Analysis of Cerebral Vasospasm in a Murine Model of Subarachnoid Hemorrhage with High Frequency Transcranial Duplex Ultrasound

Summary

The aim of this manuscript is to present a sonography-based method that allows in vivo imaging of blood flow in cerebral arteries in mice. We demonstrate its application to determine changes in blood flow velocities associated with vasospasm in murine models of subarachnoid hemorrhage (SAH).

Abstract

Cerebral vasospasm that occurs in the weeks after subarachnoid hemorrhage, a type of hemorrhagic stroke, contributes to delayed cerebral ischemia. A problem encountered in experimental studies using murine models of SAH is that methods for in vivo monitoring of cerebral vasospasm in mice are lacking. Here, we demonstrate the application of high frequency ultrasound to perform transcranial Duplex sonography examinations on mice. Using the method, the internal carotid arteries (ICA) could be identified. The blood flow velocities in the intracranial ICAs were accelerated significantly after induction of SAH, while blood flow velocities in the extracranial ICAs remained low, indicating cerebral vasospasm. In conclusion, the method demonstrated here allows functional, noninvasive in vivo monitoring of cerebral vasospasm in a murine SAH model.

Introduction

Spontaneous subarachnoid hemorrhage (SAH) is a form of hemorrhagic stroke mostly caused by the rupture of an intracranial aneurysm¹. The neurological outcome is mainly influenced by two factors: early brain injury (EBI), which is caused by the effects of the bleeding and the associated transient global cerebral ischemia, and delayed cerebral ischemia (DCI), which occurs during the weeks following the bleeding^2,3. DCI was reported to affect up to 30% of SAH patients². The pathophysiology of DCI involves angiographic cerebral vasospasm, a disturbed microcirculation....

Protocol

The animal experiments were approved by the responsible animal care committee (Landesuntersuchungsamt Rheinland-Pfalz) and conducted in accordance with the German Animal Welfare Act (TierSchG). All applicable international, national, and institutional guidelines for the care and use of animals were followed. In this study, we performed measurements of blood flow velocities of intracranial and extracranial arteries in female C57BL/6N mice aged 11-12 weeks with a body weight between 19-21 g. The mice were subjected to either SAH induction or sham surgery, which has been described in detail elsewhere^10,12,

Results

In 6 mice, in 3 of which SAH was induced using the endovascular filament perforation model while 3 obtained sham surgery, the blood flow velocities of the intracranial internal carotid artery (ICA) and of the extracranial ICA were determined one day before surgery, and 1, 3, and 7 days after surgery. The measurements were performed as part of the echocardiography examinations of another study under anesthesia with isoflurane while maintaining the body temperature at 37 °C¹⁹.

Discussion

To the best of our knowledge, this study is the first to present a protocol for monitoring of cerebral vasospasm in a murine model of SAH with high frequency transcranial color-coded Duplex ultrasound. We show that this method can measure an increase in intracranial blood flow velocities after SAH induction in mice. In human medicine this phenomenon is well known^3,15. Several clinical studies have shown that elevated blood flow velocities of the large intracrania.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Balea hair removal creme	Balea; Germany	ASIN B0759XM39V	hair removal creme
C57BL/6N mice	Janvier; Saint-Berthevin Cedex, France	n.a.	mice
Corneregel	Bausch&Lomb; Rochester, NY, USA	REF 81552983	eye ointment, lube
cotton swabs	Hecht Assistent; Sondenheim vor der Röhn, Germany	REF 44302010	cotton swabs
Ecco-XS razor	Tondeo; Soligen, Germany	DE 28693396	razor
Electrode cream	GE; Boston, MA, USA	REF 21708318	conductive paste
Heating plate	Medax; Kiel, Germany	2005-205-01
Isoflurane	Abvie; Wiesbaden, Germany	n.a.	volatile anesthetic
Leukofix	BSN medical; Hamburg, Germany	REF 02137-00	tape
Mechanical arm + micromanipulator	VisualSonics; FujiFilm, Toronto, CA	P/N 11277
Microbac tissues	Paul Hartmann AG; Hamburg, Germany	REF 981387	antimicrobial tissues
MZ400, 38 MHz linear array transducer	VisualSonics; FujiFilm, Toronto, CA	REF 51068-30	ultrasound transducer
Sonosid	ASID Bonz GmbH; Herrenberg, Germany	REF 782010	ultrasonography gel
Ultrasound platform with heating plate and ECG-recording	VisualSonics; FujiFilm, Toronto, CA	P/N 11179
UniVet-Porta	Groppler; Oberperasberg, Germany	S/N BKGM0437	isoflurane vaporizer
Vevo3100	VisualSonics; FujiFilm, Toronto, CA	REF 51073-45	ultrasonography device
VevoLab software	VisualSonics; FujiFilm, Toronto, CA	n.a.	evaluation software