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Longitudinal characterization of blood-brain barrier permeability after experimental traumatic brain injury by in vivo 2-photon microscopy.

J Neurotrauma. 2020 Oct 3. doi: 10.1089/neu.2020.7271. Epub ahead of print. PMID: 33012249.

Authors/Editors: Hu Y, Seker B, Exner C, Zhang J, Plesnila N, Schwarzmaier SM.
Publication Date: 2020

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Abstract

Vasogenic brain edema formation remains an important factor determining the fate of patients suffering from traumatic brain injury (TBI). The spatial and temporal development of VBE, however, remain poorly understood due to the lack of sufficiently sensitive measurement techniques. To close this knowledge gap, we directly visualized the full time course of vascular leakage following TBI by in vivo 2-photon microscopy (2-PM). Male C57BL/6 mice (n=6/group, 6-8 weeks old) were randomly assigned to sham-operation or brain trauma by Controlled Cortical Impact. A cranial window was prepared and tetramethylrhodamine-dextran (TMRM, MW 40,000 Da) was injected intravenously to visualize blood plasma 4, 24, 48, 72h, or 7d after surgery or trauma. Three regions with increasing distance to the primary contusion were investigated up to a depth of 300 µm by 2-PM. No TMRM extravasation was detected in sham-operated mice, while already 4h after TBI vascular leakage was significantly increased (p<0.05 vs. sham) and reached its maximum at 48h after injury. Vascular leakage was most pronounced in the vicinity of the contusion. The rate of extravasation showed a biphasic pattern, peaking 4h and 48-72h after trauma. Taken together, longitudinal quantification of vascular leakage after TBI in vivo demonstrates that vasogenic brain edema formation after TBI develops in a biphasic manner suggestive of acute and delayed mechanisms. Further studies using the currently developed dynamic in vivo imaging modalities are needed to investigate these mechanisms and potential therapeutic strategies in more detail.

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