Axis of placental ageing in adverse pregnancy outcomes

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Manna, Samprikta
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University College Cork
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Background: Pre-eclampsia (PE), an adverse pregnancy outcome affects 2-5% pregnancies worldwide and significantly adversely impacts both maternal and fetal outcomes. Intrauterine growth restriction (IUGR) is defined as the inability of the fetus to reach normal growth potential within the uterus as a result of various genetic, environmental, or placental factors. Premature ageing of the placenta in pregnancy outcomes such as PE and IUGR is associated with the persistent presence of oxidative stress and placental insufficiency reducing its functional capacity. Placental proteomics has been instrumental in improving our understanding of molecular mechanisms involved in the pathophysiology of placental insufficiency as well as identifying biomarkers to predict and diagnose pregnancy outcomes. In this study, we investigated cellular senescence phenotypes of PE and IUGR pregnancies by simultaneously measuring several biomarkers of senescence, as well as the proteomic signature of the placenta in healthy and adverse pregnancy outcomes PE and IUGR. Method: Maternal plasma and placental samples were collected at term (>37 weeks) and preterm (<37 weeks) gestation from nulliparous women undergoing prelabour elective Caesarean section with PE without intrauterine growth restriction (PE; n=5), PE associated with intrauterine growth restriction (n=8), intrauterine growth restriction (IUGR <10th centile) (n=6) and age-matched controls (n=20) from Cork University Maternity Hospital, Cork, Ireland. To assess cellular senescence absolute telomere length (aTL) and senescence associated genes in the placentas was performed by RTqPCR. Cyclin-dependent kinase inhibitors (p21 and p16) expression were determined by Western blotting. Senescence Associated Secretory Phenotype (SASP) were evaluated in maternal plasma by multiplex ELISA assay. Proteomic analysis of placental samples dissected into 3 sub-anatomical regions (maternal, middle, fetal) taken from 3 nulliparous healthy placentas was performed by mass-spectrometry and pathway analysis was conducted. Based on the differentially expressed proteins (DEPs), a placenta specific disease map using NaviCenta focusing on functional analysis to include the placenta specific context for healthy (n=4) compared to PE affected (n=4) and IUGR affected (n=4) placentas. Results: Placental expression of senescence associated genes CHEK1, PCNA, PTEN, CDKN2A, CCNB-1 was significantly upregulated in PE, while TBX-2, PCNA, ATM and CCNB-1 expression were significantly decreased in IUGR compared to controls. Moreover, placental p16 protein expression was significantly decreased in PE only when compared to controls placentas. We also observed that IL-6 was significantly increased in maternal circulation in PE when compared to controls; while IFN-γ was significantly increased in maternal circulation in women affected with IUGR when compared to controls. Proteomic profiling of healthy placentas divided into three sub-anatomical regions identified 1081, 1086, and 1101 proteins in maternal, middle, and fetal sub-anatomical regions respectively. Depending on sample site location and sub-anatomical regions, 374 differentially expressed proteins (DEP) were identified. When we investigated the proteomic variations between PE and IUGR placentas when compared to controls we observed 314, 391, and 378 proteins in healthy control, PE, and IUGR placenta, respectively. We performed functional analysis by combining ClusterCompare and NaviCenta to analyse a placenta-centric context, and observed regulatory elements predominantly involved in the immune regulation, complement cascade and antioxidant activities in PE and IUGR compared to control placentas. Conclusion: This thesis provides evidence of premature senescence in IUGR, while in PE, evidence of activated cell cycle checkpoint regulators is suggestive of cellular repair and proliferation rather than progression to cellular senescence. The heterogeneity within senescence molecular markers of these phenotypes highlights the complexity and disparity between pathophysiological insults unique to each obstetric complication. Proteomic profiling of sub-anatomical placental regions highlighted the variabilities between regions particularly providing evidence of senescence in these regions. Placental proteomic mapping of healthy placentas compared to adverse pregnancy outcomes PE and IUGR revealed the importance of complement system, inflammatory response, and antioxidant activity in placental function in PE placentas. The identification of novel targets such as transcription factor activity and synergistic miRNAs elements within the core regulatory network, might enlighten future placental research within adverse pregnancy outcomes.
Placenta , Proteomics , Bioinformatics , Systems biology , Disease map , Pre-eclampsia , Cellular senescence , Intrauterine growth restriction
Manna, S. 2023. Axis of placental ageing in adverse pregnancy outcomes. PhD Thesis, University College Cork.