Expression of Toll-Like Receptor 3 in the Preterm Brain after White Matter Injury
: A Post-Mortem Study Applying Immunohistochemistry and In Situ Hybridisation

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Toll-like receptor-3 (TLR3) has been identified in a variety of intracellular structures of cells and has been shown to detect viral molecular patterns and damage-associated molecular patterns (DAMPs). This study investigates the cellular and subcellular localization of TLR3 and its downstream signaling pathway in post-mortem brain sections from preterm infants (26-32 weeks; gestational age) with and without white matter injury (WMI) pathologies. These results were compared with a sheep model of fetal inflammation by the administration of intravenous bolus infusion of either Escherichia coli lipopolysaccharide (LPS) or saline at 102.5 +/- 0.5 days of gestation, analyzed 10 days post insult. In this study, we utilised double-labeling immunofluorescence techniques and in situ hybridization to identify the protein and messenger ribonucleic acid (mRNA) expression of TLR3. Furthermore, we assessed astroglia, microglia, oligodendroglia, neuronal populations and growth cone structures in the periventricular white matter, cortex, thalamus and in the posterior internal capsule. Additionally, we explored the TLR3 colocalisation with endosomal and phagosomal compartments. We hypothesise that after WMI or LPS exposure has occurred, the localization and activation of TLR3 alters in grey matter structures. We observed an increase in TLR3 mRNA expression in the WMI cases and the LPS exposed sheep compared to the controls. Moreover, mRNA translated into TLR3 protein expression that was more diffuse in WMI cases. We confirmed that in the WMI cases, there was an increase in TLR3 colocalisation with the endoplasmic reticulum and with the autophagosome suggesting that autophagy may be a response to stress associated with WMI. Furthermore, we show that growth cone structures and neuronal densities are altered in WMI cases. Identifying changes in TLR3 expression during fetal development may improve our understanding of disturbances seen in neuronal migration and reduced volumes of grey matter seen in preterm infants.
Date of Award2015
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorHenrik Hagberg (Supervisor) & Mary Rutherford (Supervisor)

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