[The study on mechanism of abruptio placentae caused by chorioamnionitis]

The cause of abruptio placentae has not been elucidated yet. Although preeclampsia is frequently associated with abruptio placentae, the rate of abruptio placentae caused by preeclampsia has decreased recently. Many current reports have indicated that chorioamnionitis is an important cause of abruptio placentae. To clarify the relationship between chorioamnionitis and abruptio placentae, we performed immunostaining for fibronectin, fibronectin receptor and granulocyte elastase of placenta with or without abruptio placentae. In cases of abruptio placentae caused by chorioamnionitis, granulocyte elastase was stained strongly and fibronectin receptor was stained weakly in decidual cells, especially in the parts of granulocyte elastase invased. In III stage chorioamnionitis without abruptio placentae, granulocyte elastase was stained moderately and the intensity of fibronectin receptor did not decrease. There was no difference between fibronectin staining in all cases. When purified granulocyte elastase was added to the cultured decidual cells, the staining intensity of fibronectin receptor became weak in those cells. These results suggest that marked imbalance between neutrophil invasion and an inhibitor, such as alpha 1 antitrypsin, initiates granulocyte elastase release and promotes the reduction of the fibronectin receptor in decidual cells resulting in weakening of the adherence of decidual cells. This may be one of the mechanisms of abruptio placentae caused by chorioamnionitis.