PB1259 - Platelet α-granule content induces endothelial damage and blood brain barrier breakdown in experimental stroke

Tuesday, July 12, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Vanessa Göb, MSc

PhD student
University Hospital and Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg
Würzburg, Bayern, Germany

Co-Author(s)

LZ

Lena Zimmermann

PhD Student
Department of Neurology, University Hospital Würzburg
Würzburg, Bayern, Germany
KH

Katherina Hemmen

Postdoc
Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Germany
Würzburg, Bayern, Germany
GS

Guido Stoll

Professor
University Hospital Würzburg
Würzburg, Bayern, Germany
BN

Bernhard Nieswandt

Professor
Institute of Experimental Biomedicine - Chair I, University Hospital Würzburg and Rudolf Virchow Center for Integrative and Translational Biomaging, University of Würzburg, Germany
Würzburg, Bayern, Germany
KH

Katrin Heinze

Professor
Rudolf Virchow Center for Integrative and Translational Biomaging University of Würzburg, Germany
Würzburg, Bayern, Germany
MS

Michael K. Schuhmann

Group leader
University Hospital Würzburg
Würzburg, Bayern, Germany
David Stegner, PhD

Professor
Institute of Experimental Biomedicine - Chair I, University Hospital and Rudolf Virchow Center for Integrative and Translational Bioimaging, Würzburg, Germany
Würzburg, Bayern, Germany

Background: Ischemic stroke is a major cause of death and disability worldwide. Even if a rapid recanalization is achieved, ongoing lesion development can be observed (referred to as reperfusion injury). Activation of platelets and the thereby induced secretion of granules are critically involved in stroke pathology since absence of granule secretion protects mice in experimental stroke. At the same time, loss of blood brain barrier (BBB) integrity is commonly observed especially in the early hours after stroke.

Aims: In the current study, we aimed to elucidate a potential role of platelet secretion on BBB integrity.

Methods: We subjected mice to transient middle cerebral artery occlusion (tMCAO), a model of ischemic stroke. Vascular integrity was monitored by 2-photon intravital microscopy, and the degree of albumin extravasation was assessed in brain cryosections and by western blot analysis. To investigate the influence of platelet granule content on endothelial cells we measured the trans endothelial electrical resistance (TEER) of murine brain microvascular endothelial cell (MBMEC) monolayers and assessed cell morphology by immunohistochemistry.

Results: We confirmed BBB breakdown as an early event following ischemic stroke using intravital microscopy. The degree of albumin extravasation into the brain parenchyma increased with progressive reperfusion times. Absence of platelet α-granule secretion (Nbeal2-/- mice) protected mice from this increased vascular permeability and reduced endothelial cell damage whereas this was not the case upon absent dense granule secretion (Unc13d-/- mice). Immunohistochemistry and subsequent image analysis revealed severely impaired MBMEC monolayer integrity upon incubation with α-granule content explaining the loss of barrier function. This was confirmed by TEER measurements.

Conclusion(s): Our results revealed an unexpected effect of platelet secretion on BBB integrity. Promising α-granule components could already be identified and will be validated until the ISTH conference. Targeting these α-granule components could offer an anti-platelet therapy that does not increase the risk of intracranial hemorrhages.