New Pediatric Model of Ischemic Stroke in Infant Piglets by Photothrombosis

Abstract

Background and Purpose-The etiology and pathophysiology of acute ischemic stroke in children differ greatly from those in adults. The purpose of this study was to establish a new pediatric model of ischemic stroke in infant piglets for use in future studies of the response of the developing brain to focal ischemic injury. Methods-Ischemic stroke was produced in male infant piglets (2 to 4 weeks old) by photothrombotic occlusion of the middle cerebral artery. Regional cerebral blood flow was measured with radiolabeled microspheres up to 4 hours after occlusion. Early histopathology, including caspase-3 immunohistochemistry for apoptosis, was examined 4 hours after ischemia. The nature of the thrombus and its interaction with vascular endothelium were assessed by electron microscopy. Results-Severe ischemia (0 to 15 mL/100 g per min) occurred rapidly in 1.4Ϯ0.2 g of tissue at 15 minutes and increased to 2.4Ϯ0.7 g at 4 hours. Similarly, moderate ischemia (16 to 30 mL/100 g per min) was measured in 1.2Ϯ0.3 g of tissue at 15 minutes and increased to 2.0Ϯ0.6 g at 4 hours. These regional cerebral blood flow values represent ischemic levels of blood flow in 20% to 25% of the volume of the ischemic hemisphere at 4 hours after ischemia. Ischemic infarction occurred in both gray and white matter, and cerebral microvessels in the ischemic hemisphere contained large numbers of inflammatory leukocytes. Caspase-3-positive cells were few in number and were found in the periphery of the infarct; cell death appeared to occur primarily by necrosis rather than apoptosis at 4 hours. Electron microscopy revealed a pure platelet thrombus firmly attached to the vascular endothelium, which in some areas appeared to be detached from the basement membrane. Conclusions-Ischemic stroke can be produced in infant piglets by middle cerebral artery photothrombosis. The stroke involved both gray and white matter and exhibited a robust inflammatory component. The mean infarct volume determined histopathologically amounted to 9.6Ϯ2.4% of the affected (ipsilateral) hemisphere, which was correlated well with the mass equivalent of tissue (12.0Ϯ3.5%), in which severe declines in regional cerebral blood flow were observed at 4 hours.

Tissue-Type Plasminogen Activator-A 296–299 Prevents Impairment of Cerebral Autoregulation After Stroke Through Lipoprotein-Related Receptor–Dependent Increase in cAMP and p38

“…Induction of photothrombosis was based on that described for the pig 19 , but in our studies we used the area of the closed cranial window to expose two to three main and 1–3 smaller arteries supplying the middle cerebral artery territory. Arterial occlusion was achieved by photothrombosis, in which a stable thrombus consisting of aggregating platelets, fibrin and other blood components is formed in response to endothelial peroxidative damage.…”

Novel plasminogen activator inhibitor-1-derived peptide protects against impairment of cerebrovasodilation after photothrombosis through inhibition of JNK MAPK

“…Induction of photothrombosis was based on that described for the newborn pig (11), but in our studies we used the area of the closed cranial window to expose two to three main and 1-3 smaller arteries supplying the middle cerebral artery territory. Arterial occlusion was achieved by photothrombosis, in which a stable thrombus consisting of aggregating platelets, fibrin and other blood components is formed in response to endothelial peroxidative damage.…”

Experimental Pediatric Arterial Ischemic Stroke Model Reveals Sex-specific Estrogen Signaling

“…However, there are currently few viable experimental models aimed at determining etiology and modeling pathophysiology of childhood-onset AIS. There is extensive experimental literature modeling ischemia in perinatal animals 3–5 and reports of pediatric stroke experiments in piglets 6 , with no reports of the use of rodents to model pediatric ischemia. The current study describes a variation of the middle cerebral artery occlusion (MCAO) model modified for use in juvenile mice (modeling pre-pubertal children), providing a powerful new experimental tool to begin to study the effects of ischemia in the immature brain.…”