Low expression of hsa-miR-34c-5p in sperm is associated with unexplained recurrent miscarriage

Recurrent miscarriage affects up to 1%-2% of reproductive-age couples, with nearly 50% of cases classified as unexplained recurrent miscarriage after comprehensive clinical workup. Current etiological research focuses heavily on maternal factors, while the contribution of paternal factors-especially sperm-borne miRNAs, key epigenetic regulators of preimplantation embryonic development-remains understudied. This study aimed to profile differential sperm miRNA expression in partners of women with unexplained recurrent miscarriage, and explore its association with unexplained recurrent miscarriage.

We enrolled 22 partners of women with unexplained recurrent miscarriage (case group) and 19 healthy males undergoing routine preconception screening (control group) at the Affiliated Hospital of Inner Mongolia Medical University between July 2021 and February 2023. Sperm miRNAs were profiled via high-throughput sequencing, followed by RT-qPCR validation of 3 paternal miRNAs in embryos. GO and KEGG enrichment analyses were performed for target genes of key candidate hsa-miR-34c-5p.

We identified 90 differentially expressed miRNAs in case group sperm, 4 of which were paternal miRNAs in embryos. RT-qPCR confirmed significant downregulation of sperm hsa-miR-34c-5p in cases (p = 0.001). Logistic regression identified low expression of hsa-miR-34c-5p in sperm was significantly associated with unexplained recurrent miscarriage (OR = 4.344, 95%CI 1.119-16.857, p < 0.05), with a ROC-AUC of 0.836. Its target genes were enriched in cellular membrane components, nervous system-related processes, Notch and Rap1 signaling pathways.

This study reveals the association between low sperm miR-34c-5p expression and unexplained recurrent miscarriage, further advancing our understanding of sperm-derived small RNAs in regulating embryonic development and pregnancy outcomes. Nevertheless, the limited sample size means our findings require validation in large-scale multicenter cohorts.