The Effects of miR-425-3p and Seminal Microbiota on Semen Parameters: Insights Into Male Infertility

Abstract

Male infertility is a multifaceted condition influenced by various factors, resulting in diverse phenotypic expressions. MicroRNAs (miRNAs), oxidative stress, and microbiota are potential contributors to compromised semen quality. This study explores the relationship between miR-425-3p, seminal microbiota, and oxidative stress in relation to impaired semen parameters. Semen samples were collected from 39 individuals with sperm motility <20% and 31 individuals with sperm motility >20%. Microbial cultures were performed to analyze the microbiota in the samples. DNA extraction from seminal cultured colonies, followed by PCR amplification targeting the 16S rRNA gene was conducted for sequencing, while RNA extraction from seminal plasma facilitated RT-qPCR analysis of miR-425-3p. Additionally, oxidative lipid degradation was evaluated using a thiobarbituric acid reactive species (TBARS) assay, comparing malondialdehyde (MDA) levels between samples with good and poor sperm motility. Our analysis revealed a diverse semen microbiota, predominantly consisting of Staphylococcus, Enterococcus, Bacillus, Micrococcus, and Neisseria. Less prevalent genera included Streptococcus, Acinetobacter, Corynebacterium, Actinomyces, and Escherichia coli. Higher bacterial loads were positively correlated with improved sperm motility, averaging 20,373 CFU/mL in the group with sperm motility >20% compared to 1247 CFU/mL in group with sperm motility <20% (p = 0.03). Conversely, miR-425-3p expression was significantly elevated in group with sperm motility <20%, showing a fourfold increase (p = 0.034). Reduced miR-425-3p expression was observed in samples abundant in Bacillus, particularly when Neisseria was absent. MDA levels, a marker of oxidative stress, were significantly higher in the less motile group (9.46 ± 5.07 nmol/mL) compared to the motile group (5.25 ± 3.32 nmol/mL, p = 0.038). The analysis revealed distinct microbial profiles associated with varying sperm motility levels. These findings establish a connection between increased miR-425-3p expression, elevated seminal oxidative stress, and decreased sperm motility. Our data provide insights into the roles of seminal microbiota and microRNA in the pathogenesis of impaired semen quality.