Delayed recanalization in acute ischemic stroke patients: Late is better than never?

Delayed recanalization reduced neuronal apoptosis and neurological deficits by enhancing liver-derived trefoil factor 3-mediated neuroprotection via LINGO2/EGFR/Src signaling pathway after middle cerebral artery occlusion in rats

Delayed recanalization at days or weeks beyond the therapeutic window was shown to improve functional outcomes in acute ischemic stroke (AIS) patients. However, the underlying mechanisms remain unclear. Previous preclinical study reported that trefoil factor 3 (TFF3) was secreted by liver after cerebral ischemia and acted a distant neuroprotective factor. Here, we investigated the liver-derived TFF3-mediated neuroprotective mechanism enhanced by delayed recanalization after AIS. A total of 327 male Sprague-Dawley rats and the model of middle cerebral artery occlusion (MCAO) with permanent occlusion (pMCAO) or with delayed recanalization at 3 d post-occlusion (rMCAO) were used. Partial hepatectomy was performed within 5 min after MCAO. Leucine-rich repeat and immunoglobulin-like domain-containing nogo receptor-interacting protein 2 (LINGO2) siRNA was administered intracerebroventricularly at 48 h after MCAO. Recombinant rat TFF3 (rr-TFF3, 30 μg/Kg) or recombinant rat epidermal growth factor (rr-EGF, 100 μg/Kg) was administered intranasally at 1 h after recanalization, and EGFR inhibitor Gefitinib (75 mg/Kg) was administered intranasally at 30 min before recanalization. The evaluation of outcomes included neurobehavior, ELISA, western blot and immunofluorescence staining. TFF3 in hepatocytes and serum were upregulated in a similar time-dependent manner after MCAO. Compared to pMCAO, delayed recanalization increased brain TFF3 levels and attenuated brain damage with the reduction in neuronal apoptosis, infarct volume and neurological deficits. Partial hepatectomy reduced TFF3 levels in serum and ipsilateral brain hemisphere, and abolished the benefits of delayed recanalization on neuronal apoptosis and neurobehavioral deficits in rMCAO rats. Intranasal rrTFF3 treatment reversed the changes associated with partial hepatectomy. Delayed recanalization after MCAO increased the co-immunoprecipitation of TFF3 and LINGO2, as well as expressions of p-EGFR, p-Src and Bcl-2 in the brain. LINGO2 siRNA knockdown or EGFR inhibitor reversed the effects of delayed recanalization on apoptosis and brain expressions of LINGO2, p-EGFR, p-Src and Bcl-2 in rMCAO rats. EGFR activator abolished the deleterious effects of LINGO2 siRNA. In conclusion, our investigation demonstrated for the first time that delayed recanalization may enhance the entry of liver-derived TFF3 into ischemic brain upon restoring blood flow after MCAO, which attenuated neuronal apoptosis and neurological deficits at least in part via activating LINGO2/EGFR/Src pathway.

Persistent perfusion abnormalities at day 1 correspond to different clinical trajectories after stroke

BACKGROUND

Perfusion abnormalities after thrombolysis are frequent within and surrounding ischemic lesions, but their relative frequency is not well known.

OBJECTIVE

To describe the different patterns of perfusion abnormalities observed at 24 hours and compare the characteristics of the patients according to their perfusion pattern.

METHODS

From our thrombolysis registry, we included 226 consecutive patients with an available arterial spin labeling (ASL) perfusion sequence at day 1. We performed a blinded assessment of the perfusion status (hypoperfusion-h, hyperperfusion-H, or normal-N) in the ischemic lesion and in the surrounding tissue. We compared the time course of clinical recovery, the rate of arterial recanalization, and hemorrhagic transformations in the different perfusion profiles.

RESULTS

We identified seven different perfusion profiles at day 1. Four of these (h/h, h/H, H/H, and H/N) represented the majority of the population (84.1%). The H/H profile was the most frequent (34.5%) and associated with 3-month good outcome (modified Rankin Scale (mRS): 63.5%). Patients with persistent hypoperfusion within and outside the lesion (h/h, 12.4%) exhibited worse outcomes after treatment (mRS score 0-2: 23.8%) than other patients, were less frequently recanalized (40.7%), and had more parenchymal hematoma (17.8%). The h/H profile had an intermediate clinical trajectory between the h/h profile and the hyperperfused profiles.

CONCLUSION

ASL hypoperfusion within the infarct and the surrounding tissue was associated with poor outcome. A more comprehensive view of the mechanisms in the hypoperfused surrounding tissue could help to design new therapeutic approaches during and after reperfusion therapies.

Three Days Delayed Recanalization Improved Neurological Function in pMCAO Rats by Increasing M2 Microglia-Possible Involvement of the IL-4R/STAT6/PPARγ Pathway

Current approved therapies for acute ischemic stroke have a restricted therapeutic time window. Delayed recanalization, which has been utilized clinically in patients who have missed the time window for administration, may be a promising alternative for stroke patients. However, the underlying molecular mechanisms remain undiscovered. Herein, we hypothesized that delayed recanalization would increase M2 microglial polarization through the IL-4R (interleukin-4 receptor)/STAT6 (signal transducer and activators of transcription 6)/PPARγ (peroxisome proliferator-activated receptor γ) pathway, subsequently promoting stroke recovery in rats. The permanent middle cerebral artery occlusion (pMCAO) model was induced via intravascular filament insertion. Recanalization was induced by withdrawing the filament at 3 days after MCAO (rMCAO). Interleukin (IL)-4 was administered intranasally at 3 days after pMCAO. AS1517499, a specific STAT6 inhibitor, was administered intranasally at 3 days after MCAO induction. Immunofluorescence staining, enzyme-linked immunosorbent assay (ELISA), western blot analysis, volumetric measurements of brain infarct, and neurological behavior tests were conducted. Delayed recanalization at 3 days after MCAO increased the polarization of M2 microglia, decreased inflammation, and improved neurological behavior. IL-4 treatment administered on the 3rd day after pMCAO increased M2 microglial polarization, improved neurological behavior, and reduced infarction volume of pMCAO rats. The inhibition of STAT6 decreased the level of p-STAT6 and PPARγ in rats treated with delayed recanalization. Delayed recanalization improved neurological function by increasing microglial M2 polarization, possibly involved with the IL-4R/STAT6/PPARγ pathway after MCAO in rats.

Delayed revascularization in acute ischemic stroke patients

Stroke shares a significant burden of global mortality and disability. A significant decline in the quality of life is attributed to the so-called post-stroke cognitive impairment including mild to severe cognitive alterations, dementia, and functional disability. Currently, only two clinical interventions including pharmacological and mechanical thrombolysis are advised for successful revascularization of the occluded vessel. However, their therapeutic effect is limited to the acute phase of stroke onset only. This often results in the exclusion of a significant number of patients who are unable to reach within the therapeutic window. Advances in neuroimaging technologies have allowed better assessment of salvageable penumbra and occluded vessel status. Improvement in diagnostic tools and the advent of intravascular interventional devices such as stent retrievers have expanded the potential revascularization window. Clinical studies have demonstrated positive outcomes of delayed revascularization beyond the recommended therapeutic window. This review will discuss the current understanding of ischemic stroke, the latest revascularization doctrine, and evidence from clinical studies regarding effective delayed revascularization in ischemic stroke.

Deep learning-based identification of acute ischemic core and deficit from non-contrast CT and CTA

The accurate identification of irreversible infarction and salvageable tissue is important in planning the treatments for acute ischemic stroke (AIS) patients. Computed tomographic perfusion (CTP) can be used to evaluate the ischemic core and deficit, covering most of the territories of anterior circulation, but many community hospitals and primary stroke centers do not have the capability to perform CTP scan in emergency situation. This study aimed to identify AIS lesions from widely available non-contrast computed tomography (NCCT) and CT angiography (CTA) using deep learning. A total of 345AIS patients from our emergency department were included. A multi-scale 3D convolutional neural network (CNN) was used as the predictive model with inputs of NCCT, CTA, and CTA+ (8 s delay after CTA) images. An external cohort with 108 patients was included to further validate the generalization performance of the proposed model. Strong correlations with CTP-RAPID segmentations (r = 0.84 for core, r = 0.83 for deficit) were observed when NCCT, CTA, and CTA+ images were all used in the model. The diagnostic decisions according to DEFUSE3 showed high accuracy when using NCCT, CTA, and CTA+ (0.90±0.04), followed by the combination of NCCT and CTA (0.87±0.04), CTA-alone (0.76±0.06), and NCCT-alone (0.53±0.09).

Neuroimaging Markers of Cerebral Small Vessel Disease on Hemorrhagic Transformation and Functional Outcome After Intravenous Thrombolysis in Patients With Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

Objective: The aim of this study was to perform a systematic review and meta-analysis to assess whether cerebral small vessel disease (CSVD) on neuroimaging of patients with acute ischemic stroke (AIS) treated with intravenous thrombolysis (IVT) is associated with an increased risk of hemorrhagic transformation (HT), symptomatic intracranial hemorrhage (sICH), and poor functional outcome (PFO). Methods: A thorough search of several databases was carried out to identify relevant studies up to December 2020. We included studies of patients with AIS and neuroimaging markers of CSVD treated with IVT. The primary outcome was HT, and the secondary outcomes were sICH and 3-month PFO. The quality of the studies involved was evaluated using the Newcastle-Ottawa Scale (NOS). The meta-analysis with the fixed effects model was performed. Results: Twenty-four eligible studies (n = 9,419) were pooled in the meta-analysis. All included studies were regarded as high quality with the NOS scores of at least 6 points. The meta-analysis revealed associations between the presence of CSVD and HT, sICH, and the 3-month PFO after IVT. Compared with no CSVD, the presence of CSVD was associated with an increased risk of HT (OR: 1.81, 95% CI: 1.52-2.16), sICH (OR: 2.42, 95% CI: 1.76-3.33), and 3-month PFO (OR: 2.15, 95% CI: 1.89-2.44). For patients with AIS complicated with CSVD, compared with a CSVD score of 0-1, a CSVD score of 2-4 was associated with an increased risk of HT (OR: 3.10, 95% CI: 1.67-5.77), sICH (OR: 2.86, 95% CI: 1.26-6.49), and 3-month PFO (OR: 4.58, 95% CI: 2.97-7.06). Conclusion: Patients with AIS complicated with neuroimaging markers of CSVD are at increased risk of HT and 3-month PFO after IVT. However, it is still necessary to clarify the exact role of CSVD in the occurrence, development, and prognosis of AIS. Systematic Review Registration: www.ClinicalTrials.gov, identifier CRD4202123 3900.

Variants of WNT7A and GPR124 are associated with hemorrhagic transformation following intravenous thrombolysis in ischemic stroke

AIMS

The canonical Wnt signaling pathway plays an essential role in blood-brain barrier integrity and intracerebral hemorrhage in preclinical stroke models. Here, we sought to explore the association between canonical Wnt signaling and hemorrhagic transformation (HT) following intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients as well as to determine the underlying cellular mechanisms.

METHODS

355 consecutive AIS patients receiving IVT were included. Blood samples were collected on admission, and HT was detected at 24 hours after IVT. 117 single-nucleotide polymorphisms (SNPs) of 28 Wnt signaling genes and exon sequences of 4 core cerebrovascular Wnt signaling components (GPR124, RECK, FZD4, and CTNNB1) were determined using a customized sequencing chip. The impact of identified genetic variants was further studied in HEK 293T cells using cellular and biochemical assays.

RESULTS

During the study period, 80 patients experienced HT with 27 parenchymal hematoma (PH). Compared to the non-PH patients, WNT7A SNPs (rs2163910, P = .001, OR 2.727; rs1124480, P = .002, OR 2.404) and GPR124 SNPs (rs61738775, P = .012, OR 4.883; rs146016051, P < .001, OR 7.607; rs75336000, P = .044, OR 2.503) were selectively enriched in the PH patients. Interestingly, a missense variant of GPR124 (rs75336000, c.3587G>A) identified in the PH patients resulted in a single amino acid alteration (p.Cys1196Tyr) in the intracellular domain of GPR124. This variant substantially reduced the activity of WNT7B-induced canonical Wnt signaling by decreasing the ability of GPR124 to recruit cytoplasmic DVL1 to the cellular membrane.

CONCLUSION

Variants of WNT7A and GPR124 are associated with increased risk of PH in patients with AIS after intravenous thrombolysis, likely through regulating the activity of canonical Wnt signaling.

Image-guided delayed recanalization of middle cerebral artery occlusion

Recent advance in devices, techniques, and peri-procedural patient management in the conduct of mechanical thrombectomy enables neuro-interventionists to recanalize occluded cerebral arteries with greater efficiency and safety than ever. It is conceivable that there exist a group of stroke patients who would benefit from recanalization beyond 24-h time window following the onset of symptom, if viable brain tissue remains at that time. We report a case of a 56-year-old patient who received mechanical thrombectomy 96 h after the onset of symptoms by diffusion/perfusion imaging. The application of advanced neuroimaging and analytical software can accurately estimate viable brain tissue, which enables clinicians to implement individualized therapeutic strategies for patients with acute stroke.

Delayed recanalization after MCAO ameliorates ischemic stroke by inhibiting apoptosis via HGF/c-Met/STAT3/Bcl-2 pathway in rats

The activation of tyrosine kinase receptor c-Met by hepatocyte growth factor (HGF) showed an anti-apoptotic effect in numerous disease models. This study aimed to investigate the neuroprotective mechanism of the HGF/c-Met axis-mediated anti-apoptosis underlying the delayed recanalization in a rat model of middle cerebral artery occlusion (MCAO). Permanent MCAO model (pMCAO) was induced by intravascular filament insertion. Recanalization was induced by withdrawing the filament at 3 days after MCAO (rMCAO). HGF levels in the blood serum and brain tissue expressions of HGF, c-Met, phosphorylated-STAT3 (p-STAT3), STAT3, Bcl-2, Bax, cleaved caspase-3(CC3) were assessed using ELISA and western blot, respectively. To study the mechanism, HGF small interfering ribonucleic acid (siRNA) and c-Met inhibitor, su11274, were administered intracerebroventricularly (i.c.v.) or intranasally, respectively. The concentration of HGF in the serum was increased significantly after MCAO. Brain expression of HGF was increased after MCAO and peaked at 3 days after recanalization. HGF and c-Met were both co-localized with neurons. Compared to rats received permanent MCAO, delayed recanalization after MCAO decreased the infarction volume, inhibited neuronal apoptosis, and improved neurobehavioral function, increased expressions of p-STAT3 and its downstream Bcl-2. Mechanistic studies indicated that HGF siRNA and su11274 reversed the neuroprotection including anti-apoptotic effects provided by delayed recanalization. In conclusion, the delayed recanalization after MCAO increased the expression of HGF in the brain, and reduced the infarction and neuronal apoptosis after MCAO, partly via the activation of the HGF/c-Met/STAT3/Bcl-2 signaling pathway. The delayed recanalization may serve as a therapeutic alternative for a subset of ischemic stroke patients.