Ph.D Thesis

Ph.D StudentShomer-Prital Einat
SubjectIdentifying Mechanisms through which Microparticles
Contribute to Pregnancy Related Complications
DepartmentDepartment of Medicine
Supervisors ASSISTANT PROFESSOR Anat Aharon
Full Thesis textFull thesis text - English Version


Introduction: Gestational vascular complications such as preeclampsia are a major cause of maternal morbidity and fetal mortality. Preeclampsia is characterized by poor placentation, followed by development of maternal syndrome, increase in inflammatory factors, endothelial dysfunction and shedding of trophoblast microvesicles. Microvesicles (MVs) are membrane vesicles which bud from activated or apoptotic cells. MVs carry cellular markers of their originating cells and their number can rise in different pathological conditions. The protein C system plays an important role in regulating coagulation. Changes in members of the protein C system are associated with GVC. Study aims: The central goal of this study was to identify mechanisms which could explain the association between MVs, vascular and placental dysfunction and GVC symptoms. In addition, we aimed to examine MVs thrombogenicity regarding the protein C system. We hypothesized that MVs from GVC express inflammatory, angiogenic and coagulation factors, which may reflect and affect the pathological state of the pregnancy. Results: We found that GVC-MVs demonstrate different expression patterns of inflammatory and angiogenic proteins compared to HP.  HP-MVs induced significantly higher trophoblast migration than untreated cells, mainly through ERK pathway.  Additionally, exposure of trophoblasts to HP-MVs decreased cell apoptosis and caspase 3/7 activity compared to untreated cells. In contrast to HP-MVs, GVC-MVs decreased BCL2 gene expression, inhibited cell migration and did not affected trophoblast apoptosis or caspase activity. In addition, endothelial cells incubated with GVC-MVs for 2 hours, induced 2.5 fold decrease in tubes length  compared to HP-MVs. LMWH-MVs didn't differ in their effects from HP-MVs. Regarding the protein c system; we didn't see any difference between GVC- MVs characterization and effects from HP-MVs. However, our study was the first to show that circulating MVs as well as trophoblastic MVs don't express TM on their surface.  In addition we demonstrated that trophoblastic MVs express lower levels of EPCR than their parent cells. Finally, we found that LMWH-MVs express lower levels of EPCR and PAR-1 than NP-MVs. Conclusions: Our results indicate MVs role in normal pregnancy through their effects on angiogenic and anti-apoptotic processes. These effects are altered in GVC and may emphasize mechanisms through which MVs can be involved in development of pregnancy complications. Our results support the notion of MVs as procoagulant particles, including trophoblast MVs, which may contribute to the procoagulatory nature of the placenta microenvironment. LMWH MVs might serve as both indicators and mediators of the beneficial effects conferred by LMWH treatment.