| During the first trimester of pregnancy, a series of carefully regulated interactions governs the formation of the placenta and the establishment of a hybrid fetal-maternal vasculature. A specialized subpopulation of villous cytotrophoblasts emerges from the placental villi and gives rise to highly invasive extravillous cytotrophoblasts (EVTs) that invade the uterine wall and remodel the maternal spiral arteries. Dysregulation of extravillous cytotrophoblast differentiation is associated with pregnancy complications including spontaneous abortion, intrauterine growth restriction, and preeclampsia. A number of soluble growth factors and chemokines that contribute to neuronal development also regulate differentiation of cytotrophoblasts down the invasive pathway. Human cytomegalovirus (HCMV) is a ubiquitous human pathogen that complicates approximately 1% of pregnancies in the United States. HCMV infection impairs cytotrophoblast differentiation and invasion. The studies in this dissertation test the hypothesis that infection with HCMV dysregulates neuronal guidance factor signaling in extravillous cytotrophoblasts, disrupting their ability to proliferate, migrate, and invade. HCMV-induced dysregulation of the CXCL12-CXCR4 axis was specifically addressed. This chemokine pathway has been shown to mediate cytotrophoblast proliferation and invasion. HCMV infection decreases the secretion of CXCL12 in SGHPL-4 cells and induces peri-nuclear sequestration of this chemokine. Sequestered CXCL12 colocalizes with lysosomal markers, indicating its putative degradation. Additionally, expression of the CXCL12 receptors CXCR4 and CXCR7 is altered following HCMV infection. Both receptors are upregulated to the membrane following infection and their mRNA expression is significantly increased. However, HCMV-infected cells are unable to migrate or invade toward a CXCL12 stimulus, indicating that the cells are unresponsive to this chemokine. Additionally, the role of the netrin family of neuronal guidance cues in extravillous trophoblast invasion was investigated. Netrin-1 and its receptors are expressed by EVTs and stimulate trophoblast migration and invasion. Treatment of SGHPL-4 cells with netrin-1 induces activation of the MAPK and PI3K/Akt pathways. Invasion toward netrins is inhibited following HCMV infection, suggesting that this pathway is dysregulated by cytomegalovirus infection as well. Collectively, these studies indicate that human cytomegalovirus dysregulates expression of and response to neuronal guidance cues in extravillous cytotrophoblasts, disrupting their ability to adopt an invasive phenotype. |
