ESR 6 vision / project

ESR 6

Age-induced changes in gene and microRNA expression at the mouse blood-brain barrier

Project Results

Ultrastructural and transcriptional changes were assessed in the ageing female blood-brain barrier (BBB). Structural analysis was performed on brain cortex and hippocampus using Transmission Electron Microscopy (TEM), whereas changes in gene expression were assessed only at the cortex by sequencing analysis (MACE-Seq Analysis and Small RNA analysis). TEM analysis confirmed several age-related structural changes in the female BBB including thicker basement membrane, larger and more abundant brain endothelial cell (BEC) surface pseudopods, larger pericyte mitochondria, higher pericyte coverage over BECs and higher tortuosity in endothelial tight junctions. In summary, these results suggest an immune activated state in BECs whereas pericytes develop changes in mitochondrial dynamics and interaction with the brain endothelium. Most of these alterations were observed in cortical capillaries rather than hippocampal capillaries, which suggests that ageing has a higher impact on cortex. Therefore, sequencing analysis was focused on cortical microvessels. MACE-Seq results showed prominent overexpression of mRNAs related to inflammatory response pathways which is consistent with previous studies that reported a more immune active response in the ageing female brain (Berchtold et al. 2008). According to Small RNA analysis, 9 differentially expressed microRNAs (miRs) were observed. MiR-144-3p, previously reported to be increased in ageing cortex of non-human primates and Alzheimer´s disease patients (Persengiev et al. 2011), was selected together with its predicted target, Dnmt3a, for further analysis. In vitro analyses were performed in human brain endothelial cell line (hCMEC/D3) to assess the effect of miR-144-3p/DNMT3A deregulation on cellular function. According to our results, no changes were observed in paracellular permeability. In contrast, leukocyte adhesion onto endothelial monolayer was increased when miR-144-3p was upregulated or DNMT3A was downregulated. Expression levels of adhesion molecules were also altered with miR-144-3p/DNMT3A/Dnmt3a deregulation in both human cell line and mouse tissue.

Awards

Hosting institution

The Open University, Department of Life, Health and Chemical Sciences, Blood-Brain barrier Group, Milton Keynes, UK

Main Supervisor

Nacho Romero

Early Stage Researcher

Eduardo Frias

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