MicroRNA Expression Shows Differential Regulation of Monocyte-Derived Macrophages from Johne's Disease (JD)-Positive and JD-Negative Cows Following ex vitro Challenge with Mycobacterium avium ssp. paratuberculosis

Mycobacterium avium ssp. paratuberculosis (MAP) infects ruminants, resides and slowly proliferates in macrophages/dendritic cells causing Johne’s disease (JD). The exact mechanisms are not fully understood. Previously, we characterized the peripheral blood monocyte-derived macrophages (MDM) from 12 JD-positive (JDPc) and 12 JD-negative (JDNc) cows and observed a different transcriptomic pattern using an ex vivo MAP infection. This study aimed to determine how microRNAs (miRNAs) respond to MAP infection in these MDM.

MDM from JDPc and JDNc were challenged ex vivo with the Canadian clinical MAP field strain 39382. MiRNA libraries(144) representing uninfected JDNc and JDPc controls and infection time points 1h, 4h, 8h and 24h were sequenced (HiSeq 2500 system).

255 known and 114 novel miRNAs were identified. Bioinformatics analysis identified 3, 0, 20 and 123, and 0, 0, 24, and 179 miRNAs differentially expressed(DE) between JDPc or JDNc at 1h, 4hr, 8hr, and 24h as compared to their respective controls, respectively. Among 12 highly dysregulated(P<1.0E-05) miRNAs in JDPc, miR-2284aa has associations with bacterial infections while miR-7, miR-326, miR-582 and miR-193b have roles in cell growth/apoptosis. Most highly dysregulated(P<0.1E-05) miRNAs in JDNc are associated with cellular functions (growth/apoptosis). Target genes of dysregulated miRNAs at 8hr and 24hr(JDPc and JDNc) were enriched in similar (but different intensities) top biological/molecular/physiological functions with higher intensity demonstrated by JDNc at 24h. Most enriched pathways at 24h were RhoGDI signaling (JDNc) and ERK/MAPK signaling (JDPc). Confirmation of the specific functional roles of DE miRNAs may help to elucidate the persistence of MAP infection in JD cows