Altered microRNA expression profiles of human spermatozoa in normal fertile men of different ages

MicroRNAs (miRNAs) are mediators of the aging process. The purpose of this work was to analyze the miRNA expression profiles of spermatozoa from men of different ages with normal fertility. Twenty-seven donors were divided into three groups by age (Group A, n = 8, age: 20-30 years; Group B, n = 10, age: 31-40 years; and Group C, n = 9, age: 41-55 years) for high-throughput sequencing analysis. Samples from 65 individuals (22, 22, and 21 in Groups A, B, and C, respectively) were used for validation by quantitative real-time polymerase chain reaction (qRT-PCR). A total of 2160 miRNAs were detected: 1223 were known, 937 were newly discovered and unnamed, of which 191 were expressed in all donors. A total of 7, 5, and 17 differentially expressed microRNAs (DEMs) were found in Group A vs B, Group B vs C, and Group A vs C comparisons, respectively. Twenty-two miRNAs were statistically correlated with age. Twelve miRNAs were identified as age-associated miRNAs, including hsa-miR-127-3p, mmu-miR-5100_L+2R-1, efu-miR-9226_L-2_1ss22GA, cgr-miR-1260_L+1, hsa-miR-652-3p_R+1, pal-miR-9993a-3p_L+2R-1, hsa-miR-7977_1ss6AG, hsa-miR-106b-3p_R-1, hsa-miR-186-5p, PC-3p-59611_111, hsa-miR-93-3p_R+1, and aeca-mir-8986a-p5_1ss1GA. There were 9165 target genes of age-associated miRNAs. Gene Ontology (GO) analysis of the target genes identified revealed enrichment of protein binding, membrane, cell cycle, and so on. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of age-related miRNAs for target genes revealed 139 enriched pathways, such as signaling pathways regulating stem cell pluripotency, metabolic pathways, and the Hippo signaling pathway. This suggests that miRNAs play a key role in male fertility changes with increasing age and provides new evidence for the study of the mechanism of age-related male fertility decline.