Expression of interferon-stimulated genes in the endometrium, cervix and vagina on Day 15 of pregnancy in cattle.

Interferon tau (IFNT), secreted by the trophoblast cells of the developing bovine conceptus, induces the expression of interferon-stimulated genes (ISGs) in the endometrium, leading to maternal recognition of pregnancy (MRP) around Days 15-17 in cattle and maintenance of the corpus luteum. We hypothesized that the expression of ISGs varies across different regions of the female reproductive tract in response to IFNT around the time of MRP in cattle. This study aimed to investigate the expression of ISGs in the endometrium, cervix, and vagina on Day 15 of pregnancy. Reproductive tracts from Day 15 pregnant (n = 8) and non-pregnant cyclic (control, n = 8) crossbred beef heifers were used. Individual explants (8-mm diameter) from the endometrium, cervix, and vagina were retrieved from each tract for gene expression analysis by RT-qPCR. Classical ISGs (ISG15, MX1, and MX2) were upregulated (P < 0.05) in the endometrium, cervix, and vagina in pregnant heifers compared to non-pregnant heifers. The magnitude of the difference in expression was greater (P < 0.05) in the endometrium compared to the cervix and vagina in pregnant heifers. Other selected candidate ISGs (CMPK2, IFI35, and TRIM38) were upregulated only in the endometrium of pregnant heifers. In a second experiment, endometrial, cervical, and vaginal explants from the mid-luteal stage of the estrous cycle were treated with recombinant ovine IFNT (100 ng/mL). Exposure to IFNT increased (P < 0.05) expression of all ISGs studied; however, no differences were found in the expression of ISGs between the different regions. This suggests that the cervix and vagina have the necessary machinery to respond to IFNT stimulation but are not exposed to the same concentration of IFNT in vivo as the endometrium. Findings demonstrate region-specific regulation of ISGs expression within the reproductive tract during early pregnancy in cattle. The greater expression of ISGs in the endometrium compared to the cervix and vagina indicates a localized, robust response to IFNT during early pregnancy, which may have implications for understanding the mechanisms of MRP and for developing more effective tools for early pregnancy detection in cattle.