There is a broadly recognized ambiguity in the relationship between mammalian (eutherian) pregnancy and inflammation. During implantation, inflammatory pathways are activated and important for successful implantation, but during the second trimester, intrauterine inflammation is a grave threat to the continuation of pregnancy. An investigation of the gene expression changes during opossum pregnancy led us to propose and test a model for the origin of eutherian implantation and pregnancy. In brief: if we take the opossum gestation as a model of the situation at the most recent common ancestor of marsupials and placental mammals, the evidence suggests that an acute inflammation is the result of the attachment of the trophoblast to the uterine epithelium. The difference between opossum and the eutherians is the outcome: In opossum the inflammation directly leads to parturition, while in eutherians inflammation never leads to neutrophil infiltration and soon is turned off. I will present evidence suggesting that one key innovation to achieve sustainable implantation was the origin of the decidual cell, which prevents the recruitment of neutrophils and thus prevents the development of an acute inflammation during implantation.

View YouTube video of seminar: https://youtu.be/cec0A_iwmLI