- Title
- The role of microRNAs that target the renin-angiotensin system in placental development and function
- Creator
- Arthurs, Anya Lara
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This thesis explores the role of microRNAs (miRNAs) that target the placental renin-angiotensin system (RAS) in placental development and function. The placental RAS contributes to trophoblast proliferation, migration and invasion, as well as vasoconstriction and angiogenesis. As such, the placental RAS is essential for adequate placental development and function. miRNAs targeting RAS mRNAs are present in the developing placenta, and their expression varies across gestation, along with RAS expression. Furthermore, changes in expression of these miRNAs are seen in pregnancy complications. This research investigated: the effects of low oxygen tension, such as the low oxygen environment of the first trimester placenta, on expression of miRNAs targeting the placental RAS ; the effect of miRNAs targeting the placental RAS on the functional ability of trophoblasts to proliferate, and ; the in vitro and in vivo roles of miR-155 in the placenta. I found that in HTR-8/SVneo cells (an immortalised human extravillous trophoblast cell line) cultured in low oxygen tension (~1%), there was suppressed expression of ten miRNAs predicted to target the RAS. Furthermore, this allowed increased expression of two critical RAS components. This would suggest that a low oxygen environment encourages placentation by suppressing miRNA expression to allow RAS activity. These experiments were then repeated in first trimester chorionic villus explants (CVE) obtained from primary tissue, where the expression of only four of the tested miRNAs was suppressed by low oxygen tension. The RAS components that were increased in this low oxygen milieu were also different to those increased in the cell line experiments. These experiments taken together illustrate the differing roles of miRNAs and the RAS in the extravillous trophoblasts and the chorionic villi. Investigation into the effect of miRNAs predicted to target the RAS on trophoblast proliferation showed that treatment with mimics of these miRNAs suppressed, or completely inhibited, trophoblast proliferation. In the case of many miRNAs tested, a dose-dependent response was observed, with higher mimic concentrations leading to lower proliferation of the cells. The effect of these miRNAs on their intended RAS targets was also assessed, with 7 of the 9 miRNAs suppressing mRNA expression of their RAS targets. These experiments demonstrated the functional effect of miRNA dysregulation of placental development through trophoblast proliferation. This has particular implications for a number of pregnancy complications that arise from poor placental development such as fetal growth restriction and preeclampsia. Finally, the role of miR-155 in placentation was observed, as a miR-155-/- mouse model revealed the consequences of miR-155 deletion. Placentae from miR-155-/- dams had significantly larger labyrinthine zones (responsible for substrate transfer to the fetus), but no change in placental weight, indicating an increase in the labyrinth zone to placental area ratio that would suggest that the placenta has improved efficiency of substrate transfer. These dams also had larger fetuses, possibly as a consequence of the changes in placental morphology. As mIR-155 is known to target the angiotensin II type 1 receptor (AT₁R), mRNA and protein was measured and was significantly increased in miR-155-/- placentae. Additionally, in vitro investigation into the functional effects of miR-155, utilising a miR-155 mimic, showed that treatment with this miRNA decreases trophoblast proliferation in a dose-dependent manner. Altogether, this study clarified the importance of appropriate miR-155 regulation during pregnancy. This was particularly important as miR-155 upregulation is seen in preeclampsia (PE), a dangerous pregnancy complication. Therefore, through utilising a cell line, primary tissue explants and a murine model, I have been the first to demonstrate the effects of various miRNAs targeting the placental RAS on RAS expression, both in and out of a low oxygen milieu, trophoblast proliferation, placental morphology and fetal growth.
- Subject
- placenta; renin-angiotensin; microRNA; miRNA; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1404621
- Identifier
- uon:35373
- Rights
- Copyright 2019 Anya Lara Arthurs
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 2 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 239 KB | Adobe Acrobat PDF | View Details Download |