Emerging Roles of Exosomes in Stroke Therapy.

Stroke is the number one cause of morbidity in the United States and number two cause of death worldwide. There is a critical unmet medical need for more effective treatments of ischemic stroke, and this need is increasing with the shift in demographics to an older population. Recently, several studies have reported the therapeutic potential of stem cell-derived exosomes as new candidates for cell-free treatment in stoke. This review focuses on the use of stem cell-derived exosomes as a potential treatment tool for stroke patients. Therapy using exosomes can have a clear clinical advantage over stem cell transplantation in terms of safety, cost, and convenience, as well as reducing bench-to-bed latency due to fewer regulatory milestones. In this review article, we focus on (1) the therapeutic potential of exosomes in stroke treatment, (2) the optimization process of upstream and downstream production, and (3) preclinical application in a stroke animal model. Finally, we discuss the limitations and challenges faced by exosome therapy in future clinical applications.

SOX2 is required for inner ear growth and cochlear nonsensory formation before sensory development.

The transcription factor sex determining region Y-box 2 (SOX2) is required for the formation of hair cells and supporting cells in the inner ear and is a widely used sensory marker. Paradoxically, we demonstrate via fate mapping that, initially, SOX2 primarily marks nonsensory progenitors in the mouse cochlea, and is not specific to all sensory regions until late otic vesicle stages. SOX2 fate mapping reveals an apical-to-basal gradient of SOX2 expression in the sensory region of the cochlea, reflecting the pattern of cell cycle exit. To understand SOX2 function, we undertook a timed-deletion approach, revealing that early loss of SOX2 severely impaired morphological development of the ear, whereas later deletions resulted in sensory disruptions. During otocyst stages, SOX2 shifted dramatically from a lateral to medial domain over 24-48 h, reflecting the nonsensory-to-sensory switch observed by fate mapping. Early loss or gain of SOX2 function led to changes in otic epithelial volume and progenitor proliferation, impacting growth and morphological development of the ear. Our study demonstrates a novel role for SOX2 in early otic morphological development, and provides insights into the temporal and spatial patterns of sensory specification in the inner ear.

Accelerated differentiation of human pluripotent stem cells into neural lineages via an early intermediate ectoderm population.

Differentiation of human pluripotent stem cells (hPSCs) into ectoderm provides neurons and glia useful for research, disease modeling, drug discovery, and potential cell therapies. In current protocols, hPSCs are traditionally differentiated into an obligate rostro-dorsal ectodermal fate expressing PAX6 after 6 to 12 days in vitro when protected from mesendoderm inducers. This rate-limiting step has performed a long-standing role in hindering the development of rapid differentiation protocols for ectoderm-derived cell types, as any protocol requires 6 to 10 days in vitro to simply initiate. Here, we report efficient differentiation of hPSCs into a naive early ectodermal intermediate within 24 hours using combined inhibition of bone morphogenic protein and fibroblast growth factor signaling. The induced population responds immediately to morphogen gradients to upregulate rostro-caudal neurodevelopmental landmark gene expression in a generally accelerated fashion. This method can serve as a new platform for the development of novel, rapid, and efficient protocols for the manufacture of hPSC-derived neural lineages.

Orientation selective deep brain stimulation of the subthalamic nucleus in rats.

Deep brain stimulation (DBS) has become an important tool in the management of a wide spectrum of diseases in neurology and psychiatry. Target selection is a vital aspect of DBS so that only the desired areas are stimulated. Segmented leads and current steering have been shown to be promising additions to DBS technology enabling better control of the stimulating electric field. Recently introduced orientation selective DBS (OS-DBS) is a related development permitting sensitization of the stimulus to axonal pathways with different orientations by freely controlling the primary direction of the electric field using multiple contacts. Here, we used OS-DBS to stimulate the subthalamic nucleus (STN) in healthy rats while simultaneously monitoring the induced brain activity with fMRI. Maximal activation of the sensorimotor and basal ganglia-thalamocortical networks was observed when the electric field was aligned mediolaterally in the STN pointing in the lateral direction, while no cortical activation was observed with the electric field pointing medially to the opposite direction. Such findings are consistent with mediolateral main direction of the STN fibers, as seen with high resolution diffusion imaging and histology. The asymmetry of the OS-DBS dipolar field distribution using three contacts along with the potential stimulation of the internal capsule, are also discussed. We conclude that OS-DBS offers an additional degree of flexibility for optimization of DBS of the STN which may enable a better treatment response.

Concise Review: Human-Animal Neurological Chimeras: Humanized Animals or Human Cells in an Animal?

Blastocyst complementation is an emerging methodology in which human stem cells are transferred into genetically engineered preimplantation animal embryos eventually giving rise to fully developed human tissues and organs within the animal host for use in regenerative medicine. The ethical issues surrounding this method have caused the National Institutes of Health to issue a moratorium on funding for blastocyst complementation citing the potential for human cells to substantially contribute to the brain of the chimeric animal. To address this concern, we performed an in-depth review of the neural transplantation literature to determine how the integration of human cells into the nonhuman neural circuitry has altered the behavior of the host. Despite reports of widespread integration of human cell transplants, our review of 150 transplantation studies found no evidence suggestive of humanization of the animal host, and we thus conclude that, at present, concerns over humanization should not prevent research on blastocyst complementation to continue. We suggest proceeding in a controlled and transparent manner, however, and include recommendations for future research with careful consideration for how human cells may contribute to the animal host nervous system. Stem Cells 2019;37:444-452.

T cell deficiency in spinal cord injury: altered locomotor recovery and whole-genome transcriptional analysis.

BACKGROUND: T cells undergo autoimmunization following spinal cord injury (SCI) and play both protective and destructive roles during the recovery process. T cell-deficient athymic nude (AN) rats exhibit improved functional recovery when compared to immunocompetent Sprague-Dawley (SD) rats following spinal cord transection. METHODS: In the present study, we evaluated locomotor recovery in SD and AN rats following moderate spinal cord contusion. To explain variable locomotor outcome, we assessed whole-genome expression using RNA sequencing, in the acute (1 week post-injury) and chronic (8 weeks post-injury) phases of recovery. RESULTS: Athymic nude rats demonstrated greater locomotor function than SD rats only at 1 week post-injury, coinciding with peak T cell infiltration in immunocompetent rats. Genetic markers for T cells and helper T cells were acutely enriched in SD rats, while AN rats expressed genes for T(h)2 cells, cytotoxic T cells, NK cells, mast cells, IL-1a, and IL-6 at higher levels. Acute enrichment of cell death-related genes suggested that SD rats undergo secondary tissue damage from T cells. Additionally, SD rats exhibited increased acute expression of voltage-gated potassium (Kv) channel-related genes. However, AN rats demonstrated greater chronic expression of cell death-associated genes and less expression of axon-related genes. Immunostaining for macrophage markers revealed no T cell-dependent difference in the acute macrophage infiltrate. CONCLUSIONS: We put forth a model in which T cells facilitate early tissue damage, demyelination, and Kv channel dysregulation in SD rats following contusion SCI. However, compensatory features of the immune response in AN rats cause delayed tissue death and limit long-term recovery. T cell inhibition combined with other neuroprotective treatment may thus be a promising therapeutic avenue.

Retinal dendritic cell recruitment, but not function, was inhibited in MyD88 and TRIF deficient mice.

BACKGROUND: Immune system cells are known to affect loss of neurons due to injury or disease. Recruitment of immune cells following retinal/CNS injury has been shown to affect the health and survival of neurons in several models. We detected close, physical contact between dendritic cells and retinal ganglion cells following an optic nerve crush, and sought to understand the underlying mechanisms. METHODS: CD11c-DTR/GFP mice producing a chimeric protein of diphtheria toxin receptor (DTR) and GFP from a transgenic CD11c promoter were used in conjunction with mice deficient in MyD88 and/or TRIF. Retinal ganglion cell injury was induced by an optic nerve crush, and the resulting interactions of the GFPhi cells and retinal ganglion cells were examined. RESULTS: Recruitment of GFPhi dendritic cells to the retina was significantly compromised in MyD88 and TRIF knockout mice. GFPhi dendritic cells played a significant role in clearing fluorescent-labeled retinal ganglion cells post-injury in the CD11c-DTR/GFP mice. In the TRIF and MyD88 deficient mice, the resting level of GFPhi dendritic cells was lower, and their influx was reduced following the optic nerve crush injury. The reduction in GFPhi dendritic cell numbers led to their replacement in the uptake of fluorescent-labeled debris by GFPlo microglia/macrophages. Depletion of GFPhi dendritic cells by treatment with diphtheria toxin also led to their displacement by GFPlo microglia/macrophages, which then assumed close contact with the injured neurons. CONCLUSIONS: The contribution of recruited cells to the injury response was substantial, and regulated by MyD88 and TRIF. However, the presence of these adaptor proteins was not required for interaction with neurons, or the phagocytosis of debris. The data suggested a two-niche model in which resident microglia were maintained at a constant level post-optic nerve crush, while the injury-stimulated recruitment of dendritic cells and macrophages led to their transient appearance in numbers equivalent to or greater than the resident microglia.

Non-ATG-initiated translation directed by microsatellite expansions.

Trinucleotide expansions cause disease by both protein- and RNA-mediated mechanisms. Unexpectedly, we discovered that CAG expansion constructs express homopolymeric polyglutamine, polyalanine, and polyserine proteins in the absence of an ATG start codon. This repeat-associated non-ATG translation (RAN translation) occurs across long, hairpin-forming repeats in transfected cells or when expansion constructs are integrated into the genome in lentiviral-transduced cells and brains. Additionally, we show that RAN translation across human spinocerebellar ataxia type 8 (SCA8) and myotonic dystrophy type 1 (DM1) CAG expansion transcripts results in the accumulation of SCA8 polyalanine and DM1 polyglutamine expansion proteins in previously established SCA8 and DM1 mouse models and human tissue. These results have implications for understanding fundamental mechanisms of gene expression. Moreover, these toxic, unexpected, homopolymeric proteins now should be considered in pathogenic models of microsatellite disorders.

Ex vivo method for rapid quantification of post traumatic brain injury lesion volumes using ultrasound.

BACKGROUND: Studies of traumatic brain injury often involve the quantification of the lesion volume as a major outcome measure. The determination of lesion volume typically employs the cutting and mounting of brain tissue, and the calculation of the cross-sectional area of the lesion within each section of brain after histological staining. This is a time consuming and laborious task often requiring many weeks to determine the lesion volume for an individual brain. METHODS: In this report we present a method for determining the lesion volume within the brain following traumatic brain injury that involves the use of ultrasound imaging. With this process the lesion volume can be determined within a time period of 90 min per brain rather than weeks and months. Moreover, we have developed a pipeline that will combine the cross-sectional ultrasound images of the brain with the Allen Mouse Brain Atlas to provide the precise anatomical structures that are affected by traumatic injury to the brain. The anatomical detail was lastly paired with behavioral data showing neurological deficits correlated with specific areas of brain injury. RESULTS: The accuracy and precision of this method was shown to be highly consistent with the traditional histological approach. Additionally, the mapping process and behavioral data show that neurological recovery from 1 to 3 weeks post injury is not correlated with gross anatomical recovery of the TBI lesion in our TBI model. CONCLUSION: Together these approaches will enhance the pipeline for processing brain tissue in experimental conditions where the lesion volume is an important outcome parameter and provide more high resolution information about the identity of the damaged regions of the brain.

Impact of age and sex on neuroinflammation following SARS-CoV-2 infection in a murine model.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, is known to infect people of all ages and both sexes. Senior populations have the greatest risk of severe COVID-19, and sexual dimorphism in clinical outcomes has been reported. Neurological symptoms are widely observed in COVID-19 patients, with many survivors exhibiting persistent neurological and cognitive impairment. The present study aims to investigate the impact of age and sex on the neuroinflammatory response to SARS-CoV-2 infection using a mouse model. Wild-type C57BL/6J mice were intranasally inoculated with SARS-CoV-2 lineage B.1.351, a variant known to infect mice. Older male mice exhibited a significantly greater weight loss and higher viral loads in the lung at 3 days post infection. Notably, no viral RNA was detected in the brains of infected mice. Nevertheless, expression of IL-6, TNF-α, and CCL-2 in the lung and brain increased with viral infection. RNA-seq transcriptomic analysis of brains showed that SARS-CoV-2 infection caused significant changes in gene expression profiles, implicating innate immunity, defense response to virus, and cerebrovascular and neuronal functions. These findings demonstrate that SARS-CoV-2 infection triggers a neuroinflammatory response, despite the lack of detectable virus in the brain. Aberrant activation of innate immune response, disruption of blood-brain barrier and endothelial cell integrity, and suppression of neuronal activity and axonogenesis underlie the impact of SARS-CoV-2 infection on the brain. Understanding the role of these affected pathways in SARS-CoV-2 pathogenesis helps identify appropriate points of therapeutic interventions to alleviate neurological dysfunction observed during COVID-19.

Impact of anesthesia on micromagnetic stimulation (µMS) of the vagus nerve.

To treat diseases associated with vagal nerve control of peripheral organs, it is necessary to selectively activate efferent and afferent fibers in the vagus. As a result of the nerve's complex anatomy, fiber-specific activation proves challenging. Spatially selective neuromodulation using micromagnetic stimulation(µMS) is showing incredible promise. This neuromodulation technique uses microcoils(µcoils) to generate magnetic fields by powering them with a time-varying current. Following the principles of Faraday's law of induction, a highly directional electric field is induced in the nerve from the magnetic field. In this study on rodent cervical vagus, a solenoidalµcoil was oriented at an angle to left and right branches of the nerve. The aim of this study was to measure changes in the mean arterial pressure (MAP) and heart rate (HR) followingµMS of the vagus. Theµcoils were powered by a single-cycle sinusoidal current varying in pulse widths(PW = 100, 500, and 1000µsec) at a frequency of 20 Hz. Under the influence of isoflurane,µMS of the left vagus at 1000µsec PW led to an average drop in MAP of 16.75 mmHg(n = 7). In contrast,µMS of the right vagus under isoflurane resulted in an average drop of 11.93 mmHg in the MAP(n = 7). Surprisingly, there were no changes in HR to either right or left vagalµMS suggesting the drop in MAP associated with vagusµMS was the result of stimulation of afferent, but not efferent fibers. In urethane anesthetized rats, no changes in either MAP or HR were observed uponµMS of the right or left vagus(n = 3). These findings suggest the choice of anesthesia plays a key role in determining the efficacy ofµMS on the vagal nerve. Absence of HR modulation uponµMS could offer alternative treatment options using VNS with fewer heart-related side-effects.

Cell Transplantation for Repair of the Spinal Cord and Prospects for Generating Region-Specific Exogenic Neuronal Cells.

Spinal cord injury (SCI) is associated with currently irreversible consequences in several functional components of the central nervous system. Despite the severity of injury, there remains no approved treatment to restore function. However, with a growing number of preclinical studies and clinical trials, cell transplantation has gained significant potential as a treatment for SCI. Researchers have identified several cell types as potential candidates for transplantation. To optimize successful functional outcomes after transplantation, one key factor concerns generating neuronal cells with regional and subtype specificity, thus calling on the developmental transcriptome patterning of spinal cord cells. A potential source of spinal cord cells for transplantation is the generation of exogenic neuronal progenitor cells via the emerging technologies of gene editing and blastocyst complementation. This review highlights the use of cell transplantation to treat SCI in the context of relevant developmental gene expression patterns useful for producing regionally specific exogenic spinal cells via in vitro differentiation and blastocyst complementation.

Modulation of neural stem/progenitor cell proliferation during experimental Herpes Simplex encephalitis is mediated by differential FGF-2 expression in the adult brain.

Neural stem cells (NSCs) respond to inflammatory cues induced during brain injury and are thought to be involved in recovery from brain damage. Little is known about NSC response during brain infections. The present study evaluated NSC proliferation during Herpes Simplex Virus-1 brain infection. Total numbers of nestin(+) NSCs increased significantly in infected brains at 6 days post infection (p.i.). However, by 15 days p.i. the nestin(+) population decreased significantly below levels observed in uninfected brains and remained depressed through 30 days p.i. This initial increase in NSC population occurred concurrently with increased brain cell proliferation, which peaked at 3 days p.i. On closer examination, we found that while actively proliferating Sox2(+) NSCs increased in number at 6 days p.i., proliferating DCX(+) neuroblasts contributed to the increased response at 3 days p.i. However, overall proliferation decreased steadily from 15 days p.i. to below control levels. To determine the mechanisms involved in altering NSC proliferation, neurotrophin and growth factor expression profiles were assessed. FGF-2 gene expression increased at 5 days p.i. and was robustly down-regulated at 15 days p.i. (>1000-fold), which was further confirmed by increased FGF-2 immunostaining around the lateral ventricles. Furthermore, supplementing infected animals with recombinant FGF-2, at 15 days p.i., significantly increased the number of proliferating brain cells. These findings demonstrate that the temporal changes in NSC proliferation are mediated through the regulation of FGF-2 and that the NSC niche may benefit from supplementation with FGF-2 during HSV-1 brain infection.

OM-RCA-01, a novel humanized monoclonal antibody targeting fibroblast growth factor receptor 1, in renal cell carcinoma model.

Fibroblast growth factor (FGF) receptor 1 (FGFR1) is a potential therapeutic target for treatment of metastatic renal cell carcinoma (RCC). We investigated the preclinical activity of OM-RCA-01, a novel therapeutic humanized anti-FGFR1 antibody in RCC. OM-RCA-01 has been shown to inhibit in vitro kinase activity of FGFR1 and has high affinity (Kd of 1.59 nM). In human renal carcinoma Caki-1 FGFR1-expressing cells, OM-RCA-01 potently inhibited FGF-mediated signaling and proliferation. In vivo, the tumors in untreated mice or mice treated with non-specific IgG continued their aggressive growth to reach the size of 2,000 cm3, at which point the mice were killed. In contrast, treatment with OM-RCA-01 not only significant arrested further growth of the tumors (P < 0.01) but also demonstrated differences in tumor volume compared with vehicle already on Day 13. A similar anti-tumor activity of OM-RCA-01 was observed when the antibody was given in low (1 mg/kg) or high (10 mg/kg) doses (P = 0.917). In Matrigel assay, OM-RCA-01 significantly inhibited FGF-induced endothelial cell migration, capillary-like tubular structure and mature vessels formation. Administration of 10 mg/kg antibody for up to 35 days resulted in minimal body weight loss and no observations of gross toxicity were made. Collectively, the data obtained with OM-RCA-01 are consistent with potent inhibition of FGFR1-signaling, angiogenesis, and tumor growth. OM-RCA-01 is being developed clinically as an intravenous therapy for the treatment of clear cell RCC.

A Technological and Regulatory Review on Human-Animal Chimera Research: The Current Landscape of Biology, Law, and Public Opinion.

Organ transplantation is a highly utilized treatment for many medical conditions, yet the number of patients waiting for organs far exceeds the number available. The challenges and limitations currently associated with organ transplantation and technological advances in gene editing techniques have led scientists to pursue alternate solutions to the donor organ shortage. Growing human organs in animals and harvesting those organs for transplantation into humans is one such solution. These chimeric animals usually have certain genes necessary for a specific organ's development inhibited at an early developmental stage, followed by the addition of cultured pluripotent human cells to fill that developmental niche. The result is a chimeric animal that contains human organs which are available for transplant into a patient, circumventing some of the limitations currently involved in donor organ transplantation. In this review, we will discuss both the current scientific and legal landscape of human-animal chimera (HAC) research. We present an overview of the technological advances that allow for the creation of HACs, the patents that currently exist on these methods, as well as current public attitude and understanding that can influence HAC research policy. We complement our scientific and public attitude discussion with a regulatory overview of chimera research at both the national and state level, while also contrasting current U.S. legislation with regulations in other countries. Overall, we provide a comprehensive analysis of the legal and scientific barriers to conducting research on HACs for the generation of transplantable human organs, as well as provide recommendations for the future.

Neuronal Transplantation for Alzheimer's Disease and Prospects for Generating Exogenic Neurons as a Source of Cells for Implantation.

Alzheimer's disease (AD) is a devastating neurodegenerative disease with limited therapeutic options. Cellular transplantation of healthy exogenic neurons to replace and restore neuronal cell function has previously been explored in AD animal models, yet most of these transplantation methods have utilized primary cell cultures or donor grafts. Blastocyst complementation offers a novel approach to generate a renewable exogenic source of neurons. These exogenic neurons derived from stem cells would develop with the in vivo context of the inductive cues within a host, thus recapitulating the neuron-specific characteristics and physiology. AD affects many different cell types including hippocampal neurons and limbic projection neurons, cholinergic nucleus basis and medial septal neurons, noradrenergic locus coeruleus neurons, serotonergic raphe neurons, and limbic and cortical interneurons. Blastocyst complementation can be adapted to generate these specific neuronal cells afflicted by AD pathology, by ablating important cell type and brain region-specific developmental genes. This review discusses the current state of neuronal transplantation to replace specific neural cell types affected by AD, and the developmental biology to identify candidate genes for knockout in embryos for creating niches to generate exogenic neurons via blastocyst complementation.

In Silico Stage-Matching of Human, Marmoset, Mouse, and Pig Embryos to Enhance Organ Development Through Interspecies Chimerism.

Currently, there is a significant shortage of transplantable organs for patients in need. Interspecies chimerism and blastocyst complementation are alternatives for generating transplantable human organs in host animals such as pigs to meet this shortage. While successful interspecies chimerism and organ generation have been observed between evolutionarily close species such as rat and mouse, barriers still exist for more distant species pairs such as human-mouse, marmoset-mouse, human-pig, and others. One of the proposed barriers to chimerism is the difference in developmental stages between the donor cells and the host embryo at the time the cells are introduced into the host embryo. Hence, there is a logical effort to stage-match the donor cells with the host embryos for enhancing interspecies chimerism. In this study, we used an in silico approach to simultaneously stage-match the early developing embryos of four species, including human, marmoset, mouse, and pig based on transcriptome similarities. We used an unsupervised clustering algorithm to simultaneously stage-match all four species as well as Spearman's correlation analyses to stage-match pairs of donor-host species. From our stage-matching analyses, we found that the four stages that best matched with each other are the human blastocyst (E6/E7), the gastrulating mouse embryo (E6-E6.75), the marmoset late inner cell mass, and the pig late blastocyst. We further demonstrated that human pluripotent stem cells best matched with the mouse post-implantation stages. We also performed ontology analysis of the genes upregulated and commonly expressed between donor-host species pairs at their best matched stages. The stage-matching results predicted by this study will inform in vivo and in vitro interspecies chimerism and blastocyst complementation studies and can be used to match donor cells with host embryos between multiple species pairs to enhance chimerism for organogenesis.

Nonhematopoietic Umbilical Cord Blood Stem Cell Administration Improves Long-term Neurodevelopment After Periventricular-Intraventricular Hemorrhage in Neonatal Rats.

Periventricular-intraventricular hemorrhage (PIVH) is common in extremely low gestational age neonates (ELGAN) and leads to motor and behavioral impairments. Currently there is no effective treatment for PIVH. Whether human nonhematopoietic umbilical cord blood-derived stem cell (nh-UCBSC) administration reduces the severity of brain injury and improves long-term motor and behavioral function was tested in an ELGAN-equivalent neonatal rat model of PIVH. In a collagenase-induced unilateral PIVH on postnatal day (P) 2 model, rat pups received a single dose of nh-UCBSCs at a dose of 1 × 106 cells i.p. on P6 (PIVH + UCBSC group) or were left untreated (Untreated PIVH group). Motor deficit was determined using forelimb placement, edge-push, and elevated body swing tests at 2 months (N = 5-8). Behavior was evaluated using open field exploration and rearing tests at 4 months (N =10-12). Cavity volume and hemispheric volume loss on the PIVH side were determined at 7 months (N = 6-7). Outcomes were compared between the Untreated PIVH and PIVH + UCBSC groups and a Control group. Unilateral motor deficits were present in 60%-100% of rats in the Untreated PIVH group and 12.5% rats in the PIVH + UCBSC group (P = 0.02). Untreated PIVH group exhibited a higher number of quadrant crossings in open field exploration, indicating low emotionality and poor habituation, and had a cavitary lesion and hemispheric volume loss on the PIVH side. Performance in open field exploration correlated with cavity volume (r2 = 0.25; P < 0.05). Compared with the Untreated PIVH group, performance in open field exploration was better (P = 0.0025) and hemispheric volume loss was lower (19.9 ± 4.4% vs 6.1 ± 2.6%, P = 0.018) in the PIVH + UCBSC group. These results suggest that a single dose of nh-UCBSCs administered in the subacute period after PIVH reduces the severity of injury and improves neurodevelopment in neonatal rats.

Transplanting Microglia for Treating CNS Injuries and Neurological Diseases and Disorders, and Prospects for Generating Exogenic Microglia.

Microglia are associated with a wide range of both neuroprotective and neuroinflammatory functions in the central nervous system (CNS) during development and throughout lifespan. Chronically activated and dysfunctional microglia are found in many diseases and disorders, such as Alzheimer's disease, Parkinson's disease, and CNS-related injuries, and can accelerate or worsen the condition. Transplantation studies designed to replace and supplement dysfunctional microglia with healthy microglia offer a promising strategy for addressing microglia-mediated neuroinflammation and pathologies. This review will cover microglial involvement in neurological diseases and disorders and CNS-related injuries, current microglial transplantation strategies, and different approaches and considerations for generating exogenic microglia.