Procoagulant activity and cellular origin of microparticles in human amniotic fluid

Abstract

Amniotic fluid contains various procoagulant factors involved in intro-vascular amniotic fluid-induced coagulopathies. During the progression of normal pregnancy, microparticles would be shed off from cells and accumulate in amniotic fluid over time. In this study, our aims were to investigate the cellular origin and procoagulant entity of these microparticles. Twenty amniotic fluid samples from healthy parturient women were collected, and the microparticles were isolated and stained with phycoerythrin-labeled antibodies to CD138, CD41a, CD144 and CD11b to identify their cellular origin. Their phosphatidylserine and tissue factor expression levels were quantified with fluorescein isothiocyanate-labeled annexin V and anti-tissue factor antibody staining. Their procoagulant activity was tested with plasma coagulation assay and factor Xase and prothrombinase assays. Phenotypic analysis showed 36.8% and 33.8% of amniotic fluid microparticles positive for CD138 and CD11b, respectively, indicating their epithelial cell or leukocyte origin. Of these microparticles, 66.3±5.9% expressed phosphatidylserine while 37.4±4.1% expressed tissue factor. In addition, amniotic fluid microparticles could significantly shorten the plasma coagulation time and increase the production of factor Xa and thrombin. Inhibition assays with annexin V and anti-tissue factor antibody confirmed the coagulation effects of amniotic fluid microparticles. The microparticles derived from epithelial and leukocytes may be a mechanism of amniotic fluid-induced coagulopathies.