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Table of Content

    15 May 2025, Volume 20 Issue 5 Previous Issue   
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    Exosomes: the next-generatton therapeuttc plattorm for ischemic stroke
    Wenjing Yin , Hongyin Ma , Yang Qu , Jiaxin Ren , Yingying Sun , Zhen-Ni Guo , Yi Yang
    2025, 20 (5):  1221-1235.  doi: 10.4103/NRR.NRR-D-23-02051
    Abstract ( 409 )   PDF (1835KB) ( 276 )   Save
    Current therapeutic strategies for ischemic stroke fall short of the desired objective of neurological functional recovery. Therefore, there is an urgent need to develop new methods for the treatment of this condition. Exosomes are natural cell-derived vesicles that mediate signal transduction between cells under physiological and pathological conditions. They have low immunogenicity, good stability, high delivery efficiency, and the ability to cross the blood–brain barrier. These physiological properties of exosomes have the potential to lead to new breakthroughs in the treatment of ischemic stroke. The rapid development of nanotechnology has advanced the application of engineered exosomes, which can effectively improve targeting ability, enhance therapeutic efficacy, and minimize the dosages needed. Advances in technology have also driven clinical translational research on exosomes. In this review, we describe the therapeutic effects of exosomes and their positive roles in current treatment strategies for ischemic stroke, including their anti-inflammation, anti-apoptosis, autophagy-regulation, angiogenesis, neurogenesis, and glial scar formation reduction effects. However, it is worth noting that, despite their significant therapeutic potential, there remains a dearth of standardized characterization methods and efficient isolation techniques capable of producing highly purified exosomes. Future optimization strategies should prioritize the exploration of suitable isolation techniques and the establishment of unified workflows to effectively harness exosomes for diagnostic or therapeutic applications in ischemic stroke. Ultimately, our review aims to summarize our understanding of exosome-based treatment prospects in ischemic stroke and foster innovative ideas for the development of exosome-based therapies.
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    NECAB family of neuronal calcium-binding proteins in health and disease
    Diones Bueno , Michael K.E. Schäfer , Sudena Wang , Michael J. Schmeisser , Axel Methner
    2025, 20 (5):  1236-1243.  doi: 10.4103/NRR.NRR-D-24-00094
    Abstract ( 76 )   PDF (1518KB) ( 229 )   Save
    The N-terminal EF-hand calcium-binding proteins 1–3 (NECAB1–3) constitute a family of predominantly neuronal proteins characterized by the presence of at least one EF-hand calcium-binding domain and a functionally less well characterized C-terminal antibiotic biosynthesis monooxygenase domain. All three family members were initially discovered due to their interactions with other proteins. NECAB1 associates with synaptotagmin-1, a critical neuronal protein involved in membrane trafficking and synaptic vesicle exocytosis. NECAB2 interacts with predominantly striatal G-protein-coupled receptors, while NECAB3 partners with amyloid-β A4 precursor protein-binding family A members 2 and 3, key regulators of amyloid-β production. This demonstrates the capacity of the family for interactions with various classes of proteins. NECAB proteins exhibit distinct subcellular localizations: NECAB1 is found in the nucleus and cytosol, NECAB2 resides in endosomes and the plasma membrane, and NECAB3 is present in the endoplasmic reticulum and Golgi apparatus. The antibiotic biosynthesis monooxygenase domain, an evolutionarily ancient component, is akin to atypical heme oxygenases in prokaryotes but is not wellcharacterized in vertebrates. Prokaryotic antibiotic biosynthesis monooxygenase domains typically form dimers, suggesting that calcium-mediated conformational changes in NECAB proteins may induce antibiotic biosynthesis monooxygenase domain dimerization, potentially activating some enzymatic properties. However, the substrate for this enzymatic activity remains uncertain. Alternatively, calcium-mediated conformational changes might influence protein interactions or the subcellular localization of NECAB proteins by controlling the availability of protein–protein interaction domains situated between the EF hands and the antibiotic biosynthesis monooxygenase domain. This review summarizes what is known about genomic organization, tissue expression, intracellular localization, interaction partners, and the physiological and pathophysiological role of the NECAB family.
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    The role of axon guidance molecules in the pathogenesis of epilepsy
    Zheng Liu, Chunhua Pan, Hao Huang
    2025, 20 (5):  1244-1257.  doi: 10.4103/NRR.NRR-D-23-01620
    Abstract ( 185 )   PDF (9833KB) ( 39 )   Save
    Current treatments for epilepsy can only manage the symptoms of the condition but cannot alter the initial onset or halt the progression of the disease. Consequently, it is crucial to identify drugs that can target novel cellular and molecular mechanisms and mechanisms of action. Increasing evidence suggests that axon guidance molecules play a role in the structural and functional modifications of neural networks and that the dysregulation of these molecules is associated with epilepsy susceptibility. In this review, we discuss the essential role of axon guidance molecules in neuronal activity in patients with epilepsy as well as the impact of these molecules on synaptic plasticity and brain tissue remodeling. Furthermore, we examine the relationship between axon guidance molecules and neuroinflammation, as well as the structural changes in specific brain regions that contribute to the development of epilepsy. Ample evidence indicates that axon guidance molecules, including semaphorins and ephrins, play a fundamental role in guiding axon growth and the establishment of synaptic connections. Deviations in their expression or function can disrupt neuronal connections, ultimately leading to epileptic seizures. The remodeling of neural networks is a significant characteristic of epilepsy, with axon guidance molecules playing a role in the dynamic reorganization of neural circuits. This, in turn, affects synapse formation and elimination. Dysregulation of these molecules can upset the delicate balance between excitation and inhibition within a neural network, thereby increasing the risk of overexcitation and the development of epilepsy. Inflammatory signals can regulate the expression and function of axon guidance molecules, thus influencing axonal growth, axon orientation, and synaptic plasticity. The dysregulation of neuroinflammation can intensify neuronal dysfunction and contribute to the occurrence of epilepsy. This review delves into the mechanisms associated with the pathogenicity of axon guidance molecules in epilepsy, offering a valuable reference for the exploration of therapeutic targets and presenting a fresh perspective on treatment strategies for this condition.
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    Potassium and calcium channels in different nerve cells act as therapeutic targets in neurological disorders
    Qing Qiu, Mengttng Yang , Danfeng Gong , Haiying Liang , Tingttng Chen
    2025, 20 (5):  1258-1276.  doi: 10.4103/NRR.NRR-D-23-01766
    Abstract ( 366 )   PDF (3524KB) ( 260 )   Save

    The central nervous system, information integration center of the body, is mainly composed of neurons and glial cells. The neuron is one of the most basic and important structural and functional units of the central nervous system, with sensory stimulation and excitation conduction functions. Astrocytes and microglia belong to the glial cell family, which is the main source of cytokines and represents the main defense system of the central nervous system. Nerve cells undergo neurotransmission or gliotransmission, which regulates neuronal activity via the ion channels, receptors, or transporters expressed on nerve cell membranes. Ion channels, composed of large transmembrane proteins, play crucial roles in maintaining nerve cell homeostasis. These channels are also important for control of the membrane potential and in the secretion of neurotransmitters. A variety of cellular functions and life activities, including functional regulation of the central nervous system, the generation and conduction of nerve excitation, the occurrence of receptor potential, heart pulsation, smooth muscle peristalsis, skeletal muscle contraction, and hormone secretion, are closely related to ion channels associated with passive transmembrane transport. Two types of ion channels in the central nervous system, potassium channels and calcium channels, are closely related to various neurological disorders, including Alzheimer’s disease, Parkinson’s disease, and epilepsy. Accordingly, various drugs that can affect these ion channels have been explored deeply to provide new directions for the treatment of these neurological disorders. In this review, we focus on the functions of potassium and calcium ion channels in different nerve cells and their involvement in neurological disorders such as Parkinson’s disease, Alzheimer’s disease, depression, epilepsy, autism, and rare disorders. We also describe several clinical drugs that target potassium or calcium channels in nerve cells and could be used to treat these disorders. We concluded that there are few clinical drugs that can improve the pathology these diseases by acting on potassium or calcium ions. Although a few novel ion-channel-specific modulators have been discovered, meaningful therapies have largely not yet been realized. The lack of target-specific drugs, their requirement to cross the blood–brain barrier, and their exact underlying mechanisms all need further attention. This review aims to explain the urgent problems that need research progress and provide comprehensive information aiming to arouse the research community’s interest in the development of ion channel-targeting drugs and the identification of new therapeutic targets for that can increase the cure rate of nervous system diseases and reduce the occurrence of adverse reactions in other systems.

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    T cell interactions with microglia in immuneinflammatory processes of ischemic stroke
    Yuxiao Zheng, Zilin Ren, Ying Liu, Juntang Yan, Congai Chen , Yanhui He , Yuyu Shi , Fafeng Cheng , Qingguo Wang , Changxiang Li , Xueqian Wang
    2025, 20 (5):  1277-1292.  doi: 10.4103/NRR.NRR-D-23-01385
    Abstract ( 349 )   PDF (1590KB) ( 203 )   Save

    The primary mechanism of secondary injury after cerebral ischemia may be the brain inflammation that emerges after an ischemic stroke, which promotes neuronal death and inhibits nerve tissue regeneration. As the first immune cells to be activated after an ischemic stroke, microglia play an important immunomodulatory role in the progression of the condition. After an ischemic stroke, peripheral blood immune cells (mainly T cells) are recruited to the central nervous system by chemokines secreted by immune cells in the brain, where they interact with central nervous system cells (mainly microglia) to trigger a secondary neuroimmune response. This review summarizes the interactions between T cells and microglia in the immune-inflammatory processes of ischemic stroke. We found that, during ischemic stroke, T cells and microglia demonstrate a more pronounced synergistic effect. Th1, Th17, and M1 microglia can co-secrete pro-inflammatory factors, such as interferon-γ, tumor necrosis factor-α, and interleukin-1β, to promote neuroinflammation and exacerbate brain injury. Th2, Treg, and M2 microglia jointly secrete anti-inflammatory factors, such as interleukin-4, interleukin-10, and transforming growth factor-β, to inhibit the progression of neuroinflammation, as well as growth factors such as brain-derived neurotrophic factor to promote nerve regeneration and repair brain injury. Immune interactions between microglia and T cells influence the direction of the subsequent neuroinflammation, which in turn determines the prognosis of ischemic stroke patients. Clinical trials have been conducted on the ways to modulate the interactions between T cells and microglia toward anti-inflammatory communication using the immunosuppressant fingolimod or overdosing with Treg cells to promote neural tissue repair and reduce the damage caused by ischemic stroke. However, such studies have been relatively infrequent, and clinical experience is still insufficient. In summary, in ischemic stroke, T cell subsets and activated microglia act synergistically to regulate inflammatory progression, mainly by secreting inflammatory factors. In the future, a key research direction for ischemic stroke treatment could be rooted in the enhancement of anti-inflammatory factor secretion by promoting the generation of Th2 and Treg cells, along with the activation of M2-type microglia. These approaches may alleviate neuroinflammation and facilitate the repair of neural tissues. 

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    Combinatorial therapies for spinal cord injury repair
    Carla S. Sousa , Andreia Monteiro , António J. Salgado , Nuno A. Silva
    2025, 20 (5):  1293-1308.  doi: 10.4103/NRR.NRR-D-24-00061
    Abstract ( 87 )   PDF (1620KB) ( 98 )   Save
    Spinal cord injuries have profound detrimental effects on individuals, regardless of whether they are caused by trauma or non-traumatic events. The compromised regeneration of the spinal cord is primarily attributed to damaged neurons, inhibitory molecules, dysfunctional immune response, and glial scarring. Unfortunately, currently, there are no effective treatments available that can fully repair the spinal cord and improve functional outcomes. Nevertheless, numerous pre-clinical approaches have been studied for spinal cord injury recovery, including using biomaterials, cells, drugs, or technological-based strategies. Combinatorial treatments, which target various aspects of spinal cord injury pathophysiology, have been extensively tested in the last decade. These approaches aim to synergistically enhance repair processes by addressing various obstacles faced during spinal cord regeneration. Thus, this review intends to provide scientists and clinicians with an overview of pre-clinical combinatorial approaches that have been developed toward the solution of spinal cord regeneration as well as update the current knowledge about spinal cord injury pathophysiology with an emphasis on the current clinical management.
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    The complex effects of miR-146a in the pathogenesis of Alzheimer’s disease
    Yunfan Long, Jiajia Liu , Yu Wang , Haidong Guo , Guohong Cui
    2025, 20 (5):  1309-1323.  doi: 10.4103/NRR.NRR-D-23-01566
    Abstract ( 113 )   PDF (4953KB) ( 119 )   Save
    Alzheimer’s disease is a neurodegenerative disorder characterized by cognitive dysfunction and behavioral abnormalities. Neuroinflammatory plaques formed through the extracellular deposition of amyloid-β proteins, as well as neurofibrillary tangles formed by the intracellular deposition of hyperphosphorylated tau proteins, comprise two typical pathological features of Alzheimer’s disease. Besides symptomatic treatment, there are no effective therapies for delaying Alzheimer’s disease progression. MicroRNAs (miR) are small, non-coding RNAs that negatively regulate gene expression at the transcriptional and translational levels and play important roles in multiple physiological and pathological processes. Indeed, miR-146a, a NF-κB-regulated gene, has been extensively implicated in the development of Alzheimer’s disease through several pathways. Research has demonstrated substantial dysregulation of miR-146a both during the initial phases and throughout the progression of this disorder. MiR-146a is believed to reduce amyloid-β deposition and tau protein hyperphosphorylation through the TLR/IRAK1/TRAF6 pathway; however, there is also evidence supporting that it can promote these processes through many other pathways, thus exacerbating the pathological manifestations of Alzheimer’s disease. It has been widely reported that miR-146a mediates synaptic dysfunction, mitochondrial dysfunction, and neuronal death by targeting mRNAs encoding synaptic-related proteins, mitochondrial-related proteins, and membrane proteins, as well as other mRNAs. Regarding the impact on glial cells, miR-146a also exhibits differential effects. On one hand, it causes widespread and sustained inflammation through certain pathways, while on the other hand, it can reverse the polarization of astrocytes and microglia, alleviate neuroinflammation, and promote oligodendrocyte progenitor cell differentiation, thus maintaining the normal function of the myelin sheath and exerting a protective effect on neurons. In this review, we provide a comprehensive analysis of the involvement of miR-146a in the pathogenesis of Alzheimer’s disease. We aim to elucidate the relationship between miR-146a and the key pathological manifestations of Alzheimer’s disease, such as amyloid-β deposition, tau protein hyperphosphorylation, neuronal death, mitochondrial dysfunction, synaptic dysfunction, and glial cell dysfunction, as well as summarize recent relevant studies that have highlighted the potential of miR-146a as a clinical diagnostic marker and therapeutic target for Alzheimer’s disease.
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    Complement-dependent neuroinffammatton in spinal cord injury: from pathology to therapeuttc implicattons
    Hassan Saad , Bachar El Baba , Ali Tfaily , Firas Kobeissy, Juanmarco Gutterrez Gonzalez , Daniel Refai , Gerald R. Rodts , Christtan Mustrop , David Gimbel , Jonathan Grossberg, Daniel L. Barrow, Matthew F. Gary , Ali M. Alawieh
    2025, 20 (5):  1324-1335.  doi: 10.4103/NRR.NRR-D-24-00116
    Abstract ( 128 )   PDF (22419KB) ( 44 )   Save
    Spinal cord injury remains a major cause of disability in young adults, and beyond acute decompression and rehabilitation, there are no pharmacological treatments to limit the progression of injury and optimize recovery in this population. Following the thorough investigation of the complement system in triggering and propagating cerebral neuroinflammation, a similar role for complement in spinal neuroinflammation is a focus of ongoing research. In this work, we survey the current literature investigating the role of complement in spinal cord injury including the sources of complement proteins, triggers of complement activation, and role of effector functions in the pathology. We study relevant data demonstrating the different triggers of complement activation after spinal cord injury including direct binding to cellular debris, and or activation via antibody binding to damage-associated molecular patterns. Several effector functions of complement have been implicated in spinal cord injury, and we critically evaluate recent studies on the dual role of complement anaphylatoxins in spinal cord injury while emphasizing the lack of pathophysiological understanding of the role of opsonins in spinal cord injury. Following this pathophysiological review, we systematically review the different translational approaches used in preclinical models of spinal cord injury and discuss the challenges for future translation into human subjects. This review emphasizes the need for future studies to dissect the roles of different complement pathways in the pathology of spinal cord injury, to evaluate the phases of involvement of opsonins and anaphylatoxins, and to study the role of complement in white matter degeneration and regeneration using translational strategies to supplement genetic models. 
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    Heterogeneity of mature oligodendrocytes in the central nervous system
    Chao Weng , Adam M.R. Groh, Moein Yaqubi, Qiao-Ling Cui , Jo Anne Stratton , G. R. Wayne Moore, Jack P. Antel
    2025, 20 (5):  1336-1349.  doi: 10.4103/NRR.NRR-D-24-00055
    Abstract ( 170 )   PDF (9889KB) ( 66 )   Save

    Mature oligodendrocytes form myelin sheaths that are crucial for the insulation of axons and efficient signal transmission in the central nervous system. Recent evidence has challenged the classical view of the functionally static mature oligodendrocyte and revealed a gamut of dynamic functions such as the ability to modulate neuronal circuitry and provide metabolic support to axons. Despite the recognition of potential heterogeneity in mature oligodendrocyte function, a comprehensive summary of mature oligodendrocyte diversity is lacking. We delve into early 20th-century studies by Robertson and de Río Hortega that laid the foundation for the modern identification of regional and morphological heterogeneity in mature oligodendrocytes. Indeed, recent morphologic and functional studies call into question the long-assumed homogeneity of mature oligodendrocyte function through the identification of distinct subtypes with varying myelination preferences. Furthermore, modern molecular investigations, employing techniques such as single cell/nucleus RNA sequencing, consistently unveil at least six mature oligodendrocyte subpopulations in the human central nervous system that are highly transcriptomically diverse and vary with central nervous system region. Age and disease related mature oligodendrocyte variation denotes the impact of pathological conditions such as multiple sclerosis, Alzheimer's disease, and psychiatric disorders. Nevertheless, caution is warranted when subclassifying mature oligodendrocytes because of the simplification needed to make conclusions about cell identity from temporally confined investigations. Future studies leveraging advanced techniques like spatial transcriptomics and single-cell proteomics promise a more nuanced understanding of mature oligodendrocyte heterogeneity. Such research avenues that precisely evaluate mature oligodendrocyte heterogeneity with care to understand the mitigating influence of species, sex, central nervous system region, age, and disease, hold promise for the development of therapeutic interventions targeting varied central nervous system pathology. 

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    Decoding the nexus: branched-chain amino acids and their connection with sleep, circadian rhythms, and cardiometabolic health
    Hui Li , Laurent Seugnet
    2025, 20 (5):  1350-1363.  doi: 10.4103/NRR.NRR-D-23-02020
    Abstract ( 121 )   PDF (1187KB) ( 94 )   Save
    The sleep-wake cycle stands as an integrative process essential for sustaining optimal brain function and, either directly or indirectly, overall body health, encompassing metabolic and cardiovascular well-being. Given the heightened metabolic activity of the brain, there exists a considerable demand for nutrients in comparison to other organs. Among these, the branched-chain amino acids, comprising leucine, isoleucine, and valine, display distinctive significance, from their contribution to protein structure to their involvement in overall metabolism, especially in cerebral processes. Among the first amino acids that are released into circulation post-food intake, branched-chain amino acids assume a pivotal role in the regulation of protein synthesis, modulating insulin secretion and the amino acid sensing pathway of target of rapamycin. Branched-chain amino acids are key players in influencing the brain’s uptake of monoamine precursors, competing for a shared transporter. Beyond their involvement in protein synthesis, these amino acids contribute to the metabolic cycles of γ-aminobutyric acid and glutamate, as well as energy metabolism. Notably, they impact GABAergic neurons and the excitation/inhibition balance. The rhythmicity of branchedchain amino acids in plasma concentrations, observed over a 24-hour cycle and conserved in rodent models, is under circadian clock control. The mechanisms underlying those rhythms and the physiological consequences of their disruption are not fully understood. Disturbed sleep, obesity, diabetes, and cardiovascular diseases can elevate branched-chain amino acid concentrations or modify their oscillatory dynamics. The mechanisms driving these effects are currently the focal point of ongoing research efforts, since normalizing branched-chain amino acid levels has the ability to alleviate the severity of these pathologies. In this context, the Drosophila model, though underutilized, holds promise in shedding new light on these mechanisms. Initial findings indicate its potential to introduce novel concepts, particularly in elucidating the intricate connections between the circadian clock, sleep/wake, and metabolism. Consequently, the use and transport of branched-chain amino acids emerge as critical components and orchestrators in the web of interactions across multiple organs throughout the sleep/wake cycle. They could represent one of the so far elusive mechanisms connecting sleep patterns to metabolic and cardiovascular health, paving the way for potential therapeutic interventions.
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    Stiffness-tunable biomaterials provide a good extracellular matrix environment for axon growth and regeneration
    Ronglin Han , Lanxin Luo , Caiyan Wei , Yaru Qiao , Jiming Xie , Xianchao Pan , Juan Xing
    2025, 20 (5):  1364-1376.  doi: 10.4103/NRR.NRR-D-23-01874
    Abstract ( 247 )   PDF (4109KB) ( 165 )   Save

    Neuronal growth, extension, branching, and formation of neural networks are markedly influenced by the extracellular matrix—a complex network composed of proteins and carbohydrates secreted by cells. In addition to providing physical support for cells, the extracellular matrix also conveys critical mechanical stiffness cues. During the development of the nervous system, extracellular matrix stiffness plays a central role in guiding neuronal growth, particularly in the context of axonal extension, which is crucial for the formation of neural networks. In neural tissue engineering, manipulation of biomaterial stiffness is a promising strategy to provide a permissive environment for the repair and regeneration of injured nervous tissue. Recent research has fine-tuned synthetic biomaterials to fabricate scaffolds that closely replicate the stiffness profiles observed in the nervous system. In this review, we highlight the molecular mechanisms by which extracellular matrix stiffness regulates axonal growth and regeneration. We highlight the progress made in the development of stiffness-tunable biomaterials to emulate in vivo extracellular matrix environments, with an emphasis on their application in neural repair and regeneration, along with a discussion of the current limitations and future prospects. The exploration and optimization of the stiffness-tunable biomaterials has the potential to markedly advance the development of neural tissue engineering.

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    Pharmacological intervention for chronic phase of spinal cord injury
    Chihiro Tohda
    2025, 20 (5):  1377-1389.  doi: 10.4103/NRR.NRR-D-24-00176
    Abstract ( 92 )   PDF (4651KB) ( 83 )   Save
    Spinal cord injury is an intractable traumatic injury. The most common hurdles faced during spinal cord injury are failure of axonal regrowth and reconnection to target sites. These also tend to be the most challenging issues in spinal cord injury. As spinal cord injury progresses to the chronic phase, lost motor and sensory functions are not recovered. Several reasons may be attributed to the failure of recovery from chronic spinal cord injury. These include factors that inhibit axonal growth such as activated astrocytes, chondroitin sulfate proteoglycan, myelin-associated proteins, inflammatory microglia, and fibroblasts that accumulate at lesion sites. Skeletal muscle atrophy due to denervation is another chronic and detrimental spinal cord injury–specific condition. Although several intervention strategies based on multiple outlooks have been attempted for treating spinal cord injury, few approaches have been successful. To treat chronic spinal cord injury, neural cells or tissue substitutes may need to be supplied in the cavity area to enable possible axonal growth. Additionally, stimulating axonal growth activity by extrinsic factors is extremely important and essential for maintaining the remaining host neurons and transplanted neurons. This review focuses on pharmacotherapeutic approaches using small compounds and proteins to enable axonal growth in chronic spinal cord injury. This review presents some of these candidates that have shown promising outcomes in basic research (in vivo animal studies) and clinical trials: AA-NgR(310)ecto-Fc (AXER-204), fasudil, phosphatase and tensin homolog protein antagonist peptide 4, chondroitinase ABC, intracellular sigma peptide, (-)-epigallocatechin gallate, matrine, acteoside, pyrvate kinase M2, diosgenin, granulocyte-colony stimulating factor, and fampridine-sustained release. Although the current situation suggests that drug-based therapies to recover function in chronic spinal cord injury are limited, potential candidates have been identified through basic research, and these candidates may be subjects of clinical studies in the future. Moreover, cocktail therapy comprising drugs with varied underlying mechanisms may be effective in treating the refractory status of chronic spinal cord injury. 
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    Substrate topography as a powerful tool to modify glial cell biology and interactions
    Pascal Achenbach , Haktan Alttnova, Gary A. Brook
    2025, 20 (5):  1390-1391.  doi: 10.4103/NRR.NRR-D-24-00329
    Abstract ( 75 )   PDF (2295KB) ( 47 )   Save
    Traumatic injuries to the central nervous system (CNS) result in disruptton of the intricate network of axons which connect functionally related neurons that are widely distributed throughout the brain and spinal cord. Under normal conditions, maintenance of this complex system is structurally and functionally supported by astrocytes (ACs) and other glial cells, the processes of which form a framework surrounding neuronal cell bodies, dendrites, axons, and synapses. Following injury, however, ACs adopt a reactive, scar-forming phenotype to establish a barrier that limits the spread of inffammatory cells and molecules from the primary lesion site to adjacent nervous ttssue, effecttvely limittng secondary ttssue degeneratton. Unfortunately, due to the persistent nature of the resulttng glial scar, this inittally protecttve functton acts as a double-edged sword as it also suppresses CNS axon sprouting and regeneration across the lesion site, resulting in permanent disability for those affected.
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     Translational machinery and translation regulation in axon regeneration
    Homaira Nawabi , Stephane Belin
    2025, 20 (5):  1392-1394.  doi: 10.4103/NRR.NRR-D-24-00313
    Abstract ( 91 )   PDF (494KB) ( 84 )   Save
    Over the centuries, the regeneration field has been puzzled by the dual response of the central nervous system (CNS–brain, spinal cord, cranial nerves I and II) and the peripheral nervous system (PNS that refers to all the nerves that innervate muscles, skin, organs, bones among others). Even Ramòn y Cajal had noticed that an injury to the PNS often leads to axon regrowth, in contrast to the CNS. This PNS ability is explored during spectacular surgeries where chopped limbs could be graffed back. Some of these pattents are even able to recover complex functtons such as playing the piano after double hands graft (Grenoble University Hospital, France, 2017). In contrast, CNS axons are not able to regenerate after an insult. This is true in cases of neurodegenerative diseases (Alzheimer’s or Parkinson’s diseases for example) as well as in traumattc injuries (such as spinal cord injury). These insults lead to neuronal circuit disruption and neuronal apoptosis. As no treatment is available yet, patients endure irreversible loss of motor, cognittve and/or sensory functtons that considerably impair their quality of life. Thus, understanding molecular mechanisms underlying axon regeneration and finding new therapeutic strategies are critical for patients, families, and public health. 
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    Glia-to-neuron reprogramming to the rescue?
    Jack W. Hickmott, Cindi M. Morshead
    2025, 20 (5):  1395-1396.  doi: 10.4103/NRR.NRR-D-24-00281
    Abstract ( 78 )   PDF (3074KB) ( 68 )   Save
    Over the last two decades, the dogma that cell fate is immutable has been increasingly challenged, with important implications for regenerative medicine. The breakthrough discovery that induced pluripotent stem cells could be generated from adult mouse ffbroblasts is powerful proof that cell fate can be changed. An exciting extension of the discovery of cell fate impermanence is the direct cellular reprogramming hypothesis – that terminally differentiated cells can be reprogrammed into other adult cell fates without ffrst passing through a stem cell state. A significant body of evidence demonstrates direct cellular reprogramming in vitro (Vasan et al., 2021; Bocchi et al., 2022) and an excittng applicatton of this technology is the use of direct cellular reprogramming in vivo. Indeed, the promise of direct cellular reprogramming to replace lost cells in the central nervous system following neurotrauma or neurodegenerative disease is remarkable. Here we will discuss the hope, the hype, and the scrutiny that surrounds the promise of direct cellular reprogramming, specifically related to the generation of induced neurons from glial cells in vivo. We will highlight successes in the field, examine criticisms of this body of literature, and draw on previous examples of scienttffc controversy to propose a path forward to “rescue” the ffeld. 
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    Targeting cholesterol trafficking to mitigate axonal degeneration in hereditary spastic paraplegia
    Zhenyu Chen, Xue-Jun Li
    2025, 20 (5):  1397-1398.  doi: 10.4103/NRR.NRR-D-24-00138
    Abstract ( 111 )   PDF (848KB) ( 37 )   Save
    Axonal degeneration underlies many debilitating diseases including hereditary spastic paraplegia (HSP), a genettcally and clinically diverse group of disorders characterized by spasttcity and weakness of the lower extremities. HSP is one significant cause of chronic neurodisability due to the lack of effecttve treatments and a wide range of onset ages from early childhood to 70 years. These disorders are caused by axonal degeneration of cortical projection neurons, which disrupts the transmission of signals from these neurons to spinal motor neurons and muscles (Blackstone et al., 2011). Since the discovery of the first HSP gene (SPAST) in 1999, over 80 disttnct genettc loci associated with HSP have been identtffed. How the mutations of these functionally divergent genes speciffcally result in axonal degeneratton of corttcal projectton neurons remains largely unclear. 
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    Visualizing traumatic brain injury: ocular clues for diagnosis and assessment
    Morteza Abyadeh, Vivek Gupta, Yuyi You, Joao A. Paulo, Mehdi Mirzaei
    2025, 20 (5):  1399-1340.  doi: 10.4103/NRR.NRR-D-23-01907
    Abstract ( 92 )   PDF (615KB) ( 54 )   Save
    Traumatic brain injury (TBI) is defined as damage to the brain resulting from an external sudden physical force or shock to the head. It is considered a silent public health epidemic causing significant death and disability globally. There were 64,000 TBI related deaths reported in the USA in 2020, with about US$76 billion in direct and indirect medical costs annually. TBI may have devastating chronic effects on the brain even if clinical symptoms disappear in the short term after the injury. TBI survivors have reported experiencing a range of neuropsychiatric symptoms such as amnesia, varying degrees of visual impairment, and have a higher risk of developing neurodegenerative diseases including Alzheimer’s disease (AD) later in their lives (Ramos-Cejudo et al., 2018). TBI has been shown to induce long-term neuropathological changes in the brain including amyloid‐β (Aβ) deposition and neurofibrillary tangle (NFT) formatton (Ramos‐Cejudo et al., 2018). Exposure to severe concussion or TBI has been suggested to increase the risk of AD development up to 4.5- fold. It can contribute to progressive cognitive decline which may be evident a decade affer the inittal injury depending on various factors such as sex, age, intensity, and site of injury (Tsitsopoulos and Marklund, 2013; National Academies of Sciences, Engineering, and Medicine, et al., 2019). Current diagnostic tools have their limitations, especially in detecttng mild forms of TBI, without clinical manifestattons. Advances in neuroimaging techniques such as positron emission tomography and cerebral spinal ffuid evaluatton have provided a valuable plattorm to study brain changes in TBI and associated neurodegeneration. However, ttme consuming and expensive nature of positron emission tomography and invasive cerebral spinal fluid sampling protocols limit their wide applicability in community setttngs. Given that any successful intervention to protect the neurons must be applied before a significant damage has occurred, it is imperattve to improve the existtng diagnostic approaches to detect milder forms of TBI. 
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    Microglial dysfunction and genetic risk for neurodegenerative disease
    Debra S. MacDonald, Jay Penney
    2025, 20 (5):  1401-1402.  doi: 10.4103/NRR.NRR-D-24-00146
    Abstract ( 83 )   PDF (551KB) ( 54 )   Save
    Neurodegenerattve disorders such as Alzheimer’s and Parkinson’s diseases are increasing in prevalence as world populations age. While tremendous progress has been made, our understanding of the mechanisms that underlie the development of these diseases remains far from complete. More troubling, despite the growing emottonal and ffnancial toll being taken by neurodegenerative disorders, existing treatment opttons are limited almost exclusively to those that help manage symptoms but that lack the ability to alter the progression of the disease (Liu et al., 2022).
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    Lactate is a potentially harmful substitute for brain glucose fuel: consequences for metabolic restoration of neurotransmission
    Oliver Kann , Lennart Söder, Babak Khodaie
    2025, 20 (5):  1403-1404.  doi: 10.4103/NRR.NRR-D-24-00262
    Abstract ( 124 )   PDF (1774KB) ( 83 )   Save
    The metabolite lactate (L-lactate) can be generated and released by diverse brain cells, including neurons, astrocytes, and oligodendrocytes (Kann, 2023; Rae et al., 2024). Lactate productton usually requires the degradation of glucose (D-glucose) – and glycogen in astrocytes – to pyruvate by glycolysis and subsequent conversion of pyruvate to lactate by the enzyme lactate dehydrogenase (Dienel, 2019; Rae et al., 2024). Lactate production occurs when local glycolysis exceeds oxidative phosphorylation in mitochondria, a complex metabolic process that requires the tricarboxylic acid cycle for pyruvate utilization, the respiratory chain and molecular oxygen as an electron acceptor to finally enable adenosine-5′- triphosphate (ATP) generatton (Dienel, 2019; Kann, 2023). Lactate production is generally favored during hypoxia (anaerobic glycolysis). Alternattvely, lactate is generated in the presence of oxygen (aerobic glycolysis), for example, in astrocytes or in neuronal structures that miss mitochondria like a fraction of presynaptic terminals in pyramidal cell axons (Magistretti and Allaman, 2018; Kann, 2023). Aerobic glycolysis in neurons and glial cells usually results in some net lactate efffux from the acttve brain to the blood circulatton (Dienel, 2019). By contrast to lactate, glucose is also required for essential processes such as build-up of glycogen and management of oxidattve stress (Dienel, 2019; Kann, 2023).
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    How dopamine tunes Parvalbumin Interneurons in the hippocampus: new experimental observations in Alzheimer’s disease
    Livia La Barbera, Paraskevi Krashia , Annalisa Nobili
    2025, 20 (5):  1405-1406.  doi: 10.4103/NRR.NRR-D-24-00322
    Abstract ( 64 )   PDF (1203KB) ( 54 )   Save
    Despite decades of dedi cated research, Alzheimer’s disease (AD) is an age-related and progressive neurodegenerative disorder for which the mechanisms of onset are still unclear. AD is characterized by featured histological alterations including amyloid-beta (Aβ) plaque depositton, accumulatton of neuroffbrillary tangles of hyperphosphorylated-tau, and neuronal loss, accompanied by progressive cognitive decline and behavioral changes. The sporadic form of AD primarily affects old individuals (onset around 65 years), leading to difffculttes in daily acttvittes along the disease progression. According to the last World Alzheimer Report, the number of patients suffering from AD, together with the economic and social burdens related to the disease, are expected to rapidly increase in the following years.
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    Aβ-induced disruption of axon-initial-segment mitochondria localization: consequences for TAU missorting in Alzheimer’s disease pathology
    Daniel Adam, Felix Langerscheidt, Hans Zempel
    2025, 20 (5):  1407-1408.  doi: 10.4103/NRR.NRR-D-24-00253
    Abstract ( 111 )   PDF (2437KB) ( 58 )   Save
    TAU is a neuronal microtubule-associated protein preferentially located in axons. In a battery of neurodegenerattve diseases termed “tauopathies,” including Alzheimer’s disease (AD), TAU is missorted and abnormally phosphorylated, leading to fflamentous accumulattons of hyperphosphorylated TAU, a pathological hallmark and potenttal disease driver of AD and related tauopathies (Zempel, 2024). The other hallmark of AD is the aberrant production of amyloid-β (Aβ), which accumulates in extracellular plaques. The axon initial segment (AIS) is a 20 to 60 µM long neuronal compartment separattng the axon from the axon hillock and cell body. Its molecular organization is characterized by a complex protein scaffold, consisting of transmembrane proteins, Ankyrin G (ANKG), spectrins, acttn structures (rings/patches composed of filamentous actin (F-actin), microtubules, and microtubule-associated proteins (Leterrier, 2018). Alterations of the AIS structure have been observed as a result of Aβ exposure: F-acttn is lost at the AIS after exposure to amyloid-β-oligomers (AβO; AD-like stress), likely due to aberrant activation of the F-actin severing enzyme cofilin (actin depolymerizing factor). Subsequent rapid remodeling and repolarization of F-actin might induce TAU missorttng by blocking the physiological anterograde sorting of TAU into the axon (Zempel et al., 2017, Bell-Simons et al., 2023, Buchholz and Zempel, 2024). Recently, we also provided evidence for a cluster of mitochondria in the proximal AIS, which has a functional role in the maintenance of TAU sorting: While mitochondria show relative absence in the central AIS, they cluster at the proximal AIS. The mitochondria in this cluster are largely immobile and only sparsely participate in axonal mitochondria-trafficking. Importantly, (local) impairment of this AIS-mitochondria-cluster (AMC) leads to detectable increases of somatic TAU, resembling AD-like TAU missorting (Tjiang and Zempel, 2022). While it is thus clear that both proper maintenance of F-acttn in the AIS, as well as proper functton of AIS-based mitochondria, may be crucial for neuronal function and maintenance of TAU sorttng and functton, the effect of AD-like stress on mitochondria in the AIS is underexplored.
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    β-Amyloid pathology-induced nanoscale synaptic disruption: The case of the GABAB-GIRK assembly
    Rafael Luján , Alejandro Marttn-Belmonte, Sergi Ferré, Francisco Ciruela
    2025, 20 (5):  1409-1410.  doi: 10.4103/NRR.NRR-D-24-00291
    Abstract ( 82 )   PDF (1126KB) ( 51 )   Save
    Alzheimer’s disease (AD) is characterized by an imbalance between excitatory and inhibitory brain networks, leading to aberrant homeostatic synaptic plasticity. AD has progressively been recognized as synaptopathy and synaptic dysfunction has been identified as a key component of its pathogenesis (Schirinzi et al., 2020). Synapttc dysfunctton is believed to precede synapse loss, a primary biological correlate of cognitive decline in AD, inevitably associated with neuronal death. The mechanism underlying synapse failure should depend on the specific molecular alterattons associated with the affected neuronal circuit, making it a crucial stage in AD pathogenesis. Despite the numerous dysfuncttons described in the AD brain, their underlying speciffc molecular alterattons remain unknown. Here, our goal is to highlight recent investigations focusing on the influence of amyloid-beta pathology on the nanoarchitecture of crittcal synapttc signaling proteins. Indeed, synapttc communicatton hinges on the precise molecular organization of specific signaling proteins, encompassing their density, distribution, and stoichiometry associated with each type of synapse. Consequently, the disruptton of such precise molecular organizatton can modify synaptic transmission, thereby altering neural circuits and ultimately leading to neuronal loss, contributtng to neurodegeneratton. Therefore, prevalent pathological features of neurodegenerative diseases include the loss of specific populations of synapses. For example, the pathological hallmark of AD encompasses the loss of excitatory synapses in the CA1 area of the hippocampus, observed in the early stages of the disease in both patients and animal models (Montero-Crespo et al., 2021). Importantly, we recently reported nanoscale alterations on the two-dimensional distribution of the G proteingated inwardly rectifying K+ (GIRK) channels and their spatial interplay with the gammaaminobutyric acid G protein-coupled receptor type B (GABAB receptor) in hippocampal CA1 pyramidal neurons from the APP/PS1 mouse model of AD (Martín-Belmonte et al., 2022). Overall, this nuanced exploration of nanoscale alterations of synapses on the APP/PS1 mouse provides valuable insights into the early pathological features of AD and may offer new strategies for therapeutic interventton.
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    Small extrachromosomal circular DNA in amyotrophic lateral sclerosis matter
    Marcos J. Araúzo-Bravo , Daniela Gerovska, Matthias Schwab, Alexandra Kretz
    2025, 20 (5):  1411-1413.  doi: 10.4103/NRR.NRR-D-23-01877
    Abstract ( 81 )   PDF (1458KB) ( 94 )   Save
    Comprehensive studies identify motor neuron spectrum disorders including amyotrophic lateral sclerosis (ALS) as globally rising fatal disorders with the highest prevalence in aging populattons, influenced by ethnicity and ancestry (GBD 2016 Motor Neuron Disease Collaborators, 2018). While ~10% of diagnoses involve a family history (fALS), most cases are considered sporadic (sALS). However, population-based studies suggest that even cases without a common index mutation impart heritability (Ryan et al., 2019), indicating a crucial role of rare and as yet unknown genettc denominators. Genotype-phenotype predictions remain weak despite an ever-rising resolution of background genetics and propose overlap in the (oligo-)genic architecture of simplified fALS and sALS categories. Establishing a new class of genetic biomarkers sensitive to both fALS and nominal sALS would impart paramount value in accelerating diagnosis, ascertaining patient strattffcattons, and improving predictton of disease progression. 
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    Apolipoprotein A-I binding protein-mediated neuroprotection in glaucomatous neuroinflammation and neurodegeneration
    Sinwoo Hwang, Seunghwan Choi, Soo-Ho Choi, Keun-Young Kim, Yury I. Miller, Won-Kyu Ju
    2025, 20 (5):  1414-1415.  doi: 10.4103/NRR.NRR-D-24-00221
    Abstract ( 67 )   PDF (1079KB) ( 23 )   Save
    Glaucoma is a multifactorial eye disorder that can cause vision loss and irreversible blindness, affecting individuals aged 40 to 80 years worldwide. Due to the aging population, it is expected that the number of people affected by glaucoma will surpass 111 million by 2040 as the disease becomes more prevalent. Glaucoma primarily contributes to opttc nerve axon loss and the progressive degeneration of retinal ganglion cells (RGCs), subsequently leading to vision impairment. The onset of glaucoma is affected by various factors, including genettc predisposittons, environmental influences, and physiological condittons. The major risk factors include elevated intraocular pressure (IOP), aging, genetic/ epigenettc factors, immune system dysregulatton, and vascular dysfunctton. Elevated IOP is currently the only adjustable and treatable risk factor for glaucoma through medicattons, laser procedures, and surgical interventions. However, reducing IOP by these treatments is insufffcient to manage the progression of glaucomatous optic nerve degeneration and RGC death. There is growing interest in elucidating the pathophysiological mechanisms underlying glaucoma pathogenesis, particularly regarding the involvement of gliamediated neuroinffammatton. Cholesterol is essential for the structural and functional integrity of RGCs, playing a pivotal role in maintaining cell membrane integrity, signal transduction, synaptic function, and neuroprotectton. However, excessive accumulatton of cholesterol deteriorates cellular functions by enhancing toll-like receptor (TLR) signaling, ac tivating inflammasomes, and induc ing inflammatory responses (Tall and Yvan-Charvet, 2015). Recent evidence indicates that ATPbinding cassette transporter 1 (ABCA1) deffciency triggers rettnal cholesterol accumulatton, resulttng in alterations in mitochondrial function and autophagy ffux, and RGC death (Yang et al., 2023). Addittonally, glia-speciffc ABCA1 deffciency induces cholesterol accumulatton in the astrocytes, which is linked to RGC degeneration and inflammation (Shinozaki et al., 2022). 
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    Induced neural stem cells regulate microglial activation through Akt-mediated upregulation of CXCR4 and Crry in a mouse model of closed head injury.
    Mou Gao, Qin Dong , Dan Zou , Zhijun Yang , Lili Guo , Ruxiang Xu
    2025, 20 (5):  1416-1430.  doi: 10.4103/NRR.NRR-D-23-01495
    Abstract ( 165 )   PDF (8056KB) ( 34 )   Save
    Microglial activation that occurs rapidly after closed head injury may play important and complex roles in neuroinflammation-associated neuronal damage and repair. We previously reported that induced neural stem cells can modulate the behavior of activated microglia via CXCL12/CXCR4 signaling, influencing their activation such that they can promote neurological recovery. However, the mechanism of CXCR4 upregulation in induced neural stem cells remains unclear. In this study, we found that nuclear factor-κB activation induced by closed head injury mouse serum in microglia promoted CXCL12 and tumor necrosis factor-α expression but suppressed insulin-like growth factor-1 expression. However, recombinant complement receptor 2-conjugated Crry (CR2-Crry) reduced the effects of closed head injury mouse serum-induced nuclear factor-κB activation in microglia and the levels of activated microglia, CXCL12, and tumor necrosis factor-α. Additionally, we observed that, in response to stimulation (including stimulation by CXCL12 secreted by activated microglia), CXCR4 and Crry levels can be upregulated in induced neural stem cells via the interplay among CXCL12/CXCR4, Crry, and Akt signaling to modulate microglial activation. In agreement with these in vitro experimental results, we found that Akt activation enhanced the immunoregulatory effects of induced neural stem cell grafts on microglial activation, leading to the promotion of neurological recovery via insulin-like growth factor-1 secretion and the neuroprotective effects of induced neural stem cell grafts through CXCR4 and Crry upregulation in the injured cortices of closed head injury mice. Notably, these beneficial effects of Akt activation in induced neural stem cells were positively correlated with the therapeutic effects of induced neural stem cells on neuronal injury, cerebral edema, and neurological disorders post–closed head injury. In conclusion, our findings reveal that Akt activation may enhance the immunoregulatory effects of induced neural stem cells on microglial activation via upregulation of CXCR4 and Crry, thereby promoting induced neural stem cell–mediated improvement of neuronal injury, cerebral edema, and neurological disorders following closed head injury.
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    MET receptor tyrosine kinase promotes the generation of functional synapses in adult cortical circuits
    Yuehua Cui , Xiaokuang Ma , Jing Wei , Chang Chen , Neha Shakir , Hitesch Guirram , Zhiyu Dai , Trent Anderson , Deveroux Ferguson , Shenfeng Qiu
    2025, 20 (5):  1431-1444.  doi: 10.4103/NRR.NRR-D-23-01471
    Abstract ( 150 )   PDF (4564KB) ( 105 )   Save

    Loss of synapse and functional connectivity in brain circuits is associated with aging and neurodegeneration, however, few molecular mechanisms are known to intrinsically promote synaptogenesis or enhance synapse function. We have previously shown that MET receptor tyrosine kinase in the developing cortical circuits promotes dendritic growth and dendritic spine morphogenesis. To investigate whether enhancing MET in adult cortex has synapse regenerating potential, we created a knockin mouse line, in which the human MET gene  expression and signaling can be turned on in adult (10–12 months) cortical neurons through doxycycline-containing chow. We found that similar to the developing brain, turning on MET signaling in the adult cortex activates small GTPases and increases spine density in prefrontal projection neurons. These findings are further corroborated by increased synaptic activity and transient generation of immature silent synapses. Prolonged MET signaling resulted in an increased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/N-methyl-D-aspartate (AMPA/NMDA) receptor current ratio, indicative of enhanced synaptic function and connectivity. Our data reveal that enhancing MET signaling could be an interventional approach to promote synaptogenesis and preserve functional connectivity in the adult brain. These findings may have implications for regenerative therapy in aging and neurodegeneration conditions. 

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    Exercise preconditioning alleviates ischemia-induced memory deficits by increasing circulating adiponectin
    Meifeng Zheng , Borui Zhang , Sonata S Y Yau , Kwok-Fai So , Li Zhang , Haining Ou
    2025, 20 (5):  1445-1454.  doi: 10.4103/NRR.NRR-D-23-01101
    Abstract ( 194 )   PDF (9035KB) ( 66 )   Save

    Cerebral ischemia is a major health risk that requires preventive approaches in addition to drug therapy. Physical exercise enhances neurogenesis and synaptogenesis, and has been widely used for functional rehabilitation after stroke. In this study, we determined whether exercise training before disease onset can alleviate the severity of cerebral ischemia. We also examined the role of exercise-induced circulating factors in these effects. Adult mice were subjected to 14 days of treadmill exercise training before surgery for middle cerebral artery occlusion. We found that this exercise pre-conditioning strategy effectively attenuated brain infarct area, inhibited gliogenesis, protected synaptic proteins, and improved novel object and spatial memory function. Further analysis showed that circulating adiponectin plays a critical role in these preventive effects of exercise. Agonist activation of adiponectin receptors by AdipoRon mimicked the effects of exercise, while inhibiting receptor activation abolished the exercise effects. In summary, our results suggest a crucial role of circulating adiponectin in the effects of exercise pre-conditioning in protecting against cerebral ischemia and supporting the health benefits of exercise.

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    Endoplasmic reticulum stress and autophagy in cerebral ischemia/reperfusion injury: PERK as a potential target for intervention

    Ju Zheng , Yixin Li , Ting Zhang , Yanlin Fu , Peiyan Long , Xiao Gao , Zhengwei Wang , Zhizhong Guan , Xiaolan Qi , Wei Hong , Yan Xiao
    2025, 20 (5):  1455-1466.  doi: 10.4103/NRR.NRR-D-23-00794
    Abstract ( 156 )   PDF (6581KB) ( 99 )   Save

    Several studies have shown that activation of unfolded protein response and endoplasmic reticulum (ER) stress plays a crucial role in severe cerebral ischemia/reperfusion injury. Autophagy occurs within hours after cerebral ischemia, but the relationship between ER stress and autophagy remains unclear. In this study, we established experimental models using oxygen-glucose deprivation/reoxygenation in PC12 cells and primary neurons to simulate cerebral ischemia/reperfusion injury. We found that prolongation of oxygen-glucose deprivation activated the ER stress pathway protein kinase-like endoplasmic reticulum kinase (PERK)/eukaryotic translation initiation factor 2 subunit alpha (eIF2α)-activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP), increased neuronal apoptosis, and induced autophagy. Furthermore, inhibition of ER stress using inhibitors or by siRNA knockdown of the PERK gene significantly attenuated excessive autophagy and neuronal apoptosis, indicating an interaction between autophagy and ER stress and suggesting PERK as an essential target for regulating autophagy. Blocking autophagy with chloroquine exacerbated ER stress-induced apoptosis, indicating that normal levels of autophagy play a protective role in neuronal injury following cerebral ischemia/reperfusion injury. Findings from this study indicate that cerebral ischemia/ reperfusion injury can trigger neuronal ER stress and promote autophagy, and suggest that PERK is a possible target for inhibiting excessive autophagy in cerebral ischemia/reperfusion injury. 

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    Chondroitinase ABC combined with Schwann cell transplantation enhances restoration of neural connection and functional recovery following acute and chronic spinal cord injury
    Wenrui Qu , Xiangbing Wu , Wei Wu , Ying Wang , Yan Sun , Lingxiao Deng , Melissa Walker , Chen Chen , Heqiao Dai , Qi Han , Ying Ding , Yongzhi Xia , George Smith , Rui Li , Nai-Kui Liu , Xiao-Ming Xu
    2025, 20 (5):  1467-1482.  doi: 10.4103/NRR.NRR-D-23-01338
    Abstract ( 150 )   PDF (14366KB) ( 62 )   Save

    Schwann cell transplantation is considered one of the most promising cell-based therapy to repair injured spinal cord due to its unique growth-promoting and myelin-forming properties. A the Food and Drug Administration-approved Phase I clinical trial has been conducted to evaluate the safety of transplanted human autologous Schwann cells to treat patients with spinal cord injury. A major challenge for Schwann cell transplantation is that grafted Schwann cells are confined within the lesion cavity, and they do not migrate into the host environment due to the inhibitory barrier formed by injury-induced glial scar, thus limiting axonal reentry into the host spinal cord. Here we introduce a combinatorial strategy by suppressing the inhibitory extracellular environment with injection of lentivirus-mediated transfection of chondroitinase ABC gene at the rostral and caudal borders of the lesion site and simultaneously leveraging the repair capacity of transplanted Schwann cells in adult rats following a mid-thoracic contusive spinal cord injury. We report that when the glial scar was degraded by chondroitinase ABC at the rostral and caudal lesion borders, Schwann cells migrated for considerable distances in both rostral and caudal directions. Such Schwann cell migration led to enhanced axonal regrowth, including the serotonergic and dopaminergic axons originating from supraspinal regions, and promoted recovery of locomotor and urinary bladder functions. Importantly, the Schwann cell survival and axonal regrowth persisted up to 6 months after the injury, even when treatment was delayed for 3 months to mimic chronic spinal cord injury. These findings collectively show promising evidence for a combinatorial strategy with chondroitinase ABC and Schwann cells in promoting remodeling and recovery of function following spinal cord injury. 

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    Tranylcypromine upregulates Sestrin 2 expression to ameliorate NLRP3-related noise-induced hearing loss
    Xihang Chen , Zhifeng Chen , Menghua Li , Weiwei Guo , Shuolong Yuan , Liangwei Xu , Chang Lin , Xi Shi , Wei Chen , Shiming Yang
    2025, 20 (5):  1483-1494.  doi: 10.4103/NRR.NRR-D-24-00130
    Abstract ( 83 )   PDF (15475KB) ( 13 )   Save

    Noise-induced hearing loss is the primary non-genetic factor contributing to auditory dysfunction. However, there are currently no effective pharmacological interventions for patients with noise-induced hearing loss. Here, we present evidence suggesting that the lysine-specific demethylase 1 inhibitor–tranylcypromine is an otoprotective agent that could be used to treat noise-induced hearing loss, and elucidate its underlying regulatory mechanisms. We established a mouse model of permanent threshold shift hearing loss by exposing the mice to white broadband noise at a sound pressure level of 120 dB for 4 hours. We found that tranylcypromine treatment led to the upregulation of Sestrin2 (SESN2) and activation of the autophagy markers light chain 3B and lysosome-associated membrane glycoprotein 1 in the cochleae of mice treated with tranylcypromine. The noise exposure group treated with tranylcypromine showed significantly lower average auditory brainstem response hearing thresholds at click, 4, 8, and 16 kHz frequencies compared with the noise exposure group treated with saline. These findings indicate that tranylcypromine treatment resulted in increased SESN2, light chain 3B, and lysosome-associated membrane glycoprotein 1 expression after noise exposure, leading to a reduction in levels of 4-hydroxynonenal and cleaved caspase-3, thereby reducing noise-induced hair cell loss. Additionally, immunoblot analysis demonstrated that treatment with tranylcypromine upregulated SESN2 expression via the autophagy pathway. Tranylcypromine treatment also reduced the production of NOD-like receptor family pyrin domain-containing 3 (NLRP3) production. In conclusion, our results showed that tranylcypromine treatment ameliorated cochlear inflammation by promoting the expression of SESN2, which induced autophagy, thereby restricting NLRP3-related inflammasome signaling, alleviating cochlear hair cell loss, and protecting hearing function. These findings suggest that inhibiting lysine-specific demethylase 1 is a potential therapeutic strategy for preventing hair cell loss and noise-induced hearing loss.

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    Resting-state brain network remodeling after different nerve reconstruction surgeries: a functional magnetic resonance imaging study in brachial plexus injury rats
    Yunttng Xiang , Xiangxin Xing , Xuyun Hua , Yuwen Zhang , Xin Xue , Jiajia Wu , Mouxiong Zheng , He Wang , Jianguang Xu
    2025, 20 (5):  1495-1504.  doi: 10.4103/NRR.NRR-D-23-00493
    Abstract ( 284 )   PDF (12572KB) ( 61 )   Save

    Distinct brain remodeling has been found after different nerve reconstruction strategies, including motor representation of the affected limb. However, differences among reconstruction strategies at the brain network level have not been elucidated. This study aimed to explore intra-network changes related to altered peripheral neural pathways after different nerve reconstruction surgeries, including nerve repair, end-to-end nerve transfer, and end-to-side nerve transfer. Sprague–Dawley rats underwent complete left brachial plexus transection and were divided into four equal groups of eight: no nerve repair, grafted nerve repair, phrenic nerve end-to-end transfer, and end-to-side transfer with a graft sutured to the anterior upper trunk. Resting-state brain functional magnetic resonance imaging was obtained 7 months after surgery. The independent component analysis algorithm was utilized to identify group-level network components of interest and extract resting-state functional connectivity values of each voxel within the component. Alterations in intra-network resting-state functional connectivity were compared among the groups. Target muscle reinnervation was assessed by behavioral observation (elbow flexion) and electromyography. The results showed that alterations in the sensorimotor and interoception networks were mostly related to changes in the peripheral neural pathway. Nerve repair was related to enhanced connectivity within the sensorimotor network, while end-to-side nerve transfer might be more beneficial for restoring control over the affected limb by the original motor representation. The thalamic-cortical pathway was enhanced within the interoception network after nerve repair and end-to-end nerve transfer. Brain areas related to cognition and emotion were enhanced after end-to-side nerve transfer. Our study revealed important brain networks related to different nerve reconstructions. These networks may be potential targets for enhancing motor recovery. 

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    The burden of upper motor neuron involvement is correlated with the bilateral limb involvement interval in patients with amyotrophic lateral sclerosis: a retrospective observational study
    Jieying Wu , Shan Ye , Xiangyi Liu , Yingsheng Xu , Dongsheng Fan
    2025, 20 (5):  1505-1512.  doi: 10.4103/NRR.NRR-D-23-01359
    Abstract ( 203 )   PDF (1086KB) ( 130 )   Save

    Amyotrophic lateral sclerosis is a rare neurodegenerative disease characterized by the involvement of both upper and lower motor neurons. Early bilateral limb involvement significantly affects patients’ daily lives and may lead them to be confined to bed. However, the effect of upper and lower motor neuron impairment and other risk factors on bilateral limb involvement is unclear. To address this issue, we retrospectively collected data from 586 amyotrophic lateral sclerosis patients with limb onset diagnosed at Peking University Third Hospital between January 2020 and May 2022. A univariate analysis revealed no significant differences in the time intervals of spread in different directions between individuals with upper motor neuron-dominant amyotrophic lateral sclerosis and those with classic amyotrophic lateral sclerosis. We used causal directed acyclic graphs for risk factor determination and Cox proportional hazards models to investigate the association between the duration of bilateral limb involvement and clinical baseline characteristics in amyotrophic lateral sclerosis patients. Multiple factor analyses revealed that higher upper motor neuron scores (hazard ratio [HR] = 1.05, 95% confidence interval [CI] = 1.01–1.09, P = 0.018), onset in the left limb (HR = 0.72, 95% CI = 0.58–0.89, P = 0.002), and a horizontal pattern of progression (HR = 0.46, 95% CI = 0.37–0.58, P < 0.001) were risk factors for a shorter interval until bilateral limb involvement. The results demonstrated that a greater degree of upper motor neuron involvement might cause contralateral limb involvement to progress more quickly in limb-onset amyotrophic lateral sclerosis patients. These findings may improve the management of amyotrophic lateral sclerosis patients with limb onset and the prediction of patient prognosis.

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