Eyeballing stroke: Blood flow alterations in the eye and visual impairments following transient middle cerebral artery occlusion in adult rats

Abstract

Middle cerebral artery occlusion in rodents remains a widely used model of ischemic stroke. Recently, we reported the occurrence of retinal ischemia in animals subjected to middle cerebral artery occlusion, owing in part to the circulatory juxtaposition of the ophthalmic artery to the middle cerebral artery. In this study, we examined the eye hemodynamics and visual deficits in middle cerebral artery occlusion-induced stroke rats. The brain and eye were evaluated by laser Doppler at baseline (prior to middle cerebral artery occlusion), during and after middle cerebral artery occlusion. Retinal function-relevant behavioral and histological outcomes were performed at 3 and 14 days post-middle cerebral artery occlusion. Laser Doppler revealed a typical reduction of at least 80% in the ipsilateral frontoparietal cortical area of the brain during middle cerebral artery occlusion compared to baseline, which returned to near-baseline levels during reperfusion. Retinal perfusion defects closely paralleled the timing of cerebral blood flow alterations in the acute stages of middle cerebral artery occlusion in adult rats, characterized by a significant blood flow defect in the ipsilateral eye with at least 90% reduction during middle cerebral artery occlusion compared to baseline, which was restored to near-baseline levels during reperfusion. Moreover, retinal ganglion cell density and optic nerve depth were significantly decreased in the ipsilateral eye. In addition, the stroke rats displayed eye closure. Behavioral performance in a light stimulus-mediated avoidance test was significantly impaired in middle cerebral artery occlusion rats compared to control animals. In view of visual deficits in stroke patients, closely monitoring of brain and retinal perfusion via laser Doppler measurements and examination of visual impairments may facilitate the diagnosis and the treatment of stroke, including retinal ischemia.

Neuroprotective effects of human amniotic fluid stem cells-derived secretome in an ischemia/reperfusion model

“…To date, tissue plasminogen activator is the only therapeutic approach used in stroke patients. [4][5][6] Reperfusion injury occurring in consequence of ischemic stroke is an intricate process involving several processes. Also, thrombolytic therapy itself can lead to brain injuries, named cerebral ischemia/reperfusion (I/R) injury.…”

“…Furthermore, the inhibition of some molecular targets demonstrates to be ineffective due to secondary effects. To date, tissue plasminogen activator is the only therapeutic approach used in stroke patients 4‐6 . Reperfusion injury occurring in consequence of ischemic stroke is an intricate process involving several processes.…”

NLRP3 Inflammasome: A Potential Target in Isoflurane Pretreatment Alleviates Stroke-Induced Retinal Injury in Diabetes

“…Approximately 25% of patients with ischemic stroke have complete occlusion of the OPA, leading to retinal ischemia and subsequent retinal damage (Helenius et al, 2012). Similar effects have been observed in rodent MCAO models, with the blood flow of the ipsilateral eye shown to be significantly reduced once the filament is inserted into the MCA (Steele et al, 2008;Nguyen et al, 2019;Lee et al, 2020). Furthermore, decreased blood flow leads to retinal ischemia with the severity of injury proportional to the cerebral ischemic area (Allen et al, 2014).…”

Taurine and oxidative stress in retinal health and disease

“…26 Blood flow alterations in the brain, due to ischemia for example, are strictly related to blood flow alterations occurring in the eye following by visual impairments. 27,28 Visual processing starts in the retina: a thin, multilayered tissue composed of light-sensitive neurons lining the back of the vertebrate eye. 29 The retina elaborates the light produced from visual images through transduction (transferring energy from one form to another) and transfers these data to the brain for the perceptual appreciation of the images.…”