Regulation of Microparticles and Adhesion Molecules in Pregnancy. Diagnostic and Pathophysiologic Implications.

OBJECTIVE In addition to increased levels of coagulation factors and platelet counts,, microparticles are also found in increased numbers in pregnancy and are generated due to cellular activation and consumption. Microparticles may also be capable of amplifying the procoagulant and inflammatory responses by up regulating the adhesion molecules such as P, E and L selectins. This study will provide newer data on the regulation of microparticles in different trimesters of pregnancy and their relevance to the generation of adhesion molecules and tissue factor (TF).

STUDY DESIGN Blood samples from pregnant women at their first prenatal visit and during the second and third trimester (n=50) were collected and citrated plasma samples were profiled for TF (American Diagnostica, Stamford, CT), E, L and P-selection (R &D Systems, Minneapolis, MN) by using commercially available sandwich ELISA methods and microparticles utilizing a functional method from Hyphen Biomed (Neuville-Sur-Oise, France). The results were compiled for each trimester and compared to aged match non-pregnant controls (n=40).

RESULTS During the first trimester all of the mediators were increased in comparison to the controls. The relative increase was mediator dependent. L-selectin remained elevated, at a steady level, throughout the pregnancy. E-selectin showed a decrease in the second trimester with a rebound increase in the third trimester. A gradual increase in the TF and microparticles was evident throughout the pregnancy. The P-selectin levels decreased during the second trimester and stayed at this level for the remainder of the pregnancy.

CONCLUSION Throughout pregnancy the TF levels directly correlated with an increase in the MP levels indicating that TF cause cellular activation leading to the formation of MPs. However, the levels of the adhesion molecules, which were initially elevated, fluctuate throughout the 2^nd and 3^rd trimester. These results suggest that increased levels of TF and MPs are progressively generated during pregnancy and may be responsible for the observed thrombotic complications and prothrombotic state in pregnancy.