Rose Bengal Photothrombosis by Confocal Optical Imaging In Vivo: A Model of Single Vessel Stroke

Summary

Here, we describe a semi-invasive optical microscopy approach for the induction of a Rose Bengal photothrombotic clot in the somatosensory cortex of a mouse in vivo. The technical aspects of the imaging procedure are described from induction of a photothrombotic event to application and data collection.

Abstract

In vivo imaging techniques have increased in utilization due to recent advances in imaging dyes and optical technologies, allowing for the ability to image cellular events in an intact animal. Additionally, the ability to induce physiological disease states such as stroke in vivo increases its utility. The technique described herein allows for physiological assessment of cellular responses within the CNS following a stroke and can be adapted for other pathological conditions being studied. The technique presented uses laser excitation of the photosensitive dye Rose Bengal in vivo to induce a focal ischemic event in a single blood vessel.

The video protocol demonstrates the preparation of a thin-skulled cranial window over the somatosensory cortex in a mouse for the induction of a Rose Bengal photothrombotic event keeping injury to the underlying dura matter and brain at a minimum. Surgical preparation is initially performed under a dissecting microscope with a custom-made surgical/imaging platform, which is then transferred to a confocal microscope equipped with an inverted objective adaptor. Representative images acquired utilizing this protocol are presented as well as time-lapse sequences of stroke induction. This technique is powerful in that the same area can be imaged repeatedly on subsequent days facilitating longitudinal in vivo studies of pathological processes following stroke.

Introduction

The technique described permits visualization of in vivo cellular responses immediately following induction of Rose Bengal photothrombosis in an intact mouse. Rose Bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is a photosensitive dye used to induce ischemic stroke in animal models (mouse and rat). Following a bolus injection of RB through the tail vein and subsequent illumination through a thinned skull with a 564 nm laser light, a thrombus is induced causing a physiologic stroke¹. The method was originally described by Rosenblum and El-Sabban in 1977, and was later adapted by Watson in the mid 1980s^1,2. I....

Protocol

Note: All animal procedures were approved by the Institutional Animal Care and Use Committee of the University of Texas Health Science Center San Antonio and were consistent with the ARRIVE guidelines.

1. Anesthetizing for Cortical Preparation

1. Place the mouse in an induction chamber with 2-3% isofluorane mixed with oxygen to induce anesthesia. Observe the respiration rate decrease as the mouse is induced. Pinch the paw of the mouse to determine whether the mouse is ready to move to the nose cone. Note: Anesthesia level is a critical step in any in vivo preparation and care should be taken not to induce a level that....

Results

The aim of this method was to induce an ischemic stroke in animal models (mouse and rat) following a bolus injection of RB through the tail vein and subsequent illumination of a thinned skull with a 561 nm laser light. The images in Figure 4 demonstrate the progression of clot formation within a single vessel following irradiation of the area at 0, 1, 1.5 and 2 min. Prior to clot formation the entire vessel is white due to free flowing Rose Bengal. Following the induction of irradiation of the vessel the.......

Discussion

The ability to translate experimental stroke pathophysiology from animal to human application has been plagued with failure. However, the use of animal models, such as the photothrombosis model, allows for improved understanding of stroke pathophysiology and the exploration of new therapeutic approaches to provide neuroprotection following a stroke. Small cortical strokes and microinfarctions produced by the photothrombotic model are clinically relevant to subclinical or “silent” stroke^13-15, which.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Reagents
Rose Bengal	Sigma	330000
Isoflurane Anesthetic	MWI Veterinary Supply	088-076
Vetbond	1469SB	1469SB
aCSF	126 mM NaCl, 2.5 mM KCl, 1.25 mM NaH2PO4, 2 mM MgCl2, 2 mM CaCl2, 10 mM glucose and 26 mM NaHCO3 (pH 7.4).
[header]
Equipment
Dissecting Scissors	Bioindustrial Products	500-410
Operating scissors 14 cm	Bioindustrial Products	12-055
Forceps Dumont High Tech #5 style, straight	Bioindustrial Products	TWZ-301.22
LabJack 132X80	Optosigma Co	123-6670
Platform for Labjack 8X 8	Optosigma Co	145-1110
Ear bar holder from stereotaxic setup	Stoelting/Cyborg	51654
Dispomed Labvent Rodent anesthesia machine	DRE, Inc.	15001
Tech IV Isoflurane vaporizer	DRE, Inc.	34001
F Air Canister	DRE, Inc	80120
Bain circuit breathing tube	DRE, Inc	86111B
Rodent adapter for bain tube	DRE, Inc	891000
O2 regulator for oxygen tanks	DRE, Inc	CE001E
Rodent induction chamber	DRE, Inc	15004C
Ethicon Silk 6-0; 18 in with P-3 needle	Suture Express	1639G
Objective inverter Optical Adapter	LSM technologies
Foredom drill Dual voltage 110/120	Foredom	134.53
Meisinger 3.9 mm drill bit	Meisinger		(Ref#310 104 001 001 009)