Summary
Amniotic fluid (AF) may induce disseminated intravascular coagulation (DIC) when it
enters maternal circulation by breaching the placental-maternal circulation barrier.
The precise mechanism of the procoagulant activity of AF is unclear, but tissue factor
(TF) has been proposed to be the main cause. As one constituent of AF, AF cells accumulate
and undergo apoptosis continuously. Therefore, we speculate that AF cells have procoagulant
activity due to the externalisation of phosphatidylserine (PS). The present study
aims to demonstrate that, in addition to TF, the PS that is externalised on AF cells
is important for the procoagulant activity of AF. Ten AF samples from parturient women
were analysed using lactadherin as the probe for PS. Anti-TF antibody also was used
to identify TF and its associated coagulation functions in AF cells. Normal platelets,
neutrophils, and lymphocytes were harvested as controls. Confocal microscopy and flow
cytometry was used to assess PS expression on AF cells. The procoagulant activity
of AF cells was demonstrated by a plasma coagulation assay and further confirmed by
factor Xase/prothrombinase assays. PS and TF were present on most AF cells, providing
substantial procoagulant activity. Furthermore, factor Xase and prothrombinase assays
showed that AF cells substantially enforced the activation of factor X and prothrombin.
PS on AF cells is an important procoagulant source for AF. Lactadherin is an ideal
anticoagulant for inhibiting the procoagulant activity of AF cells.
Keywords
Amniotic fluid cells - phosphatidylserine - procoagulant activity - lactadherin