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Proc Natl Acad Sci U S A. 2019 Feb 20. pii: 201814766. doi: 10.1073/pnas.1814766116. [Epub ahead of print]

Podocalyxin is required for maintaining blood-brain barrier function during acute inflammation.

Author information

1
Biomedical Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
2
Biomedical Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 1Z3; mhughes@brc.ubc.ca kelly@brc.ubc.ca.
3
ICORD Centre, University of British Columbia, Vancouver, BC, Canada V5Z 1M9.
4
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
5
Centre for Heart and Lung Innovation, St Paul's Hospital, Vancouver, BC, Canada V6Z 1Y6.
6
Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada V6T 2A1.
7
Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
8
Djavad Mowafaghian Center for Brain Health, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
9
Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada T6G 2R3.
10
Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada T6G 2R3.
11
Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
12
Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
13
Department of Anaesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.

Abstract

Podocalyxin (Podxl) is broadly expressed on the luminal face of most blood vessels in adult vertebrates, yet its function on these cells is poorly defined. In the present study, we identified specific functions for Podxl in maintaining endothelial barrier function. Using electrical cell substrate impedance sensing and live imaging, we found that, in the absence of Podxl, human umbilical vein endothelial cells fail to form an efficient barrier when plated on several extracellular matrix substrates. In addition, these monolayers lack adherens junctions and focal adhesions and display a disorganized cortical actin cytoskeleton. Thus, Podxl has a key role in promoting the appropriate endothelial morphogenesis required to form functional barriers. This conclusion is further supported by analyses of mutant mice in which we conditionally deleted a floxed allele of Podxl in vascular endothelial cells (vECs) using Tie2Cre mice (Podxl ΔTie2Cre). Although we did not detect substantially altered permeability in naïve mice, systemic priming with lipopolysaccharide (LPS) selectively disrupted the blood-brain barrier (BBB) in Podxl ΔTie2Cre mice. To study the potential consequence of this BBB breach, we used a selective agonist (TFLLR-NH2) of the protease-activated receptor-1 (PAR-1), a thrombin receptor expressed by vECs, neuronal cells, and glial cells. In response to systemic administration of TFLLR-NH2, LPS-primed Podxl ΔTie2Cre mice become completely immobilized for a 5-min period, coinciding with severely dampened neuroelectric activity. We conclude that Podxl expression by CNS tissue vECs is essential for BBB maintenance under inflammatory conditions.

KEYWORDS:

CD34 family; barrier function; blood–brain barrier; endothelial; podocalyxin

PMID:
30787191
PMCID:
PMC6410846
[Available on 2019-09-05]
DOI:
10.1073/pnas.1814766116

Conflict of interest statement

The authors declare no conflict of interest.

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