Novel subsets of peripheral immune cells associated with promoting stroke recovery in mice.

AIMS: Peripheral immune cells infiltrating into the brain trigger neuroinflammation after an ischemic stroke. Partial immune cells reprogram their function for neural repair. Which immune cells promote ischemic brain recovery needs further identification. METHODS: We performed single-cell transcriptomic profiling of CD45high immune cells isolated from the ischemic hemisphere at subacute (5 days) and chronic (14 days) stages after ischemic stroke. RESULTS: A subset of phagocytic macrophages was associated with neuron projection regeneration and tissue remodeling. We also identified a unique type of T cells with highly expressed macrophage markers, including C1q, Apoe, Hexb, and Fcer1g, which showed high abilities in tissue remodeling, myelination regulation, wound healing, and anti-neuroinflammation. Moreover, natural killer cells decreased cytotoxicity and increased energy and metabolic function in the chronic stage after ischemic stroke. Two subgroups of neutrophils upregulated CCL signals to recruit peripheral immune cells and released CXCL2 to keep self-recruiting at the chronic stage. CONCLUSIONS: We identified subsets of peripheral immune cells that may provide potential therapeutic targets for promoting poststroke recovery.

Regulatory T Cells Secrete IL10 to Suppress Neuroinflammation in Early Stage after Subarachnoid Hemorrhage.

Objective: Accumulating evidence supports neuroprotective effects of regulatory T cells (Tregs) in response to brain injury. However, the precise mechanisms underlying the beneficial effects of Tregs on suppressing neuroinflammation after subarachnoid hemorrhage (SAH) remain unclear. Methods: We performed flow cytometry to detect the infiltration of Tregs into the brain at different time points after SAH. Behavioral tests, including Adhesive and Rotarod, were performed to assess neurological deficits in mice after SAH. Bulk RNA sequencing was used to investigate the transcriptomic change of Tregs infiltrating into the brain after SAH. qPCR was performed to verify the variation of inflammatory cytokines expression in the brain after Tregs exogenous infusion. FoxP3-DTR mice and Il10 gene KO mice were used to explore the mechanism of Tregs inhibiting neuron apoptosis after infiltrating the brain following SAH onset. Results: Peripheral Tregs infiltrated into the brain one day after SAH and gradually accumulated in the hemorrhagic hemisphere. An exogenous infusion of Tregs significantly improved the neurological function of mice after SAH, while poor recovery of neurological function was observed in Tregs depletion mice. Transcriptome sequencing data suggested that the immunosuppressive function of brain-infiltrated Tregs was significantly upregulated. qPCR showed that the expression of pro-inflammatory cytokines decreased in the brain of SAH mice after exogenous Tregs infusion. Bioinformatic analysis revealed that IL-10 and other cytokines secreted by brain-infiltrated Tregs were upregulated after SAH. Moreover, exogenous infusion of Il10 gene KO Tregs did not totally improve neurological function in SAH mice. Conclusions: Tregs infiltrated into the brain in the early stage after SAH and exerted neuroprotective effect by secreting IL-10 to suppress neuroinflammation and reduce neuron apoptosis.

Microglia and Neuroinflammation: Crucial Pathological Mechanisms in Traumatic Brain Injury-Induced Neurodegeneration.

Traumatic brain injury (TBI) is one of the most common diseases in the central nervous system (CNS) with high mortality and morbidity. Patients with TBI usually suffer many sequelae in the life time post injury, including neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, the pathological mechanisms connecting these two processes have not yet been fully elucidated. It is important to further investigate the pathophysiological mechanisms underlying TBI and TBI-induced neurodegeneration, which will promote the development of precise treatment target for these notorious neurodegenerative consequences after TBI. A growing body of evidence shows that neuroinflammation is a pivotal pathological process underlying chronic neurodegeneration following TBI. Microglia, as the immune cells in the CNS, play crucial roles in neuroinflammation and many other CNS diseases. Of interest, microglial activation and functional alteration has been proposed as key mediators in the evolution of chronic neurodegenerative pathology following TBI. Here, we review the updated studies involving phenotypical and functional alterations of microglia in neurodegeneration after injury, survey key molecules regulating the activities and functional responses of microglia in TBI pathology, and explore their potential implications to chronic neurodegeneration after injury. The work will give us a comprehensive understanding of mechanisms driving TBI-related neurodegeneration and offer novel ideas of developing corresponding prevention and treatment strategies for this disease.

Efficacy and Safety of Botulinum Toxin vs. Placebo in Depression: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background: Major depressive disorder (MDD) is a serious mental disorder that represents a substantial public health problem. Several trials have been undertaken to investigate the role of botulinum toxin type A (BTX-A) in the treatment of MDD, but the conclusions were controversial. To examine the efficacy and safety of BTX-A vs. placebo on patients with a clinical diagnosis of MDD, we conducted this systematic review and meta-analysis. Methods: A systematic search was conducted for all relevant randomized controlled trials (RCTs) in PubMed and Web of Science from inception to June 17, 2020. All published studies that investigated the efficacy and safety of BTX-A injections on patients with a clinical diagnosis of MDD were included. The overall effect size was summarized using a random-effects meta-analysis model. The primary outcomes of the present meta-analysis were the changes in depressive rating scale at week 6 after BTX-A injection compared with placebo. The safety of BTX-A injections also was assessed. Results: Five RCTs with a total of 417 participants (189 patients in the BTX-A group, 228 patients in placebo group) were eligible in this meta-analysis. The results indicated an overall positive effect of BTX-A injections for reducing the depressive symptoms of patients with MDD (Hedges' g, -0.82; 95% CI, -1.38 to -0.27) with large effect size. Differences are likely explained by the dose of BTX-As and the gender of the participants. Our findings also highlighted that BTX-A injections were generally well-tolerated, with only mild and temporary adverse events reported. Conclusions: The present meta-analysis provides evidence that BTX-A injections are associated with a statistically significant improvement in depressive symptoms. BTX-A injections are generally safe and may provide a new, alternative option for the treatment of depression.

Oncogenic State and Cell Identity Combinatorially Dictate the Susceptibility of Cells within Glioma Development Hierarchy to IGF1R Targeting.

Glioblastoma is the most malignant cancer in the brain and currently incurable. It is urgent to identify effective targets for this lethal disease. Inhibition of such targets should suppress the growth of cancer cells and, ideally also precancerous cells for early prevention, but minimally affect their normal counterparts. Using genetic mouse models with neural stem cells (NSCs) or oligodendrocyte precursor cells (OPCs) as the cells-of-origin/mutation, it is shown that the susceptibility of cells within the development hierarchy of glioma to the knockout of insulin-like growth factor I receptor (IGF1R) is determined not only by their oncogenic states, but also by their cell identities/states. Knockout of IGF1R selectively disrupts the growth of mutant and transformed, but not normal OPCs, or NSCs. The desirable outcome of IGF1R knockout on cell growth requires the mutant cells to commit to the OPC identity regardless of its development hierarchical status. At the molecular level, oncogenic mutations reprogram the cellular network of OPCs and force them to depend more on IGF1R for their growth. A new-generation brain-penetrable, orally available IGF1R inhibitor harnessing tumor OPCs in the brain is also developed. The findings reveal the cellular window of IGF1R targeting and establish IGF1R as an effective target for the prevention and treatment of glioblastoma.

Mitochondrial Fusion and Fission in Neuronal Death Induced by Cerebral Ischemia-Reperfusion and Its Clinical Application: A Mini-Review.

Mitochondria are highly dynamic organelles which are joined by mitochondrial fusion and divided by mitochondrial fission. The balance of mitochondrial fusion and fission plays a critical role in maintaining the normal function of neurons, of which the processes are both mediated by several proteins activated by external stimulation. Cerebral ischemia-reperfusion (I/R) injury can disrupt the balance of mitochondrial fusion and fission through regulating the expression and post-translation modification of fusion- and fission-related proteins, thereby destroying homeostasis of the intracellular environment and causing neuronal death. Furthermore, human intervention in fusion- and fission-related proteins can influence the function of neurons and change the outcomes of cerebral I/R injury. In recent years, researchers have found that mitochondrial dysfunction was one of the main factors involved in I/R, and mitochondria is an attractive target in I/R neuroprotection. Therefore, mitochondrial-targeted therapy of the nervous system for I/R gradually started from basic study to clinical application. In the present review, we highlight recent progress in mitochondria fusion and fission in neuronal death induced by cerebral I/R to help understanding the regulatory factors and signaling networks of aberrant mitochondrial fusion and fission contributing to neuronal death during I/R, as well as the potential neuroprotective therapeutics targeting mitochondrial dynamics, which may help clinical treatment and development of relevant dugs.

Phosphorylated TDP-43 Staging of Primary Age-Related Tauopathy.

Primary age-related tauopathy (PART) is characterized by tau neurofibrillary tangles (NFTs) in the absence of amyloid plaque pathology. In the present study, we analyzed the distribution patterns of phosphorylated 43-kDa TAR DNA-binding protein (pTDP-43) in the brains of patients with PART. Immunohistochemistry and immunofluorescence double-labeling in multiple brain regions was performed on brain tissues from PART, Alzheimer's disease (AD), and aging control cases. We examined the regional distribution patterns of pTDP-43 intraneuronal inclusions in PART with Braak NFT stages > 0 and ≤ IV, and a Thal phase of 0 (no beta-amyloid present). We found four stages which indicated potentially sequential dissemination of pTDP-43 in PART. Stage I was characterized by the presence of pTDP-43 lesions in the amygdala, stage II by such lesions in the hippocampus, stage III by spread of pTDP-43 to the neocortex, and stage IV by pTDP-43 lesions in the putamen, pallidum, and insular cortex. In general, the distribution pattern of pTDP-43 pathology in PART cases was similar to the early TDP-43 stages reported in AD, but tended to be more restricted to the limbic system. However, there were some differences in the distribution patterns of pTDP-43 between PART and AD, especially in the dentate gyrus of the hippocampus. Positive correlations were found in PART between the Braak NFT stage and the pTDP-43 stage and density.

Revisit the Candidacy of Brain Cell Types as the Cell(s) of Origin for Human High-Grade Glioma.

High-grade glioma, particularly, glioblastoma, is the most aggressive cancer of the central nervous system (CNS) in adults. Due to its heterogeneous nature, glioblastoma almost inevitably relapses after surgical resection and radio-/chemotherapy, and is thus highly lethal and associated with a dismal prognosis. Identifying the cell of origin has been considered an important aspect in understanding tumor heterogeneity, thereby holding great promise in designing novel therapeutic strategies for glioblastoma. Taking advantage of genetic lineage-tracing techniques, performed mainly on genetically engineered mouse models (GEMMs), multiple cell types in the CNS have been suggested as potential cells of origin for glioblastoma, among which adult neural stem cells (NSCs) and oligodendrocyte precursor cells (OPCs) are the major candidates. However, it remains highly debated whether these cell types are equally capable of transforming in patients, given that in the human brain, some cell types divide so slowly, therefore may never have a chance to transform. With the recent advances in studying adult NSCs and OPCs, particularly from the perspective of comparative biology, we now realize that notable differences exist among mammalian species. These differences have critical impacts on shaping our understanding of the cell of origin of glioma in humans. In this perspective, we update the current progress in this field and clarify some misconceptions with inputs from important findings about the biology of adult NSCs and OPCs. We propose to re-evaluate the cellular origin candidacy of these cells, with an emphasis on comparative studies between animal models and humans.

Frozen tissue preparation for high-resolution multiplex histological analyses of human brain specimens.

The availability of a comprehensive tissue library is essential for elucidating the function and pathology of human brains. Considering the irreplaceable status of the formalin-fixation-paraffin-embedding (FFPE) preparation in routine pathology and the advantage of ultra-low temperature to preserve nucleic acids and proteins for multi-omics studies, these methods have become major modalities for the construction of brain tissue libraries. Nevertheless, the use of FFPE and snap-frozen samples is limited in high-resolution histological analyses because the preparation destroys tissue integrity and/or many important cellular markers. To overcome these limitations, we detailed a protocol to prepare and analyze frozen human brain samples that is particularly suitable for high-resolution multiplex immunohistological studies. As an alternative, we offered an optimized procedure to rescue snap-frozen tissues for the same purpose. Importantly, we provided a guideline to construct libraries of frozen tissue with minimal effort, cost and space. Taking advantage of this new tissue preparation modality to nicely preserve the cellular information that was otherwise damaged using conventional methods and to effectively remove tissue autofluorescence, we described the high-resolution landscape of the cellular composition in both lower-grade gliomas and glioblastoma multiforme samples. Our work showcases the great value of fixed frozen tissue in understanding the cellular mechanisms of CNS functions and abnormalities.

Efficacy of Progesterone for Acute Traumatic Brain Injury: a Meta-analysis of Randomized Controlled Trials.

Progesterone, a steroid hormone, has been shown to have multifactorial neuroprotective effects in a variety of animal models of acute traumatic brain injury (TBI). Translation to humans showed positive effects in previous phase II trials, but unfortunately, negative results were observed in two recent phase III trials. The present study focuses on the efficacy of progesterone on acute TBI based on the published data of randomized controlled trials (RCTs). MEDLINE, EMBASE, and Cochrane Library were used to search from January 1980 to August 2015 for English language studies. The primary outcome was a favorable outcome in the Glasgow outcome scale (GOS). The secondary outcomes included mortality and adverse events. A total of 2396 patients from 5 RCTs were included in the present study. There were no significant differences in favorable outcome (relative risk (RR) 1.07, 95 % confidence interval (CI) 0.91 to 1.27, P = 0.41) and mortality rate (RR 0.85, 95 % CI 0.65 to 1.13, P = 0.27) between progesterone and placebo groups. In a subgroup analysis, favorable outcome (RR 1.45, 95 % CI 1.11 to 1.89, P = 0.007) and decreased mortality rate (RR 0.58, 95 % CI 0.41 to 0.84, P = 0.004) are only observed in the phase II RCTs. The included factors were the severity of TBI, method of drug administration, and duration of observation and had no influence on the observed outcomes. Sensitivity analysis showed that all the outcomes were stable after excluding Shakeri (Clin Neurol Neurosurg 115: 2019-2022, 2013) or Wright (N Engl J Med 371: 2457-2466, 2014) trials. The quality of the evidence was varied from high to low. In conclusion, progesterone has no significant improvement in the functional recovery and mortality rate after acute TBI.