Background: The identification of plasma sEV miRNA as robust biomarkers of fertility is limited; however, they are considered as excellent diagnostic and prognostic biomarker candidates. Mir-181b-5p is of particular interest as it is upregulated in inflammatory tumour tissues (1) and demonstrates elevated expression in bovine endometrial stromal cells prior to decidualization (2).
Methods: Plasma samples were collected from 10-month-old Holstein-Friesian (Bos taurus) dairy cows of distinct fertility; High fertile (HF) and low fertile (LF) groups (n=8 each). ExoEasy Maxi and Midi spin columns (77023, QIAGEN) were used to isolate plasma sEV total RNA. Real-time PCR was conducted using miRCURY LNA miRNA PCR Assays (339306, QIAGEN) for the previously identified differentially expressed (DE) miRNAs between HF and LF groups.
Results: The expression of miR-181b-5p was upregulated in LF sEV, in contrast to HF sEV (P value = 0.0093, Fold change = 2.665). Interestingly, bovine endometrial cells demonstrated extremely high levels of miR-181b-5p, similar to Graham et al (2), in contrast to the expression levels in the blood plasma sEV. MiR-12054 and miR-2285aw were upregulated in LF sEV, and miR-17-5p, miR-2285dd and miR-2335 were upregulated in HF sEV; however, these upregulations were not statistically significant.
Conclusion: MiR-181b-5p was validated as a prognostic sEV miRNA biomarker of infertility, exhibiting upregulation in LF animals as a subsequent pro-inflammatory response.