Neutrophil-mediated dynamic capillary stalls in ischemic penumbra: persistent traffic jams after reperfusion contribute to injury

Abstract

the study objectives, designed and performed the experiments, acquired, processed and analyzed the data, wrote the manuscript. J.T. set up and optimized the OCT equipment, wrote acquisition codes and processing algorithms. K.K. designed surgical procedures and performed experiments. D.P set up and optimized the laser speckle imaging equipment, S.K wrote data analysis codes, analyzed data. A.C and J.G. set up and optimized two-photon microscope, prepared data analysis codes and performed the experiments. T.V. performed experiments, acquired and analyzed data. S.S. and C.B.S. contributed to study objectives and experimental design and critically evaluated the manuscript. D.A.B. supervised the project in overall, contributed to study objectives and experimental design, and critically evaluated the manuscript. AbstractEver since the introduction of thrombolysis and the subsequent expansion of endovascular treatments for acute ischemic stroke, it remains to be identified why the actual outcomes are less favorable despite recanalization. Here, by high spatio-temporal resolution imaging of capillary circulation in mice, we introduce the pathological phenomenon of dynamic flow stalls in cerebral capillaries, occurring persistently in the salvageable penumbra after recanalization. These stalls, which are distinct from permanent cellular plugs that can lead to no-flow, were temporarily and repetitively occurring in the capillary network, impairing the overall circulation like small focal traffic jams. In vivo microscopy in the ischemic penumbra revealed leukocytes traveling through capillary lumen or getting stuck, while red blood cell flow was being disturbed in the neighboring segments, within 3 hours after stroke onset. Stall dynamics could be modulated, by injection of an anti-Ly6G antibody specifically targeting neutrophils. By decreasing the number and duration of stalls, we were able to improve the blood flow in the penumbra within 2-24 hours after reperfusion, increase capillary oxygenation, decrease cellular damage and improve functional outcome. Thereby the dynamic microcirculatory stall phenomenon contributes to the ongoing penumbral injury and is a potential hyperacute stage mechanism adding on previous observations of detrimental effects of activated neutrophils in ischemic stroke. SignificanceThis work provides in vivo evidence that, even in perfused capillaries, abnormal capillary flow patterns in the form of dynamic stalls can contribute to ongoing tissue injury in the salvageable penumbra in very early hours of cerebral ischemia. These events resembling micro traffic jams in a complex road network, are mediated by passage of neutrophils through the microcirculation and persist despite recanalization of the occluded artery.

Increased capillary stalling is associated with endothelial glycocalyx loss in subcortical vascular dementia

“…Recent studies have revealed the significance of capillary stalling in aging, stroke, Alzheimer's disease, polycythemia and thrombocythemia 3,4,5,6,11,21,22,23 . In fact, capillary stalling largely impacts on CBF, and cognitive functions can be improved by suppressing capillary stalling in Alzheimer's disease 6,24 .…”

“…An increased number of stalled segments has been reported in several neurological diseases, such as Alzheimer's disease and stroke 6,11 . Here, we investigated capillary stalling in a model of subcortical vascular dementia (SVaD).…”

Increased capillary stalling is associated with endothelial glycocalyx loss in subcortical vascular dementia

“…5 Capillary stalling plays a role in aging, stroke, Alzheimer’s disease, polycythemia, and thrombocythemia. 2–9 While previous studies have shown that capillary stalling is induced by leukocyte plugging, its underlying mechanism needs to be corroborated. 5,10…”

“…5 Capillary stalling plays a role in aging, stroke, Alzheimer's disease, polycythemia, and thrombocythemia. [2][3][4][5][6][7][8][9] While previous studies have shown that capillary stalling is induced by leukocyte plugging, its underlying mechanism needs to be corroborated. 5,10 The endothelial glycocalyx (EG), a layer of proteoglycans and glycoproteins on the luminal side of the vessels, plays an important role in the maintenance of proper microcirculation.…”

Neutrophil dynamics and inflammaging in acute ischemic stroke: A transcriptomic review

“…However, in IS, leukocytes, and specifically neutrophils, may clog the capillaries and disrupt blood flow (Doerschuk et al, 1993). Impeding inflammatory responses and, recently, reducing these neutrophil stalls have been shown to ameliorate injury in animal stroke models (Cuartero et al, 2013;Drieu et al, 2018;Kelly et al, 2018;El Amki et al, 2020;Erdener et al, 2021). For instance, inhibiting CXCR1 and CXCR2 in rat MCAO model, which are among the biomarkers of inflammation, improves behavioral measures, reduces ischemic brain damage, and decreases IL-1β level in the brain (Villa et al, 2007).…”