miRNA-185 regulates the VEGFA signaling pathway in dairy cows with retained fetal membranes

Retention of fetal membranes (RFM) of cows is an important reproductive disturbance, and is related to miRNAs. Vascular endothelial growth factor (VEGF)A, regulated by miRNA-185, can activate arachidonic acid (ARA) release via the VEGFA signaling pathway, which influences RFM. The aim of this study was to explore the pathogenic mechanism of RFM by investigating the regulatory relationship between miRNA-185 and the VEGFA signaling pathway. Serum samples of healthy Holstein dairy cows (n = 20) and RFM cows (n = 12), with a similar age, parity, weight, and milk yield, were collected to detect VEGFA and ARA concentrations at 6, 12, and 24 h after calving. Caruncle tissues were collected from healthy (n = 6) and RFM cows (n = 6) at 12 h after calving. Quantitative polymerase chain reaction (qPCR) and western blotting (WB) were performed to detect the mRNA and proteins levels, respectively, of genes involved in the VEGFA signaling pathway. Uterine caruncle epithelial (UCE) cells were cultured by the explant culture method, further purified, and subsequently treated with miRNA-185 mimics, miRNA-185 mimics + MEK inhibitor, or left untreated as a control for detection of the mRNA and protein levels of genes involved in the VEGFA signaling pathway. The cellular supernatant was collected for measurement of ARA levels at 12, 24 and 48 h after treatment. Serum levels of VEGFA and ARA from RFM cows were abnormally increased at 12 h after calving, as compared to those in healthy dairy cows. Expression levels of most of the investigated genes (VEGFA, PLC, PRK, RAF, MEK, MAPK, and PLA) were down-regulated in the caruncle tissue of RFM cows. However, P-p44/42 MAPK was up-regulated in the caruncle tissues of cows with RFM (p < .01). In UCE cells treated with the miRNA-185 mimics, expression of VEGFA, PLC, RAF, MEK, MAPK and PLA was significantly down-regulated, while that of P-p44/42 MAPK was significantly up-regulated. Expression of genes involved in the VEGFA signaling pathway was similar to that in the in vivo assay. In UCE cells treated with the miRNA-185 mimics + MEK inhibitors, expression of VEGFA, PLC, RAF, MEK, MAPK and P-p44/42 MAPK was significantly down-regulated, while that of PLA was significantly up-regulated. Meanwhile, the release of ARA was increased (p < .01). These results demonstrate that miRNA-185 can regulate the VEGFA signaling pathway, especially via abnormal expression of P-p44/42 MAPK, which influences the release of the fetal placenta after calving.