Michelle Y. Cheng

Background: Acute hyperglycemia affects approximately 40% of stroke patients and is associated with worse outcomes. The underlying mechanisms linking this metabolic stress to stroke-induced brain injury remains unclear, and effective therapies are lacking. Methods: In a mouse model of acute hyperglycemic stroke, luminal disruption, blood-brain barrier (BBB) leakage, neurological deficit, motor function, and mortality were evaluated. Vascular luminal glycocalyx and complement activation were assessed by immunostaining, with glycocalyx loss confirmed by electron microscopy. Complement C3’s causal role was tested using C3 knockout mice and site-targeted inhibition with CR2-Crry. To enhance translational relevance, post-mortem human stroke and control brains were immunostained to assess the association between endothelial glycocalyx loss and vascular complement activation. In a separate stroke patient cohort, soluble complement activation products were measured in pre-thrombectomy plasma, and their predictive value for modified Rankin Scale (mRS) outcomes evaluated using elastic net regression. Results: Hyperglycemic stroke mice exhibited accelerated and more severe BBB breakdown, greater functional deficits, and higher mortality than normoglycemic controls, mirroring clinical observations. Acute hyperglycemia triggered rapid vascular luminal injury characterized by loss of endothelial luminal glycocalyx, luminal IgM/IgG deposition, and vascular complement C3 activation, leading to BBB disruption. This vascular luminal injury was corroborated in human stroke brain tissue. These luminal changes persisted despite glucose normalization and were exacerbated by reperfusion, driving injury into the brain parenchyma. Genetic and pharmacological approaches confirmed vascular complement activation as a causal driver of severe BBB disruption and poor outcomes. Importantly, site-targeted pharmacological inhibition of complement after reperfusion preserved BBB integrity and improved outcomes, defining a time-specific, luminal-directed strategy as a promising adjunct to thrombectomy. Notably, soluble complement activation markers in pre-thrombectomy stroke plasma predicted clinical outcomes, highlighting their potential as pre-intervention markers for patient stratification and tailored therapy. Conclusion: This study reframes acute hyperglycemic stroke as a vascular luminal disorder, establishing a novel Metabolic–Complement–Vascular (MCV) axis linking metabolic stress to endothelial luminal glycocalyx loss, vascular complement activation, and BBB breakdown in both mice and humans. This new mechanistic understanding transforms the therapeutic landscape of hyperglycemic stroke, offering a potential time-defined, luminal-focused adjunct therapy alongside thrombectomy. Clinical Perspective: What Is New?: - This study reframes hyperglycemic stroke as an acute vascular luminal problem, marked by rapid loss of endothelial luminal glycocalyx and complement C3 activation at the vascular luminal surface. - The rapid luminal changes, identified in both rodent and human stroke brain tissues, establish a novel Metabolic–Complement–Vascular (MCV) axis linking metabolic stress to luminal damage, blood-brain barrier (BBB) breakdown, and injury progression into the brain parenchyma. - The first clinical evidence that pre-thrombectomy plasma complement activation markers independently predict stroke outcomes — laying the foundation for risk stratification before reperfusion and precision adjunct therapies. What Are the Clinical Implications?: - The rapidity and persistence of the MCV axis activation—even after glucose normalization—help explain the limited efficacy of insulin therapy, shifting the therapeutic focus from glycemic control to luminal-targeted interventions. - Identification of a narrow but actionable window following reperfusion where complement C3 inhibition preserves the BBB and limits injury progression to the parenchyma, offers a promising adjunct to thrombectomy in metabolically vulnerable stroke patients. - Targeting the vascular luminal surface reshapes the therapeutic landscape for hyperglycemic stroke by enabling systemic interventions—bypassing the challenge of BBB penetration, supporting rapid clinical translation using existing FDA-approved C3 inhibitors, and framing the endothelial glycocalyx as a promising area for therapeutic and diagnostic exploration in hyperglycemic stroke and broader cerebrovascular disease.

Moyamoya disease (MMD) is a chronic cerebrovascular disorder that can lead to stroke and neurological dysfunctions. Given the largely sporadic nature and the role of gene-environment interactions in various diseases, we examined epigenetic modifications in MMD. We performed genome-wide DNA methylation using Illumina 850 K Methylation EPIC BeadChip, in two racially distinct adult female cohorts: a non-Asian cohort (13 MMD patients and 7 healthy controls) and an Asian cohort (14 MMD patients and 3 healthy controls). An additional external cohort with both sexes (females: 5 MMD patients and 5 healthy controls, males: 5 MMD patients and 5 healthy controls) was included for validation. Our findings revealed strikingly low DNA methylation variability between MMD patients and healthy controls, in both MMD female cohorts. In the non-Asian cohort, only 6 probes showed increased variability versus 647 probes that showed decreased variability. Similarly, in the Asian cohort, the MMD group also displayed a reduced methylation variability across all 2845 probes. Subsequent analysis showed that these differentially variable probes are located on genes involved in key biological processes such as methylation and transcription, DNA repair, cytoskeletal remodeling, natural killer cell signaling, cellular growth, and migration. These findings mark the first observation of low methylation variability in any disease, contrasting with the high variability observed in other disorders. This reduced methylation variability in MMD may hinder patients’ adaptability to environmental shifts, such as hemodynamic stress, thereby influencing vascular homeostasis and contributing to MMD pathology. These findings offer new insights into the mechanisms of MMD and potential treatment strategies.

Optogenetic fMRI highlights the involvement of corticothalamic circuit as an early mediator of recovery after stroke.

Background and Purpose: Stroke disrupts neuronal functions in both local and remotely connected regions, leading to network-wide deficits that can hinder recovery. The thalamus is particularly affected, with progressive development of neurodegeneration accompanied by inflammatory responses. However, the complexity of the involved inflammatory responses is poorly understood. Herein we investigated the spatiotemporal changes in the secondary degenerative thalamus after cortical stroke, using targeted transcriptome approach in conjunction with histology and flow cytometry. Methods: Cortical ischemic stroke was generated by permanent occlusion of the left middle cerebral artery in male C57BL6J mice. Neurodegeneration, neuroinflammatory responses, and microglial activation were examined in naive and stroke mice at from poststroke days (PD) 1 to 84, in both ipsilesional somatosensory cortex and ipsilesional thalamus. NanoString neuropathology panel (780 genes) was used to examine transcriptome changes at PD7 and PD28. Fluorescence activated cell sorting was used to collect CD11c ⁺ microglia from ipsilesional thalamus, and gene expressions were validated by quantitative real-time polymerase chain reaction. Results: Neurodegeneration in the thalamus was detected at PD7 and progressively worsened by PD28. This was accompanied by rapid microglial activation detected as early as PD1, which preceded the neurodegenerative changes. Transcriptome analysis showed higher number of differentially expressed genes in ipsilesional thalamus at PD28. Notably, neuroinflammation was the top activated pathway, and microglia was the most enriched cell type. Itgax (CD11c) was the most significantly increased gene, and its expression was highly detected in microglia. Flow-sorted CD11c ⁺ microglia from degenerative thalamus indicated molecular signatures similar to neurodegenerative disease–associated microglia; these included downregulated Tmem119 and CX3CR1 and upregulated ApoE, Axl, LpL, CSF1, and Cst7. Conclusions: Our findings demonstrate the dynamic changes of microglia after stroke and highlight the importance of investigating stroke network-wide deficits. Importantly, we report the existence of a unique subtype of microglia (CD11c ⁺ ) with neurodegenerative disease–associated microglia features in the degenerative thalamus after stroke.

Post-stroke optogenetic stimulation has been shown to enhance neurovascular coupling and functional recovery. Neuronal nitric oxide synthase (nNOS) has been implicated as a key regulator of the neurovascular response in acute stroke; however, its role in subacute recovery remains unclear. We investigated the expression of nNOS in stroke mice undergoing optogenetic stimulation of the contralesional lateral cerebellar nucleus (cLCN). We also examined the effects of nNOS inhibition on functional recovery using a pharmacological inhibitor targeting nNOS. Optogenetically stimulated stroke mice demonstrated significant improvement on the horizontal rotating beam task at post-stroke days 10 and 14. nNOS mRNA and protein expression was significantly and selectively decreased in the contralesional primary motor cortex (cM1) of cLCN-stimulated mice. The nNOS expression in cM1 was negatively correlated with improved recovery. nNOS inhibitor (ARL 17477)-treated stroke mice exhibited a significant functional improvement in speed at post-stroke day 10, when compared to stroke mice receiving vehicle (saline) only. Our results show that optogenetic stimulation of cLCN and systemic nNOS inhibition both produce functional benefits after stroke, and suggest that nNOS may play a maladaptive role in post-stroke recovery.

Stroke is one of the major causes of chronic disability worldwide and increasing efforts have focused on studying brain repair and recovery after stroke. Following stroke, the primary injury site can disrupt functional connections in nearby and remotely connected brain regions, resulting in the development of secondary injuries that may impede long-term functional recovery. In particular, secondary degenerative injury occurs in the connected ipsilesional thalamus following a cortical stroke. Although secondary thalamic injury was first described decades ago, the underlying mechanisms still remain unclear. We performed a systematic literature review using the NCBI PubMed database for studies that focused on the secondary thalamic degeneration after cortical ischemic stroke. In this review, we discussed emerging studies that characterized the pathological changes in the secondary degenerative thalamus after stroke; these included excitotoxicity, apoptosis, amyloid beta protein accumulation, blood-brain-barrier breakdown and inflammatory responses. In particular, we highlighted key findings of the dynamic inflammatory responses in the secondary thalamic injury and discussed the involvement of several cell types in this process. We also discussed studies that investigated the effects of blocking secondary thalamic injury on inflammatory responses and stroke outcome. Targeting secondary injuries after stroke may alleviate network-wide deficits, and ultimately promote stroke recovery.

3D histology, slice-based connectivity atlases, and diffusion MRI are common techniques to map brain wiring. While there are many modality-specific tools to process these data, there is a lack of integration across modalities. We develop an automated resource that combines histologically cleared volumes with connectivity atlases and MRI, enabling the analysis of histological features across multiple fiber tracts and networks, and their correlation within-vivobiomarkers. We apply our pipeline in a murine stroke model, demonstrating not only strong correspondence between MRI abnormalities and CLARITY-tissue staining, but also uncovering acute cellular effects in areas connected to the ischemic core. We provide improved maps of connectivity by quantifying projection terminals from CLARITY viral injections, and integrate diffusion MRI with CLARITY viral tracing to compare connectivity maps across scales. Finally, we demonstrate tract-level histological changes of stroke through this multimodal integration. This resource can propel investigations of network alterations underlying neurological disorders.

The cerebellum is best known for its role in controlling motor behaviors. However, recent work supports the view that it also influences non-motor behaviors. The contribution of the cerebellum towards different brain functions is underscored by its involvement in a diverse and increasing number of neurological and neuropsychiatric conditions including ataxia, dystonia, essential tremor, Parkinson’s disease (PD), epilepsy, stroke, multiple sclerosis, autism spectrum disorders, dyslexia, attention deficit hyperactivity disorder (ADHD), and schizophrenia. Although there are no cures for these conditions, cerebellar stimulation is quickly gaining attention for symptomatic alleviation, as cerebellar circuitry has arisen as a promising target for invasive and non-invasive neuromodulation. This consensus paper brings together experts from the fields of neurophysiology, neurology, and neurosurgery to discuss recent efforts in using the cerebellum as a therapeutic intervention. We report on the most advanced techniques for manipulating cerebellar circuits in humans and animal models and define key hurdles and questions for moving forward.

SUMMARY: Magnetic particle imaging is an emerging tomographic technique with the potential for simultaneous high-resolution, high-sensitivity, and real-time imaging. Magnetic particle imaging is based on the unique behavior of superparamagnetic iron oxide nanoparticles modeled by the Langevin theory, with the ability to track and quantify nanoparticle concentrations without tissue background noise. It is a promising new imaging technique for multiple applications, including vascular and perfusion imaging, oncology imaging, cell tracking, inflammation imaging, and trauma imaging. In particular, many neuroimaging applications may be enabled and enhanced with magnetic particle imaging. In this review, we will provide an overview of magnetic particle imaging principles and implementation, current applications, promising neuroimaging applications, and practical considerations.