Differential expression profiles of extracellular vesicle-coupled miRNA in follicular fluid of cows at different metabolic status

This study was performed to discover the association between postpartum during negative energy balance and the expression of extracellular vesicle-coupled microRNAs signatures in follicular fluid of large follicle in dairy cows. For this, next-generation sequencing to total RNA miRNA was performed. Overall design: Collected of follicular fluid was performed from both postpartum cows and heifers using an ovum pick-up technique from large follicles. Follicular fluid from postpartum cows was collected from week 5-10 of postpartum in weekly bases. Follicular fluid from heifers was collected for continuous 5 weeks. Prior to pooling of samples, the energy balance statuses of individual postpartum cows were assessed using three criteria: blood serum metabolite analysis, body weight curves, and overall energy balance based on dry matter intake. Based on these three criteria's, animals were grouped in to three phenotypes namely: Transient cows (TCs) (n=20), Always Negative cows (ANCs) (n=5) and Always positive cows (APCs) (n=5). Follicular fluid samples from cystic ovaries and blood contamination are discarded from the analysis. Follicular fluid samples from TCs at week 5 and 6 (n=11) and at week 9 and 10 (n=7) were separately pooled to create three biological replicates. Follicular fluid collected from ANCs (n=2) and APCs (n=2) at week 5 and 6 were pooled to generate two biological replicate per group of cows. For heifers, follicular fluid recovered from eight heifers was also pooled to generate three biological replicates after the analysis of their metabolites and all was at positive energy balance.