Introduction: Follicular condition is reflected in granulosa cells (GCs) and follicular fluid (FF), and miRNAs in GCs and FF play crucial roles in follicular and oocyte development. Materials and methods: In the present study, FF and GCs were collected from 10 cows, and miRNAs in FF and GCs, as well as mRNAs in GCs, were examined by miRNA-seq and RNA-seq. Results: A comparison of the miRNA profiles between the GCs and FF revealed that, although overall miRNA composition in FF reflects that in GCs, the miRNA expression profiles in FF do not fully correspond to those in GCs. The Weighted Gene Co-expression Network Analysis (WGCNA) and motif analysis showed that miRNA clusters in FF differ from those in GCs, and that each miRNA cluster in FF shares several conserved motifs. To examine the relationship between miRNAs and mRNAs in GCs, we developed a Predicted Targeting Efficacy (PTE) index that considers both miRNA abundance and the expression of its target genes. The PTE index showed a negative correlation with the genome-wide expression levels of genes. In addition, the miRNA–mRNA correlation analysis revealed specific clusters of miRNAs and genes with strong correlations. Based on miRNA concentrations in GCs or FF, GC samples were classified into enriched (n = 3) and deficient (n = 3) groups, and differentially expressed genes (DEGs) were identified. Ingenuity Pathway Analysis of the DEGs identified several molecules as activated upstream regulators associated with specific miRNAs. Conclusions: The present study provides a robust foundation for understanding miRNA release from GCs, miRNA–mRNA expression within GCs, and the granulose cellular condition contributing the presence of specific miRNAs in both GCs and FFs.
Inoue et al. (Mon,) studied this question.