first time, a sequential staining protocol was applied, which allowed researchers to analyse 5mC/5hmC levels by immunofluorescence staining, with a previously determined chromatin protamination status (aniline blue staining), using the same spermatozoa. TUNEL assay determined the sperm DNA fragmentation level. The 5mC/5hmC levels were diversified with respect to chromatin protamination status in both studied groups of males, with the highest values observed in protaminated spermatozoa. The linkage between chromatin protamination and 5mC/5hmC levels in control males disappeared in patients with deteriorated semen parameters. A relationship between 5mC/5hmC and sperm motility/morphology was identified in the patient group. Measuring the 5mC/5hmC status of sperm DNA according to sperm chromatin integrity provides evidence of correct spermatogenesis, and its disruption may represent a prognostic marker for reproductive failure.