Awake chronic mouse model of targeted pial vessel occlusion via photothrombosis

Abstract

Animal models of stroke are used extensively to study the mechanisms involved in the acute and chronic phases of recovery following stroke. A translatable animal model that closely mimics the mechanisms of a human stroke is essential in understanding recovery processes as well as developing therapies that improve functional outcomes. We describe a photothrombosis stroke model that is capable of targeting a single distal pial branch of the middle cerebral artery with minimal damage to the surrounding parenchyma in awake head-fixed mice. Mice are implanted with chronic cranial windows above one hemisphere of the brain that allow optical access to study recovery mechanisms for over a month following occlusion. Additionally, we study the effect of laser spot size used for occlusion and demonstrate that a spot size with small axial and lateral resolution has the advantage of minimizing unwanted photodamage while still monitoring macroscopic changes to cerebral blood flow during photothrombosis. We show that temporally guiding illumination using real-time feedback of blood flow dynamics also minimized unwanted photodamage to the vascular network. Finally, through quantifiable behavior deficits and chronic imaging we show that this model can be used to study recovery mechanisms or the effects of therapeutics longitudinally. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Chronic Cranial Windows for Long Term Multimodal Neurovascular Imaging in Mice

“…Some of the abovementioned imaging modalities can be readily combined in a multimodal setup that allow simultaneous use of the systems. Examples include (1) LSCI, IOSI and photothrombosis (Kazmi et al, 2013;Sunil et al, 2020) (2) 2-P microscopy and optogenetic stimulation (Bovetti et al, 2017;Yang et al, 2018), and (3) MRI and optical imaging and/or optogenetic stimulation (Lin et al, 2016;Schlegel et al, 2018;Chen et al, 2019).…”

“…We have modified this protocol using half of this commercially available curved glass (labmaker.org) to prevent the disruption of blood flow in sagittal sinus while extending the coverage to visualize the distal branching points of MCA and the entirety of barrel cortex which are more laterally positioned than the original design of Crystal Skull placement. We have used our version of preparation in several studies including Sunil et al (2020). In cases where a large cortical area is desired to be imaged, surgery using crystal skull glass can be performed (Kim et al, 2016).…”

Chronic Imaging of Mouse Brain: From Optical Systems to Functional Ultrasound

“…OCT images were acquired with a commercial system (Thorlabs Telesto III, with 1310-nm center wavelength, and 170-nm bandwidth). A laser speckle imaging system (Postnov, Erdener, Kılıç, & Boas, 2018) and intrinsic optical imaging system were custom built (Sunil et al, 2020). The ultrasound signal was acquired with a commercial ultrafast ultrasound imaging system (Vantage 256, Verasonics) and a linear ultrasonic probe (L22-14v, Verasonics) (Tang et al, 2019).…”

“…Although we have not applied the preparation method in Basic Protocol 1 for MRI, previous preparations using similar polymers (PEEK and PMP) make us hopeful that our preparation is also MRI compatible (Boido et al, 2019;Sunil et al, 2020) because they do not involve any metal implants. Due to the high optical transparency of 50-μmthick PMP, it should also be possible to use these preparations for diverse optical manipulation methods, like optogenetic stimulation and photothrombosis, in addition to a wide spectrum of imaging techniques, including calcium imaging and voltage-sensitive sensor imaging.…”

Guidelines for obtaining an absolute blood flow index with laser speckle contrast imaging

“…Laser speckle contrast imaging (LSCI) provides a rapid wide field qualitative characterization of the motion of light scattering particles. Over the past 20 years, it has become widely used as an imaging tool to measure blood flow in the brain [1][2][3][4][5][6] , skin [7][8][9] , retina [10][11][12] and other organs. LSCI has had a broad impact on fundamental research, for instance enabling the connection between migraine aura and headache 2 , and has a rising number of clinical applications 12,13 thanks to the approval of LSCI imaging systems by the US Food and Drug Administration.…”