Transplantation of Embryonic Neural Stem Cells and Differentiated Cells in a Controlled Cortical Impact (CCI) Model of Adult Mouse Somatosensory Cortex

Human Neural Stem Cell Therapy for Traumatic Brain Injury-A Systematic Review of Pre-Clinical Studies

Human neural stem cells (hNSCs) possess significant therapeutic potential for the treatment of traumatic brain injury (TBI), a leading cause of global death and disability. Recent pre-clinical studies have shown that hNSCs reduce tissue damage and promote functional recovery through neuroprotective and regenerative signaling and cell replacement. Yet the overall efficacy of hNSCs for TBI indications remains unclear. Therefore, this systematic review aims to evaluate hNSC interventions compared with controls in pre-clinical TBI models. Through this process, variations in hNSC administration protocols were consolidated, and key knowledge gaps were identified. Meta-analysis was applied to primary outcomes of lesion volume, Morris Water Maze (MWM) performance, modified Neurological Severity Scores (mNSS), and the rotarod task. Narrative review of secondary outcomes included hNSC survival and differentiation, endogenous neuron survival, axonal injury, and inflammation. Overall, hNSC intervention reduced lesion volume, enhanced MWM performance, and led to trending decreases in acute and chronic neurological deficits at acute and chronic time points. These results suggest hNSCs demonstrate clear efficacy in pre-clinical TBI models. However, further studies are needed to address key questions regarding optimal hNSC administration (e.g., dosing, treatment window) and underlying mechanisms of action prior to progressing to human clinical trials.

Blood-brain barrier disruption: a pervasive driver and mechanistic link between traumatic brain injury and Alzheimer's disease

Traumatic brain injury (TBI) has emerged as a significant risk factor for Alzheimer's disease (AD), a complex and devastating neurodegenerative disorder characterized by progressive cognitive decline and memory loss. Both conditions share a common feature: blood‒brain barrier (BBB) dysfunction, which is believed to play a pivotal role in linking TBI to the development of AD. This review delves into the intricate relationship between TBI and AD, with a focus on BBB dysfunction and its critical role in disease mechanisms and therapeutic development. We first present recent evidence from epidemiological studies highlighting the increased incidence of AD among individuals with a history of TBI, as well as pathological and animal model studies that demonstrate how TBI can accelerate AD-like pathology. Next, we explore the mechanisms by which BBB dysfunction may mediate TBI-induced AD pathology. Finally, we investigate the shared molecular pathways associated with BBB dysfunction in both TBI and AD conditions and discuss the latest findings on how targeting these pathways and employing regenerative approaches, such as stem cell therapy and pharmacological interventions, can enhance BBB function and mitigate neurodegeneration.

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

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.

PHF6-mediated transcriptional control of NSC via Ephrin receptors is impaired in the intellectual disability syndrome BFLS

The plant homeodomain zinc-finger protein, PHF6, is a transcriptional regulator, and PHF6 germline mutations cause the X-linked intellectual disability (XLID) Börjeson-Forssman-Lehmann syndrome (BFLS). The mechanisms by which PHF6 regulates transcription and how its mutations cause BFLS remain poorly characterized. Here, we show genome-wide binding of PHF6 in the developing cortex in the vicinity of genes involved in central nervous system development and neurogenesis. Characterization of BFLS mice harbouring PHF6 patient mutations reveals an increase in embryonic neural stem cell (eNSC) self-renewal and a reduction of neural progenitors. We identify a panel of Ephrin receptors (EphRs) as direct transcriptional targets of PHF6. Mechanistically, we show that PHF6 regulation of EphR is impaired in BFLS mice and in conditional Phf6 knock-out mice. Knockdown of EphR-A phenocopies the PHF6 loss-of-function defects in altering eNSCs, and its forced expression rescues defects of BFLS mice-derived eNSCs. Our data indicate that PHF6 directly promotes Ephrin receptor expression to control eNSC behaviour in the developing brain, and that this pathway is impaired in BFLS.

Overexpress miR-132 in the Brain Parenchyma by a Non-invasive Way Improves Tissue Repairment and Releases Memory Impairment After Traumatic Brain Injury

Traumatic brain injury (TBI) is a serious public health problem worldwide, which could lead to an extremely high percentage of mortality and disability. Current treatment strategies mainly concentrate on neuronal protection and reconstruction, among them, exogenous neural stem cell (NSC) transplantation has long been regarded as the most effective curative treatment. However, due to secondary trauma, transplant rejection, and increased incidence of brain malignant tumor, a non-invasive therapy that enhanced endogenous neurogenesis was more suitable for TBI treatment. Our previous work has shown that miR-132 overexpression could improve neuronal differentiation of NSCs in vitro and in vivo. So, we engineered a new kind of AAV vector named AAV-PHP.eB which can transfect brain parenchyma through intravenous injection to overexpress miR-132 in brain after TBI. We found that miR-132 overexpression could reduce impact volume, promote neurogenesis in the dentate gyrus (DG), accelerate neuroblast migrating into the impact cortex, ameliorate microglia-mediated inflammatory reaction, and ultimately restore learning memory function. Our results revealed that AAV-PHP.eB-based miR-132 overexpression could improve endogenous tissue repairment and release clinical symptoms after traumatic brain injury. This work would provide a new therapeutic strategy for TBI treatment and other neurological disorders characterized by markable neuronal loss and memory impairment. miR-132 overexpression accelerates endogenous neurogenesis and releases TBI-induced tissue repairment and memory impairment. Controlled cortical impact onto the cortex would induce serious cortical injury and microglia accumulation in both cortex and hippocampus. Moreover, endogenous neuroblast could migrate around the injury core. miR-132 overexpression could accelerate neuroblast migration toward the injury core and decreased microglia accumulation in the ipsilateral cortex and hippocampus. miR-132 could be a suitable target on neuroprotective therapy after TBI.

mNSCs overexpressing Rimkla transplantation facilitates cognitive recovery in a mouse model of traumatic brain injury

N-acetyl aspartyl-glutamate (NAAG) is easily inactivated for the hydrolysis of NAAG peptidase on the surface of glial cells, thereby losing its endogenous neuroprotective effect after traumatic brain injury. In this study, lentiviral vectors were used to over express/knock out NAAG synthetase II (Rimkla) in mouse embryonic neural stem cells (mNSCs) in vitro and these mNSCs were transplanted at the lesion site in a mouse model of controlled cortical impact (CCI). In vivo experiments showed that transplantation of mNSCs overexpressing Rimkla regulated glutamate-glutamine cycling between adjacent astrocytes and neurons in the subacute phase of CCI, thereby enhancing support for neuronal metabolism and promoting neuronal synaptic repair in the hippocampal CA3 region. Taken together, these findings demonstrate that transplantation of neural stem cells overexpressing Rimkla can effectively increase the NAAG concentration in local brain regions, which opens up new ideas for the maintenance of NAAG neuroprotective effects after TBI.

A Tale of Two: When Neural Stem Cells Encounter Hypoxia

Normoxia is defined as an oxygen concentration of 20.9%, as in room air, whereas hypoxia refers to any oxygen concentration less than this. Any physiological oxygen deficiency or tissue oxygen deficiency relative to demand is called hypoxia. Neural stem cells (NSCs) are multipotent stem cells that can differentiate into multiple cell lines such as neurons, oligodendrocytes, and astrocytes. Under hypoxic conditions, the apoptosis rate of NSCs increases remarkably in vitro or in vivo. However, some hypoxia promotes the proliferation and differentiation of NSCs. The difference is related to the oxygen concentration, the duration of hypoxia, the hypoxia tolerance threshold of the NSCs, and the tissue source of the NSCs. The main mechanism of hypoxia-induced proliferation and differentiation involves an increase in cyclin and erythropoietin concentrations, and hypoxia-inducible factors play a key role. Multiple molecular pathways are activated during hypoxia, including Notch, Wnt/β-catenin, PI3K/Akt, and altered microRNA expression. In addition, we review the protective effect of exogenous NSCs transplantation on ischemic or anoxic organs, the therapeutic potential of hypoxic preconditioning on exogenous NSCs and clinical application of NSCs.

OUP accepted manuscript

Traumatic injury of the central nervous system (CNS) is a worldwide health problem affecting millions of people. Trauma of the CNS, that is, traumatic brain injury (TBI) and spinal cord injury (SCI), lead to massive and progressive cell loss and axonal degeneration, usually with very limited regeneration. At present, there are no treatments to protect injured CNS tissue or to replace the lost tissue. Stem cells are a cell type that by definition can self-renew and give rise to multiple cell lineages. In recent years, therapies using stem and progenitor cells have shown promising effects in experimental CNS trauma, particularly in the acute-subacute stage, but also in chronic injuries. However, the therapeutic mechanisms by which transplanted cells achieve the structural and/or functional improvements are often not clear. Stem cell therapies for CNS trauma can be categorized into 2 main concepts, transplantation of exogenous neural stem cells and neural progenitor cells and recruitment of endogenous stem and progenitor cells. In this review, focusing on the advances during the last decade, we will discuss the major cell therapies, the pros and cons of these 2 concepts for TBI and SCI, and the treatment strategies we believe will be successful.

Vascular Dysfunction after Modeled Traumatic Brain Injury Is Preserved with Administration of Umbilical Cord Derived Mesenchymal Stromal Cells and Is Associated with Modulation of the Angiogenic Response

Vascular dysfunction arising from blood-brain barrier (BBB) breakdown after traumatic brain injury (TBI) can adversely affect neuronal health and behavioral outcome. Pericytes and endothelial cells of the neurovascular unit (NVU) function collectively to maintain strict regulation of the BBB through tight junctions. Secondary injury mechanisms, such as pro-angiogenic signals that contribute to pericyte loss, can prolong and exacerbate primary vascular injury. Human umbilical cord perivascular cells (HUCPVCs) are a source of mesenchymal stromal cells (MSCs) that have been shown to reduce vascular dysfunction after neurotrauma. We hypothesized that the perivascular properties of HUCPVCs can reduce vascular dysfunction after modeled TBI by preserving the pericyte-endothelial interactions. Rats were subjected to a moderate fluid percussion injury (FPI) and intravenously infused with 1,500,000 HUCPVCs post-injury. At acute time points (24 h and 48 h) quantitative polymerase chain reaction (qPCR) analysis demonstrated that the gene expression of angiopoietin-2 was increased with FPI and reduced with HUCPVCs. Immunofluorescent assessment of RECA-1 (endothelial cells) and platelet-derived growth factor receptors (PDGFR-β) (pericytes) revealed that capillary and pericyte densities as well as the co-localization of the two cells were decreased with FPI and preserved with HUCPVC administration. These acute HUCPVC-mediated protective effects were associated with less permeability to Evan's blue dye and increased expression of the tight junction occludin, suggesting less vascular leakage. Further, at 4 weeks post-injury, HUCPVC administration was associated with reduced anxiety and decreased β-amyloid precursor protein (β-APP) accumulation. In summary, HUCPVCs promoted pericyte-endothelial barrier function that was associated with improved long-term outcome.

Neural stem cell therapy for brain disease

Brain diseases, including brain tumors, neurodegenerative disorders, cerebrovascular diseases, and traumatic brain injuries, are among the major disorders influencing human health, currently with no effective therapy. Due to the low regeneration capacity of neurons, insufficient secretion of neurotrophic factors, and the aggravation of ischemia and hypoxia after nerve injury, irreversible loss of functional neurons and nerve tissue damage occurs. This damage is difficult to repair and regenerate the central nervous system after injury. Neural stem cells (NSCs) are pluripotent stem cells that only exist in the central nervous system. They have good self-renewal potential and ability to differentiate into neurons, astrocytes, and oligodendrocytes and improve the cellular microenvironment. NSC transplantation approaches have been made for various neurodegenerative disorders based on their regenerative potential. This review summarizes and discusses the characteristics of NSCs, and the advantages and effects of NSCs in the treatment of brain diseases and limitations of NSC transplantation that need to be addressed for the treatment of brain diseases in the future.

Transplantation of rat dental pulp stem cells facilities post-lesion recovery in the somatosensory whisker cortex of male Wistar rats

Damage to somatosensory "barrel" cortex reduces the rats' behavioral sensitivity in discrimination of tactile stimuli. Here, we examined how transplantation of stem cells into the lesioned barrel cortex can help in recovery of sensory capacities. We induced mechanical lesions in the right barrel cortex area of male rats. Three days after lesioning, rats received one of three transplantation types: un-differentiated dental pulp stem cells (U-DPSCs) or differentiated dental pulp stem cells (D-DPSCs), or cell medium (vehicle). A fourth group of rats were control without any Surgery. For 4 consecutive weeks, starting one week after transplantation, we evaluated the rats' preference to explore novel textures as a measure of sensory discrimination ability, also measured the expression of glial fibrillary acidic protein (GFAP), Olig 2, nestin, neuronal nuclei (NeuN), brain-derived neurotrophic factor (BDNF) and neuroligin1 by immunohistochemistry and western blotting. Unilateral mechanical lesion decreased the rats' preferential exploration of novel textures compared to the control group across the 4-week behavioral tests. Following stem cell therapy, the rats' performance significantly improved at week 2-4 compared to the vehicle group. Compared to the control group, there was a significant decrease in the expression of nestin, NeuN, Olig 2, BDNF, neuroligin1 and a significant increase in the expression of GFAP in the vehicle group. The expression of the neural markers was significantly higher in DPSCs compared with the vehicle group whereas GFAP level was lower in DPSCs compared to vehicle. We found that DPSCs therapy affected a range of neuronal markers in the barrel cortex post lesion, and improved the rats' recovery for sensory discrimination.

Neglected No More: Emerging Cellular Therapies in Traumatic Injury

Traumatic injuries are a leading cause of death and disability in both military and civilian populations. Given the complexity and diversity of traumatic injuries, novel and individualized treatment strategies are required to optimize outcomes. Cellular therapies have potential benefit for the treatment of acute or chronic injuries, and various cell-based pharmaceuticals are currently being tested in preclinical studies or in clinical trials. Cellular therapeutics may have the ability to complement existing therapies, especially in restoring organ function lost due to tissue disruption, prolonged hypoxia or inflammatory damage. In this article we highlight the current status and discuss future directions of cellular therapies for the treatment of traumatic injury. Both published research and ongoing clinical trials are discussed here.

Conversion of Neural Stem Cells into Functional Neuron-Like Cells by MicroRNA-218: Differential Expression of Functionality Genes

Conversion of mesenchymal stem cells (MSC) into neuron-like cells (NLC) is a feasible cell therapy strategy for replacing lost neurons in neuronal disorders. In this study, adipose-derived MSC (ADMSC) were converted into neural stem cells (NSC) via neurosphere. The resulting NSC were then differentiated into NLC by transduction with microRNA-218, using a lentiviral vector. ADMSC, NSC, and NLC were first characterized by flow cytometry, RT-PCR, and immunocytochemistry. The functionality of the NLC was evaluated by qRT-PCR and patch clamp recording. Immunophenotyping of ADMSC showed their immunoreactivity to MSC markers CD90, CD73, CD105, and CD49d, but not to CD31 and CD45. RT-PCR results demonstrated the expression of nestin, neurogenin, neurod1, neurofilament light, and GAP43 genes in NSC while NLC expressed synaptophysin, neurofilament heavy, and GAP43. In addition, NSC morphology changed into multipolar with long processes after transduction with miR-218. Moreover, using qRT-PCR, the expression levels of miR-218 and functionality genes CACNA1C, SNAP25, KCNH1, KCNMA1, and SCN9A were significantly increased in NLC, compared with NSC, and ADMSC at 3 weeks and 5 months post-transduction. Furthermore, the generated NLC expressed significantly higher protein levels of neurofilament heavy polypeptide (NFh) and enolase 2 (Eno2) neuronal markers, compared with ADMSC and NSC. Finally, action potentials were successfully recorded by the generated NLC, using patch clamp. In summary, ADMSC-derived NSC differentiated into functional NLC by transduction with miR-218. The generated NLC expressed functional SNAP25, CACNA1C, KCNH1, KCNMA1, and SCN9A and produced an action potential, which provides useful insights into the generation of functional neuronal cells.

Harnessing the anti-inflammatory properties of stem cells for transplant therapy in hemorrhagic stroke

Hemorrhagic stroke is a global health crisis plagued by neuroinflammation in the acute and chronic phases. Neuroinflammation approximates secondary cell death, which in turn robustly contributes to stroke pathology. Both the physiological and behavioral symptoms of stroke correlate with various inflammatory responses in animal and human studies. That slowing the secondary cell death mediated by this inflammation may attenuate stroke pathology presents a novel treatment strategy. To this end, experimental therapies employing stem cell transplants support their potential for neuroprotection and neuroregeneration after hemorrhagic stroke. In this review, we evaluate experiments using different types of stem cell transplants as treatments for stroke-induced neuroinflammation. We also update this emerging area by examining recent preclinical and clinical trials that have deployed these therapies. While further investigations are warranted to solidify their therapeutic profile, the reviewed studies largely posit stem cells as safe and potent biologics for stroke, specifically owing to their mode of action for sequestering neuroinflammation and promoting neuroregenerative processes.

Exosomal 2',3'-CNP from mesenchymal stem cells promotes hippocampus CA1 neurogenesis/neuritogenesis and contributes to rescue of cognition/learning deficiencies of damaged brain

Mesenchymal stem cells (MSCs) have been used in clinical studies to treat neurological diseases and damage. However, implanted MSCs do not achieve their regenerative effects by differentiating into and replacing neural cells. Instead, MSC secretome components mediate the regenerative effects of MSCs. MSC-derived extracellular vesicles (EVs)/exosomes carry cargo responsible for rescuing brain damage. We previously showed that EP₄ antagonist-induced MSC EVs/exosomes have enhanced regenerative potential to rescue hippocampal damage, compared with EVs/exosomes from untreated MSCs. Here we show that EP₄ antagonist-induced MSC EVs/exosomes promote neurosphere formation in vitro and increase neurogenesis and neuritogenesis in damaged hippocampi; basal MSC EVs/exosomes do not contribute to these regenerative effects. 2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) levels in EP₄ antagonist-induced MSC EVs/exosomes are 20-fold higher than CNP levels in basal MSC EVs/exosomes. Decreasing elevated exosomal CNP levels in EP₄ antagonist-induced MSC EVs/exosomes reduced the efficacy of these EVs/exosomes in promoting β3-tubulin polymerization and in converting toxic 2',3'-cAMP into neuroprotective adenosine. CNP-depleted EP₄ antagonist-induced MSC EVs/exosomes lost the ability to promote neurogenesis and neuritogenesis in damaged hippocampi. Systemic administration of EV/exosomes from EP₄ -antagonist derived MSC EVs/exosomes repaired cognition, learning, and memory deficiencies in mice caused by hippocampal damage. In contrast, CNP-depleted EP₄ antagonist-induced MSC EVs/exosomes failed to repair this damage. Exosomal CNP contributes to the ability of EP₄ antagonist-elicited MSC EVs/exosomes to promote neurogenesis and neuritogenesis in damaged hippocampi and recovery of cognition, memory, and learning. This experimental approach should be generally applicable to identifying the role of EV/exosomal components in eliciting a variety of biological responses.

Transplanted interneurons improve memory precision after traumatic brain injury

Repair of the traumatically injured brain has been envisioned for decades, but regenerating new neurons at the site of brain injury has been challenging. We show GABAergic progenitors, derived from the embryonic medial ganglionic eminence, migrate long distances following transplantation into the hippocampus of adult mice with traumatic brain injury, functionally integrate as mature inhibitory interneurons and restore post-traumatic decreases in synaptic inhibition. Grafted animals had improvements in memory precision that were reversed by chemogenetic silencing of the transplanted neurons and a long-lasting reduction in spontaneous seizures. Our results reveal a striking ability of transplanted interneurons for incorporating into injured brain circuits, and this approach is a powerful therapeutic strategy for correcting post-traumatic memory and seizure disorders.

Neuroprotection, Recovery of Function and Endogenous Neurogenesis in Traumatic Spinal Cord Injury Following Transplantation of Activated Adipose Tissue

Spinal cord injury (SCI) is a devastating disease, which leads to paralysis and is associated to substantially high costs for the individual and society. At present, no effective therapies are available. Here, the use of mechanically-activated lipoaspirate adipose tissue (MALS) in a murine experimental model of SCI is presented. Our results show that, following acute intraspinal MALS transplantation, there is an engraftment at injury site with the acute powerful inhibition of the posttraumatic inflammatory response, followed by a significant progressive improvement in recovery of function. This is accompanied by spinal cord tissue preservation at the lesion site with the promotion of endogenous neurogenesis as indicated by the significant increase of Nestin-positive cells in perilesional areas. Cells originated from MALS infiltrate profoundly the recipient cord, while the extra-dural fat transplant is gradually impoverished in stromal cells. Altogether, these novel results suggest the potential of MALS application in the promotion of recovery in SCI.