Molecular magnetic resonance imaging discloses endothelial activation after transient ischaemic attack

Abstract

About 20% of patients with ischaemic stroke have a preceding transient ischaemic attack, which is clinically defined as focal neurological symptoms of ischaemic origin resolving spontaneously. Failure to diagnose transient ischaemic attack is a wasted opportunity to prevent recurrent disabling stroke. Unfortunately, diagnosis can be difficult, due to numerous mimics, and to the absence of a specific test. New diagnostic tools are thus needed, in particular for radiologically silent cases, which correspond to the recommended tissue-based definition of transient ischaemic attack. As endothelial activation is a hallmark of cerebrovascular events, we postulated that this may also be true for transient ischaemic attack, and that it would be clinically relevant to develop non-invasive in vivo imaging to detect this endothelial activation. Using transcriptional and immunohistological analyses for adhesion molecules in a mouse model, we identified brain endothelial P-selectin as a potential biomarker for transient ischaemic attack. We thus developed ultra-sensitive molecular magnetic resonance imaging using antibody-based microparticles of iron oxide targeting P-selectin. This highly sensitive imaging strategy unmasked activated endothelial cells after experimental transient ischaemic attack and allowed discriminating transient ischaemic attack from epilepsy and migraine, two important transient ischaemic attack mimics. We provide preclinical evidence that combining conventional magnetic resonance imaging with molecular magnetic resonance imaging targeting P-selectin might aid in the diagnosis of transient ischaemic attack.

Alcohol exposure–induced neurovascular inflammatory priming impacts ischemic stroke and is linked with brain perivascular macrophages

“…Vascular adhesion molecular imaging. MPIOs (diameter 1.08 mm) (Invitrogen) covalently conjugated to purified polyclonal goat anti-mouse antibodies for P-selectin (R&D Systems, clone AF737) were prepared as previously described (46). Details are provided in the Supplemental Methods.…”

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

“…Progressively increasing leukocyte plugging has already been shown in skeletal and myocardial muscle after ischemia and reperfusion, increasing microvascular resistance, negatively affecting the blood flow (68)(69)(70). Neutrophils have previously been shown to increase their endothelial adhesion after stroke (38,71) and occlude the capillary bed (72). Endothelial adhesion molecules like VCAM1 and P-selectin are rapidly upregulated under ischemic conditions as a possible trigger for increased leukocyte-endothelium interactions (38,(73)(74)(75).…”

“…Neutrophils have previously been shown to increase their endothelial adhesion after stroke (38,71) and occlude the capillary bed (72). Endothelial adhesion molecules like VCAM1 and P-selectin are rapidly upregulated under ischemic conditions as a possible trigger for increased leukocyte-endothelium interactions (38,(73)(74)(75). Neutrophils can extend tissue injury by permanently occluding capillaries and also by releasing proteases after their recruitment and passage into the brain parenchyma (14,15,72,76,77).…”

“…We utilized a mouse model of transient dMCAO by applying mechanical compression with a device made by fusing two glass micropipettes with blunted tips (Fig1/a-c), with slight modifications of a previously reported model (23,37,38) that ensured stable occlusions for 60 minutes. This technique also avoided nonspecific intracranial pressure effects as shown by sham experiments (see below).…”

“…This technique also avoided nonspecific intracranial pressure effects as shown by sham experiments (see below). Complete recanalization of dMCA was achieved simply by release of the compression after 1 hour, without any requirement for a thrombolytic agent (23,38). Cerebral blood flow was continuously monitored during experiments by real-time laser speckle contrast imaging to ensure successful occlusion and recanalization (Supplementary Movies 1 and 2, Fig2/ac).…”