High plasma complement C4 levels as a novel predictor of clinical outcome in intracerebral hemorrhage

Blood-brain barrier repair: potential and challenges of stem cells and exosomes in stroke treatment

Stroke is characterized with high morbidity, mortality and disability all over the world, and one of its core pathologies is blood-brain barrier (BBB) dysfunction. BBB plays a crucial physiological role in protecting brain tissues and maintaining homeostasis in central nervous system (CNS). BBB dysfunction serves as a key factor in the development of cerebral edema, inflammation, and further neurological damage in stroke patients. Currently, stem cells and their derived exosomes have shown remarkable potential in repairing the damaged BBB and improving neurological function after stroke. Stem cells repair the integrity of BBB through anti-inflammatory, antioxidant, angiogenesis and regulation of intercellular signaling mechanisms, while stem cell-derived exosomes, as natural nanocarriers, further enhance the therapeutic effect by carrying active substances such as proteins, RNAs and miRNAs. This review will present the latest research advances in stem cells and their exosomes in stroke treatment, as well as the challenges of cell source, transplantation timing, dosage, and route of administration in clinical application, aiming to discuss their mechanisms of repairing BBB integrity and potential for clinical application, and proposes future research directions. Stem cells and exosomes are expected to provide new strategies for early diagnosis and precise treatment of stroke, and promote breakthroughs in the field of stroke.

Potential blood biomarkers that can be used as prognosticators of spontaneous intracerebral hemorrhage: A systematic review and meta-analysis

BACKGROUND

Predicting nontraumatic spontaneous intracerebral hemorrhage (SICH) patient prognosis has been commonly practiced, particularly when providing informed consent and considering surgical treatment. Biomarkers might provide more real-time evaluation of SICH patients' condition than clinical prognostic scoring systems. This study aimed to evaluate the reliability of blood biomarkers in predicting prognosis in SICH patients by systematic review and meta-analysis.

METHODS

Studies that evaluated the association of blood biomarker(s) with mortality and/or functional outcome in SICH patients up to October 11, 2024, were identified through PubMed, Google Scholars, Scopus databases, and reference lists. Studies that satisfied the inclusion criteria were included in the meta-analyses. Good functional outcome was defined by patient's Glasgow Outcome Scale (GOS) ≥ 4 or modified Rankin scale mRS ≤ 2. Blood biomarkers were classified into the following categories: angiogenic factors, growth factors, inflammatory biomarkers, coagulation parameters, blood counts, and others. Individual meta-analysis was performed for every evaluation endpoint:7 days, 30 days, 3 months, 6 months, and 1 year. Meta-analyses were performed using Random Effect Mean-Difference with a 95% Confidence Interval for continuous data and visualized as forest plots in RevMan version 5.3 software. Cochrane Tool to Assess Risk of Bias in Cohort Studies was used to assess potential risk of bias of the included studies. GRADE Profiler was used to assess quality of evidence.

RESULTS

Seventy-seven studies fulfilled the inclusion criteria. Surviving SICH patients have significantly lower C-reactive protein (CRP), D-dimer, copeptin, S100β, white blood cell (WBC), monocyte, and glucose than non-surviving patients. SICH patients with good functional outcome have lower D-dimer, Interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), WBC count, neutrophil count, monocyte count, copeptin and significantly higher lymphocyte counts and calcium levels. Out of all blood biomarkers that were evaluated, only S100β and copeptin had very high effect size and high certainty of evidence.

CONCLUSION

It is interesting to notice that many blood biomarkers significantly associated with SICH patients' outcomes are related to inflammatory responses. This suggests that modulation of inflammation might be essential to improve SICH patients' prognosis. We confidently concluded that S100β and copeptin are the most reliable blood biomarkers that can be used as prognosticators in SICH patients. On other biomarkers, in addition to heterogeneities and inconsistencies, several factors might affect the conclusions of current meta-analysis; thus, future studies to increase the certainties of evidence and effect size on other biomarkers are crucial.

The Role of the Complement System in Synaptic Pruning after Stroke

Stroke is a serious disease that can lead to local neurological dysfunction and cause great harm to the patient's health due to blood cerebral circulation disorder. Synaptic pruning is critical for the normal development of the human brain, which makes the synaptic circuit completer and more efficient by removing redundant synapses. The complement system is considered a key player in synaptic loss and cognitive impairment in neurodegenerative disease. After stroke, the complement system is over-activated, and complement proteins can be labeled on synapses. Microglia and astrocytes can recognize and engulf synapses through corresponding complement receptors. Complement-mediated excessive synaptic pruning can cause post-stroke cognitive impairment (PSCI) and secondary brain damage. This review summarizes the latest progress of complement-mediated synaptic pruning after stroke and the potential mechanisms. Targeting complement-mediated synaptic pruning may be essential for exploring therapeutic strategies for secondary brain injury (SBI) and neurological dysfunction after stroke.

Current evidence of synaptic dysfunction after stroke: Cellular and molecular mechanisms

BACKGROUND

Stroke is an acute cerebrovascular disease in which brain tissue is damaged due to sudden obstruction of blood flow to the brain or the rupture of blood vessels in the brain, which can prompt ischemic or hemorrhagic stroke. After stroke onset, ischemia, hypoxia, infiltration of blood components into the brain parenchyma, and lysed cell fragments, among other factors, invariably increase blood-brain barrier (BBB) permeability, the inflammatory response, and brain edema. These changes lead to neuronal cell death and synaptic dysfunction, the latter of which poses a significant challenge to stroke treatment.

RESULTS

Synaptic dysfunction occurs in various ways after stroke and includes the following: damage to neuronal structures, accumulation of pathologic proteins in the cell body, decreased fluidity and release of synaptic vesicles, disruption of mitochondrial transport in synapses, activation of synaptic phagocytosis by microglia/macrophages and astrocytes, and a reduction in synapse formation.

CONCLUSIONS

This review summarizes the cellular and molecular mechanisms related to synapses and the protective effects of drugs or compounds and rehabilitation therapy on synapses in stroke according to recent research. Such an exploration will help to elucidate the relationship between stroke and synaptic damage and provide new insights into protecting synapses and restoring neurologic function.

Normobaric hyperoxia alleviates complement C3-mediated synaptic pruning and brain injury after intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease, and the complement cascade exacerbates brain injury after ICH. As the most abundant component of the complement system, complement component 3 (C3) plays essential roles in all three complement pathways. However, the effects of C3 on neurological impairment and brain injury in ICH patients and the related mechanism have not been fully elucidated. Normobaric hyperoxia (NBO) is regarded as a treatment for ICH patients, and recent clinical studies also have confirmed the neuroprotective role of NBO against acute ICH-mediated brain damage, but the underlying mechanism still remains elusive.

AIMS

In the present study, we investigated the effects of complement C3 on NBO-treated ICH patients and model mice, and the underlying mechanism of NBO therapy in ICH-mediated brain injury.

RESULTS

Hemorrhagic injury resulted in the high plasma C3 levels in ICH patients, and the plasma C3 levels were closely related to hemorrhagic severity and clinical outcomes after ICH. BO treatment alleviated neurologic impairments and rescued the hemorrhagic-induced increase in plasma C3 levels in ICH patients and model mice. Moreover, the results indicated that NBO exerted its protective effects of on brain injury after ICH by downregulating the expression of C3 in microglia and alleviating microglia-mediated synaptic pruning.

CONCLUSIONS

Our results revealed that NBO exerts its neuroprotective effects by reducing C3-mediated synaptic pruning, which suggested that NBO therapy could be used for the clinical treatment of ICH.

Revisiting the role of the complement system in intracerebral hemorrhage and therapeutic prospects

Intracerebral hemorrhage (ICH) is a stroke subtype characterized by non-traumatic rupture of blood vessels in the brain, resulting in blood pooling in the brain parenchyma. Despite its lower incidence than ischemic stroke, ICH remains a significant contributor to stroke-related mortality, and most survivors experience poor outcomes that significantly impact their quality of life. ICH has been accompanied by various complex pathological damage, including mechanical damage of brain tissue, hematoma mass effect, and then leads to inflammatory response, thrombin activation, erythrocyte lysis, excitatory amino acid toxicity, complement activation, and other pathological changes. Accumulating evidence has demonstrated that activation of complement cascade occurs in the early stage of brain injury, and the excessive complement activation after ICH will affect the occurrence of secondary brain injury (SBI) through multiple complex pathological processes, aggravating brain edema, and pathological brain injury. Therefore, the review summarized the pathological mechanisms of brain injury after ICH, specifically the complement role in ICH, and its related pathological mechanisms, to comprehensively understand the specific mechanism of different complements at different stages after ICH. Furthermore, we systematically reviewed the current state of complement-targeted therapies for ICH, providing a reference and basis for future clinical transformation of complement-targeted therapy for ICH.