Capacity of astrocytes to promote axon growth in the injured mammalian central nervous system

An in vitro and in vivo efficacy evaluation of gene therapy candidate SBT101 in mouse models of adrenomyeloneuropathy and in NHPs

Adrenomyeloneuropathy is a progressive neurodegenerative disease caused by pathogenic variants in the ABCD1 gene, resulting in very-long-chain fatty acid (VLCFA) accumulation that leads to dying-back axonopathy. Our candidate gene therapy, SBT101 (AAV9-human ABCD1 [hABCD1]), aims to ameliorate pathology by delivering functional copies of hABCD1 to the spinal cord. Transduced cells produce functional ABCD1 protein, thereby repairing the underlying biochemical defect. In vitro and in vivo mouse studies were conducted to assess the biochemical and functional efficacy of SBT101 and show effective delivery to target tissues involved in the disease pathology: spinal cord and dorsal root ganglia. Administration of SBT101 to mixed glial cell cultures from Abcd1-Null mice, and to male Abcd1 knockout (Abcd1 -/y ) and double-knockout (Abcd1 -/y /Abcd2 -/- ) mice led to increased hABCD1 production and reduced VLCFA. Double-knockout mice also exhibited improved grip strength. Furthermore, we conducted biodistribution and safety assessments in nonhuman primates. Six-hour intrathecal lumbar infusions demonstrated effective transduction throughout target tissues, supporting the clinical feasibility of the procedure. SBT101 was well tolerated, with no observed SBT101-related mortality or clinical signs. These findings not only provide preclinical efficacy data for SBT101 but also inform clinically relevant SBT101 dose selection for patients with adrenomyeloneuropathy.

Lentivirus-mediated Knockdown of Ski Improves Neurological Function After Spinal Cord Injury in Rats

The glial scar that forms at the site of injury after spinal cord injury (SCI) is an important physical and biochemical barrier that prevents axonal regeneration and thus delays functional recovery. Ski is a multifunctional transcriptional co-regulator that is involved in a wide range of physiological and pathological processes in humans. Previous studies by our group found that Ski is significantly upregulated in the spinal cord after in vivo injury and in astrocytes after in vitro activation, suggesting that Ski may be a novel molecule regulating astrocyte activation after spinal cord injury. Further studies revealed that knockdown or overexpression intervention of Ski expression could significantly affect the proliferation and migration of activated astrocytes. To further verify the effect of knockdown of Ski expression in vivo on glial scar formation and neurological function after spinal cord injury, we prepared a rat spinal cord injury model using Allen's percussion method and used lentivirus as a vector to mediate the downregulation of Ski in the injured spinal cord. The results showed that knockdown of Ski expression after spinal cord injury significantly suppressed the expression of glial fibrillary acidic protein (Gfap) and vimentin, hallmark molecules of glial scarring, and increased the expression of neurofilament protein-200 (Nf-200) and growth-associated protein (Gap43), key molecules of axon regeneration, as well as Synaptophysin, a key molecule of synapse formation expression. In addition, knockdown of Ski after spinal cord injury also promoted the recovery of motor function. Taken together, these results suggest that Ski is able to inhibit the expression of key molecules of glial scar formation, and at the same time promotes the expression of molecules that are markers of axonal regeneration and synapse formation after spinal cord injury, making it a potential target for targeted therapy after spinal cord injury.

Synergistic effects of human umbilical cord mesenchymal stem cells/neural stem cells and epidural electrical stimulation on spinal cord injury rehabilitation

Spinal cord injury (SCI) is a severe neurological condition marked by a complex pathology leading to irreversible functional loss, which current treatments fail to improve. Epidural electrical stimulation (EES) shows promise in alleviating pathological pain, regulating hemodynamic disturbances, and enhancing motor function by modulating residual interneurons in the lower spinal cord. Cell transplantation (CT), especially using human umbilical cord mesenchymal stem cells (hUCMSCs) and neural stem cells (NSCs), has significantly improved sensory and motor recovery in SCI. However, the limitations of single treatments have driven the exploration of a multifaceted strategy, combining various modalities to optimize recovery at different stages. To comprehensively investigate the effectiveness of in situ transplantation of hUCMSCs/NSCs combined with subacute epidural electrical stimulation in a murine spinal cord crush injury model, providing valuable references for future animal studies and clinical research. In this study, we first examined neural stem cell changes via mRNA sequencing in an in vitro Transwell co-culture model. We then explored cell interaction mechanisms using proliferation assays, differentiation assays, and neuron complexity analysis. For animal experiments, 40 C57BL/6 mice were assigned to four groups (Injury/EES/CT/Combination). Histological evaluations employed HE and immunofluorescence staining, while electrophysiological and behavioral tests assessed motor recovery. Quantitative data were reported as mean ± standard error, with statistical analyses performed using GraphPad Prism and SPSS. Initially, we found that NSCs in the in vitro co-culture model showed a unique expression profile of differentially expressed genes (DEGs) compared to controls. GO/KEGG analysis indicated these DEGs were mainly linked to cell differentiation and growth factor secretion pathways. Neuronal and astrocytic markers further confirmed enhanced NSC differentiation and neuronal maturation in the co-culture model. In vivo, live imaging and human nuclei immunofluorescence staining revealed that transplanted cells persisted for some time post-transplantation. Histological analysis showed that during acute inflammation, both the stem cell and combined therapy groups significantly inhibited microglial polarization. In the chronic phase, these groups reduced fibrotic scar formation and encouraged astrocytic bridging. Behavioral tests, including swimming and gait analysis, demonstrated that combined CT and EES therapy was more effective than either treatment alone. In summary, the combined therapy offers a promising approach for spinal cord injury treatment, providing superior outcomes over individual treatments. Our findings underscore the potential of a combined treatment approach utilizing stem cells transplantation and EES as an effective strategy for the comprehensive management of spinal cord crush injury in mice. This integrated approach holds promise for enhancing functional recovery and improving the quality of life for individuals with spinal cord injury (SCI).

Development of Tissue-Engineered Model of Fibrotic Scarring after Spinal Cord Injury to Study Astrocyte Activation and Neurite Outgrowth In Vitro

Traumatic spinal cord injuries (SCI) are debilitating injuries affecting twenty-seven million people worldwide and cause functional impairments. Despite decades of research and medical advancements, current treatment options for SCI remain limited, in part due to the complex pathophysiology of spinal cord lesions including cellular transformation and extracellular matrix (ECM) remodeling. Recent studies have increased focus on fibrotic scarring after SCI, and yet much remains unclear about the impact of fibrotic scarring on SCI lesion progression. Here, using collagen and decellularized spinal cord-based composite hydrogels, a three-dimensional (3D) cell culture model mimicking the fibrous core of spinal cord lesions was implemented to investigate its influence on the surrounding astrocytes. To mimic the fibrotic milieu, collagen fibril thickness was tuned using previously established temperature-controlled casting methods. In our platforms, astrocytes in fibro-mimetic hydrogels exhibited increased levels of activation markers such as glial fibrillary acidic protein and N-cadherin. Furthermore, astrocytes in fibro-mimetic hydrogels deposited more fibronectin and laminin, further hinting that astrocytes may also contribute to fibrotic scarring. These markers were decreased when Rho-ROCK and integrin β1 were inhibited via pharmacological inhibitors. Mechanistic analysis of Yes-associated protein reveals that blocking integrin β1 prevents mechanosensing of astrocytes, contributing to altered phenotypes in variable culture conditions. In the presence of these inhibitors, astrocytes increased the secretion of brain-derived neurotrophic factor, and a greater degree of dorsal root ganglia neurite infiltration into the underlying hydrogels was observed. Altogether, this study presents a novel tissue-engineered platform to study fibrotic scarring after SCI and may be a useful platform to advance our understanding of SCI lesion aggravation.

A facilitatory role of astrocytes in axonal regeneration after acute and chronic spinal cord injury

Neuroscience dogma avers that astrocytic "scars" inhibit axonal regeneration after spinal cord injury (SCI). A recent report suggested however that astrocytes form "borders" around lesions that are permissive rather than inhibitory to axonal growth. We now provide further evidence supporting a facilitatory role of astrocytes in axonal regeneration after SCI. First, even 6months after SCI, injured axons are retained within regions of densely reactive astrocytes, in direct contact with astrocyte processes without being repelled. Second, 6 month-delayed implants of neural stem cells extend axons into reactive astrocyte borders surrounding lesions, densely contacting astrocyte surfaces. Third, bioengineered hydrogels implanted into sites of SCI re-orient reactive astrocytic processes to align along the rostral-to-caudal spinal cord axis resulting in successful regeneration into the lesion/scaffold in close association with astrocytic processes. Fourth, corticospinal axons regenerate into neural progenitor cells implanted six months after injury in close association with host astrocytic processes. Thus, astrocytes do not appear to inhibit axonal regeneration, and the close association of newly growing axons with astrocytic processes suggests a facilitatory role in axonal regeneration.

Spinal Cord Injury Management Based on Microglia-Targeting Therapies

Spinal cord injury is a complicated medical condition both from the clinician's point of view in terms of management and from the patient's perspective in terms of unsatisfactory recovery. Depending on the severity, this disorder can be devastating despite the rapid and appropriate use of modern imaging techniques and convenient surgical spinal cord decompression and stabilization. In this context, there is a mandatory need for novel adjunctive therapeutic approaches to classical treatments to improve rehabilitation chances and clinical outcomes. This review offers a new and original perspective on therapies targeting the microglia, one of the most relevant immune cells implicated in spinal cord disorders. The first part of the manuscript reviews the anatomical and pathophysiological importance of the blood-spinal cord barrier components, including the role of microglia in post-acute neuroinflammation. Subsequently, the authors present the emerging therapies based on microglia modulation, such as cytokines modulators, stem cell, microRNA, and nanoparticle-based treatments that could positively impact spinal cord injury management. Finally, future perspectives and challenges are also highlighted based on the ongoing clinical trials related to medications targeting microglia.

Conditioned medium-enriched umbilical cord mesenchymal stem cells: a potential therapeutic strategy for spinal cord injury, unveiling transcriptomic and secretomic insights

INTRODUCTION

Spinal cord injury (SCI) leads to significant destruction of nerve tissue, causing the degeneration of axons and the formation of cystic cavities. This study aimed to examine the characteristics of human umbilical cord-derived mesenchymal stem cells (HUCMSCs) cultured in a serum-free conditioned medium (CM) and assess their effectiveness in a well-established hemitransection SCI model.

MATERIALS AND METHODS

In this study, HUCMSCs cultured medium was collected and characterized by measuring IL-10 and identifying proteomics using mass spectroscopy. This collected serum-free CM was further used in the experiments to culture and characterize the HUMSCs. Later, neuronal cells derived from CM-enriched HUCMSC were tested sequentially using an injectable caffeic acid-bioconjugated gelatin (CBG), which was further transplanted in a hemitransection SCI model. In vitro, characterization of CM-enriched HUCMSCs and differentiated neuronal cells was performed using flow cytometry, immunofluorescence, electron microscopy, and post-transplant analysis using immunohistology analysis, qPCR, in vivo bioluminescence imaging, and behavioral analysis using an infrared actimeter.

RESULTS

The cells that were cultured in the conditioned media produced a pro-inflammatory cytokine called IL-10. Upon examining the secretome of the conditioned media, the Kruppel-like family of KRAB and zinc-finger proteins (C2H2 and C4) were found to be activated. Transcriptome analysis also revealed an increased expression of ELK-1, HOXD8, OTX2, YY1, STAT1, ETV7, and PATZ1 in the conditioned media. Furthermore, the expression of Human Stem-101 confirmed proliferation during the first 3 weeks after transplantation, along with the migration of CBG-UCNSC cells within the transplanted area. The gene analysis showed increased expression of Nestin, NeuN, Calb-2, Msi1, and Msi2. The group that received CBG-UCNSC therapy showed a smooth recovery by the end of week 2, with most rats regaining their walking abilities similar to those before the spinal cord injury by week 5.

CONCLUSIONS

In conclusion, the CBG-UCNSC method effectively preserved the integrity of the transplanted neuronal-like cells and improved locomotor function. Thus, CM-enriched cells can potentially reduce biosafety risks associated with animal content, making them a promising option for clinical applications in treating spinal cord injuries.

Asteroid impact: the potential of astrocytes to modulate human neural networks within organoids

Astrocytes are a vital cellular component of the central nervous system that impact neuronal function in both healthy and pathological states. This includes intercellular signals to neurons and non-neuronal cells during development, maturation, and aging that can modulate neural network formation, plasticity, and maintenance. Recently, human pluripotent stem cell-derived neural aggregate cultures, known as neurospheres or organoids, have emerged as improved experimental platforms for basic and pre-clinical neuroscience compared to traditional approaches. Here, we summarize the potential capability of using organoids to further understand the mechanistic role of astrocytes upon neural networks, including the production of extracellular matrix components and reactive signaling cues. Additionally, we discuss the application of organoid models to investigate the astrocyte-dependent aspects of neuropathological diseases and to test astrocyte-inspired technologies. We examine the shortcomings of organoid-based experimental platforms and plausible improvements made possible by cutting-edge neuroengineering technologies. These advancements are expected to enable the development of improved diagnostic strategies and high-throughput translational applications regarding neuroregeneration.

The role and potential therapeutic targets of astrocytes in central nervous system demyelinating diseases

Astrocytes play vital roles in the central nervous system, contributing significantly to both its normal functioning and pathological conditions. While their involvement in various diseases is increasingly recognized, their exact role in demyelinating lesions remains uncertain. Astrocytes have the potential to influence demyelination positively or negatively. They can produce and release inflammatory molecules that modulate the activation and movement of other immune cells. Moreover, they can aid in the clearance of myelin debris through phagocytosis and facilitate the recruitment and differentiation of oligodendrocyte precursor cells, thereby promoting axonal remyelination. However, excessive or prolonged astrocyte phagocytosis can exacerbate demyelination and lead to neurological impairments. This review provides an overview of the involvement of astrocytes in various demyelinating diseases, emphasizing the underlying mechanisms that contribute to demyelination. Additionally, we discuss the interactions between oligodendrocytes, oligodendrocyte precursor cells and astrocytes as therapeutic options to support myelin regeneration. Furthermore, we explore the role of astrocytes in repairing synaptic dysfunction, which is also a crucial pathological process in these disorders.

A systematic review and multilevel meta-analysis of the prenatal and early life stress effects on rodent microglia, astrocyte, and oligodendrocyte density and morphology

Exposure to stress during early development may lead to altered neurobiological functions, thus increasing the risk for psychiatric illnesses later in life. One potential mechanism associated with those outcomes is the disruption of glial density and morphology, despite results from rodent studies have been conflicting. To address that we performed a systematic review and meta-analysis of rodent studies that investigated the effects of prenatal stress (PNS) and early life stress (ELS) on microglia, astrocyte, and oligodendrocyte density and morphology within the offspring. Our meta-analysis demonstrates that animals exposed to PNS or ELS showed significant increase in microglia density, as well as decreased oligodendrocyte density. Moreover, ELS exposure induced an increase in microglia soma size. However, we were unable to identify significant effects on astrocytes. Meta-regression indicated that experimental stress protocol, sex, age, and type of tissue analyzed are important covariates that impact those results. Importantly, PNS microglia showed higher estimates in young animals, while the ELS effects were stronger in adult animals. This set of data reinforces that alterations in glial cells could play a role in stress-induced dysfunctions throughout development.

Traumatic brain injury: Mechanisms, manifestations, and visual sequelae

Traumatic brain injury (TBI) results when external physical forces impact the head with sufficient intensity to cause damage to the brain. TBI can be mild, moderate, or severe and may have long-term consequences including visual difficulties, cognitive deficits, headache, pain, sleep disturbances, and post-traumatic epilepsy. Disruption of the normal functioning of the brain leads to a cascade of effects with molecular and anatomical changes, persistent neuronal hyperexcitation, neuroinflammation, and neuronal loss. Destructive processes that occur at the cellular and molecular level lead to inflammation, oxidative stress, calcium dysregulation, and apoptosis. Vascular damage, ischemia and loss of blood brain barrier integrity contribute to destruction of brain tissue. This review focuses on the cellular damage incited during TBI and the frequently life-altering lasting effects of this destruction on vision, cognition, balance, and sleep. The wide range of visual complaints associated with TBI are addressed and repair processes where there is potential for intervention and neuronal preservation are highlighted.

Pathophysiology and Therapeutic Approaches for Spinal Cord Injury

Spinal cord injury (SCI) is a disabling condition that disrupts motor, sensory, and autonomic functions. Despite extensive research in the last decades, SCI continues to be a global health priority affecting thousands of individuals every year. The lack of effective therapeutic strategies for patients with SCI reflects its complex pathophysiology that leads to the point of no return in its function repair and regeneration capacity. Recently, however, several studies started to uncover the intricate network of mechanisms involved in SCI leading to the development of new therapeutic approaches. In this work, we present a detailed description of the physiology and anatomy of the spinal cord and the pathophysiology of SCI. Additionally, we provide an overview of different molecular strategies that demonstrate promising potential in the modulation of the secondary injury events that promote neuroprotection or neuroregeneration. We also briefly discuss other emerging therapies, including cell-based therapies, biomaterials, and epidural electric stimulation. A successful therapy might target different pathologic events to control the progression of secondary damage of SCI and promote regeneration leading to functional recovery.