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Title: Physical factors regulating human trophoblast invasion
Author: Abbas, Yassen Raad
ISNI:       0000 0004 7426 5028
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2018
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Pre-eclampsia, fetal growth restriction and stillbirth are major pregnancy disorders throughout the world. The underlying pathogenesis of these diseases is defective placentation characterised by inadequate invasion of extravillous trophoblast (EVT) cells into the uterine decidua. This invasion is necessary to transform the uterine arteries, ensuring an adequate maternal blood supply into the intervillous space for normal fetal growth and development. The mechanisms that regulate trophoblast invasion remains poorly understood, but it is known to be influenced by a number of factors in the uterine environment. These include interactions with maternal immune cells as well as cytokines and the products from the uterine glands. In this thesis, physical factors, specifically, tissue stiffness and oxygen are studied as regulators of trophoblast invasion. The mechanical environment is known to regulate cell fate and the migratory behaviour of cells. Despite invasion of EVT cells through decidual tissue rich in extracellular matrix (ECM) proteins, there has been no study investigating how tissue stiffness might regulate EVT invasion. Oxygen has also long been investigated as a regulator for trophoblast invasion, but evidence is conflicting on whether low oxygen promotes or inhibits invasion. This is in part because of the wide variation in methods used and the over-reliance on trophoblast cell lines. To examine the effects of tissue stiffness and oxygen tension, a robust in vitro method to examine the motility and migration of primary EVT cells in three-dimensions (3D) was first established. This system offers significant benefits compared with two-dimensional (2D) systems used previously. Importantly, only cells expressing the HLAG antigen, a marker for the extravillous phenotype are analysed. The stiffness of decidual tissues at the maternal-fetal interface was determined using atomic force microscopy. In patient matched samples, a 3-4 fold increase in stiffness was found where the placenta implants into the decidua, compared to where there is no implantation. Migration of single EVT cells under different matrix stiffness and oxygen concentrations in 3D were investigated. To determine whether EVT migration is directed, a microfluidic system was established, which models the oxygen gradient at the maternal-fetal interface in the first trimester of pregnancy. This system is simple and economical to setup, and permits analysis of the migration dynamics of trophoblast cells in 3D and in real-time under different oxygen concentrations. In conclusion, the change in stiffness at the site of implantation, is further evidence of the dramatic change that occurs in the uterine wall during pregnancy. A microfluidic system to study whether primary EVT cell invasion is directed under oxygen gradients was developed.
Supervisor: Oyen, Michelle L. ; Burton, Graham J. Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Trohphoblast ; Placentation ; Mechanics ; Microfluidics ; Oxygen