Impaired placentomal interferon signaling as the possible cause of retained fetal membrane in parturition-induced cows.

Although hormonal induction of parturition in cattle results in the successful delivery of healthy calves, the risk of retained fetal membrane is significantly increased. In a previous study, a combination of the long-acting glucocorticoid, triamcinolone acetonide, with a high dose of betamethasone partially normalized the placentomal gene expression during parturition; however, the incidence of retained fetal membrane remained high. This study further explored placentomal dysfunction and aimed to elucidate the mechanism of retained fetal membrane in parturition-induced cows. In this study, transcriptome analysis revealed that enhanced glucocorticoid exposure normalized the expression of a substantial fraction of genes in the cotyledons. In contrast, a significant reduction in the multiple signaling pathway activities, including interferon signaling, was found in the caruncles during induced parturition. Real-time PCR showed that the expression of interferon-tau in the caruncles, but not interferon-alpha or interferon-gamma, was significantly lower in induced parturition than spontaneous parturition. Interferon-stimulated gene expression was also significantly decreased in the caruncles during induced parturition. These results indicate that interferon signaling could be important for immunological control in placentomes during parturition. Additionally, this suggests that interferon-tau might be a pivotal ligand for interferon receptors in the caruncles. This study revealed that peripheral blood leukocytes in prepartum cows transcribed interferon-tau. Macrophage infiltration in the placentome is known to participate in the detachment of the fetal membrane from the caruncle. Thus, this study raised the possibility that immune cells migrating into the caruncles at parturition may act as a source of ligands that activate interferon signaling.