Background Coliform mastitis is a symptom of postpartum dysgalactia syndrome
(PDS), a multifactorial infectious disease of sows. Our previous study showed
gene expression profile change after bacterial challenge of porcine mammary
epithelial cells (PMECs). These mRNA expression changes may be regulated
through microRNAs (miRNAs) which play critical roles in biological processes.
Therefore, miRNA expression profile was investigated in PMECs. Results PMECs
were isolated from three lactating sows and challenged with heat-inactivated
potential mastitis-causing pathogen Escherichia coli (E. coli) for 3 h and 24
h, in vitro. At 3 h post-challenge with E. coli, target gene prediction
identified a critical role of miRNAs in regulation of host immune responses
and homeostasis of PMECs mediated by affecting pathways including cytokine
binding (miR-202, miR-3277, miR-4903); IL-10/PPAR signaling (miR-3277,
miR-4317, miR-548); and NF-ĸB/TNFR2 signaling (miR-202, miR-2262, miR-885-3p).
Target genes of miRNAs in PMECs at 24 h were significantly enriched in
pathways associated with interferon signaling (miR-210, miR-23a, miR-1736) and
protein ubiquitination (miR-125, miR-128, miR-1280). Conclusions This study
provides first large-scale miRNA expression profiles and their predicted
target genes in PMECs after contact with a potential mastitis-causing E. coli
strain. Both, highly conserved miRNAs known from other species as well as
novel miRNAs were identified in PMECs, representing candidate predictive
biomarkers for PDS. Time-dependent pathogen clearance suggests an important
role of PMECs in inflammatory response of the first cellular barrier of the
porcine mammary gland