Tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the placenta and myometrium

Placental abruption is mainly due to the rupture of the uterine spiral arteries, but adjacent tissues are also damaged and substances derived from disintegrated placenta and myometrium probably cause coagulation disturbances, such as hypofibrinogenemia and disseminated intravascular coagulation (DIC).

To measure whether placenta and myometrium are significant sources of tissue factor (TF) and tissue factor pathway inhibitor (TFPI), the components of key role in the initiation of coagulation.

Strips of placenta and myometrium were obtained from 48 women delivered by cesarean section at term. TF and TFPI concentrations were measured by immunoenzymatic method (ELISA) in tissue homogenates.

Concentration of TF in placenta and myometrium was 31 (25-37) and 7.4 (4.9-11.4) ng/mg of total protein, respectively. In the plasma of the same women, it was 0.004ng/mg of total protein. TFPI concentration was 13 (10-17) ng/mg of total protein in placenta, 4.5 (3.1-7.3) ng/mg in myometrium, and 0.70 (0.50-0.80) ng/mg in blood plasma protein.

The levels of TF in placenta and myometrium, over TF in blood plasma may be clinically significant in obstetrics, for instance, in the etiology of DIC in placental abruption. The concentration of TFPI-natural inhibitor of TF-seems to be too low to prevent initiation of coagulation.