Transplantation of A2 type astrocytes promotes neural repair and remyelination after spinal cord injury

Impacts of PI3K/protein kinase B pathway activation in reactive astrocytes: from detrimental effects to protective functions

Astrocytes are the most abundant type of glial cell in the central nervous system. Upon injury and inflammation, astrocytes become reactive and undergo morphological and functional changes. Depending on their phenotypic classification as A1 or A2, reactive astrocytes contribute to both neurotoxic and neuroprotective responses, respectively. However, this binary classification does not fully capture the diversity of astrocyte responses observed across different diseases and injuries. Transcriptomic analysis has revealed that reactive astrocytes have a complex landscape of gene expression profiles, which emphasizes the heterogeneous nature of their reactivity. Astrocytes actively participate in regulating central nervous system inflammation by interacting with microglia and other cell types, releasing cytokines, and influencing the immune response. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway is a central player in astrocyte reactivity and impacts various aspects of astrocyte behavior, as evidenced by in silico , in vitro , and in vivo results. In astrocytes, inflammatory cues trigger a cascade of molecular events, where nuclear factor-κB serves as a central mediator of the pro-inflammatory responses. Here, we review the heterogeneity of reactive astrocytes and the molecular mechanisms underlying their activation. We highlight the involvement of various signaling pathways that regulate astrocyte reactivity, including the PI3K/AKT/mammalian target of rapamycin (mTOR), α v β 3 integrin/PI3K/AKT/connexin 43, and Notch/PI3K/AKT pathways. While targeting the inactivation of the PI3K/AKT cellular signaling pathway to control reactive astrocytes and prevent central nervous system damage, evidence suggests that activating this pathway could also yield beneficial outcomes. This dual function of the PI3K/AKT pathway underscores its complexity in astrocyte reactivity and brain function modulation. The review emphasizes the importance of employing astrocyte-exclusive models to understand their functions accurately and these models are essential for clarifying astrocyte behavior. The findings should then be validated using in vivo models to ensure real-life relevance. The review also highlights the significance of PI3K/AKT pathway modulation in preventing central nervous system damage, although further studies are required to fully comprehend its role due to varying factors such as different cell types, astrocyte responses to inflammation, and disease contexts. Specific strategies are clearly necessary to address these variables effectively.

Schwann cell transplantation for remyelination, regeneration, tissue sparing, and functional recovery in spinal cord injury: A systematic review and meta-analysis of animal studies

INTRODUCTION

Spinal cord injury (SCI) is a significant global health challenge that results in profound physical and neurological impairments. Despite progress in medical care, the treatment options for SCI are still restricted and often focus on symptom management rather than promoting neural repair and functional recovery. This study focused on clarifying the impact of Schwann cell (SC) transplantation on the molecular, cellular, and functional basis of recovery in animal models of SCI.

MATERIAL AND METHODS

Relevant studies were identified by conducting searches across multiple databases, which included PubMed, Web of Science, Scopus, and ProQuest. The data were analyzed via comprehensive meta-analysis software. We assessed the risk of bias via the SYRCLE method.

RESULTS

The analysis included 59 studies, 48 of which provided quantitative data. The results revealed significant improvements in various outcome variables, including protein zero structures (SMD = 1.66, 95 %CI: 0.96-2.36; p < 0.001; I2 = 49.8 %), peripherally myelinated axons (SMD = 1.81, 95 %CI: 0.99-2.63; p < 0.001; I2 = 39.3 %), biotinylated dextran amine-labeled CST only rostral (SMD = 1.31, 95 % CI: 0.50-2.12, p < 0.01, I2 = 49.7 %), fast blue-labeled reticular formation (SMD = 0.96, 95 %CI: 0.43-1.49, p < 0.001, I2 = 0.0 %), 5-hydroxytryptamine caudally (SMD = 0.83, 95 %CI: 0.36-1.29, p < 0.001, I2 = 17.2 %) and epicenter (SMD = 0.85, 95 %CI: 0.17-1.53, p < 0.05, I2 = 62.7 %), tyrosine hydroxylase caudally (SMD = 1.86, 95 %CI: 1.14-2.59, p < 0.001, I2 = 0.0 %) and epicenter (SMD = 1.82, 95 %CI: 1.18-2.47, p < 0.001, I2 = 0.0 %), cavity volume (SMD = -2.07, 95 %CI: -2.90 - -1.24, p < 0.001, I2 = 67.2 %), and Basso, Beattie, and Bresnahan (SMD = 1.26, 95 %CI: 0.93-1.58; p < 0.001; I2 = 79.4 %).

CONCLUSIONS

This study demonstrates the promising potential of SC transplantation as a therapeutic approach for SCI, clarifying its impact on various biological processes critical for recovery.

Transcranial alternating current stimulation inhibits ferroptosis and promotes functional recovery in spinal cord injury via the cGMP-PKG signalling pathway

AIMS

This study explores the potential of neuromodulation, specifically transcranial alternating current stimulation (tACS), as a promising rehabilitative therapy in spinal cord injury (SCI).

MAIN METHODS

By meticulously optimizing treatment parameters and durations, our objective was to enhance nerve regeneration and facilitate functional recovery. To assess the efficacy of tACS, our experiments used the rat T10 SCI model. Motor function outcomes were measured using the Basso-Beattie-Bresnahan (BBB) scoring scale and footprint analysis. To thoroughly understand the impact of tACS, we conducted a series of histological evaluations two weeks post-injury. These included q-PCR, enzyme-linked immunosorbent assays (ELISA), transmission electron microscopy (TEM), immunofluorescence staining, and Western blotting. The mechanisms underlying the role of tACS will be elucidated through comprehensive analyses.

KEY FINDINGS

Simultaneously, tACS reduced the levels of reactive oxygen species (ROS), Fe, and malondialdehyde (MDH), and increased the levels of glutathione (GSH) after SCI. Additionally, tACS significantly enhanced motor function, reduced fibrotic scar tissue formation, and provided substantial neuroprotection. It also contributed to the restoration of the blood-spinal cord barrier and supported the regeneration of essential neural components, including axons, myelin, and synapses. The cGMP-PKG signalling pathway was identified as playing a crucial role in these processes.

SIGNIFICANCE

Our findings suggest that tACS inhibits ferroptosis and necrotic degeneration by modulating the cGMP-PKG signalling pathway. This highlights the importance of tACS in promoting neural repair and functional recovery in SCI patients. Overall, tACS emerges as a highly effective and cost-efficient rehabilitative approach for SCI, offering new hope for improving patient outcomes.

Mechanism of S100A9-mediated astrocyte activation via TLR4/NF-κB in Parkinson's disease

Astrocyte-mediated neuroinflammation plays a key role in Parkinson's disease (PD) progression. The proinflammatory protein S100A9 is linked to various neurodegenerative diseases, but its involvement in astrocyte activation in PD remains unclear. Here, we investigate the role of S100A9 in astrocyte-mediated neuroinflammation in PD. C57BL/6J mice were intraperitoneally injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 15 mg/kg four times daily) and subsequently treated with Paquinimod, a S100A9 inhibitor (7 mg/kg, once daily for 7 days, totaling 8 doses). We observed an abnormal increase in S100A9 protein expression and a rise in S100A9-positive cells in the striatum of PD mice. Paquinimod treatment significantly improved behavioral deficits (pole test, rotarod test, traction test, and open field tests), prevented the reduction in striatal tyrosine hydroxylase (TH) protein and the loss of dopaminergic neurons (TH+) in the substantia nigra (SN) in PD mice. Interestingly, S100A9 was predominantly expressed in astrocytes (GFAP+S100A9+ cells) rather than in neurons or microglia, and its inhibition significantly reduced astrocyte activation (GFAP+ cells), reversed A1 astrocyte gene upregulation (H2-D1, C3, Serping1), and increased A2 astrocyte gene expression (Emp1, Ptx3, S100a10). Moreover, S100A9 inhibition also reduced the expression of inflammatory markers (IL-6, IL-1β, TNF-α) and suppressed the TLR4/NF-κB signaling pathway. In vitro, TLR4/NF-κB inhibitors mitigated inflammation and A1/A2 polarization of astrocytic MA cells induced by recombinant S100A9 (rS100A9). These findings suggest that S100A9 mediates astrocyte neuroinflammation and A1/A2 polarization via TLR4/NF-κB signaling, highlighting its potential as a therapeutic target for PD.

Extracellular vesicles: biological mechanisms and emerging therapeutic opportunities in neurodegenerative diseases

Extracellular vesicles (EVs) are membrane vesicles originating from different cells within the brain. The pathophysiological role of EVs in neurodegenerative diseases is progressively acknowledged. This field has advanced from basic biological research to essential clinical significance. The capacity to selectively enrich specific subsets of EVs from biofluids via distinctive surface markers has opened new avenues for molecular understandings across various tissues and organs, notably in the brain. In recent years, brain-derived EVs have been extensively investigated as biomarkers, therapeutic targets, and drug-delivery vehicles for neurodegenerative diseases. This review provides a brief overview of the characteristics and physiological functions of the various classes of EVs, focusing on the biological mechanisms by which various types of brain-derived EVs mediate the occurrence and development of neurodegenerative diseases. Concurrently, novel therapeutic approaches and challenges for the use of EVs as delivery vehicles are delineated.

Promoting remyelination in central nervous system diseases: Potentials and prospects of natural products and herbal medicine

Myelin damage is frequently associated with central nervous system (CNS) diseases and is a critical factor influencing neurological function and disease prognosis. Nevertheless, the majority of current treatments for the CNS concentrate on gray matter injury and repair strategies, while clinical interventions specifically targeting myelin repair remain unavailable. In recent years, natural products and herbal medicine have achieved considerable progress in the domain of myelin repair, given their remarkable curative effect and low toxic side effects, demonstrating significant therapeutic potential. In this review, we present a rather comprehensive account of the mechanisms underlying myelin formation, injury, and repair, with a particular emphasis on the interactions between oligodendrocytes and other glial cells. Furthermore, we summarize the natural products and herbal medicine currently employed in remyelination along with their mechanisms of action, highlighting the potential and challenges of certain natural compounds to enhance myelin repair. This review aims to facilitate the expedited development of innovative therapeutics derived from natural products and herbal medicine and furnish novel insights into myelin repair in the CNS.

Neuroinflammation and major depressive disorder: astrocytes at the crossroads

Major depressive disorder is a complex and multifactorial condition, increasingly linked to neuroinflammation and astrocytic dysfunction. Astrocytes, along with other glial cells, beyond their classic functions in maintaining brain homeostasis, play a crucial role in regulating neuroinflammation and neuroplasticity, key processes in the pathophysiology of depression. This mini-review explores the involvement of astrocytes in depression emphasizing their mediation in neuroinflammation processes, the impact of astrocytic dysfunction on neuroplasticity, and the effect of some antidepressants on astrocyte reactivity. Recent evidence suggests that targeting astrocyte-related signaling pathways, particularly the balance between different astrocytic phenotypes, could offer promising evidence for therapeutic strategies for affective disorders. Therefore, a deeper understanding of astrocyte biology may open the way to innovative treatments aimed at mitigating depressive symptoms by impacting both neuroinflammation and imbalances in neuroplasticity.

Neuroinflammatory Proteins in Huntington's Disease: Insights into Mechanisms, Diagnosis, and Therapeutic Implications

Huntington's disease (HD) is a hereditary neurodegenerative disorder caused by a CAG tract expansion in the huntingtin gene (HTT). HD is characterized by involuntary movements, cognitive decline, and behavioral changes. Pathologically, patients with HD show selective striatal neuronal vulnerability at the early disease stage, although the mutant protein is ubiquitously expressed. Activation of the immune system and glial cell-mediated neuroinflammatory responses are early pathological features and have been found in all neurodegenerative diseases (NDDs), including HD. However, the role of inflammation in HD, as well as its therapeutic significance, has been less extensively studied compared to other NDDs. This review highlights the significantly elevated levels of inflammatory proteins and cellular markers observed in various HD animal models and HD patient tissues, emphasizing the critical roles of microglia, astrocytes, and oligodendrocytes in mediating neuroinflammation in HD. Moreover, it expands on recent discoveries related to the peripheral immune system's involvement in HD. Although current immunomodulatory treatments and inflammatory biomarkers for adjunctive diagnosis in HD are limited, targeting inflammation in combination with other therapies, along with comprehensive personalized treatment approaches, shows promising therapeutic potential.

Ruxolitinib improves the inflammatory microenvironment, restores glutamate homeostasis, and promotes functional recovery after spinal cord injury

JOURNAL/nrgr/04.03/01300535-202419110-00030/figure1/v/2024-03-08T184507Z/r/image-tiff The inflammatory microenvironment and neurotoxicity can hinder neuronal regeneration and functional recovery after spinal cord injury. Ruxolitinib, a JAK-STAT inhibitor, exhibits effectiveness in autoimmune diseases, arthritis, and managing inflammatory cytokine storms. Although studies have shown the neuroprotective potential of ruxolitinib in neurological trauma, the exact mechanism by which it enhances functional recovery after spinal cord injury, particularly its effect on astrocytes, remains unclear. To address this gap, we established a mouse model of T10 spinal cord contusion and found that ruxolitinib effectively improved hindlimb motor function and reduced the area of spinal cord injury. Transcriptome sequencing analysis showed that ruxolitinib alleviated inflammation and immune response after spinal cord injury, restored EAAT2 expression, reduced glutamate levels, and alleviated excitatory toxicity. Furthermore, ruxolitinib inhibited the phosphorylation of JAK2 and STAT3 in the injured spinal cord and decreased the phosphorylation level of nuclear factor kappa-B and the expression of inflammatory factors interleukin-1β, interleukin-6, and tumor necrosis factor-α. Additionally, in glutamate-induced excitotoxicity astrocytes, ruxolitinib restored EAAT2 expression and increased glutamate uptake by inhibiting the activation of STAT3, thereby reducing glutamate-induced neurotoxicity, calcium influx, oxidative stress, and cell apoptosis, and increasing the complexity of dendritic branching. Collectively, these results indicate that ruxolitinib restores glutamate homeostasis by rescuing the expression of EAAT2 in astrocytes, reduces neurotoxicity, and effectively alleviates inflammatory and immune responses after spinal cord injury, thereby promoting functional recovery after spinal cord injury.

Targeting astrocytes polarization after spinal cord injury: a promising direction

Spinal cord injury (SCI) is a serious neurological injury that causes severe trauma to motor and sensory functions. Although long considered incurable, recent research has brought new hope for functional recovery from SCI. After SCI, astrocytes are activated into many polarization states. Here we discuss the two most important classical phenotypes: the 'A1' neurotoxic phenotype and the 'A2' neuroprotective phenotype, with A1 astrocytes being neurotoxic and impeding neurorecovery, and A2 astrocytes being neuroprotective. This paper discusses the changes in astrocyte responsiveness after SCI and the pros and cons of their polarization in SCI. It also elucidates the feasibility of astrocyte polarization as a therapeutic target for neuroprotection. In the future, multiple intervention strategies targeting astrocyte polarization are expected to gain wider clinical application, ultimately improving motor-sensory function and quality of life in SCI patients.

Delivery of TGFβ3 from Magnetically Responsive Coaxial Fibers Reduces Spinal Cord Astrocyte Reactivity In Vitro

A spinal cord injury (SCI) compresses the spinal cord, killing neurons and glia at the injury site and resulting in prolonged inflammation and scarring that prevents regeneration. Astrocytes, the main glia in the spinal cord, become reactive following SCI and contribute to adverse outcomes. The anti-inflammatory cytokine transforming growth factor beta 3 (TGFβ3) has been shown to mitigate astrocyte reactivity; however, the effects of prolonged TGFβ3 exposure on reactive astrocyte phenotype have not yet been explored. This study investigates whether magnetic core-shell electrospun fibers can be used to alter the release rate of TGFβ3 using externally applied magnetic fields, with the eventual application of tailored drug delivery based on SCI severity. Magnetic core-shell fibers are fabricated by incorporating superparamagnetic iron oxide nanoparticles (SPIONs) into the shell and TGFβ3 into the core solution for coaxial electrospinning. Magnetic field stimulation increased the release rate of TGFβ3 from the fibers by 25% over 7 days and released TGFβ3 reduced gene expression of key astrocyte reactivity markers by at least twofold. This is the first study to magnetically deliver bioactive proteins from magnetic fibers and to assess the effect of sustained release of TGFβ3 on reactive astrocyte phenotype.

Unravelling the Road to Recovery: Mechanisms of Wnt Signalling in Spinal Cord Injury

Spinal cord injury (SCI) is a complex neurodegenerative pathology that consistently harbours a poor prognostic outcome. At present, there are few therapeutic strategies that can halt neuronal cell death and facilitate functional motor recovery. However, recent studies have highlighted the Wnt pathway as a key promoter of axon regeneration following central nervous system (CNS) injuries. Emerging evidence also suggests that the temporal dysregulation of Wnt may drive cell death post-SCI. A major challenge in SCI treatment resides in developing therapeutics that can effectively target inflammation and facilitate glial scar repair. Before Wnt signalling is exploited for SCI therapy, further research is needed to clarify the implications of Wnt on neuroinflammation during chronic stages of injury. In this review, an attempt is made to dissect the impact of canonical and non-canonical Wnt pathways in relation to individual aspects of glial and fibrotic scar formation. Furthermore, it is also highlighted how modulating Wnt activity at chronic time points may aid in limiting lesion expansion and promoting axonal repair.

Astrocyte-secreted lipocalin-2 elicits bioenergetic failure-induced neuronal death that is causally related to high fatality in a mouse model of hepatic encephalopathy

Hepatic encephalopathy (HE) is a neurological complication arising from acute liver failure with poor prognosis and high mortality; the underlying cellular mechanisms are still wanting. We previously found that neuronal death caused by mitochondrial dysfunction in rostral ventrolateral medulla (RVLM), which leads to baroreflex dysregulation, is related to high fatality in an animal model of HE. Lipocalin-2 (Lcn2) is a secreted glycoprotein mainly released by astrocytes in the brain. We noted the presence of Lcn2 receptor (Lcn2R) in RVLM neurons and a parallel increase of Lcn2 gene in astrocytes purified from RVLM during experimental HE. Therefore, our guiding hypothesis is that Lcn2 secreted by reactive astrocytes in RVLM may underpin high fatality during HE by eliciting bioenergetic failure-induced neuronal death in this neural substrate. In this study, we first established the role of astrocyte-secreted Lcn2 in a liver toxin model of HE induced by azoxymethane (100 μg/g, ip) in C57BL/6 mice, followed by mechanistic studies in primary astrocyte and neuron cultures prepared from postnatal day 1 mouse pups. In animal study, immunoneutralization of Lcn2 reduced apoptotic cell death in RVLM, reversed defunct baroreflex-mediated vasomotor tone and prolonged survival during experimental HE. In our primary cell culture experiments, Lcn2 produced by cultured astrocytes and released into the astrocyte-conditioned medium significantly reduced cell viability of cultured neurons. Recombinant Lcn2 protein reduced cell viability, mitochondrial ATP (mitoATP) production, and pyruvate dehydrogenase (PDH) activity but enhanced the expression of pyruvate dehydrogenase kinase (PDK) 1, PDK3 and phospho-PDHA1 (inactive PDH) through MAPK/ERK pathway in cultured neurons, with all cellular actions reversed by Lcn2R knockdown. Our results suggest that astrocyte-secreted Lcn2 upregulates PDKs through MAPK/ERK pathway, which leads to reduced PDH activity and mitoATP production; the reinforced neuronal death in RVLM is causally related to baroreflex dysregulation that underlies high fatality associated with HE.

Crosstalk Among Glial Cells in the Blood-Brain Barrier Injury After Ischemic Stroke

Blood-brain barrier (BBB) is comprised of brain microvascular endothelial cells (ECs), astrocytes, perivascular microglia, pericytes, neuronal processes, and the basal lamina. As a complex and dynamic interface between the blood and the central nervous system (CNS), BBB is responsible for transporting nutrients essential for the normal metabolism of brain cells and hinders many toxic compounds entering into the CNS. The loss of BBB integrity following stroke induces tissue damage, inflammation, edema, and neural dysfunction. Thus, BBB disruption is an important pathophysiological process of acute ischemic stroke. Understanding the mechanism underlying BBB disruption can uncover more promising biological targets for developing treatments for ischemic stroke. Ischemic stroke-induced activation of microglia and astrocytes leads to increased production of inflammatory mediators, containing chemokines, cytokines, matrix metalloproteinases (MMPs), etc., which are important factors in the pathological process of BBB breakdown. In this review, we discussed the current knowledges about the vital and dual roles of astrocytes and microglia on the BBB breakdown during ischemic stroke. Specifically, we provided an updated overview of phenotypic transformation of microglia and astrocytes, as well as uncovered the crosstalk among astrocyte, microglia, and oligodendrocyte in the BBB disruption following ischemic stroke.

Tetramethylpyrazine alleviates ferroptosis and promotes functional recovery in spinal cord injury by regulating GPX4/ACSL4

OBJECTIVE

Tetramethylpyrazine (TMP) has been demonstrated to alleviate neuronal ferroptosis following spinal cord injury (SCI), thereby promoting neural repair. However, the precise underlying mechanisms remain elusive.

METHODS

The SCI model was established using a modified version of Allen's method. TMP (40, 80, 120, and 160 mg/kg) and ras-selective lethal 3 (RSL3) (5 mg/kg) were administered intraperitoneally once daily for 7 days. HE and Nissl staining were employed to examine histomorphology and neurons, respectively. Perls staining was used to identify the distribution of iron. A transmission electron microscope was used to observe the microcosmic morphology of mitochondria. Immunofluorescence staining and Western blot were used to analyze neuronal nuclear protein (NeuN) and glial fibrillary acidic protein (GFAP) surrounding injury sites. Additionally, glutathione peroxidase 4 (GPX4)/NeuN + cells and acyl-CoA synthetase long-chain family member 4 (ACSL4)/NeuN + cells were observed. RT-qPCR was conducted to examine the mRNA expression levels of GPX4 and ACSL4. ELISA were used to quantify the concentrations of GPX4, reactive oxygen species (ROS), L-glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), and tissue iron.

RESULTS

TMP had an inhibitory effect on the concentrations of tissue iron, ROS, GSH, MDA, and SOD. TMP improved the microcosmic morphology of mitochondria and increased GPX4 level while decreasing that of ACSL4. TMP reduced lesion sizes, enhanced neuronal survival, and inhibited glial scar formation. However, the effect of TMP can be effectively reversed by RSL3.

CONCLUSION

TMP alleviates neuronal ferroptosis by regulating the GPX4/ACSL4 axis, thereby protecting the remaining neurons surrounding injury sites and reducing glial scar formation.

Differential Expression of PACAP/VIP Receptors in the Post-Mortem CNS White Matter of Multiple Sclerosis Donors

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two neuroprotective and anti-inflammatory molecules of the central nervous system (CNS). Both bind to three G protein-coupled receptors, namely PAC1, VPAC1 and VPAC2, to elicit their beneficial effects in various CNS diseases, including multiple sclerosis (MS). In this study, we assessed the expression and distribution of PACAP/VIP receptors in the normal-appearing white matter (NAWM) of MS donors with a clinical history of either relapsing-remitting MS (RRMS), primary MS (PPMS), secondary progressive MS (SPMS) or in aged-matched non-MS controls. Gene expression studies revealed MS-subtype specific changes in PACAP and VIP and in the receptors' levels in the NAWM, which were partly corroborated by immunohistochemical analyses. Most PAC1 immunoreactivity was restricted to myelin-producing cells, whereas VPAC1 reactivity was diffused within the neuropil and in axonal bundles, and VPAC2 in small vessel walls. Within and around lesioned areas, glial cells were the predominant populations showing reactivity for the different PACAP/VIP receptors, with distinctive patterns across MS subtypes. Together, these data identify the differential expression patterns of PACAP/VIP receptors among the different MS clinical entities. These results may offer opportunities for the development of personalized therapeutic approaches to treating MS and/or other demyelinating disorders.

A2 reactive astrocyte-derived exosomes alleviate cerebral ischemia-reperfusion injury by delivering miR-628

Ischemia and hypoxia activate astrocytes into reactive types A1 and A2, which play roles in damage and protection, respectively. However, the function and mechanism of A1 and A2 astrocyte exosomes are unknown. After astrocyte exosomes were injected into the lateral ventricle, infarct volume, damage to the blood-brain barrier (BBB), apoptosis and the expression of microglia-related proteins were measured. The dual luciferase reporter assay was used to detect the target genes of miR-628, and overexpressing A2-Exos overexpressed and knocked down miR-628 were constructed. qRT-PCR, western blotting and immunofluorescence staining were subsequently performed. A2-Exos obviously reduced the infarct volume, damage to the BBB and apoptosis and promoted M2 microglial polarization. RT-PCR showed that miR-628 was highly expressed in A2-Exos. Dual luciferase reporter assays revealed that NLRP3, S1PR3 and IRF5 are target genes of miR-628. After miR-628 was overexpressed or knocked down, the protective effects of A2-Exos increased or decreased, respectively. A2-Exos reduced pyroptosis and BBB damage and promoted M2 microglial polarization through the inhibition of NLRP3, S1PR3 and IRF5 via the delivery of miR-628. This study explored the mechanism of action of A2-Exos and provided new therapeutic targets and concepts for treating cerebral ischemia.

Effect of Myelin Debris on the Phenotypic Transformation of Astrocytes after Spinal Cord Injury in Rats

After spinal cord injury (SCI), the accumulation of myelin debris can serve as proinflammatory agents, hindering axon regrowth and exacerbating damage. While astrocytes have been implicated in the phagocytosis of myelin debris, the impact of this process on the phenotypic transformation of astrocytes and their characteristics following SCI in rats is not well understood. Here, we demonstrated that the conditioned medium of myelin debris can trigger apoptosis in rat primary astrocytes in vitro. Using a compressional SCI model in rats, we observed that astrocytes can engulf myelin debris through ATP-binding cassette transporter sub-family A member 1 (ABCA1), and these engulfed cells tend to transform into A1 astrocytes, as indicated by C3 expression. At 4 days post-injury (dpi), astrocytes rapidly transitioned into A1 astrocytes and maintained this phenotype from 4 to 28 dpi, while A2 astrocytes, characterized by S100, were only detected at 14 and 28 dpi. Reactive astrocytes, identified by Nestin, emerged at 4 and 7 dpi, whereas scar-forming astrocytes, marked by N-cadherin, were evident at 14 and 28 dpi. This study illustrates the distribution patterns of astrocyte subtypes and the potential interplay between astrocytes and myelin debris after SCI in rats. We emphasize that myelin debris can induce astrocyte apoptosis in vitro and promote the transformation of astrocytes into A1 astrocytes in vivo. These two classification methods are not mutually exclusive, but rather complementary.

Effect of total flavonoids of Dracocephalum moldavica L. On neuroinflammation in Alzheimer's disease model amyloid-β (Aβ1-42)-peptide-induced astrocyte activation

One of the main pathological features noted in Alzheimer's disease (AD) is the presence of plagues of aggregated β-amyloid (Aβ1-42)-peptides. Excess deposition of amyloid-β oligomers (AβO) are known to promote neuroinflammation. Sequentially, following neuroinflammation astrocytes become activated with cellular characteristics to initiate activated astrocytes. The purpose of this study was to determine whether total flavonoids derived from Dracocephalum moldavica L. (TFDM) inhibited Aβ1-42-induced damage attributed to activated C8-D1A astrocytes. Western blotting and ELISA were used to determine the expression of glial fibrillary acidic protein (GFAP), and complement C3 to establish the activation status of astrocytes following induction from exposure to Aβ1-42. Data demonstrated that stimulation of C8-D1A astrocytes by treatment with 40 μM Aβ1-42 for 24 hr produced significant elevation in protein expression and protein levels of acidic protein (GFAP) and complement C3 accompanied by increased expression and levels of inflammatory cytokines. Treatment with TFDM or the clinically employed drug donepezil in AD therapy reduced production of inflammatory cytokines, and toxicity initiated following activation of C8-D1A astrocytes following exposure to Aβ1-42. Therefore, TFDM similar to donepezil inhibited inflammatory secretion in reactive astrocytes, suggesting that TFDM may be considered as a potential compound to be utilized in AD therapy.

Reprogramming of astrocytes to neuronal-like cells in spinal cord injury: a systematic review

STUDY DESIGN

A Systematic Review OBJECTIVES: To determine the therapeutic efficacy of in vivo reprogramming of astrocytes into neuronal-like cells in animal models of spinal cord injury (SCI).

METHODS

PRISMA 2020 guidelines were utilized, and search engines Medline, Web of Science, Scopus, and Embase until June 2023 were used. Studies that examined the effects of converting astrocytes into neuron-like cells with any vector in all animal models were included, while conversion from other cells except for spinal astrocytes, chemical mechanisms to provide SCI models, brain injury population, and conversion without in-vivo experience were excluded. The risk of bias was calculated independently.

RESULTS

5302 manuscripts were initially identified and after eligibility assessment, 43 studies were included for full-text analysis. After final analysis, 13 manuscripts were included. All were graded as high-quality assessments. The transduction factors Sox2, Oct4, Klf4, fibroblast growth factor 4 (Fgf4) antibody, neurogenic differentiation 1 (Neurod1), zinc finger protein 521 (Zfp521), ginsenoside Rg1, and small molecules (LDN193189, CHIR99021, and DAPT) could effectively reprogramme astrocytes into neuron-like cells. The process was enhanced by p21-p53, or Notch signaling knockout, valproic acid, or chondroitin sulfate proteoglycan inhibitors. The type of mature neurons was both excitatory and inhibitory.

CONCLUSION

Astrocyte reprogramming to neuronal-like cells in an animal model after SCI appears promising. The molecular and functional improvements after astrocyte reprogramming were demonstrated in vivo, and further investigation is required in this field.

The role of astrocyte in neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI), a significant contributor to mortality and morbidity worldwide, is a devastating condition characterized by initial mechanical damage followed by subsequent biochemical processes, including neuroinflammation. Astrocytes, the predominant glial cells in the central nervous system, play a vital role in maintaining brain homeostasis and supporting neuronal function. Nevertheless, in response to TBI, astrocytes undergo substantial phenotypic alternations and actively contribute to the neuroinflammatory response. This article explores the multifaceted involvement of astrocytes in neuroinflammation subsequent to TBI, with a particular emphasis on their activation, release of inflammatory mediators, modulation of the blood-brain barrier, and interactions with other immune cells. A comprehensive understanding the dynamic interplay between astrocytes and neuroinflammation in the condition of TBI can provide valuable insights into the development of innovative therapeutic approaches aimed at mitigating secondary damage and fostering neuroregeneration.

[Experimental study of M2 microglia transplantation promoting spinal cord injury repair in mice]

Objective

To investigate the effect of M2 microglia (M2-MG) transplantation on spinal cord injury (SCI) repair in mice.

Methods

Primary MG were obtained from the cerebral cortex of 15 C57BL/6 mice born 2-3 days old by pancreatic enzyme digestion and identified by immunofluorescence staining of Iba1. Then the primary MG were co-cultured with interleukin 4 for 48 hours (experimental group) to induce into M2 phenotype and identified by immunofluorescence staining of Arginase 1 (Arg-1) and Iba1. The normal MG were harvested as control (control group). The dorsal root ganglion (DRG) of 5 C57BL/6 mice born 1 week old were co-cultured with M2-MG for 5 days to observe the axon length, the DRG alone was used as control. Forty-two 6-week-old female C57BL/6 mice were randomly divided into sham group ( n=6), SCI group ( n=18), and SCI+M2-MG group ( n=18). In sham group, only the laminae of T 10 level were removed; SCI group and SCI+M2-MG group underwent SCI modeling, and SCI+M2-MG group was simultaneously injected with M2-MG. The survival of mice in each group was observed after operation. At immediate (0), 3, 7, 14, 21, and 28 days after operation, the motor function of mice was evaluated by Basso Mouse Scale (BMS) score, and the gait was evaluated by footprint experiment at 28 days. The spinal cord tissue was taken after operation for immunofluorescence staining, in which glial fibrillary acidic protein (GFAP) staining at 7, 14, and 28 days was used to observe the injured area of the spinal cord, neuronal nuclei antigen staining at 28 days was used to observe the survival of neurons, and GFAP/C3 double staining at 7 and 14 days was used to observe the changes in the number of A1 astrocytes.

Results

The purity of MG in vitro reached 90%, and the most of the cells were polarized into M2 phenotype identified by Arg-1 immunofluorescence staining. M2-MG promoted the axon growth when co-cultured with DRGs in vitro ( P<0.05). All groups of mice survived until the experiment was completed. The hind limb motor function of SCI group and SCI+M2-MG group gradually recovered over time. Among them, the SCI+M2-MG group had significantly higher BMS scores than the SCI group at 21 and 28 days ( P<0.05), and the dragging gait significantly improved at 28 days, but it did not reach the level of the sham group. Immunofluorescence staining showed that compared with the SCI group, the SCI+M2-MG group had a smaller injury area at 7, 14, and 28 days, an increase in neuronal survival at 28 days, and a decrease in the number of A1 astrocytes at 7 and 14 days, with significant differences ( P<0.05).

Conclusion

M2-MG transplantation improves the motor function of the hind limbs of SCI mice by promoting neuron survival and axon regeneration. This neuroprotective effect is related to the inhibition of A1 astrocytes polarization.

Management of the Brain: Essential Oils as Promising Neuroinflammation Modulator in Neurodegenerative Diseases

Neuroinflammation, a pivotal factor in the pathogenesis of various brain disorders, including neurodegenerative diseases, has become a focal point for therapeutic exploration. This review highlights neuroinflammatory mechanisms that hallmark neurodegenerative diseases and the potential benefits of essential oils in counteracting neuroinflammation and oxidative stress, thereby offering a novel strategy for managing and mitigating the impact of various brain disorders. Essential oils, derived from aromatic plants, have emerged as versatile compounds with a myriad of health benefits. Essential oils exhibit robust antioxidant activity, serving as scavengers of free radicals and contributing to cellular defense against oxidative stress. Furthermore, essential oils showcase anti-inflammatory properties, modulating immune responses and mitigating inflammatory processes implicated in various chronic diseases. The intricate mechanisms by which essential oils and phytomolecules exert their anti-inflammatory and antioxidant effects were explored, shedding light on their multifaceted properties. Notably, we discussed their ability to modulate diverse pathways crucial in maintaining oxidative homeostasis and suppressing inflammatory responses, and their capacity to rescue cognitive deficits observed in preclinical models of neurotoxicity and neurodegenerative diseases.

[Exosomes from ectoderm mesenchymal stem cells inhibits lipopolysaccharide-induced microglial M1 polarization and promotes survival of H2O2-exposed PC12 cells by suppressing inflammatory response and oxidative stress]

OBJECTIVE

To investigate the potential value of exosomes derived from rat ectoderm mesenchymal stem cells (EMSCs-exo) for repairing secondary spinal cord injury.

METHODS

EMSCs-exo were obtained using ultracentrifugation from EMSCs isolated from rat nasal mucosa, identified by transmission electron microscope, nanoparticle tracking analysis (NTA), and Western blotting, and quantified using the BCA method. Neonatal rat microglia purified by differential attachment were induced with 100 μg/L lipopolysaccharide (LPS) and treated with 37.5 or 75 mg/L EMSCs-exo. PC12 cells were exposed to 400 μmol/L H2O2 and treated with EMSCs-exo at 37.5 or 75 mg/L. The protein and mRNA expressions of Arg1 and iNOS in the treated cells were determined with Western blotting and qRT- PCR, and the concentrations of IL- 6, IL-10, and IGF-1 in the supernatants were measured with ELISA. The viability and apoptosis of PC12 cells were detected using CCK-8 assay and flow cytometry.

RESULTS

The isolated rat EMSCs showed high expressions of nestin, CD44, CD105, and vimentin. The obtained EMSCs-exo had a typical cup-shaped structure under transmission electron microscope with an average particle size of 142 nm and positivity for CD63, CD81, and TSG101 but not vimentin. In LPS-treated microglia, EMSCs-exo treatment at 75 mg/L significantly increased Arg1 protein level and lowered iNOS protein expression (P < 0.05). EMSCs-exo treatment at 75 mg/L, as compared with the lower concentration at 37.5 mg/L, more strongly increased Arg1 mRNA expression and IGF-1 and IL-10 production and decreased iNOS mRNA expression and IL-6 production in LPS-induced microglia, and more effectively promoted cell survival and decreased apoptosis rate of H2O2-induced PC12 cells (P < 0.05).

CONCLUSION

EMSCs-exo at 75 mg/L can effectively reduce the proportion of M1 microglia and alleviate neuronal apoptosis under oxidative stress to promote neuronal survival, suggesting its potential in controlling secondary spinal cord injury.

TL1A promotes the postoperative cognitive dysfunction in mice through NLRP3-mediated A1 differentiation of astrocytes

AIM

We investigated the mechanism, whereby tumor necrosis factor-like ligand 1A (TL1A) mediates the A1 differentiation of astrocytes in postoperative cognitive dysfunction (POCD).

METHODS

The cognitive and behavioral abilities of mice were assessed by Morris water maze and open field tests, while the levels of key A1 and A2 astrocyte factors were detected by RT-qPCR. Immunohistochemical (IHC) staining was used to examine the expression of GFAP, western blot was used to assay the levels of related proteins, and enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of inflammatory cytokines.

RESULTS

The results showed that TL1A could promote the progression of cognitive dysfunction in mice. Astrocytes differentiated into A1 phenotype, while unobvious changes were noted in astrocyte A2 biomarkers. Knockout of NLRP3 or intervention with NLRP3 inhibitor could inhibit the effect of TL1A, improving the cognitive dysfunction and suppressing the A1 differentiation.

CONCLUSION

Our results demonstrate that TL1A plays an important role in POCD in mice, which promotes the A1 differentiation of astrocytes through NLRP3, thereby exacerbating the progression of cognitive dysfunction.

Mesenchymal Stem Cell Therapy in Traumatic Spinal Cord Injury: A Systematic Review

Recovery from a traumatic spinal cord injury (TSCI) is challenging due to the limited regenerative capacity of the central nervous system to restore cells, myelin, and neural connections. Cell therapy, particularly with mesenchymal stem cells (MSCs), holds significant promise for TSCI treatment. This systematic review aims to analyze the efficacy, safety, and therapeutic potential of MSC-based cell therapies in TSCI. A comprehensive search of PUBMED and COCHRANE databases until February 2023 was conducted, combining terms such as "spinal cord injury," "stem cells," "stem cell therapy," "mesenchymal stem cells," and "traumatic spinal cord injury". Among the 53 studies initially identified, 22 (21 clinical trials and 1 case series) were included. Findings from these studies consistently demonstrate improvements in AIS (ASIA Impairment Scale) grades, sensory scores, and, to a lesser extent, motor scores. Meta-analyses further support these positive outcomes. MSC-based therapies have shown short- and medium-term safety, as indicated by the absence of significant adverse events within the studied timeframe. However, caution is required when drawing generalized recommendations due to the limited scientific evidence available. Further research is needed to elucidate the long-term safety and clinical implications of these advancements. Although significant progress has been made, particularly with MSC-based therapies, additional studies exploring other potential future therapies such as gene therapies, neurostimulation techniques, and tissue engineering approaches are essential for a comprehensive understanding of the evolving TSCI treatment landscape.

Tackling the glial scar in spinal cord regeneration: new discoveries and future directions

Axonal regeneration and functional recovery are poor after spinal cord injury (SCI), typified by the formation of an injury scar. While this scar was traditionally believed to be primarily responsible for axonal regeneration failure, current knowledge takes a more holistic approach that considers the intrinsic growth capacity of axons. Targeting the SCI scar has also not reproducibly yielded nearly the same efficacy in animal models compared to these neuron-directed approaches. These results suggest that the major reason behind central nervous system (CNS) regeneration failure is not the injury scar but a failure to stimulate axon growth adequately. These findings raise questions about whether targeting neuroinflammation and glial scarring still constitute viable translational avenues. We provide a comprehensive review of the dual role of neuroinflammation and scarring after SCI and how future research can produce therapeutic strategies targeting the hurdles to axonal regeneration posed by these processes without compromising neuroprotection.