(T0930-10-55) Differential Gene Expression of Human Brain Endothelial Cells Compared to Endothelial Cells Co-cultured with Pericytes

Purpose: The brain is a highly vascularized organ with a large network of capillaries. The endothelial cell monolayer, sealed by paracellular tight junctions lines the capillary lumen and forms the blood brain barrier (BBB). The BBB which tightly regulates solute exchange between blood and the brain. It is widely believed that pericytes, which wrap around endothelial cells on the abluminal side, regulate blood flow by controlling capillary dilation. Recent reports have outlined other roles of pericytes, particularly in the maintenance of the BBB integrity and function. Pericyte dysfunction is associated with several neurovascular pathologies. In Alzheimer's disease (AD), pericyte degeneration appears to accelerate β-amyloid peptide deposition, abnormal tau protein accumulation, and neurodegeneration.^1,2 The objective of the current study is to analyze dynamic gene expression changes of human brain endothelial cells compared to endothelial cells co-cultured with pericytes in order to elucidate molecular level interactions between these two cell types, and to identify key pathways that may be disrupted at the BBB following pericyte degeneration.

Methods: Differential gene expression analysis was performed on a publicly available dataset deposited in the gene expression omnibus database (GEO ID GSE144474). In this study, human brain capillary endothelial cells (HBCEC) were cultured solo or co-cultured with pericytes on Transwell^â filters. Gene expression of HBCEC solo cultures and HBCEC-pericyte cocultures was determined at four time points over 96 hours using Massive Analysis of cDNA Ends (MACE) technology, measuring RNA expression levels of more than 25,000 genes.³

Results: Gene expression levels were stable in the solo HBCEC cultures over time, while nearly 1,300 genes showed significant differential expression in one or another direction at all time points when solo cultures were compared with co-cultures – 520 were down-regulated and 770 were up-regulated. Of these, 200 genes were found to have a steady increase in expression. Among the top 30 was INSR, which codes for the insulin receptor protein.

Conclusion: These results suggest that interactions between endothelial cells and pericytes encompass a spectrum of pathways, including insulin signaling pathway. The role played by insulin singling in cerebrovascular physiology is widely recognized. The role of pericytes in BBB dysfunction as it relates to AD and metabolic disorders will be thoroughly investigated in future studies.

References: 1 Sweeney, M., Ayyadurai, S. & Zlokovic, B. Pericytes of the neurovascular unit: key functions and signaling pathways. Nat Neurosci 19, 771–783 (2016). https://doi.org
2 Sagare, A., Bell, R., Zhao, Z. et al. Pericyte loss influences Alzheimer-like neurodegeneration in mice. Nat Commun 4, 2932 (2013). https://doi.org/10.1038/ncomms3932
3 Heymans, M., Figueiredo, R., Dehouck, L. et al. Contribution of brain pericytes in blood–brain barrier formation and maintenance: a transcriptomic study of cocultured human endothelial cells derived from hematopoietic stem cells. Fluids Barriers CNS 17, 48 (2020). https://doi.org/10.1186/s12987-020-00208-1